diff --git a/native/jni/src/defines.h b/native/jni/src/defines.h
index 742e388..9a26fe0 100644
--- a/native/jni/src/defines.h
+++ b/native/jni/src/defines.h
@@ -298,6 +298,7 @@
 #define NOT_AN_INDEX (-1)
 #define NOT_A_PROBABILITY (-1)
 #define NOT_A_DICT_POS (S_INT_MIN)
+#define NOT_A_TIMESTAMP (-1)
 
 // A special value to mean the first word confidence makes no sense in this case,
 // e.g. this is not a multi-word suggestion.
@@ -341,12 +342,21 @@
 #define INPUTLENGTH_FOR_DEBUG (-1)
 #define MIN_OUTPUT_INDEX_FOR_DEBUG (-1)
 
-#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
-  TypeName(const TypeName&);               \
+#define DISALLOW_DEFAULT_CONSTRUCTOR(TypeName) \
+  TypeName()
+
+#define DISALLOW_COPY_CONSTRUCTOR(TypeName) \
+  TypeName(const TypeName&)
+
+#define DISALLOW_ASSIGNMENT_OPERATOR(TypeName) \
   void operator=(const TypeName&)
 
+#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
+  DISALLOW_COPY_CONSTRUCTOR(TypeName);     \
+  DISALLOW_ASSIGNMENT_OPERATOR(TypeName)
+
 #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
-  TypeName();                                    \
+  DISALLOW_DEFAULT_CONSTRUCTOR(TypeName);        \
   DISALLOW_COPY_AND_ASSIGN(TypeName)
 
 // Used as a return value for character comparison
@@ -392,24 +402,4 @@
     // Create new word with space substitution
     CT_NEW_WORD_SPACE_SUBSTITUTION,
 } CorrectionType;
-
-// ErrorType is mainly decided by CorrectionType but it is also depending on if
-// the correction has really been performed or not.
-typedef enum {
-    // Substitution, omission and transposition
-    ET_EDIT_CORRECTION,
-    // Proximity error
-    ET_PROXIMITY_CORRECTION,
-    // Completion
-    ET_COMPLETION,
-    // New word
-    // TODO: Remove.
-    // A new word error should be an edit correction error or a proximity correction error.
-    ET_NEW_WORD,
-    // Treat error as an intentional omission when the CorrectionType is omission and the node can
-    // be intentional omission.
-    ET_INTENTIONAL_OMISSION,
-    // Not treated as an error. Tracked for checking exact match
-    ET_NOT_AN_ERROR
-} ErrorType;
 #endif // LATINIME_DEFINES_H
diff --git a/native/jni/src/suggest/core/dicnode/dic_node.h b/native/jni/src/suggest/core/dicnode/dic_node.h
index 49cfdec..0b2b4a9 100644
--- a/native/jni/src/suggest/core/dicnode/dic_node.h
+++ b/native/jni/src/suggest/core/dicnode/dic_node.h
@@ -99,7 +99,7 @@
     virtual ~DicNode() {}
 
     // Init for copy
-    void initByCopy(const DicNode *dicNode) {
+    void initByCopy(const DicNode *const dicNode) {
         mIsUsed = true;
         mIsCachedForNextSuggestion = dicNode->mIsCachedForNextSuggestion;
         mDicNodeProperties.init(&dicNode->mDicNodeProperties);
@@ -107,25 +107,25 @@
         PROF_NODE_COPY(&dicNode->mProfiler, mProfiler);
     }
 
-    // Init for root with prevWordNodePos which is used for bigram
-    void initAsRoot(const int rootGroupPos, const int prevWordNodePos) {
+    // Init for root with prevWordPtNodePos which is used for bigram
+    void initAsRoot(const int rootPtNodeArrayPos, const int prevWordPtNodePos) {
         mIsUsed = true;
         mIsCachedForNextSuggestion = false;
         mDicNodeProperties.init(
-                NOT_A_DICT_POS /* pos */, rootGroupPos, NOT_A_CODE_POINT /* nodeCodePoint */,
+                NOT_A_DICT_POS /* pos */, rootPtNodeArrayPos, NOT_A_CODE_POINT /* nodeCodePoint */,
                 NOT_A_PROBABILITY /* probability */, false /* isTerminal */,
                 true /* hasChildren */, false /* isBlacklistedOrNotAWord */, 0 /* depth */,
                 0 /* terminalDepth */);
-        mDicNodeState.init(prevWordNodePos);
+        mDicNodeState.init(prevWordPtNodePos);
         PROF_NODE_RESET(mProfiler);
     }
 
     // Init for root with previous word
-    void initAsRootWithPreviousWord(DicNode *dicNode, const int rootGroupPos) {
+    void initAsRootWithPreviousWord(const DicNode *const dicNode, const int rootPtNodeArrayPos) {
         mIsUsed = true;
         mIsCachedForNextSuggestion = dicNode->mIsCachedForNextSuggestion;
         mDicNodeProperties.init(
-                NOT_A_DICT_POS /* pos */, rootGroupPos, NOT_A_CODE_POINT /* nodeCodePoint */,
+                NOT_A_DICT_POS /* pos */, rootPtNodeArrayPos, NOT_A_CODE_POINT /* nodeCodePoint */,
                 NOT_A_PROBABILITY /* probability */, false /* isTerminal */,
                 true /* hasChildren */, false /* isBlacklistedOrNotAWord */,  0 /* depth */,
                 0 /* terminalDepth */);
@@ -138,7 +138,7 @@
         mDicNodeState.mDicNodeStatePrevWord.init(
                 dicNode->mDicNodeState.mDicNodeStatePrevWord.getPrevWordCount() + 1,
                 dicNode->mDicNodeProperties.getProbability(),
-                dicNode->mDicNodeProperties.getPos(),
+                dicNode->mDicNodeProperties.getPtNodePos(),
                 dicNode->mDicNodeState.mDicNodeStatePrevWord.mPrevWord,
                 dicNode->mDicNodeState.mDicNodeStatePrevWord.getPrevWordLength(),
                 dicNode->getOutputWordBuf(),
@@ -148,26 +148,27 @@
         PROF_NODE_COPY(&dicNode->mProfiler, mProfiler);
     }
 
-    void initAsPassingChild(DicNode *parentNode) {
+    void initAsPassingChild(DicNode *parentDicNode) {
         mIsUsed = true;
-        mIsCachedForNextSuggestion = parentNode->mIsCachedForNextSuggestion;
-        const int c = parentNode->getNodeTypedCodePoint();
-        mDicNodeProperties.init(&parentNode->mDicNodeProperties, c);
-        mDicNodeState.init(&parentNode->mDicNodeState);
-        PROF_NODE_COPY(&parentNode->mProfiler, mProfiler);
+        mIsCachedForNextSuggestion = parentDicNode->mIsCachedForNextSuggestion;
+        const int parentCodePoint = parentDicNode->getNodeTypedCodePoint();
+        mDicNodeProperties.init(&parentDicNode->mDicNodeProperties, parentCodePoint);
+        mDicNodeState.init(&parentDicNode->mDicNodeState);
+        PROF_NODE_COPY(&parentDicNode->mProfiler, mProfiler);
     }
 
-    void initAsChild(const DicNode *const dicNode, const int pos, const int childrenPos,
-            const int probability, const bool isTerminal, const bool hasChildren,
-            const bool isBlacklistedOrNotAWord, const uint16_t mergedNodeCodePointCount,
-            const int *const mergedNodeCodePoints) {
+    void initAsChild(const DicNode *const dicNode, const int ptNodePos,
+            const int childrenPtNodeArrayPos, const int probability, const bool isTerminal,
+            const bool hasChildren, const bool isBlacklistedOrNotAWord,
+            const uint16_t mergedNodeCodePointCount, const int *const mergedNodeCodePoints) {
         mIsUsed = true;
         uint16_t newDepth = static_cast<uint16_t>(dicNode->getNodeCodePointCount() + 1);
         mIsCachedForNextSuggestion = dicNode->mIsCachedForNextSuggestion;
         const uint16_t newLeavingDepth = static_cast<uint16_t>(
                 dicNode->mDicNodeProperties.getLeavingDepth() + mergedNodeCodePointCount);
-        mDicNodeProperties.init(pos, childrenPos, mergedNodeCodePoints[0], probability,
-                isTerminal, hasChildren, isBlacklistedOrNotAWord, newDepth, newLeavingDepth);
+        mDicNodeProperties.init(ptNodePos, childrenPtNodeArrayPos, mergedNodeCodePoints[0],
+                probability, isTerminal, hasChildren, isBlacklistedOrNotAWord, newDepth,
+                newLeavingDepth);
         mDicNodeState.init(&dicNode->mDicNodeState, mergedNodeCodePointCount,
                 mergedNodeCodePoints);
         PROF_NODE_COPY(&dicNode->mProfiler, mProfiler);
@@ -234,7 +235,7 @@
     }
 
     bool isFirstWord() const {
-        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordNodePos() == NOT_A_DICT_POS;
+        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordPtNodePos() == NOT_A_DICT_POS;
     }
 
     bool isCompletion(const int inputSize) const {
@@ -246,29 +247,30 @@
     }
 
     // Used to get bigram probability in DicNodeUtils
-    int getPos() const {
-        return mDicNodeProperties.getPos();
+    int getPtNodePos() const {
+        return mDicNodeProperties.getPtNodePos();
     }
 
     // Used to get bigram probability in DicNodeUtils
-    int getPrevWordPos() const {
-        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordNodePos();
+    int getPrevWordTerminalPtNodePos() const {
+        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordPtNodePos();
     }
 
     // Used in DicNodeUtils
-    int getChildrenPos() const {
-        return mDicNodeProperties.getChildrenPos();
+    int getChildrenPtNodeArrayPos() const {
+        return mDicNodeProperties.getChildrenPtNodeArrayPos();
     }
 
     int getProbability() const {
         return mDicNodeProperties.getProbability();
     }
 
-    AK_FORCE_INLINE bool isTerminalWordNode() const {
-        const bool isTerminalNodes = mDicNodeProperties.isTerminal();
-        const int currentNodeDepth = getNodeCodePointCount();
-        const int terminalNodeDepth = mDicNodeProperties.getLeavingDepth();
-        return isTerminalNodes && currentNodeDepth > 0 && currentNodeDepth == terminalNodeDepth;
+    AK_FORCE_INLINE bool isTerminalDicNode() const {
+        const bool isTerminalPtNode = mDicNodeProperties.isTerminal();
+        const int currentDicNodeDepth = getNodeCodePointCount();
+        const int terminalDicNodeDepth = mDicNodeProperties.getLeavingDepth();
+        return isTerminalPtNode && currentDicNodeDepth > 0
+                && currentDicNodeDepth == terminalDicNodeDepth;
     }
 
     bool shouldBeFilteredBySafetyNetForBigram() const {
@@ -374,8 +376,8 @@
     }
 
     // Used to commit input partially
-    int getPrevWordNodePos() const {
-        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordNodePos();
+    int getPrevWordPtNodePos() const {
+        return mDicNodeState.mDicNodeStatePrevWord.getPrevWordPtNodePos();
     }
 
     AK_FORCE_INLINE const int *getOutputWordBuf() const {
@@ -410,7 +412,7 @@
     // TODO: Remove once touch path is merged into ProximityInfoState
     // Note: Returned codepoint may be a digraph codepoint if the node is in a composite glyph.
     int getNodeCodePoint() const {
-        const int codePoint = mDicNodeProperties.getNodeCodePoint();
+        const int codePoint = mDicNodeProperties.getDicNodeCodePoint();
         const DigraphUtils::DigraphCodePointIndex digraphIndex =
                 mDicNodeState.mDicNodeStateScoring.getDigraphIndex();
         if (digraphIndex == DigraphUtils::NOT_A_DIGRAPH_INDEX) {
@@ -423,8 +425,8 @@
     // Utils for cost calculation //
     ////////////////////////////////
     AK_FORCE_INLINE bool isSameNodeCodePoint(const DicNode *const dicNode) const {
-        return mDicNodeProperties.getNodeCodePoint()
-                == dicNode->mDicNodeProperties.getNodeCodePoint();
+        return mDicNodeProperties.getDicNodeCodePoint()
+                == dicNode->mDicNodeProperties.getDicNodeCodePoint();
     }
 
     // TODO: remove
@@ -574,7 +576,8 @@
     // Caveat: Must not be called outside Weighting
     // This restriction is guaranteed by "friend"
     AK_FORCE_INLINE void addCost(const float spatialCost, const float languageCost,
-            const bool doNormalization, const int inputSize, const ErrorType errorType) {
+            const bool doNormalization, const int inputSize,
+            const ErrorTypeUtils::ErrorType errorType) {
         if (DEBUG_GEO_FULL) {
             LOGI_SHOW_ADD_COST_PROP;
         }
diff --git a/native/jni/src/suggest/core/dicnode/dic_node_utils.cpp b/native/jni/src/suggest/core/dicnode/dic_node_utils.cpp
index ec65114..5540b6d 100644
--- a/native/jni/src/suggest/core/dicnode/dic_node_utils.cpp
+++ b/native/jni/src/suggest/core/dicnode/dic_node_utils.cpp
@@ -22,7 +22,6 @@
 #include "suggest/core/dicnode/dic_node_vector.h"
 #include "suggest/core/dictionary/multi_bigram_map.h"
 #include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
-#include "utils/char_utils.h"
 
 namespace latinime {
 
@@ -32,19 +31,20 @@
 
 /* static */ void DicNodeUtils::initAsRoot(
         const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-        const int prevWordNodePos, DicNode *const newRootNode) {
-    newRootNode->initAsRoot(dictionaryStructurePolicy->getRootPosition(), prevWordNodePos);
+        const int prevWordPtNodePos, DicNode *const newRootDicNode) {
+    newRootDicNode->initAsRoot(dictionaryStructurePolicy->getRootPosition(), prevWordPtNodePos);
 }
 
 /*static */ void DicNodeUtils::initAsRootWithPreviousWord(
         const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-        DicNode *const prevWordLastNode, DicNode *const newRootNode) {
-    newRootNode->initAsRootWithPreviousWord(
-            prevWordLastNode, dictionaryStructurePolicy->getRootPosition());
+        const DicNode *const prevWordLastDicNode, DicNode *const newRootDicNode) {
+    newRootDicNode->initAsRootWithPreviousWord(
+            prevWordLastDicNode, dictionaryStructurePolicy->getRootPosition());
 }
 
-/* static */ void DicNodeUtils::initByCopy(DicNode *srcNode, DicNode *destNode) {
-    destNode->initByCopy(srcNode);
+/* static */ void DicNodeUtils::initByCopy(const DicNode *const srcDicNode,
+        DicNode *const destDicNode) {
+    destDicNode->initByCopy(srcDicNode);
 }
 
 ///////////////////////////////////
@@ -52,14 +52,14 @@
 ///////////////////////////////////
 /* static */ void DicNodeUtils::getAllChildDicNodes(DicNode *dicNode,
         const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-        DicNodeVector *childDicNodes) {
+        DicNodeVector *const childDicNodes) {
     if (dicNode->isTotalInputSizeExceedingLimit()) {
         return;
     }
     if (!dicNode->isLeavingNode()) {
         childDicNodes->pushPassingChild(dicNode);
     } else {
-        dictionaryStructurePolicy->createAndGetAllChildNodes(dicNode, childDicNodes);
+        dictionaryStructurePolicy->createAndGetAllChildDicNodes(dicNode, childDicNodes);
     }
 }
 
@@ -71,11 +71,11 @@
  */
 /* static */ float DicNodeUtils::getBigramNodeImprobability(
         const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-        const DicNode *const node, MultiBigramMap *multiBigramMap) {
-    if (node->hasMultipleWords() && !node->isValidMultipleWordSuggestion()) {
+        const DicNode *const dicNode, MultiBigramMap *const multiBigramMap) {
+    if (dicNode->hasMultipleWords() && !dicNode->isValidMultipleWordSuggestion()) {
         return static_cast<float>(MAX_VALUE_FOR_WEIGHTING);
     }
-    const int probability = getBigramNodeProbability(dictionaryStructurePolicy, node,
+    const int probability = getBigramNodeProbability(dictionaryStructurePolicy, dicNode,
             multiBigramMap);
     // TODO: This equation to calculate the improbability looks unreasonable.  Investigate this.
     const float cost = static_cast<float>(MAX_PROBABILITY - probability)
@@ -85,19 +85,19 @@
 
 /* static */ int DicNodeUtils::getBigramNodeProbability(
         const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-        const DicNode *const node, MultiBigramMap *multiBigramMap) {
-    const int unigramProbability = node->getProbability();
-    const int wordPos = node->getPos();
-    const int prevWordPos = node->getPrevWordPos();
-    if (NOT_A_DICT_POS == wordPos || NOT_A_DICT_POS == prevWordPos) {
+        const DicNode *const dicNode, MultiBigramMap *const multiBigramMap) {
+    const int unigramProbability = dicNode->getProbability();
+    const int ptNodePos = dicNode->getPtNodePos();
+    const int prevWordTerminalPtNodePos = dicNode->getPrevWordTerminalPtNodePos();
+    if (NOT_A_DICT_POS == ptNodePos || NOT_A_DICT_POS == prevWordTerminalPtNodePos) {
         // Note: Normally wordPos comes from the dictionary and should never equal
         // NOT_A_VALID_WORD_POS.
         return dictionaryStructurePolicy->getProbability(unigramProbability,
                 NOT_A_PROBABILITY);
     }
     if (multiBigramMap) {
-        return multiBigramMap->getBigramProbability(dictionaryStructurePolicy, prevWordPos,
-                wordPos, unigramProbability);
+        return multiBigramMap->getBigramProbability(dictionaryStructurePolicy,
+                prevWordTerminalPtNodePos, ptNodePos, unigramProbability);
     }
     return dictionaryStructurePolicy->getProbability(unigramProbability,
             NOT_A_PROBABILITY);
@@ -109,7 +109,7 @@
 
 // TODO: Move to char_utils?
 /* static */ int DicNodeUtils::appendTwoWords(const int *const src0, const int16_t length0,
-        const int *const src1, const int16_t length1, int *dest) {
+        const int *const src1, const int16_t length1, int *const dest) {
     int actualLength0 = 0;
     for (int i = 0; i < length0; ++i) {
         if (src0[i] == 0) {
diff --git a/native/jni/src/suggest/core/dicnode/dic_node_utils.h b/native/jni/src/suggest/core/dicnode/dic_node_utils.h
index 3fb351a..3f1514a 100644
--- a/native/jni/src/suggest/core/dicnode/dic_node_utils.h
+++ b/native/jni/src/suggest/core/dicnode/dic_node_utils.h
@@ -31,20 +31,20 @@
 class DicNodeUtils {
  public:
     static int appendTwoWords(const int *src0, const int16_t length0, const int *src1,
-            const int16_t length1, int *dest);
+            const int16_t length1, int *const dest);
     static void initAsRoot(
             const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-            const int prevWordNodePos, DicNode *newRootNode);
+            const int prevWordPtNodePos, DicNode *const newRootDicNode);
     static void initAsRootWithPreviousWord(
             const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-            DicNode *prevWordLastNode, DicNode *newRootNode);
-    static void initByCopy(DicNode *srcNode, DicNode *destNode);
+            const DicNode *const prevWordLastDicNode, DicNode *const newRootDicNode);
+    static void initByCopy(const DicNode *const srcDicNode, DicNode *const destDicNode);
     static void getAllChildDicNodes(DicNode *dicNode,
             const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
             DicNodeVector *childDicNodes);
     static float getBigramNodeImprobability(
             const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-            const DicNode *const node, MultiBigramMap *const multiBigramMap);
+            const DicNode *const dicNode, MultiBigramMap *const multiBigramMap);
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DicNodeUtils);
@@ -53,7 +53,7 @@
 
     static int getBigramNodeProbability(
             const DictionaryStructureWithBufferPolicy *const dictionaryStructurePolicy,
-            const DicNode *const node, MultiBigramMap *multiBigramMap);
+            const DicNode *const dicNode, MultiBigramMap *const multiBigramMap);
 };
 } // namespace latinime
 #endif // LATINIME_DIC_NODE_UTILS_H
diff --git a/native/jni/src/suggest/core/dicnode/dic_node_vector.h b/native/jni/src/suggest/core/dicnode/dic_node_vector.h
index 42addae..9364e77 100644
--- a/native/jni/src/suggest/core/dicnode/dic_node_vector.h
+++ b/native/jni/src/suggest/core/dicnode/dic_node_vector.h
@@ -62,14 +62,14 @@
         mDicNodes.back().initAsPassingChild(dicNode);
     }
 
-    void pushLeavingChild(const DicNode *const dicNode, const int pos, const int childrenPos,
-            const int probability, const bool isTerminal, const bool hasChildren,
-            const bool isBlacklistedOrNotAWord, const uint16_t mergedNodeCodePointCount,
-            const int *const mergedNodeCodePoints) {
+    void pushLeavingChild(const DicNode *const dicNode, const int ptNodePos,
+            const int childrenPtNodeArrayPos, const int probability, const bool isTerminal,
+            const bool hasChildren, const bool isBlacklistedOrNotAWord,
+            const uint16_t mergedNodeCodePointCount, const int *const mergedNodeCodePoints) {
         ASSERT(!mLock);
         mDicNodes.push_back(mEmptyNode);
-        mDicNodes.back().initAsChild(dicNode, pos, childrenPos, probability, isTerminal,
-                hasChildren, isBlacklistedOrNotAWord, mergedNodeCodePointCount,
+        mDicNodes.back().initAsChild(dicNode, ptNodePos, childrenPtNodeArrayPos, probability,
+                isTerminal, hasChildren, isBlacklistedOrNotAWord, mergedNodeCodePointCount,
                 mergedNodeCodePoints);
     }
 
diff --git a/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h b/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
index 9e0f62c..c41a724 100644
--- a/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
+++ b/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
@@ -24,15 +24,14 @@
 namespace latinime {
 
 /**
- * Node for traversing the lexicon trie.
+ * PtNode information related to the DicNode from the lexicon trie.
  */
-// TODO: Introduce a dictionary node class which has attribute members required to understand the
-// dictionary structure.
 class DicNodeProperties {
  public:
     AK_FORCE_INLINE DicNodeProperties()
-            : mPos(0), mChildrenPos(0), mProbability(0), mNodeCodePoint(0), mIsTerminal(false),
-              mHasChildren(false), mIsBlacklistedOrNotAWord(false), mDepth(0), mLeavingDepth(0) {}
+            : mPtNodePos(0), mChildrenPtNodeArrayPos(0), mProbability(0), mDicNodeCodePoint(0),
+              mIsTerminal(false), mHasChildrenPtNodes(false), mIsBlacklistedOrNotAWord(false),
+              mDepth(0), mLeavingDepth(0) {}
 
     virtual ~DicNodeProperties() {}
 
@@ -40,57 +39,57 @@
     void init(const int pos, const int childrenPos, const int nodeCodePoint, const int probability,
             const bool isTerminal, const bool hasChildren, const bool isBlacklistedOrNotAWord,
             const uint16_t depth, const uint16_t leavingDepth) {
-        mPos = pos;
-        mChildrenPos = childrenPos;
-        mNodeCodePoint = nodeCodePoint;
+        mPtNodePos = pos;
+        mChildrenPtNodeArrayPos = childrenPos;
+        mDicNodeCodePoint = nodeCodePoint;
         mProbability = probability;
         mIsTerminal = isTerminal;
-        mHasChildren = hasChildren;
+        mHasChildrenPtNodes = hasChildren;
         mIsBlacklistedOrNotAWord = isBlacklistedOrNotAWord;
         mDepth = depth;
         mLeavingDepth = leavingDepth;
     }
 
     // Init for copy
-    void init(const DicNodeProperties *const nodeProp) {
-        mPos = nodeProp->mPos;
-        mChildrenPos = nodeProp->mChildrenPos;
-        mNodeCodePoint = nodeProp->mNodeCodePoint;
-        mProbability = nodeProp->mProbability;
-        mIsTerminal = nodeProp->mIsTerminal;
-        mHasChildren = nodeProp->mHasChildren;
-        mIsBlacklistedOrNotAWord = nodeProp->mIsBlacklistedOrNotAWord;
-        mDepth = nodeProp->mDepth;
-        mLeavingDepth = nodeProp->mLeavingDepth;
+    void init(const DicNodeProperties *const dicNodeProp) {
+        mPtNodePos = dicNodeProp->mPtNodePos;
+        mChildrenPtNodeArrayPos = dicNodeProp->mChildrenPtNodeArrayPos;
+        mDicNodeCodePoint = dicNodeProp->mDicNodeCodePoint;
+        mProbability = dicNodeProp->mProbability;
+        mIsTerminal = dicNodeProp->mIsTerminal;
+        mHasChildrenPtNodes = dicNodeProp->mHasChildrenPtNodes;
+        mIsBlacklistedOrNotAWord = dicNodeProp->mIsBlacklistedOrNotAWord;
+        mDepth = dicNodeProp->mDepth;
+        mLeavingDepth = dicNodeProp->mLeavingDepth;
     }
 
     // Init as passing child
-    void init(const DicNodeProperties *const nodeProp, const int codePoint) {
-        mPos = nodeProp->mPos;
-        mChildrenPos = nodeProp->mChildrenPos;
-        mNodeCodePoint = codePoint; // Overwrite the node char of a passing child
-        mProbability = nodeProp->mProbability;
-        mIsTerminal = nodeProp->mIsTerminal;
-        mHasChildren = nodeProp->mHasChildren;
-        mIsBlacklistedOrNotAWord = nodeProp->mIsBlacklistedOrNotAWord;
-        mDepth = nodeProp->mDepth + 1; // Increment the depth of a passing child
-        mLeavingDepth = nodeProp->mLeavingDepth;
+    void init(const DicNodeProperties *const dicNodeProp, const int codePoint) {
+        mPtNodePos = dicNodeProp->mPtNodePos;
+        mChildrenPtNodeArrayPos = dicNodeProp->mChildrenPtNodeArrayPos;
+        mDicNodeCodePoint = codePoint; // Overwrite the node char of a passing child
+        mProbability = dicNodeProp->mProbability;
+        mIsTerminal = dicNodeProp->mIsTerminal;
+        mHasChildrenPtNodes = dicNodeProp->mHasChildrenPtNodes;
+        mIsBlacklistedOrNotAWord = dicNodeProp->mIsBlacklistedOrNotAWord;
+        mDepth = dicNodeProp->mDepth + 1; // Increment the depth of a passing child
+        mLeavingDepth = dicNodeProp->mLeavingDepth;
     }
 
-    int getPos() const {
-        return mPos;
+    int getPtNodePos() const {
+        return mPtNodePos;
     }
 
-    int getChildrenPos() const {
-        return mChildrenPos;
+    int getChildrenPtNodeArrayPos() const {
+        return mChildrenPtNodeArrayPos;
     }
 
     int getProbability() const {
         return mProbability;
     }
 
-    int getNodeCodePoint() const {
-        return mNodeCodePoint;
+    int getDicNodeCodePoint() const {
+        return mDicNodeCodePoint;
     }
 
     uint16_t getDepth() const {
@@ -107,7 +106,7 @@
     }
 
     bool hasChildren() const {
-        return mHasChildren || mDepth != mLeavingDepth;
+        return mHasChildrenPtNodes || mDepth != mLeavingDepth;
     }
 
     bool isBlacklistedOrNotAWord() const {
@@ -118,12 +117,12 @@
     // Caution!!!
     // Use a default copy constructor and an assign operator because shallow copies are ok
     // for this class
-    int mPos;
-    int mChildrenPos;
+    int mPtNodePos;
+    int mChildrenPtNodeArrayPos;
     int mProbability;
-    int mNodeCodePoint;
+    int mDicNodeCodePoint;
     bool mIsTerminal;
-    bool mHasChildren;
+    bool mHasChildrenPtNodes;
     bool mIsBlacklistedOrNotAWord;
     uint16_t mDepth;
     uint16_t mLeavingDepth;
diff --git a/native/jni/src/suggest/core/dicnode/internal/dic_node_state_prevword.h b/native/jni/src/suggest/core/dicnode/internal/dic_node_state_prevword.h
index b898620..dba5705 100644
--- a/native/jni/src/suggest/core/dicnode/internal/dic_node_state_prevword.h
+++ b/native/jni/src/suggest/core/dicnode/internal/dic_node_state_prevword.h
@@ -30,7 +30,7 @@
  public:
     AK_FORCE_INLINE DicNodeStatePrevWord()
             : mPrevWordCount(0), mPrevWordLength(0), mPrevWordStart(0), mPrevWordProbability(0),
-              mPrevWordNodePos(NOT_A_DICT_POS), mSecondWordFirstInputIndex(NOT_AN_INDEX) {
+              mPrevWordPtNodePos(NOT_A_DICT_POS), mSecondWordFirstInputIndex(NOT_AN_INDEX) {
         memset(mPrevWord, 0, sizeof(mPrevWord));
     }
 
@@ -41,7 +41,7 @@
         mPrevWordCount = 0;
         mPrevWordStart = 0;
         mPrevWordProbability = -1;
-        mPrevWordNodePos = NOT_A_DICT_POS;
+        mPrevWordPtNodePos = NOT_A_DICT_POS;
         mSecondWordFirstInputIndex = NOT_AN_INDEX;
     }
 
@@ -50,7 +50,7 @@
         mPrevWordCount = 0;
         mPrevWordStart = 0;
         mPrevWordProbability = -1;
-        mPrevWordNodePos = prevWordNodePos;
+        mPrevWordPtNodePos = prevWordNodePos;
         mSecondWordFirstInputIndex = NOT_AN_INDEX;
     }
 
@@ -60,7 +60,7 @@
         mPrevWordCount = prevWord->mPrevWordCount;
         mPrevWordStart = prevWord->mPrevWordStart;
         mPrevWordProbability = prevWord->mPrevWordProbability;
-        mPrevWordNodePos = prevWord->mPrevWordNodePos;
+        mPrevWordPtNodePos = prevWord->mPrevWordPtNodePos;
         mSecondWordFirstInputIndex = prevWord->mSecondWordFirstInputIndex;
         memcpy(mPrevWord, prevWord->mPrevWord, prevWord->mPrevWordLength * sizeof(mPrevWord[0]));
     }
@@ -71,7 +71,7 @@
             const int prevWordSecondWordFirstInputIndex, const int lastInputIndex) {
         mPrevWordCount = min(prevWordCount, static_cast<int16_t>(MAX_RESULTS));
         mPrevWordProbability = prevWordProbability;
-        mPrevWordNodePos = prevWordNodePos;
+        mPrevWordPtNodePos = prevWordNodePos;
         int twoWordsLen =
                 DicNodeUtils::appendTwoWords(src0, length0, src1, length1, mPrevWord);
         if (twoWordsLen >= MAX_WORD_LENGTH) {
@@ -116,8 +116,8 @@
         return mPrevWordStart;
     }
 
-    int getPrevWordNodePos() const {
-        return mPrevWordNodePos;
+    int getPrevWordPtNodePos() const {
+        return mPrevWordPtNodePos;
     }
 
     int getPrevWordCodePointAt(const int id) const {
@@ -147,7 +147,7 @@
     int16_t mPrevWordLength;
     int16_t mPrevWordStart;
     int16_t mPrevWordProbability;
-    int mPrevWordNodePos;
+    int mPrevWordPtNodePos;
     int mSecondWordFirstInputIndex;
 };
 } // namespace latinime
diff --git a/native/jni/src/suggest/core/dicnode/internal/dic_node_state_scoring.h b/native/jni/src/suggest/core/dicnode/internal/dic_node_state_scoring.h
index 3c85d0e..74f9eee 100644
--- a/native/jni/src/suggest/core/dicnode/internal/dic_node_state_scoring.h
+++ b/native/jni/src/suggest/core/dicnode/internal/dic_node_state_scoring.h
@@ -21,6 +21,7 @@
 
 #include "defines.h"
 #include "suggest/core/dictionary/digraph_utils.h"
+#include "suggest/core/dictionary/error_type_utils.h"
 
 namespace latinime {
 
@@ -31,7 +32,7 @@
               mDigraphIndex(DigraphUtils::NOT_A_DIGRAPH_INDEX),
               mEditCorrectionCount(0), mProximityCorrectionCount(0),
               mNormalizedCompoundDistance(0.0f), mSpatialDistance(0.0f), mLanguageDistance(0.0f),
-              mRawLength(0.0f), mExactMatch(true),
+              mRawLength(0.0f), mContainingErrorTypes(ErrorTypeUtils::NOT_AN_ERROR),
               mNormalizedCompoundDistanceAfterFirstWord(MAX_VALUE_FOR_WEIGHTING) {
     }
 
@@ -47,7 +48,7 @@
         mDoubleLetterLevel = NOT_A_DOUBLE_LETTER;
         mDigraphIndex = DigraphUtils::NOT_A_DIGRAPH_INDEX;
         mNormalizedCompoundDistanceAfterFirstWord = MAX_VALUE_FOR_WEIGHTING;
-        mExactMatch = true;
+        mContainingErrorTypes = ErrorTypeUtils::NOT_AN_ERROR;
     }
 
     AK_FORCE_INLINE void init(const DicNodeStateScoring *const scoring) {
@@ -59,34 +60,21 @@
         mRawLength = scoring->mRawLength;
         mDoubleLetterLevel = scoring->mDoubleLetterLevel;
         mDigraphIndex = scoring->mDigraphIndex;
-        mExactMatch = scoring->mExactMatch;
+        mContainingErrorTypes = scoring->mContainingErrorTypes;
         mNormalizedCompoundDistanceAfterFirstWord =
                 scoring->mNormalizedCompoundDistanceAfterFirstWord;
     }
 
     void addCost(const float spatialCost, const float languageCost, const bool doNormalization,
-            const int inputSize, const int totalInputIndex, const ErrorType errorType) {
+            const int inputSize, const int totalInputIndex,
+            const ErrorTypeUtils::ErrorType errorType) {
         addDistance(spatialCost, languageCost, doNormalization, inputSize, totalInputIndex);
-        switch (errorType) {
-            case ET_EDIT_CORRECTION:
-                ++mEditCorrectionCount;
-                mExactMatch = false;
-                break;
-            case ET_PROXIMITY_CORRECTION:
-                ++mProximityCorrectionCount;
-                mExactMatch = false;
-                break;
-            case ET_COMPLETION:
-                mExactMatch = false;
-                break;
-            case ET_NEW_WORD:
-                mExactMatch = false;
-                break;
-            case ET_INTENTIONAL_OMISSION:
-                mExactMatch = false;
-                break;
-            case ET_NOT_AN_ERROR:
-                break;
+        mContainingErrorTypes = mContainingErrorTypes | errorType;
+        if (ErrorTypeUtils::isEditCorrectionError(errorType)) {
+            ++mEditCorrectionCount;
+        }
+        if (ErrorTypeUtils::isProximityCorrectionError(errorType)) {
+            ++mProximityCorrectionCount;
         }
     }
 
@@ -182,7 +170,7 @@
     }
 
     bool isExactMatch() const {
-        return mExactMatch;
+        return ErrorTypeUtils::isExactMatch(mContainingErrorTypes);
     }
 
  private:
@@ -199,7 +187,8 @@
     float mSpatialDistance;
     float mLanguageDistance;
     float mRawLength;
-    bool mExactMatch;
+    // All accumulated error types so far
+    ErrorTypeUtils::ErrorType mContainingErrorTypes;
     float mNormalizedCompoundDistanceAfterFirstWord;
 
     AK_FORCE_INLINE void addDistance(float spatialDistance, float languageDistance,
diff --git a/native/jni/src/suggest/core/dictionary/bigram_dictionary.cpp b/native/jni/src/suggest/core/dictionary/bigram_dictionary.cpp
index 71f4ef6..2a62b55 100644
--- a/native/jni/src/suggest/core/dictionary/bigram_dictionary.cpp
+++ b/native/jni/src/suggest/core/dictionary/bigram_dictionary.cpp
@@ -144,7 +144,7 @@
 int BigramDictionary::getBigramListPositionForWord(const int *prevWord, const int prevWordLength,
         const bool forceLowerCaseSearch) const {
     if (0 >= prevWordLength) return NOT_A_DICT_POS;
-    int pos = mDictionaryStructurePolicy->getTerminalNodePositionOfWord(prevWord, prevWordLength,
+    int pos = mDictionaryStructurePolicy->getTerminalPtNodePositionOfWord(prevWord, prevWordLength,
             forceLowerCaseSearch);
     if (NOT_A_DICT_POS == pos) return NOT_A_DICT_POS;
     return mDictionaryStructurePolicy->getBigramsPositionOfPtNode(pos);
@@ -155,7 +155,7 @@
     int pos = getBigramListPositionForWord(word0, length0, false /* forceLowerCaseSearch */);
     // getBigramListPositionForWord returns 0 if this word isn't in the dictionary or has no bigrams
     if (NOT_A_DICT_POS == pos) return NOT_A_PROBABILITY;
-    int nextWordPos = mDictionaryStructurePolicy->getTerminalNodePositionOfWord(word1, length1,
+    int nextWordPos = mDictionaryStructurePolicy->getTerminalPtNodePositionOfWord(word1, length1,
             false /* forceLowerCaseSearch */);
     if (NOT_A_DICT_POS == nextWordPos) return NOT_A_PROBABILITY;
 
@@ -163,7 +163,8 @@
             mDictionaryStructurePolicy->getBigramsStructurePolicy(), pos);
     while (bigramsIt.hasNext()) {
         bigramsIt.next();
-        if (bigramsIt.getBigramPos() == nextWordPos) {
+        if (bigramsIt.getBigramPos() == nextWordPos
+                && bigramsIt.getProbability() != NOT_A_PROBABILITY) {
             return mDictionaryStructurePolicy->getProbability(
                     mDictionaryStructurePolicy->getUnigramProbabilityOfPtNode(nextWordPos),
                     bigramsIt.getProbability());
diff --git a/native/jni/src/suggest/core/dictionary/bloom_filter.h b/native/jni/src/suggest/core/dictionary/bloom_filter.h
index 5205456..5f97004 100644
--- a/native/jni/src/suggest/core/dictionary/bloom_filter.h
+++ b/native/jni/src/suggest/core/dictionary/bloom_filter.h
@@ -50,6 +50,8 @@
     }
 
  private:
+    DISALLOW_ASSIGNMENT_OPERATOR(BloomFilter);
+
     // Size, in bytes, of the bloom filter index for bigrams
     // 128 gives us 1024 buckets. The probability of false positive is (1 - e ** (-kn/m))**k,
     // where k is the number of hash functions, n the number of bigrams, and m the number of
diff --git a/native/jni/src/suggest/core/dictionary/dictionary.cpp b/native/jni/src/suggest/core/dictionary/dictionary.cpp
index 59ead18..e68c0a6 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.cpp
+++ b/native/jni/src/suggest/core/dictionary/dictionary.cpp
@@ -21,46 +21,39 @@
 #include <stdint.h>
 
 #include "defines.h"
-#include "suggest/core/dictionary/bigram_dictionary.h"
 #include "suggest/core/policy/dictionary_header_structure_policy.h"
-#include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
 #include "suggest/core/session/dic_traverse_session.h"
 #include "suggest/core/suggest.h"
 #include "suggest/core/suggest_options.h"
 #include "suggest/policyimpl/gesture/gesture_suggest_policy_factory.h"
 #include "suggest/policyimpl/typing/typing_suggest_policy_factory.h"
 #include "utils/log_utils.h"
+#include "utils/time_keeper.h"
 
 namespace latinime {
 
 const int Dictionary::HEADER_ATTRIBUTE_BUFFER_SIZE = 32;
 
-Dictionary::Dictionary(JNIEnv *env,
-        DictionaryStructureWithBufferPolicy *const dictionaryStructureWithBufferPolicy)
+Dictionary::Dictionary(JNIEnv *env, const DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+        &dictionaryStructureWithBufferPolicy)
         : mDictionaryStructureWithBufferPolicy(dictionaryStructureWithBufferPolicy),
-          mBigramDictionary(new BigramDictionary(mDictionaryStructureWithBufferPolicy)),
+          mBigramDictionary(new BigramDictionary(mDictionaryStructureWithBufferPolicy.get())),
           mGestureSuggest(new Suggest(GestureSuggestPolicyFactory::getGestureSuggestPolicy())),
           mTypingSuggest(new Suggest(TypingSuggestPolicyFactory::getTypingSuggestPolicy())) {
     logDictionaryInfo(env);
 }
 
-Dictionary::~Dictionary() {
-    delete mBigramDictionary;
-    delete mGestureSuggest;
-    delete mTypingSuggest;
-    delete mDictionaryStructureWithBufferPolicy;
-}
-
 int Dictionary::getSuggestions(ProximityInfo *proximityInfo, DicTraverseSession *traverseSession,
         int *xcoordinates, int *ycoordinates, int *times, int *pointerIds, int *inputCodePoints,
         int inputSize, int *prevWordCodePoints, int prevWordLength, int commitPoint,
         const SuggestOptions *const suggestOptions, int *outWords, int *frequencies,
         int *spaceIndices, int *outputTypes, int *outputAutoCommitFirstWordConfidence) const {
+    TimeKeeper::setCurrentTime();
     int result = 0;
     if (suggestOptions->isGesture()) {
         DicTraverseSession::initSessionInstance(
                 traverseSession, this, prevWordCodePoints, prevWordLength, suggestOptions);
-        result = mGestureSuggest->getSuggestions(proximityInfo, traverseSession, xcoordinates,
+        result = mGestureSuggest.get()->getSuggestions(proximityInfo, traverseSession, xcoordinates,
                 ycoordinates, times, pointerIds, inputCodePoints, inputSize, commitPoint, outWords,
                 frequencies, spaceIndices, outputTypes, outputAutoCommitFirstWordConfidence);
         if (DEBUG_DICT) {
@@ -70,7 +63,7 @@
     } else {
         DicTraverseSession::initSessionInstance(
                 traverseSession, this, prevWordCodePoints, prevWordLength, suggestOptions);
-        result = mTypingSuggest->getSuggestions(proximityInfo, traverseSession, xcoordinates,
+        result = mTypingSuggest.get()->getSuggestions(proximityInfo, traverseSession, xcoordinates,
                 ycoordinates, times, pointerIds, inputCodePoints, inputSize, commitPoint,
                 outWords, frequencies, spaceIndices, outputTypes,
                 outputAutoCommitFirstWordConfidence);
@@ -83,12 +76,15 @@
 
 int Dictionary::getBigrams(const int *word, int length, int *outWords, int *frequencies,
         int *outputTypes) const {
+    TimeKeeper::setCurrentTime();
     if (length <= 0) return 0;
-    return mBigramDictionary->getPredictions(word, length, outWords, frequencies, outputTypes);
+    return mBigramDictionary.get()->getPredictions(word, length, outWords, frequencies,
+            outputTypes);
 }
 
 int Dictionary::getProbability(const int *word, int length) const {
-    int pos = getDictionaryStructurePolicy()->getTerminalNodePositionOfWord(word, length,
+    TimeKeeper::setCurrentTime();
+    int pos = getDictionaryStructurePolicy()->getTerminalPtNodePositionOfWord(word, length,
             false /* forceLowerCaseSearch */);
     if (NOT_A_DICT_POS == pos) {
         return NOT_A_PROBABILITY;
@@ -98,39 +94,60 @@
 
 int Dictionary::getBigramProbability(const int *word0, int length0, const int *word1,
         int length1) const {
-    return mBigramDictionary->getBigramProbability(word0, length0, word1, length1);
+    TimeKeeper::setCurrentTime();
+    return mBigramDictionary.get()->getBigramProbability(word0, length0, word1, length1);
 }
 
-void Dictionary::addUnigramWord(const int *const word, const int length, const int probability) {
-    mDictionaryStructureWithBufferPolicy->addUnigramWord(word, length, probability);
+void Dictionary::addUnigramWord(const int *const word, const int length, const int probability,
+        const int *const shortcutTargetCodePoints, const int shortcutLength,
+        const int shortcutProbability, const bool isNotAWord, const bool isBlacklisted,
+        const int timestamp) {
+    TimeKeeper::setCurrentTime();
+    mDictionaryStructureWithBufferPolicy.get()->addUnigramWord(word, length, probability,
+            shortcutTargetCodePoints, shortcutLength, shortcutProbability, isNotAWord,
+            isBlacklisted, timestamp);
 }
 
 void Dictionary::addBigramWords(const int *const word0, const int length0, const int *const word1,
-        const int length1, const int probability) {
-    mDictionaryStructureWithBufferPolicy->addBigramWords(word0, length0, word1, length1,
-            probability);
+        const int length1, const int probability, const int timestamp) {
+    TimeKeeper::setCurrentTime();
+    mDictionaryStructureWithBufferPolicy.get()->addBigramWords(word0, length0, word1, length1,
+            probability, timestamp);
 }
 
 void Dictionary::removeBigramWords(const int *const word0, const int length0,
         const int *const word1, const int length1) {
-    mDictionaryStructureWithBufferPolicy->removeBigramWords(word0, length0, word1, length1);
+    TimeKeeper::setCurrentTime();
+    mDictionaryStructureWithBufferPolicy.get()->removeBigramWords(word0, length0, word1, length1);
 }
 
 void Dictionary::flush(const char *const filePath) {
-    mDictionaryStructureWithBufferPolicy->flush(filePath);
+    TimeKeeper::setCurrentTime();
+    mDictionaryStructureWithBufferPolicy.get()->flush(filePath);
 }
 
 void Dictionary::flushWithGC(const char *const filePath) {
-    mDictionaryStructureWithBufferPolicy->flushWithGC(filePath);
+    TimeKeeper::setCurrentTime();
+    mDictionaryStructureWithBufferPolicy.get()->flushWithGC(filePath);
 }
 
 bool Dictionary::needsToRunGC(const bool mindsBlockByGC) {
-    return mDictionaryStructureWithBufferPolicy->needsToRunGC(mindsBlockByGC);
+    TimeKeeper::setCurrentTime();
+    return mDictionaryStructureWithBufferPolicy.get()->needsToRunGC(mindsBlockByGC);
 }
 
-void Dictionary::getProperty(const char *const query, char *const outResult,
+void Dictionary::getProperty(const char *const query, const int queryLength, char *const outResult,
         const int maxResultLength) {
-    return mDictionaryStructureWithBufferPolicy->getProperty(query, outResult, maxResultLength);
+    TimeKeeper::setCurrentTime();
+    return mDictionaryStructureWithBufferPolicy.get()->getProperty(query, queryLength, outResult,
+            maxResultLength);
+}
+
+const UnigramProperty Dictionary::getUnigramProperty(const int *const codePoints,
+        const int codePointCount) {
+    TimeKeeper::setCurrentTime();
+    return mDictionaryStructureWithBufferPolicy.get()->getUnigramProperty(
+            codePoints, codePointCount);
 }
 
 void Dictionary::logDictionaryInfo(JNIEnv *const env) const {
diff --git a/native/jni/src/suggest/core/dictionary/dictionary.h b/native/jni/src/suggest/core/dictionary/dictionary.h
index 0195d5b..b37b4aa 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.h
+++ b/native/jni/src/suggest/core/dictionary/dictionary.h
@@ -21,15 +21,20 @@
 
 #include "defines.h"
 #include "jni.h"
+#include "suggest/core/dictionary/bigram_dictionary.h"
+#include "suggest/core/dictionary/unigram_property.h"
+#include "suggest/core/policy/dictionary_header_structure_policy.h"
+#include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
+#include "suggest/core/suggest_interface.h"
+#include "utils/exclusive_ownership_pointer.h"
 
 namespace latinime {
 
-class BigramDictionary;
 class DictionaryStructureWithBufferPolicy;
 class DicTraverseSession;
 class ProximityInfo;
-class SuggestInterface;
 class SuggestOptions;
+class UnigramProperty;
 
 class Dictionary {
  public:
@@ -53,8 +58,8 @@
     static const int KIND_FLAG_POSSIBLY_OFFENSIVE = 0x80000000;
     static const int KIND_FLAG_EXACT_MATCH = 0x40000000;
 
-    Dictionary(JNIEnv *env,
-            DictionaryStructureWithBufferPolicy *const dictionaryStructureWithBufferPoilcy);
+    Dictionary(JNIEnv *env, const DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+            &dictionaryStructureWithBufferPolicy);
 
     int getSuggestions(ProximityInfo *proximityInfo, DicTraverseSession *traverseSession,
             int *xcoordinates, int *ycoordinates, int *times, int *pointerIds, int *inputCodePoints,
@@ -69,10 +74,13 @@
 
     int getBigramProbability(const int *word0, int length0, const int *word1, int length1) const;
 
-    void addUnigramWord(const int *const word, const int length, const int probability);
+    void addUnigramWord(const int *const word, const int length, const int probability,
+            const int *const shortcutTargetCodePoints, const int shortcutLength,
+            const int shortcutProbability, const bool isNotAWord, const bool isBlacklisted,
+            const int timestamp);
 
     void addBigramWords(const int *const word0, const int length0, const int *const word1,
-            const int length1, const int probability);
+            const int length1, const int probability, const int timestamp);
 
     void removeBigramWords(const int *const word0, const int length0, const int *const word1,
             const int length1);
@@ -83,24 +91,33 @@
 
     bool needsToRunGC(const bool mindsBlockByGC);
 
-    void getProperty(const char *const query, char *const outResult,
+    void getProperty(const char *const query, const int queryLength, char *const outResult,
             const int maxResultLength);
 
+    const UnigramProperty getUnigramProperty(const int *const codePoints, const int codePointCount);
+
     const DictionaryStructureWithBufferPolicy *getDictionaryStructurePolicy() const {
-        return mDictionaryStructureWithBufferPolicy;
+        return mDictionaryStructureWithBufferPolicy.get();
     }
 
-    virtual ~Dictionary();
+    int getFormatVersionNumber() const {
+        return mDictionaryStructureWithBufferPolicy.get()->getHeaderStructurePolicy()
+                ->getFormatVersionNumber();
+    }
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(Dictionary);
 
+    typedef ExclusiveOwnershipPointer<BigramDictionary> BigramDictionaryPtr;
+    typedef ExclusiveOwnershipPointer<SuggestInterface> SuggestInterfacePtr;
+
     static const int HEADER_ATTRIBUTE_BUFFER_SIZE;
 
-    DictionaryStructureWithBufferPolicy *const mDictionaryStructureWithBufferPolicy;
-    const BigramDictionary *const mBigramDictionary;
-    const SuggestInterface *const mGestureSuggest;
-    const SuggestInterface *const mTypingSuggest;
+    const DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+            mDictionaryStructureWithBufferPolicy;
+    const BigramDictionaryPtr mBigramDictionary;
+    const SuggestInterfacePtr mGestureSuggest;
+    const SuggestInterfacePtr mTypingSuggest;
 
     void logDictionaryInfo(JNIEnv *const env) const;
 };
diff --git a/native/jni/src/suggest/core/dictionary/digraph_utils.cpp b/native/jni/src/suggest/core/dictionary/digraph_utils.cpp
index 3271c1b..5f9b8f3 100644
--- a/native/jni/src/suggest/core/dictionary/digraph_utils.cpp
+++ b/native/jni/src/suggest/core/dictionary/digraph_utils.cpp
@@ -28,11 +28,8 @@
         { { 'a', 'e', 0x00E4 }, // U+00E4 : LATIN SMALL LETTER A WITH DIAERESIS
         { 'o', 'e', 0x00F6 },   // U+00F6 : LATIN SMALL LETTER O WITH DIAERESIS
         { 'u', 'e', 0x00FC } }; // U+00FC : LATIN SMALL LETTER U WITH DIAERESIS
-const DigraphUtils::digraph_t DigraphUtils::FRENCH_LIGATURES_DIGRAPHS[] =
-        { { 'a', 'e', 0x00E6 }, // U+00E6 : LATIN SMALL LETTER AE
-        { 'o', 'e', 0x0153 } }; // U+0153 : LATIN SMALL LIGATURE OE
 const DigraphUtils::DigraphType DigraphUtils::USED_DIGRAPH_TYPES[] =
-        { DIGRAPH_TYPE_GERMAN_UMLAUT, DIGRAPH_TYPE_FRENCH_LIGATURES };
+        { DIGRAPH_TYPE_GERMAN_UMLAUT };
 
 /* static */ bool DigraphUtils::hasDigraphForCodePoint(
         const DictionaryHeaderStructurePolicy *const headerPolicy,
@@ -50,9 +47,6 @@
     if (headerPolicy->requiresGermanUmlautProcessing()) {
         return DIGRAPH_TYPE_GERMAN_UMLAUT;
     }
-    if (headerPolicy->requiresFrenchLigatureProcessing()) {
-        return DIGRAPH_TYPE_FRENCH_LIGATURES;
-    }
     return DIGRAPH_TYPE_NONE;
 }
 
@@ -86,10 +80,6 @@
         *digraphs = GERMAN_UMLAUT_DIGRAPHS;
         return NELEMS(GERMAN_UMLAUT_DIGRAPHS);
     }
-    if (digraphType == DIGRAPH_TYPE_FRENCH_LIGATURES) {
-        *digraphs = FRENCH_LIGATURES_DIGRAPHS;
-        return NELEMS(FRENCH_LIGATURES_DIGRAPHS);
-    }
     return 0;
 }
 
diff --git a/native/jni/src/suggest/core/dictionary/digraph_utils.h b/native/jni/src/suggest/core/dictionary/digraph_utils.h
index 6ae16e3..bec2cd6 100644
--- a/native/jni/src/suggest/core/dictionary/digraph_utils.h
+++ b/native/jni/src/suggest/core/dictionary/digraph_utils.h
@@ -34,7 +34,6 @@
     typedef enum {
         DIGRAPH_TYPE_NONE,
         DIGRAPH_TYPE_GERMAN_UMLAUT,
-        DIGRAPH_TYPE_FRENCH_LIGATURES
     } DigraphType;
 
     typedef struct { int first; int second; int compositeGlyph; } digraph_t;
@@ -55,7 +54,6 @@
             const DigraphType digraphType, const int compositeGlyphCodePoint);
 
     static const digraph_t GERMAN_UMLAUT_DIGRAPHS[];
-    static const digraph_t FRENCH_LIGATURES_DIGRAPHS[];
     static const DigraphType USED_DIGRAPH_TYPES[];
 };
 } // namespace latinime
diff --git a/native/jni/src/suggest/core/dictionary/error_type_utils.cpp b/native/jni/src/suggest/core/dictionary/error_type_utils.cpp
new file mode 100644
index 0000000..0635fef
--- /dev/null
+++ b/native/jni/src/suggest/core/dictionary/error_type_utils.cpp
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/core/dictionary/error_type_utils.h"
+
+namespace latinime {
+
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::NOT_AN_ERROR = 0x0;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::MATCH_WITH_CASE_ERROR = 0x1;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::MATCH_WITH_ACCENT_ERROR = 0x2;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::MATCH_WITH_DIGRAPH = 0x4;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::INTENTIONAL_OMISSION = 0x8;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::EDIT_CORRECTION = 0x10;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::PROXIMITY_CORRECTION = 0x20;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::COMPLETION = 0x40;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::NEW_WORD = 0x80;
+
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::ERRORS_TREATED_AS_AN_EXACT_MATCH =
+        NOT_AN_ERROR | MATCH_WITH_CASE_ERROR | MATCH_WITH_ACCENT_ERROR | MATCH_WITH_DIGRAPH;
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/core/dictionary/error_type_utils.h b/native/jni/src/suggest/core/dictionary/error_type_utils.h
new file mode 100644
index 0000000..ab4a65e
--- /dev/null
+++ b/native/jni/src/suggest/core/dictionary/error_type_utils.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_ERROR_TYPE_UTILS_H
+#define LATINIME_ERROR_TYPE_UTILS_H
+
+#include <stdint.h>
+
+#include "defines.h"
+
+namespace latinime {
+
+class ErrorTypeUtils {
+ public:
+    // ErrorType is mainly decided by CorrectionType but it is also depending on if
+    // the correction has really been performed or not.
+    typedef uint32_t ErrorType;
+
+    static const ErrorType NOT_AN_ERROR;
+    static const ErrorType MATCH_WITH_CASE_ERROR;
+    static const ErrorType MATCH_WITH_ACCENT_ERROR;
+    static const ErrorType MATCH_WITH_DIGRAPH;
+    // Treat error as an intentional omission when the CorrectionType is omission and the node can
+    // be intentional omission.
+    static const ErrorType INTENTIONAL_OMISSION;
+    // Substitution, omission and transposition
+    static const ErrorType EDIT_CORRECTION;
+    // Proximity error
+    static const ErrorType PROXIMITY_CORRECTION;
+    // Completion
+    static const ErrorType COMPLETION;
+    // New word
+    // TODO: Remove.
+    // A new word error should be an edit correction error or a proximity correction error.
+    static const ErrorType NEW_WORD;
+
+    // TODO: Differentiate errors.
+    static bool isExactMatch(const ErrorType containingErrors) {
+        return (containingErrors & ~ERRORS_TREATED_AS_AN_EXACT_MATCH) == 0;
+    }
+
+    static bool isEditCorrectionError(const ErrorType errorType) {
+        return (errorType & EDIT_CORRECTION) != 0;
+    }
+
+    static bool isProximityCorrectionError(const ErrorType errorType) {
+        return (errorType & PROXIMITY_CORRECTION) != 0;
+    }
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(ErrorTypeUtils);
+
+    static const ErrorType ERRORS_TREATED_AS_AN_EXACT_MATCH;
+};
+} // namespace latinime
+#endif // LATINIME_ERROR_TYPE_UTILS_H
diff --git a/native/jni/src/suggest/core/dictionary/multi_bigram_map.cpp b/native/jni/src/suggest/core/dictionary/multi_bigram_map.cpp
index b1d2f4b..49d82e6 100644
--- a/native/jni/src/suggest/core/dictionary/multi_bigram_map.cpp
+++ b/native/jni/src/suggest/core/dictionary/multi_bigram_map.cpp
@@ -30,4 +30,75 @@
 // Most common previous word contexts currently have 100 bigrams
 const int MultiBigramMap::BigramMap::DEFAULT_HASH_MAP_SIZE_FOR_EACH_BIGRAM_MAP = 100;
 
+// Look up the bigram probability for the given word pair from the cached bigram maps.
+// Also caches the bigrams if there is space remaining and they have not been cached already.
+int MultiBigramMap::getBigramProbability(
+        const DictionaryStructureWithBufferPolicy *const structurePolicy,
+        const int wordPosition, const int nextWordPosition, const int unigramProbability) {
+    hash_map_compat<int, BigramMap>::const_iterator mapPosition =
+            mBigramMaps.find(wordPosition);
+    if (mapPosition != mBigramMaps.end()) {
+        return mapPosition->second.getBigramProbability(structurePolicy, nextWordPosition,
+                unigramProbability);
+    }
+    if (mBigramMaps.size() < MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP) {
+        addBigramsForWordPosition(structurePolicy, wordPosition);
+        return mBigramMaps[wordPosition].getBigramProbability(structurePolicy,
+                nextWordPosition, unigramProbability);
+    }
+    return readBigramProbabilityFromBinaryDictionary(structurePolicy, wordPosition,
+            nextWordPosition, unigramProbability);
+}
+
+void MultiBigramMap::BigramMap::init(
+        const DictionaryStructureWithBufferPolicy *const structurePolicy, const int nodePos) {
+    const int bigramsListPos = structurePolicy->getBigramsPositionOfPtNode(nodePos);
+    BinaryDictionaryBigramsIterator bigramsIt(structurePolicy->getBigramsStructurePolicy(),
+            bigramsListPos);
+    while (bigramsIt.hasNext()) {
+        bigramsIt.next();
+        if (bigramsIt.getBigramPos() == NOT_A_DICT_POS) {
+            continue;
+        }
+        mBigramMap[bigramsIt.getBigramPos()] = bigramsIt.getProbability();
+        mBloomFilter.setInFilter(bigramsIt.getBigramPos());
+    }
+}
+
+int MultiBigramMap::BigramMap::getBigramProbability(
+        const DictionaryStructureWithBufferPolicy *const structurePolicy,
+        const int nextWordPosition, const int unigramProbability) const {
+    int bigramProbability = NOT_A_PROBABILITY;
+    if (mBloomFilter.isInFilter(nextWordPosition)) {
+        const hash_map_compat<int, int>::const_iterator bigramProbabilityIt =
+                mBigramMap.find(nextWordPosition);
+        if (bigramProbabilityIt != mBigramMap.end()) {
+            bigramProbability = bigramProbabilityIt->second;
+        }
+    }
+    return structurePolicy->getProbability(unigramProbability, bigramProbability);
+}
+
+void MultiBigramMap::addBigramsForWordPosition(
+        const DictionaryStructureWithBufferPolicy *const structurePolicy, const int position) {
+    mBigramMaps[position].init(structurePolicy, position);
+}
+
+int MultiBigramMap::readBigramProbabilityFromBinaryDictionary(
+        const DictionaryStructureWithBufferPolicy *const structurePolicy, const int nodePos,
+        const int nextWordPosition, const int unigramProbability) {
+    int bigramProbability = NOT_A_PROBABILITY;
+    const int bigramsListPos = structurePolicy->getBigramsPositionOfPtNode(nodePos);
+    BinaryDictionaryBigramsIterator bigramsIt(structurePolicy->getBigramsStructurePolicy(),
+            bigramsListPos);
+    while (bigramsIt.hasNext()) {
+        bigramsIt.next();
+        if (bigramsIt.getBigramPos() == nextWordPosition) {
+            bigramProbability = bigramsIt.getProbability();
+            break;
+        }
+    }
+    return structurePolicy->getProbability(unigramProbability, bigramProbability);
+}
+
 } // namespace latinime
diff --git a/native/jni/src/suggest/core/dictionary/multi_bigram_map.h b/native/jni/src/suggest/core/dictionary/multi_bigram_map.h
index 4633c07..421b268 100644
--- a/native/jni/src/suggest/core/dictionary/multi_bigram_map.h
+++ b/native/jni/src/suggest/core/dictionary/multi_bigram_map.h
@@ -38,21 +38,7 @@
     // Look up the bigram probability for the given word pair from the cached bigram maps.
     // Also caches the bigrams if there is space remaining and they have not been cached already.
     int getBigramProbability(const DictionaryStructureWithBufferPolicy *const structurePolicy,
-            const int wordPosition, const int nextWordPosition, const int unigramProbability) {
-        hash_map_compat<int, BigramMap>::const_iterator mapPosition =
-                mBigramMaps.find(wordPosition);
-        if (mapPosition != mBigramMaps.end()) {
-            return mapPosition->second.getBigramProbability(structurePolicy, nextWordPosition,
-                    unigramProbability);
-        }
-        if (mBigramMaps.size() < MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP) {
-            addBigramsForWordPosition(structurePolicy, wordPosition);
-            return mBigramMaps[wordPosition].getBigramProbability(structurePolicy,
-                    nextWordPosition, unigramProbability);
-        }
-        return readBigramProbabilityFromBinaryDictionary(structurePolicy, wordPosition,
-                nextWordPosition, unigramProbability);
-    }
+            const int wordPosition, const int nextWordPosition, const int unigramProbability);
 
     void clear() {
         mBigramMaps.clear();
@@ -67,33 +53,11 @@
         ~BigramMap() {}
 
         void init(const DictionaryStructureWithBufferPolicy *const structurePolicy,
-                const int nodePos) {
-            const int bigramsListPos = structurePolicy->getBigramsPositionOfPtNode(nodePos);
-            BinaryDictionaryBigramsIterator bigramsIt(structurePolicy->getBigramsStructurePolicy(),
-                    bigramsListPos);
-            while (bigramsIt.hasNext()) {
-                bigramsIt.next();
-                if (bigramsIt.getBigramPos() == NOT_A_DICT_POS) {
-                    continue;
-                }
-                mBigramMap[bigramsIt.getBigramPos()] = bigramsIt.getProbability();
-                mBloomFilter.setInFilter(bigramsIt.getBigramPos());
-            }
-        }
+                const int nodePos);
 
-        AK_FORCE_INLINE int getBigramProbability(
+        int getBigramProbability(
                 const DictionaryStructureWithBufferPolicy *const structurePolicy,
-                const int nextWordPosition, const int unigramProbability) const {
-            int bigramProbability = NOT_A_PROBABILITY;
-            if (mBloomFilter.isInFilter(nextWordPosition)) {
-                const hash_map_compat<int, int>::const_iterator bigramProbabilityIt =
-                        mBigramMap.find(nextWordPosition);
-                if (bigramProbabilityIt != mBigramMap.end()) {
-                    bigramProbability = bigramProbabilityIt->second;
-                }
-            }
-            return structurePolicy->getProbability(unigramProbability, bigramProbability);
-        }
+                const int nextWordPosition, const int unigramProbability) const;
 
      private:
         // NOTE: The BigramMap class doesn't use DISALLOW_COPY_AND_ASSIGN() because its default
@@ -103,27 +67,12 @@
         BloomFilter mBloomFilter;
     };
 
-    AK_FORCE_INLINE void addBigramsForWordPosition(
-            const DictionaryStructureWithBufferPolicy *const structurePolicy, const int position) {
-        mBigramMaps[position].init(structurePolicy, position);
-    }
+    void addBigramsForWordPosition(
+            const DictionaryStructureWithBufferPolicy *const structurePolicy, const int position);
 
-    AK_FORCE_INLINE int readBigramProbabilityFromBinaryDictionary(
+    int readBigramProbabilityFromBinaryDictionary(
             const DictionaryStructureWithBufferPolicy *const structurePolicy, const int nodePos,
-            const int nextWordPosition, const int unigramProbability) {
-        int bigramProbability = NOT_A_PROBABILITY;
-        const int bigramsListPos = structurePolicy->getBigramsPositionOfPtNode(nodePos);
-        BinaryDictionaryBigramsIterator bigramsIt(structurePolicy->getBigramsStructurePolicy(),
-                bigramsListPos);
-        while (bigramsIt.hasNext()) {
-            bigramsIt.next();
-            if (bigramsIt.getBigramPos() == nextWordPosition) {
-                bigramProbability = bigramsIt.getProbability();
-                break;
-            }
-        }
-        return structurePolicy->getProbability(unigramProbability, bigramProbability);
-    }
+            const int nextWordPosition, const int unigramProbability);
 
     static const size_t MAX_CACHED_PREV_WORDS_IN_BIGRAM_MAP;
     hash_map_compat<int, BigramMap> mBigramMaps;
diff --git a/native/jni/src/suggest/core/dictionary/unigram_property.cpp b/native/jni/src/suggest/core/dictionary/unigram_property.cpp
new file mode 100644
index 0000000..16bbb69
--- /dev/null
+++ b/native/jni/src/suggest/core/dictionary/unigram_property.cpp
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/core/dictionary/unigram_property.h"
+
+namespace latinime {
+
+void UnigramProperty::outputProperties(JNIEnv *const env, jintArray outCodePoints,
+        jbooleanArray outFlags, jintArray outProbability, jintArray outHistoricalInfo,
+        jobject outShortcutTargets, jobject outShortcutProbabilities) const {
+    env->SetIntArrayRegion(outCodePoints, 0 /* start */, mCodePointCount, mCodePoints);
+    jboolean flags[] = {mIsNotAWord, mIsBlacklisted, mHasBigrams, mHasShortcuts};
+    env->SetBooleanArrayRegion(outFlags, 0 /* start */, NELEMS(flags), flags);
+    env->SetIntArrayRegion(outProbability, 0 /* start */, 1 /* len */, &mProbability);
+    int historicalInfo[] = {mTimestamp, mLevel, mCount};
+    env->SetIntArrayRegion(outHistoricalInfo, 0 /* start */, NELEMS(historicalInfo),
+            historicalInfo);
+
+    jclass integerClass = env->FindClass("java/lang/Integer");
+    jmethodID intToIntegerConstructorId = env->GetMethodID(integerClass, "<init>", "(I)V");
+    jclass arrayListClass = env->FindClass("java/util/ArrayList");
+    jmethodID addMethodId = env->GetMethodID(arrayListClass, "add", "(Ljava/lang/Object;)Z");
+    const int shortcutTargetCount = mShortcutTargets.size();
+    for (int i = 0; i < shortcutTargetCount; ++i) {
+        jintArray shortcutTargetCodePointArray = env->NewIntArray(mShortcutTargets[i].size());
+        env->SetIntArrayRegion(shortcutTargetCodePointArray, 0 /* start */,
+                mShortcutTargets[i].size(), &mShortcutTargets[i][0]);
+        env->CallVoidMethod(outShortcutTargets, addMethodId, shortcutTargetCodePointArray);
+        env->DeleteLocalRef(shortcutTargetCodePointArray);
+        jobject integerProbability = env->NewObject(integerClass, intToIntegerConstructorId,
+                mShortcutProbabilities[i]);
+        env->CallVoidMethod(outShortcutProbabilities, addMethodId, integerProbability);
+        env->DeleteLocalRef(integerProbability);
+    }
+    env->DeleteLocalRef(integerClass);
+    env->DeleteLocalRef(arrayListClass);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/core/dictionary/unigram_property.h b/native/jni/src/suggest/core/dictionary/unigram_property.h
new file mode 100644
index 0000000..c4ebb86
--- /dev/null
+++ b/native/jni/src/suggest/core/dictionary/unigram_property.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_UNIGRAM_PROPERTY_H
+#define LATINIME_UNIGRAM_PROPERTY_H
+
+#include <cstring>
+#include <vector>
+
+#include "defines.h"
+#include "jni.h"
+
+namespace latinime {
+
+// This class is used for returning information belonging to a unigram to java side.
+class UnigramProperty {
+ public:
+    // Invalid unigram.
+    UnigramProperty()
+            : mCodePoints(), mCodePointCount(0), mIsNotAWord(false), mIsBlacklisted(false),
+              mHasBigrams(false), mHasShortcuts(false), mProbability(NOT_A_PROBABILITY),
+              mTimestamp(0), mLevel(0), mCount(0), mShortcutTargets(), mShortcutProbabilities() {}
+
+    UnigramProperty(const UnigramProperty &unigramProperty)
+            : mCodePoints(), mCodePointCount(unigramProperty.mCodePointCount),
+              mIsNotAWord(unigramProperty.mIsNotAWord),
+              mIsBlacklisted(unigramProperty.mIsBlacklisted),
+              mHasBigrams(unigramProperty.mHasBigrams),
+              mHasShortcuts(unigramProperty.mHasShortcuts),
+              mProbability(unigramProperty.mProbability),
+              mTimestamp(unigramProperty.mTimestamp), mLevel(unigramProperty.mLevel),
+              mCount(unigramProperty.mCount), mShortcutTargets(unigramProperty.mShortcutTargets),
+              mShortcutProbabilities(unigramProperty.mShortcutProbabilities) {
+        memcpy(mCodePoints, unigramProperty.mCodePoints, sizeof(mCodePoints));
+    }
+
+    UnigramProperty(const int *const codePoints, const int codePointCount,
+            const bool isNotAWord, const bool isBlacklisted, const bool hasBigrams,
+            const bool hasShortcuts, const int probability, const int timestamp,
+            const int level, const int count,
+            const std::vector<std::vector<int> > *const shortcutTargets,
+            const std::vector<int> *const shortcutProbabilities)
+            : mCodePoints(), mCodePointCount(codePointCount),
+              mIsNotAWord(isNotAWord), mIsBlacklisted(isBlacklisted), mHasBigrams(hasBigrams),
+              mHasShortcuts(hasShortcuts), mProbability(probability), mTimestamp(timestamp),
+              mLevel(level), mCount(count), mShortcutTargets(*shortcutTargets),
+              mShortcutProbabilities(*shortcutProbabilities) {
+        memcpy(mCodePoints, codePoints, sizeof(mCodePoints));
+    }
+
+    void outputProperties(JNIEnv *const env, jintArray outCodePoints, jbooleanArray outFlags,
+            jintArray outProbability, jintArray outHistoricalInfo, jobject outShortcutTargets,
+            jobject outShortcutProbabilities) const;
+
+ private:
+    DISALLOW_ASSIGNMENT_OPERATOR(UnigramProperty);
+
+    int mCodePoints[MAX_WORD_LENGTH];
+    int mCodePointCount;
+    bool mIsNotAWord;
+    bool mIsBlacklisted;
+    bool mHasBigrams;
+    bool mHasShortcuts;
+    int mProbability;
+    // Historical information
+    int mTimestamp;
+    int mLevel;
+    int mCount;
+    // Shortcut
+    std::vector<std::vector<int> > mShortcutTargets;
+    std::vector<int> mShortcutProbabilities;
+};
+} // namespace latinime
+#endif // LATINIME_UNIGRAM_PROPERTY_H
diff --git a/native/jni/src/suggest/core/layout/proximity_info.cpp b/native/jni/src/suggest/core/layout/proximity_info.cpp
index e64476d..ee8e59e 100644
--- a/native/jni/src/suggest/core/layout/proximity_info.cpp
+++ b/native/jni/src/suggest/core/layout/proximity_info.cpp
@@ -71,7 +71,7 @@
                   && sweetSpotCenterYs && sweetSpotRadii),
           mProximityCharsArray(new int[GRID_WIDTH * GRID_HEIGHT * MAX_PROXIMITY_CHARS_SIZE
                   /* proximityCharsLength */]),
-          mCodeToKeyMap() {
+          mLowerCodePointToKeyMap() {
     /* Let's check the input array length here to make sure */
     const jsize proximityCharsLength = env->GetArrayLength(proximityChars);
     if (proximityCharsLength != GRID_WIDTH * GRID_HEIGHT * MAX_PROXIMITY_CHARS_SIZE) {
@@ -147,7 +147,14 @@
     if (keyIndex < 0 || keyIndex >= KEY_COUNT) {
         return NOT_A_CODE_POINT;
     }
-    return mKeyIndexToCodePointG[keyIndex];
+    return mKeyIndexToLowerCodePointG[keyIndex];
+}
+
+int ProximityInfo::getOriginalCodePointOf(const int keyIndex) const {
+    if (keyIndex < 0 || keyIndex >= KEY_COUNT) {
+        return NOT_A_CODE_POINT;
+    }
+    return mKeyIndexToOriginalCodePoint[keyIndex];
 }
 
 void ProximityInfo::initializeG() {
@@ -164,8 +171,9 @@
             const float gapY = sweetSpotCenterY - mCenterYsG[i];
             mSweetSpotCenterYsG[i] = static_cast<int>(mCenterYsG[i] + gapY * verticalScale);
         }
-        mCodeToKeyMap[lowerCode] = i;
-        mKeyIndexToCodePointG[i] = lowerCode;
+        mLowerCodePointToKeyMap[lowerCode] = i;
+        mKeyIndexToOriginalCodePoint[i] = code;
+        mKeyIndexToLowerCodePointG[i] = lowerCode;
     }
     for (int i = 0; i < KEY_COUNT; i++) {
         mKeyKeyDistancesG[i][i] = 0;
diff --git a/native/jni/src/suggest/core/layout/proximity_info.h b/native/jni/src/suggest/core/layout/proximity_info.h
index f259490..a91b9d6 100644
--- a/native/jni/src/suggest/core/layout/proximity_info.h
+++ b/native/jni/src/suggest/core/layout/proximity_info.h
@@ -39,6 +39,7 @@
     float getNormalizedSquaredDistanceFromCenterFloatG(
             const int keyId, const int x, const int y, const bool isGeometric) const;
     int getCodePointOf(const int keyIndex) const;
+    int getOriginalCodePointOf(const int keyIndex) const;
     bool hasSweetSpotData(const int keyIndex) const {
         // When there are no calibration data for a key,
         // the radius of the key is assigned to zero.
@@ -76,11 +77,11 @@
         ProximityInfoUtils::initializeProximities(inputCodes, inputXCoordinates, inputYCoordinates,
                 inputSize, mKeyXCoordinates, mKeyYCoordinates, mKeyWidths, mKeyHeights,
                 mProximityCharsArray, CELL_HEIGHT, CELL_WIDTH, GRID_WIDTH, MOST_COMMON_KEY_WIDTH,
-                KEY_COUNT, mLocaleStr, &mCodeToKeyMap, allInputCodes);
+                KEY_COUNT, mLocaleStr, &mLowerCodePointToKeyMap, allInputCodes);
     }
 
     AK_FORCE_INLINE int getKeyIndexOf(const int c) const {
-        return ProximityInfoUtils::getKeyIndexOf(KEY_COUNT, c, &mCodeToKeyMap);
+        return ProximityInfoUtils::getKeyIndexOf(KEY_COUNT, c, &mLowerCodePointToKeyMap);
     }
 
     AK_FORCE_INLINE bool isCodePointOnKeyboard(const int codePoint) const {
@@ -117,9 +118,9 @@
     // Sweet spots for geometric input. Note that we have extra sweet spots only for Y coordinates.
     float mSweetSpotCenterYsG[MAX_KEY_COUNT_IN_A_KEYBOARD];
     float mSweetSpotRadii[MAX_KEY_COUNT_IN_A_KEYBOARD];
-    hash_map_compat<int, int> mCodeToKeyMap;
-
-    int mKeyIndexToCodePointG[MAX_KEY_COUNT_IN_A_KEYBOARD];
+    hash_map_compat<int, int> mLowerCodePointToKeyMap;
+    int mKeyIndexToOriginalCodePoint[MAX_KEY_COUNT_IN_A_KEYBOARD];
+    int mKeyIndexToLowerCodePointG[MAX_KEY_COUNT_IN_A_KEYBOARD];
     int mCenterXsG[MAX_KEY_COUNT_IN_A_KEYBOARD];
     int mCenterYsG[MAX_KEY_COUNT_IN_A_KEYBOARD];
     int mKeyKeyDistancesG[MAX_KEY_COUNT_IN_A_KEYBOARD][MAX_KEY_COUNT_IN_A_KEYBOARD];
diff --git a/native/jni/src/suggest/core/layout/proximity_info_state.cpp b/native/jni/src/suggest/core/layout/proximity_info_state.cpp
index fbabd92..bb4b417 100644
--- a/native/jni/src/suggest/core/layout/proximity_info_state.cpp
+++ b/native/jni/src/suggest/core/layout/proximity_info_state.cpp
@@ -30,6 +30,12 @@
 
 namespace latinime {
 
+int ProximityInfoState::getPrimaryOriginalCodePointAt(const int index) const {
+    const int primaryCodePoint = getPrimaryCodePointAt(index);
+    const int keyIndex = mProximityInfo->getKeyIndexOf(primaryCodePoint);
+    return mProximityInfo->getOriginalCodePointOf(keyIndex);
+}
+
 // TODO: Remove the dependency of "isGeometric"
 void ProximityInfoState::initInputParams(const int pointerId, const float maxPointToKeyLength,
         const ProximityInfo *proximityInfo, const int *const inputCodes, const int inputSize,
diff --git a/native/jni/src/suggest/core/layout/proximity_info_state.h b/native/jni/src/suggest/core/layout/proximity_info_state.h
index c94060f..e941e43 100644
--- a/native/jni/src/suggest/core/layout/proximity_info_state.h
+++ b/native/jni/src/suggest/core/layout/proximity_info_state.h
@@ -65,6 +65,8 @@
         return getProximityCodePointsAt(index)[0];
     }
 
+    int getPrimaryOriginalCodePointAt(const int index) const;
+
     inline bool sameAsTyped(const int *word, int length) const {
         if (length != mSampledInputSize) {
             return false;
diff --git a/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h b/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
index 5492c60..b76b139 100644
--- a/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
+++ b/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
@@ -29,12 +29,10 @@
  public:
     virtual ~DictionaryHeaderStructurePolicy() {}
 
-    virtual bool supportsDynamicUpdate() const = 0;
+    virtual int getFormatVersionNumber() const = 0;
 
     virtual bool requiresGermanUmlautProcessing() const = 0;
 
-    virtual bool requiresFrenchLigatureProcessing() const = 0;
-
     virtual float getMultiWordCostMultiplier() const = 0;
 
     virtual int getLastDecayedTime() const = 0;
diff --git a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
index 41f8204..c74a4eb 100644
--- a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
+++ b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
@@ -18,6 +18,8 @@
 #define LATINIME_DICTIONARY_STRUCTURE_POLICY_H
 
 #include "defines.h"
+#include "suggest/core/dictionary/unigram_property.h"
+#include "utils/exclusive_ownership_pointer.h"
 
 namespace latinime {
 
@@ -28,23 +30,25 @@
 class DictionaryShortcutsStructurePolicy;
 
 /*
- * This class abstracts structure of dictionaries.
+ * This class abstracts the structure of dictionaries.
  * Implement this policy to support additional dictionaries.
  */
 class DictionaryStructureWithBufferPolicy {
  public:
+    typedef ExclusiveOwnershipPointer<DictionaryStructureWithBufferPolicy> StructurePolicyPtr;
+
     virtual ~DictionaryStructureWithBufferPolicy() {}
 
     virtual int getRootPosition() const = 0;
 
-    virtual void createAndGetAllChildNodes(const DicNode *const dicNode,
+    virtual void createAndGetAllChildDicNodes(const DicNode *const dicNode,
             DicNodeVector *const childDicNodes) const = 0;
 
     virtual int getCodePointsAndProbabilityAndReturnCodePointCount(
             const int nodePos, const int maxCodePointCount, int *const outCodePoints,
             int *const outUnigramProbability) const = 0;
 
-    virtual int getTerminalNodePositionOfWord(const int *const inWord,
+    virtual int getTerminalPtNodePositionOfWord(const int *const inWord,
             const int length, const bool forceLowerCaseSearch) const = 0;
 
     virtual int getProbability(const int unigramProbability,
@@ -64,11 +68,13 @@
 
     // Returns whether the update was success or not.
     virtual bool addUnigramWord(const int *const word, const int length,
-            const int probability) = 0;
+            const int probability, const int *const shortcutTargetCodePoints,
+            const int shortcutLength, const int shortcutProbability, const bool isNotAWord,
+            const bool isBlacklisted,const int timestamp) = 0;
 
     // Returns whether the update was success or not.
     virtual bool addBigramWords(const int *const word0, const int length0, const int *const word1,
-            const int length1, const int probability) = 0;
+            const int length1, const int probability, const int timestamp) = 0;
 
     // Returns whether the update was success or not.
     virtual bool removeBigramWords(const int *const word0, const int length0,
@@ -82,9 +88,13 @@
 
     // Currently, this method is used only for testing. You may want to consider creating new
     // dedicated method instead of this if you want to use this in the production.
-    virtual void getProperty(const char *const query, char *const outResult,
+    virtual void getProperty(const char *const query, const int queryLength, char *const outResult,
             const int maxResultLength) = 0;
 
+    // Used for testing.
+    virtual const UnigramProperty getUnigramProperty(const int *const codePonts,
+            const int codePointCount) const = 0;
+
  protected:
     DictionaryStructureWithBufferPolicy() {}
 
diff --git a/native/jni/src/suggest/core/policy/weighting.cpp b/native/jni/src/suggest/core/policy/weighting.cpp
index 0c40168..c202b81 100644
--- a/native/jni/src/suggest/core/policy/weighting.cpp
+++ b/native/jni/src/suggest/core/policy/weighting.cpp
@@ -20,6 +20,7 @@
 #include "suggest/core/dicnode/dic_node.h"
 #include "suggest/core/dicnode/dic_node_profiler.h"
 #include "suggest/core/dicnode/dic_node_utils.h"
+#include "suggest/core/dictionary/error_type_utils.h"
 #include "suggest/core/session/dic_traverse_session.h"
 
 namespace latinime {
@@ -82,8 +83,8 @@
             traverseSession, parentDicNode, dicNode, &inputStateG);
     const float languageCost = Weighting::getLanguageCost(weighting, correctionType,
             traverseSession, parentDicNode, dicNode, multiBigramMap);
-    const ErrorType errorType = weighting->getErrorType(correctionType, traverseSession,
-            parentDicNode, dicNode);
+    const ErrorTypeUtils::ErrorType errorType = weighting->getErrorType(correctionType,
+            traverseSession, parentDicNode, dicNode);
     profile(correctionType, dicNode);
     if (inputStateG.mNeedsToUpdateInputStateG) {
         dicNode->updateInputIndexG(&inputStateG);
diff --git a/native/jni/src/suggest/core/policy/weighting.h b/native/jni/src/suggest/core/policy/weighting.h
index 2d49e98..bd6b3cf 100644
--- a/native/jni/src/suggest/core/policy/weighting.h
+++ b/native/jni/src/suggest/core/policy/weighting.h
@@ -18,6 +18,7 @@
 #define LATINIME_WEIGHTING_H
 
 #include "defines.h"
+#include "suggest/core/dictionary/error_type_utils.h"
 
 namespace latinime {
 
@@ -84,7 +85,7 @@
     virtual float getSpaceSubstitutionCost(const DicTraverseSession *const traverseSession,
             const DicNode *const dicNode) const = 0;
 
-    virtual ErrorType getErrorType(const CorrectionType correctionType,
+    virtual ErrorTypeUtils::ErrorType getErrorType(const CorrectionType correctionType,
             const DicTraverseSession *const traverseSession,
             const DicNode *const parentDicNode, const DicNode *const dicNode) const = 0;
 
diff --git a/native/jni/src/suggest/core/session/dic_traverse_session.cpp b/native/jni/src/suggest/core/session/dic_traverse_session.cpp
index 50f2bbd..5070491 100644
--- a/native/jni/src/suggest/core/session/dic_traverse_session.cpp
+++ b/native/jni/src/suggest/core/session/dic_traverse_session.cpp
@@ -35,16 +35,16 @@
             ->getMultiWordCostMultiplier();
     mSuggestOptions = suggestOptions;
     if (!prevWord) {
-        mPrevWordPos = NOT_A_DICT_POS;
+        mPrevWordPtNodePos = NOT_A_DICT_POS;
         return;
     }
     // TODO: merge following similar calls to getTerminalPosition into one case-insensitive call.
-    mPrevWordPos = getDictionaryStructurePolicy()->getTerminalNodePositionOfWord(
+    mPrevWordPtNodePos = getDictionaryStructurePolicy()->getTerminalPtNodePositionOfWord(
             prevWord, prevWordLength, false /* forceLowerCaseSearch */);
-    if (mPrevWordPos == NOT_A_DICT_POS) {
+    if (mPrevWordPtNodePos == NOT_A_DICT_POS) {
         // Check bigrams for lower-cased previous word if original was not found. Useful for
         // auto-capitalized words like "The [current_word]".
-        mPrevWordPos = getDictionaryStructurePolicy()->getTerminalNodePositionOfWord(
+        mPrevWordPtNodePos = getDictionaryStructurePolicy()->getTerminalPtNodePositionOfWord(
                 prevWord, prevWordLength, true /* forceLowerCaseSearch */);
     }
 }
diff --git a/native/jni/src/suggest/core/session/dic_traverse_session.h b/native/jni/src/suggest/core/session/dic_traverse_session.h
index e0b1c67..6e4dda4 100644
--- a/native/jni/src/suggest/core/session/dic_traverse_session.h
+++ b/native/jni/src/suggest/core/session/dic_traverse_session.h
@@ -59,7 +59,7 @@
     }
 
     AK_FORCE_INLINE DicTraverseSession(JNIEnv *env, jstring localeStr, bool usesLargeCache)
-            : mPrevWordPos(NOT_A_DICT_POS), mProximityInfo(0),
+            : mPrevWordPtNodePos(NOT_A_DICT_POS), mProximityInfo(0),
               mDictionary(0), mSuggestOptions(0), mDicNodesCache(usesLargeCache),
               mMultiBigramMap(), mInputSize(0), mPartiallyCommited(false), mMaxPointerCount(1),
               mMultiWordCostMultiplier(1.0f) {
@@ -86,11 +86,9 @@
     //--------------------
     const ProximityInfo *getProximityInfo() const { return mProximityInfo; }
     const SuggestOptions *getSuggestOptions() const { return mSuggestOptions; }
-    int getPrevWordPos() const { return mPrevWordPos; }
+    int getPrevWordPtNodePos() const { return mPrevWordPtNodePos; }
     // TODO: REMOVE
-    void setPrevWordPos(int pos) { mPrevWordPos = pos; }
-    // TODO: Use proper parameter when changed
-    int getDicRootPos() const { return 0; }
+    void setPrevWordPtNodePos(const int ptNodePos) { mPrevWordPtNodePos = ptNodePos; }
     DicNodesCache *getDicTraverseCache() { return &mDicNodesCache; }
     MultiBigramMap *getMultiBigramMap() { return &mMultiBigramMap; }
     const ProximityInfoState *getProximityInfoState(int id) const {
@@ -119,26 +117,13 @@
         return true;
     }
 
-    void getSearchKeys(const DicNode *node, std::vector<int> *const outputSearchKeyVector) const {
-        for (int i = 0; i < MAX_POINTER_COUNT_G; ++i) {
-            if (!mProximityInfoStates[i].isUsed()) {
-                continue;
-            }
-            const int pointerId = node->getInputIndex(i);
-            const std::vector<int> *const searchKeyVector =
-                    mProximityInfoStates[i].getSearchKeyVector(pointerId);
-            outputSearchKeyVector->insert(outputSearchKeyVector->end(), searchKeyVector->begin(),
-                    searchKeyVector->end());
-        }
-    }
-
-    ProximityType getProximityTypeG(const DicNode *const node, const int childCodePoint) const {
+    ProximityType getProximityTypeG(const DicNode *const dicNode, const int childCodePoint) const {
         ProximityType proximityType = UNRELATED_CHAR;
         for (int i = 0; i < MAX_POINTER_COUNT_G; ++i) {
             if (!mProximityInfoStates[i].isUsed()) {
                 continue;
             }
-            const int pointerId = node->getInputIndex(i);
+            const int pointerId = dicNode->getInputIndex(i);
             proximityType = mProximityInfoStates[i].getProximityTypeG(pointerId, childCodePoint);
             ASSERT(proximityType == UNRELATED_CHAR || proximityType == MATCH_CHAR);
             // TODO: Make this more generic
@@ -192,7 +177,7 @@
             const int *const inputYs, const int *const times, const int *const pointerIds,
             const int inputSize, const float maxSpatialDistance, const int maxPointerCount);
 
-    int mPrevWordPos;
+    int mPrevWordPtNodePos;
     const ProximityInfo *mProximityInfo;
     const Dictionary *mDictionary;
     const SuggestOptions *mSuggestOptions;
diff --git a/native/jni/src/suggest/core/suggest.cpp b/native/jni/src/suggest/core/suggest.cpp
index 73ccebc..f84c841 100644
--- a/native/jni/src/suggest/core/suggest.cpp
+++ b/native/jni/src/suggest/core/suggest.cpp
@@ -98,7 +98,7 @@
             // Continue suggestion after partial commit.
             DicNode *topDicNode =
                     traverseSession->getDicTraverseCache()->setCommitPoint(commitPoint);
-            traverseSession->setPrevWordPos(topDicNode->getPrevWordNodePos());
+            traverseSession->setPrevWordPtNodePos(topDicNode->getPrevWordPtNodePos());
             traverseSession->getDicTraverseCache()->continueSearch();
             traverseSession->setPartiallyCommited();
         }
@@ -109,7 +109,7 @@
         // Create a new dic node here
         DicNode rootNode;
         DicNodeUtils::initAsRoot(traverseSession->getDictionaryStructurePolicy(),
-                traverseSession->getPrevWordPos(), &rootNode);
+                traverseSession->getPrevWordPtNodePos(), &rootNode);
         traverseSession->getDicTraverseCache()->copyPushActive(&rootNode);
     }
 }
@@ -231,12 +231,15 @@
             BinaryDictionaryShortcutIterator shortcutIt(
                     traverseSession->getDictionaryStructurePolicy()->getShortcutsStructurePolicy(),
                     traverseSession->getDictionaryStructurePolicy()
-                            ->getShortcutPositionOfPtNode(terminalDicNode->getPos()));
+                            ->getShortcutPositionOfPtNode(terminalDicNode->getPtNodePos()));
             // Shortcut is not supported for multiple words suggestions.
             // TODO: Check shortcuts during traversal for multiple words suggestions.
             const bool sameAsTyped = TRAVERSAL->sameAsTyped(traverseSession, terminalDicNode);
+            const int shortcutBaseScore = SCORING->doesAutoCorrectValidWord() ?
+                     SCORING->calculateFinalScore(compoundDistance, traverseSession->getInputSize(),
+                             true /* forceCommit */) : finalScore;
             const int updatedOutputWordIndex = ShortcutUtils::outputShortcuts(&shortcutIt,
-                    outputWordIndex,  finalScore, outputCodePoints, frequencies, outputTypes,
+                    outputWordIndex, shortcutBaseScore, outputCodePoints, frequencies, outputTypes,
                     sameAsTyped);
             const int secondWordFirstInputIndex = terminalDicNode->getSecondWordFirstInputIndex(
                     traverseSession->getProximityInfoState(0));
@@ -421,15 +424,15 @@
                         }
                         break;
                     case UNRELATED_CHAR:
-                        // Just drop this node and do nothing.
+                        // Just drop this dicNode and do nothing.
                         break;
                     default:
-                        // Just drop this node and do nothing.
+                        // Just drop this dicNode and do nothing.
                         break;
                 }
             }
 
-            // Push the node for look-ahead correction
+            // Push the dicNode for look-ahead correction
             if (allowsErrorCorrections && canDoLookAheadCorrection) {
                 traverseSession->getDicTraverseCache()->copyPushNextActive(&dicNode);
             }
@@ -442,7 +445,7 @@
     if (dicNode->getCompoundDistance() >= static_cast<float>(MAX_VALUE_FOR_WEIGHTING)) {
         return;
     }
-    if (!dicNode->isTerminalWordNode()) {
+    if (!dicNode->isTerminalDicNode()) {
         return;
     }
     if (dicNode->shouldBeFilteredBySafetyNetForBigram()) {
@@ -463,7 +466,7 @@
 
 /**
  * Adds the expanded dicNode to the next search priority queue. Also creates an additional next word
- * (by the space omission error correction) search path if input dicNode is on a terminal node.
+ * (by the space omission error correction) search path if input dicNode is on a terminal.
  */
 void Suggest::processExpandedDicNode(
         DicTraverseSession *traverseSession, DicNode *dicNode) const {
@@ -505,7 +508,7 @@
     processExpandedDicNode(traverseSession, childDicNode);
 }
 
-// Process the node codepoint as a digraph. This means that composite glyphs like the German
+// Process the DicNode codepoint as a digraph. This means that composite glyphs like the German
 // u-umlaut is expanded to the transliteration "ue". Note that this happens in parallel with
 // the normal non-digraph traversal, so both "uber" and "ueber" can be corrected to "[u-umlaut]ber".
 void Suggest::processDicNodeAsDigraph(DicTraverseSession *traverseSession,
@@ -518,7 +521,7 @@
 /**
  * Handle the dicNode as an omission error (e.g., ths => this). Skip the current letter and consider
  * matches for all possible next letters. Note that just skipping the current letter without any
- * other conditions tends to flood the search dic nodes cache with omission nodes. Instead, check
+ * other conditions tends to flood the search DicNodes cache with omission DicNodes. Instead, check
  * the possible *next* letters after the omission to better limit search to plausible omissions.
  * Note that apostrophes are handled as omissions.
  */
@@ -605,7 +608,7 @@
 }
 
 /**
- * Weight child node by aligning it to the key
+ * Weight child dicNode by aligning it to the key
  */
 void Suggest::weightChildNode(DicTraverseSession *traverseSession, DicNode *dicNode) const {
     const int inputSize = traverseSession->getInputSize();
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.cpp
index 1926b98..7d0d096 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.cpp
@@ -16,7 +16,6 @@
 
 #include "suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h"
 
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
 #include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
 
@@ -38,7 +37,6 @@
 // Mask for attribute probability, stored on 4 bits inside the flags byte.
 const BigramListReadWriteUtils::BigramFlags
         BigramListReadWriteUtils::MASK_ATTRIBUTE_PROBABILITY = 0x0F;
-const int BigramListReadWriteUtils::ATTRIBUTE_ADDRESS_SHIFT = 4;
 
 /* static */ void BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
         const uint8_t *const bigramsBuf, BigramFlags *const outBigramFlags,
@@ -79,11 +77,6 @@
             offset = ByteArrayUtils::readUint24AndAdvancePosition(bigramsBuf, pos);
             break;
     }
-    if (offset == DynamicPatriciaTrieReadingUtils::DICT_OFFSET_INVALID) {
-        return NOT_A_DICT_POS;
-    } else if (offset == DynamicPatriciaTrieReadingUtils::DICT_OFFSET_ZERO_OFFSET) {
-        return origin;
-    }
     if (isOffsetNegative(flags)) {
         return origin - offset;
     } else {
@@ -91,92 +84,4 @@
     }
 }
 
-/* static */ bool BigramListReadWriteUtils::setHasNextFlag(
-        BufferWithExtendableBuffer *const buffer, const bool hasNext, const int entryPos) {
-    const bool usesAdditionalBuffer = buffer->isInAdditionalBuffer(entryPos);
-    int readingPos = entryPos;
-    if (usesAdditionalBuffer) {
-        readingPos -= buffer->getOriginalBufferSize();
-    }
-    BigramFlags bigramFlags = ByteArrayUtils::readUint8AndAdvancePosition(
-            buffer->getBuffer(usesAdditionalBuffer), &readingPos);
-    if (hasNext) {
-        bigramFlags = bigramFlags | FLAG_ATTRIBUTE_HAS_NEXT;
-    } else {
-        bigramFlags = bigramFlags & (~FLAG_ATTRIBUTE_HAS_NEXT);
-    }
-    int writingPos = entryPos;
-    return buffer->writeUintAndAdvancePosition(bigramFlags, 1 /* size */, &writingPos);
-}
-
-/* static */ bool BigramListReadWriteUtils::createAndWriteBigramEntry(
-        BufferWithExtendableBuffer *const buffer, const int targetPos, const int probability,
-        const bool hasNext, int *const writingPos) {
-    BigramFlags flags;
-    if (!createAndGetBigramFlags(*writingPos, targetPos, probability, hasNext, &flags)) {
-        return false;
-    }
-    return writeBigramEntry(buffer, flags, targetPos, writingPos);
-}
-
-/* static */ bool BigramListReadWriteUtils::writeBigramEntry(
-        BufferWithExtendableBuffer *const bufferToWrite, const BigramFlags flags,
-        const int targetPtNodePos, int *const writingPos) {
-    const int offset = getBigramTargetOffset(targetPtNodePos, *writingPos);
-    const BigramFlags flagsToWrite = (offset < 0) ?
-            (flags | FLAG_ATTRIBUTE_OFFSET_NEGATIVE) : (flags & ~FLAG_ATTRIBUTE_OFFSET_NEGATIVE);
-    if (!bufferToWrite->writeUintAndAdvancePosition(flagsToWrite, 1 /* size */, writingPos)) {
-        return false;
-    }
-    const uint32_t absOffest = abs(offset);
-    const int bigramTargetFieldSize = attributeAddressSize(flags);
-    return bufferToWrite->writeUintAndAdvancePosition(absOffest, bigramTargetFieldSize,
-            writingPos);
-}
-
-// Returns true if the bigram entry is valid and put entry flags into out*.
-/* static */ bool BigramListReadWriteUtils::createAndGetBigramFlags(const int entryPos,
-        const int targetPtNodePos, const int probability, const bool hasNext,
-        BigramFlags *const outBigramFlags) {
-    BigramFlags flags = probability & MASK_ATTRIBUTE_PROBABILITY;
-    if (hasNext) {
-        flags |= FLAG_ATTRIBUTE_HAS_NEXT;
-    }
-    const int offset = getBigramTargetOffset(targetPtNodePos, entryPos);
-    if (offset < 0) {
-        flags |= FLAG_ATTRIBUTE_OFFSET_NEGATIVE;
-    }
-    const uint32_t absOffest = abs(offset);
-    if ((absOffest >> 24) != 0) {
-        // Offset is too large.
-        return false;
-    } else if ((absOffest >> 16) != 0) {
-        flags |= FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES;
-    } else if ((absOffest >> 8) != 0) {
-        flags |= FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES;
-    } else {
-        flags |= FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE;
-    }
-    // Currently, all newly written bigram position fields are 3 bytes to simplify dictionary
-    // writing.
-    // TODO: Remove following 2 lines and optimize memory space.
-    flags = (flags & (~MASK_ATTRIBUTE_ADDRESS_TYPE)) | FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES;
-    *outBigramFlags = flags;
-    return true;
-}
-
-/* static */ int BigramListReadWriteUtils::getBigramTargetOffset(const int targetPtNodePos,
-        const int entryPos) {
-    if (targetPtNodePos == NOT_A_DICT_POS) {
-        return DynamicPatriciaTrieReadingUtils::DICT_OFFSET_INVALID;
-    } else {
-        const int offset = targetPtNodePos - (entryPos + 1 /* bigramFlagsField */);
-        if (offset == 0) {
-            return DynamicPatriciaTrieReadingUtils::DICT_OFFSET_ZERO_OFFSET;
-        } else {
-            return offset;
-        }
-    }
-}
-
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h b/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h
index eabe4e0..7e10383 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h
@@ -45,34 +45,6 @@
    // Bigrams reading methods
    static void skipExistingBigrams(const uint8_t *const bigramsBuf, int *const bigramListPos);
 
-   // Returns the size of the bigram position field that is stored in bigram flags.
-   static AK_FORCE_INLINE int attributeAddressSize(const BigramFlags flags) {
-       return (flags & MASK_ATTRIBUTE_ADDRESS_TYPE) >> ATTRIBUTE_ADDRESS_SHIFT;
-       /* Note: this is a value-dependant optimization of what may probably be
-          more readably written this way:
-          switch (flags * BinaryFormat::MASK_ATTRIBUTE_ADDRESS_TYPE) {
-          case FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE: return 1;
-          case FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES: return 2;
-          case FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTE: return 3;
-          default: return 0;
-          }
-       */
-   }
-
-   static bool setHasNextFlag(BufferWithExtendableBuffer *const buffer,
-           const bool hasNext, const int entryPos);
-
-   static AK_FORCE_INLINE BigramFlags setProbabilityInFlags(const BigramFlags flags,
-           const int probability) {
-       return (flags & (~MASK_ATTRIBUTE_PROBABILITY)) | (probability & MASK_ATTRIBUTE_PROBABILITY);
-   }
-
-   static bool createAndWriteBigramEntry(BufferWithExtendableBuffer *const buffer,
-           const int targetPos, const int probability, const bool hasNext, int *const writingPos);
-
-   static bool writeBigramEntry(BufferWithExtendableBuffer *const buffer, const BigramFlags flags,
-           const int targetOffset, int *const writingPos);
-
 private:
    DISALLOW_IMPLICIT_CONSTRUCTORS(BigramListReadWriteUtils);
 
@@ -83,11 +55,6 @@
    static const BigramFlags FLAG_ATTRIBUTE_OFFSET_NEGATIVE;
    static const BigramFlags FLAG_ATTRIBUTE_HAS_NEXT;
    static const BigramFlags MASK_ATTRIBUTE_PROBABILITY;
-   static const int ATTRIBUTE_ADDRESS_SHIFT;
-
-   // Returns true if the bigram entry is valid and put entry flags into out*.
-   static bool createAndGetBigramFlags(const int entryPos, const int targetPos,
-           const int probability, const bool hasNext, BigramFlags *const outBigramFlags);
 
    static AK_FORCE_INLINE bool isOffsetNegative(const BigramFlags flags) {
        return (flags & FLAG_ATTRIBUTE_OFFSET_NEGATIVE) != 0;
@@ -95,8 +62,6 @@
 
    static int getBigramAddressAndAdvancePosition(const uint8_t *const bigramsBuf,
            const BigramFlags flags, int *const pos);
-
-   static int getBigramTargetOffset(const int targetPtNodePos, const int entryPos);
 };
 } // namespace latinime
 #endif // LATINIME_BIGRAM_LIST_READ_WRITE_UTILS_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
deleted file mode 100644
index b1170e2..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
+++ /dev/null
@@ -1,391 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
-
-#include "suggest/core/policy/dictionary_shortcuts_structure_policy.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
-
-namespace latinime {
-
-const int DynamicBigramListPolicy::CONTINUING_BIGRAM_LINK_COUNT_LIMIT = 10000;
-const int DynamicBigramListPolicy::BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT = 100000;
-
-void DynamicBigramListPolicy::getNextBigram(int *const outBigramPos, int *const outProbability,
-        bool *const outHasNext, int *const bigramEntryPos) const {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*bigramEntryPos);
-    const uint8_t *const buffer = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        *bigramEntryPos -= mBuffer->getOriginalBufferSize();
-    }
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int originalBigramPos;
-    BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(buffer, &bigramFlags,
-            &originalBigramPos, bigramEntryPos);
-    if (usesAdditionalBuffer && originalBigramPos != NOT_A_DICT_POS) {
-        originalBigramPos += mBuffer->getOriginalBufferSize();
-    }
-    *outProbability = BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags);
-    *outHasNext = BigramListReadWriteUtils::hasNext(bigramFlags);
-    if (mIsDecayingDict && !ForgettingCurveUtils::isValidEncodedProbability(*outProbability)) {
-        // This bigram is too weak to output.
-        *outBigramPos = NOT_A_DICT_POS;
-    } else {
-        *outBigramPos = followBigramLinkAndGetCurrentBigramPtNodePos(originalBigramPos);
-    }
-    if (usesAdditionalBuffer) {
-        *bigramEntryPos += mBuffer->getOriginalBufferSize();
-    }
-}
-
-void DynamicBigramListPolicy::skipAllBigrams(int *const bigramListPos) const {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*bigramListPos);
-    const uint8_t *const buffer = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        *bigramListPos -= mBuffer->getOriginalBufferSize();
-    }
-    BigramListReadWriteUtils::skipExistingBigrams(buffer, bigramListPos);
-    if (usesAdditionalBuffer) {
-        *bigramListPos += mBuffer->getOriginalBufferSize();
-    }
-}
-
-bool DynamicBigramListPolicy::copyAllBigrams(BufferWithExtendableBuffer *const bufferToWrite,
-        int *const fromPos, int *const toPos, int *const outBigramsCount) const {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*fromPos);
-    if (usesAdditionalBuffer) {
-        *fromPos -= mBuffer->getOriginalBufferSize();
-    }
-    *outBigramsCount = 0;
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int bigramEntryCount = 0;
-    int lastWrittenEntryPos = NOT_A_DICT_POS;
-    do {
-        if (++bigramEntryCount > BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT) {
-            AKLOGE("Too many bigram entries. Entry count: %d, Limit: %d",
-                    bigramEntryCount, BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT);
-            ASSERT(false);
-            return false;
-        }
-        // The buffer address can be changed after calling buffer writing methods.
-        int originalBigramPos;
-        BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
-                mBuffer->getBuffer(usesAdditionalBuffer), &bigramFlags, &originalBigramPos,
-                fromPos);
-        if (originalBigramPos == NOT_A_DICT_POS) {
-            // skip invalid bigram entry.
-            continue;
-        }
-        if (usesAdditionalBuffer) {
-            originalBigramPos += mBuffer->getOriginalBufferSize();
-        }
-        const int bigramPos = followBigramLinkAndGetCurrentBigramPtNodePos(originalBigramPos);
-        if (bigramPos == NOT_A_DICT_POS) {
-            // Target PtNode has been invalidated.
-            continue;
-        }
-        lastWrittenEntryPos = *toPos;
-        if (!BigramListReadWriteUtils::createAndWriteBigramEntry(bufferToWrite, bigramPos,
-                BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags),
-                BigramListReadWriteUtils::hasNext(bigramFlags), toPos)) {
-            return false;
-        }
-        (*outBigramsCount)++;
-    } while(BigramListReadWriteUtils::hasNext(bigramFlags));
-    // Makes the last entry the terminal of the list. Updates the flags.
-    if (lastWrittenEntryPos != NOT_A_DICT_POS) {
-        if (!BigramListReadWriteUtils::setHasNextFlag(bufferToWrite, false /* hasNext */,
-                lastWrittenEntryPos)) {
-            return false;
-        }
-    }
-    if (usesAdditionalBuffer) {
-        *fromPos += mBuffer->getOriginalBufferSize();
-    }
-    return true;
-}
-
-// Finding useless bigram entries and remove them. Bigram entry is useless when the target PtNode
-// has been deleted or is not a valid terminal.
-bool DynamicBigramListPolicy::updateAllBigramEntriesAndDeleteUselessEntries(
-        int *const bigramListPos, int *const outValidBigramEntryCount) {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*bigramListPos);
-    if (usesAdditionalBuffer) {
-        *bigramListPos -= mBuffer->getOriginalBufferSize();
-    }
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, this /* bigramsPolicy */, mShortcutPolicy);
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int bigramEntryCount = 0;
-    do {
-        if (++bigramEntryCount > BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT) {
-            AKLOGE("Too many bigram entries. Entry count: %d, Limit: %d",
-                    bigramEntryCount, BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT);
-            ASSERT(false);
-            return false;
-        }
-        int bigramEntryPos = *bigramListPos;
-        int originalBigramPos;
-        // The buffer address can be changed after calling buffer writing methods.
-        BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
-                mBuffer->getBuffer(usesAdditionalBuffer), &bigramFlags, &originalBigramPos,
-                bigramListPos);
-        if (usesAdditionalBuffer) {
-            bigramEntryPos += mBuffer->getOriginalBufferSize();
-        }
-        if (originalBigramPos == NOT_A_DICT_POS) {
-            // This entry has already been removed.
-            continue;
-        }
-        if (usesAdditionalBuffer) {
-            originalBigramPos += mBuffer->getOriginalBufferSize();
-        }
-        const int bigramTargetNodePos =
-                followBigramLinkAndGetCurrentBigramPtNodePos(originalBigramPos);
-        nodeReader.fetchNodeInfoInBufferFromPtNodePos(bigramTargetNodePos);
-        if (nodeReader.isDeleted() || !nodeReader.isTerminal()
-                || bigramTargetNodePos == NOT_A_DICT_POS) {
-            // The target is no longer valid terminal. Invalidate the current bigram entry.
-            if (!BigramListReadWriteUtils::writeBigramEntry(mBuffer, bigramFlags,
-                    NOT_A_DICT_POS /* targetPtNodePos */, &bigramEntryPos)) {
-                return false;
-            }
-            continue;
-        }
-        bool isRemoved = false;
-        if (!updateProbabilityForDecay(bigramFlags, bigramTargetNodePos, &bigramEntryPos,
-                &isRemoved)) {
-            return false;
-        }
-        if (!isRemoved) {
-            (*outValidBigramEntryCount) += 1;
-        }
-    } while(BigramListReadWriteUtils::hasNext(bigramFlags));
-    return true;
-}
-
-// Updates bigram target PtNode positions in the list after the placing step in GC.
-bool DynamicBigramListPolicy::updateAllBigramTargetPtNodePositions(int *const bigramListPos,
-        const DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap *const
-                ptNodePositionRelocationMap, int *const outBigramEntryCount) {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*bigramListPos);
-    if (usesAdditionalBuffer) {
-        *bigramListPos -= mBuffer->getOriginalBufferSize();
-    }
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int bigramEntryCount = 0;
-    do {
-        if (++bigramEntryCount > BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT) {
-            AKLOGE("Too many bigram entries. Entry count: %d, Limit: %d",
-                    bigramEntryCount, BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT);
-            ASSERT(false);
-            return false;
-        }
-        int bigramEntryPos = *bigramListPos;
-        if (usesAdditionalBuffer) {
-            bigramEntryPos += mBuffer->getOriginalBufferSize();
-        }
-        int bigramTargetPtNodePos;
-        // The buffer address can be changed after calling buffer writing methods.
-        BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
-                mBuffer->getBuffer(usesAdditionalBuffer), &bigramFlags, &bigramTargetPtNodePos,
-                bigramListPos);
-        if (bigramTargetPtNodePos == NOT_A_DICT_POS) {
-            continue;
-        }
-        if (usesAdditionalBuffer) {
-            bigramTargetPtNodePos += mBuffer->getOriginalBufferSize();
-        }
-
-        DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap::const_iterator it =
-                ptNodePositionRelocationMap->find(bigramTargetPtNodePos);
-        if (it != ptNodePositionRelocationMap->end()) {
-            bigramTargetPtNodePos = it->second;
-        } else {
-            bigramTargetPtNodePos = NOT_A_DICT_POS;
-        }
-        if (!BigramListReadWriteUtils::writeBigramEntry(mBuffer, bigramFlags,
-                bigramTargetPtNodePos, &bigramEntryPos)) {
-            return false;
-        }
-    } while(BigramListReadWriteUtils::hasNext(bigramFlags));
-    (*outBigramEntryCount) = bigramEntryCount;
-    return true;
-}
-
-bool DynamicBigramListPolicy::addNewBigramEntryToBigramList(const int bigramTargetPos,
-        const int probability, int *const bigramListPos, bool *const outAddedNewBigram) {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*bigramListPos);
-    if (usesAdditionalBuffer) {
-        *bigramListPos -= mBuffer->getOriginalBufferSize();
-    }
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int bigramEntryCount = 0;
-    do {
-        if (++bigramEntryCount > BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT) {
-            AKLOGE("Too many bigram entries. Entry count: %d, Limit: %d",
-                    bigramEntryCount, BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT);
-            ASSERT(false);
-            return false;
-        }
-        int entryPos = *bigramListPos;
-        if (usesAdditionalBuffer) {
-            entryPos += mBuffer->getOriginalBufferSize();
-        }
-        int originalBigramPos;
-        // The buffer address can be changed after calling buffer writing methods.
-        BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
-                mBuffer->getBuffer(usesAdditionalBuffer), &bigramFlags, &originalBigramPos,
-                bigramListPos);
-        if (usesAdditionalBuffer && originalBigramPos != NOT_A_DICT_POS) {
-            originalBigramPos += mBuffer->getOriginalBufferSize();
-        }
-        if (followBigramLinkAndGetCurrentBigramPtNodePos(originalBigramPos) == bigramTargetPos) {
-            // Update this bigram entry.
-            *outAddedNewBigram = false;
-            const int originalProbability = BigramListReadWriteUtils::getProbabilityFromFlags(
-                    bigramFlags);
-            const int probabilityToWrite = mIsDecayingDict ?
-                    ForgettingCurveUtils::getUpdatedEncodedProbability(originalProbability,
-                            probability) : probability;
-            const BigramListReadWriteUtils::BigramFlags updatedFlags =
-                    BigramListReadWriteUtils::setProbabilityInFlags(bigramFlags,
-                            probabilityToWrite);
-            return BigramListReadWriteUtils::writeBigramEntry(mBuffer, updatedFlags,
-                    originalBigramPos, &entryPos);
-        }
-        if (BigramListReadWriteUtils::hasNext(bigramFlags)) {
-            continue;
-        }
-        // The current last entry is found.
-        // First, update the flags of the last entry.
-        if (!BigramListReadWriteUtils::setHasNextFlag(mBuffer, true /* hasNext */, entryPos)) {
-            *outAddedNewBigram = false;
-            return false;
-        }
-        if (usesAdditionalBuffer) {
-            *bigramListPos += mBuffer->getOriginalBufferSize();
-        }
-        // Then, add a new entry after the last entry.
-        *outAddedNewBigram = true;
-        return writeNewBigramEntry(bigramTargetPos, probability, bigramListPos);
-    } while(BigramListReadWriteUtils::hasNext(bigramFlags));
-    // We return directly from the while loop.
-    ASSERT(false);
-    return false;
-}
-
-bool DynamicBigramListPolicy::writeNewBigramEntry(const int bigramTargetPos, const int probability,
-        int *const writingPos) {
-    // hasNext is false because we are adding a new bigram entry at the end of the bigram list.
-    const int probabilityToWrite = mIsDecayingDict ?
-            ForgettingCurveUtils::getUpdatedEncodedProbability(NOT_A_PROBABILITY, probability) :
-                    probability;
-    return BigramListReadWriteUtils::createAndWriteBigramEntry(mBuffer, bigramTargetPos,
-            probabilityToWrite, false /* hasNext */, writingPos);
-}
-
-bool DynamicBigramListPolicy::removeBigram(const int bigramListPos, const int bigramTargetPos) {
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(bigramListPos);
-    int pos = bigramListPos;
-    if (usesAdditionalBuffer) {
-        pos -= mBuffer->getOriginalBufferSize();
-    }
-    BigramListReadWriteUtils::BigramFlags bigramFlags;
-    int bigramEntryCount = 0;
-    do {
-        if (++bigramEntryCount > BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT) {
-            AKLOGE("Too many bigram entries. Entry count: %d, Limit: %d",
-                    bigramEntryCount, BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT);
-            ASSERT(false);
-            return false;
-        }
-        int bigramEntryPos = pos;
-        int originalBigramPos;
-        // The buffer address can be changed after calling buffer writing methods.
-        BigramListReadWriteUtils::getBigramEntryPropertiesAndAdvancePosition(
-                mBuffer->getBuffer(usesAdditionalBuffer), &bigramFlags, &originalBigramPos, &pos);
-        if (usesAdditionalBuffer) {
-            bigramEntryPos += mBuffer->getOriginalBufferSize();
-        }
-        if (usesAdditionalBuffer && originalBigramPos != NOT_A_DICT_POS) {
-            originalBigramPos += mBuffer->getOriginalBufferSize();
-        }
-        const int bigramPos = followBigramLinkAndGetCurrentBigramPtNodePos(originalBigramPos);
-        if (bigramPos != bigramTargetPos) {
-            continue;
-        }
-        // Target entry is found. Write an invalid target position to mark the bigram invalid.
-        return BigramListReadWriteUtils::writeBigramEntry(mBuffer, bigramFlags,
-                NOT_A_DICT_POS /* targetOffset */, &bigramEntryPos);
-    } while(BigramListReadWriteUtils::hasNext(bigramFlags));
-    return false;
-}
-
-int DynamicBigramListPolicy::followBigramLinkAndGetCurrentBigramPtNodePos(
-        const int originalBigramPos) const {
-    if (originalBigramPos == NOT_A_DICT_POS) {
-        return NOT_A_DICT_POS;
-    }
-    int currentPos = originalBigramPos;
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, this /* bigramsPolicy */, mShortcutPolicy);
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(currentPos);
-    int bigramLinkCount = 0;
-    while (nodeReader.getBigramLinkedNodePos() != NOT_A_DICT_POS) {
-        currentPos = nodeReader.getBigramLinkedNodePos();
-        nodeReader.fetchNodeInfoInBufferFromPtNodePos(currentPos);
-        bigramLinkCount++;
-        if (bigramLinkCount > CONTINUING_BIGRAM_LINK_COUNT_LIMIT) {
-            AKLOGE("Bigram link is invalid. start position: %d", originalBigramPos);
-            ASSERT(false);
-            return NOT_A_DICT_POS;
-        }
-    }
-    return currentPos;
-}
-
-bool DynamicBigramListPolicy::updateProbabilityForDecay(
-        const BigramListReadWriteUtils::BigramFlags bigramFlags, const int targetPtNodePos,
-        int *const bigramEntryPos, bool *const outRemoved) const {
-    *outRemoved = false;
-    if (mIsDecayingDict) {
-        // Update bigram probability for decaying.
-        const int newProbability = ForgettingCurveUtils::getEncodedProbabilityToSave(
-                BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags), mHeaderPolicy);
-        if (ForgettingCurveUtils::isValidEncodedProbability(newProbability)) {
-            // Write new probability.
-            const BigramListReadWriteUtils::BigramFlags updatedBigramFlags =
-                    BigramListReadWriteUtils::setProbabilityInFlags(
-                            bigramFlags, newProbability);
-            if (!BigramListReadWriteUtils::writeBigramEntry(mBuffer, updatedBigramFlags,
-                    targetPtNodePos, bigramEntryPos)) {
-                return false;
-            }
-        } else {
-            // Remove current bigram entry.
-            *outRemoved = true;
-            if (!BigramListReadWriteUtils::writeBigramEntry(mBuffer, bigramFlags,
-                    NOT_A_DICT_POS /* targetPtNodePos */, bigramEntryPos)) {
-                return false;
-            }
-        }
-    }
-    return true;
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h
deleted file mode 100644
index 0504b59..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h
+++ /dev/null
@@ -1,92 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_BIGRAM_LIST_POLICY_H
-#define LATINIME_DYNAMIC_BIGRAM_LIST_POLICY_H
-
-#include <stdint.h>
-
-#include "defines.h"
-#include "suggest/core/policy/dictionary_bigrams_structure_policy.h"
-#include "suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
-
-namespace latinime {
-
-class BufferWithExtendableBuffer;
-class DictionaryHeaderStructurePolicy;
-class DictionaryShortcutsStructurePolicy;
-
-/*
- * This is a dynamic version of BigramListPolicy and supports an additional buffer.
- */
-class DynamicBigramListPolicy : public DictionaryBigramsStructurePolicy {
- public:
-    DynamicBigramListPolicy(const DictionaryHeaderStructurePolicy *const headerPolicy,
-            BufferWithExtendableBuffer *const buffer,
-            const DictionaryShortcutsStructurePolicy *const shortcutPolicy,
-            const bool isDecayingDict)
-            : mHeaderPolicy(headerPolicy), mBuffer(buffer), mShortcutPolicy(shortcutPolicy),
-              mIsDecayingDict(isDecayingDict) {}
-
-    ~DynamicBigramListPolicy() {}
-
-    void getNextBigram(int *const outBigramPos, int *const outProbability, bool *const outHasNext,
-            int *const bigramEntryPos) const;
-
-    void skipAllBigrams(int *const bigramListPos) const;
-
-    // Copy bigrams from the bigram list that starts at fromPos in mBuffer to toPos in
-    // bufferToWrite and advance these positions after bigram lists. This method skips invalid
-    // bigram entries and write the valid bigram entry count to outBigramsCount.
-    bool copyAllBigrams(BufferWithExtendableBuffer *const bufferToWrite, int *const fromPos,
-            int *const toPos, int *const outBigramsCount) const;
-
-    bool updateAllBigramEntriesAndDeleteUselessEntries(int *const bigramListPos,
-            int *const outBigramEntryCount);
-
-    bool updateAllBigramTargetPtNodePositions(int *const bigramListPos,
-            const DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap *const
-                    ptNodePositionRelocationMap, int *const outValidBigramEntryCount);
-
-    bool addNewBigramEntryToBigramList(const int bigramTargetPos, const int probability,
-            int *const bigramListPos, bool *const outAddedNewBigram);
-
-    bool writeNewBigramEntry(const int bigramTargetPos, const int probability,
-            int *const writingPos);
-
-    // Return whether or not targetBigramPos is found.
-    bool removeBigram(const int bigramListPos, const int bigramTargetPos);
-
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicBigramListPolicy);
-
-    static const int CONTINUING_BIGRAM_LINK_COUNT_LIMIT;
-    static const int BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT;
-
-    const DictionaryHeaderStructurePolicy *const mHeaderPolicy;
-    BufferWithExtendableBuffer *const mBuffer;
-    const DictionaryShortcutsStructurePolicy *const mShortcutPolicy;
-    const bool mIsDecayingDict;
-
-    // Follow bigram link and return the position of bigram target PtNode that is currently valid.
-    int followBigramLinkAndGetCurrentBigramPtNodePos(const int originalBigramPos) const;
-
-    bool updateProbabilityForDecay(const BigramListReadWriteUtils::BigramFlags bigramFlags,
-            const int targetPtNodePos, int *const bigramEntryPos, bool *const outRemoved) const;
-};
-} // namespace latinime
-#endif // LATINIME_DYNAMIC_BIGRAM_LIST_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.cpp
new file mode 100644
index 0000000..cd22430
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.cpp
@@ -0,0 +1,240 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h"
+
+#include "suggest/policyimpl/dictionary/bigram/bigram_list_read_write_utils.h"
+#include "suggest/policyimpl/dictionary/header/header_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+
+namespace latinime {
+
+void Ver4BigramListPolicy::getNextBigram(int *const outBigramPos, int *const outProbability,
+        bool *const outHasNext, int *const bigramEntryPos) const {
+    const BigramEntry bigramEntry =
+            mBigramDictContent->getBigramEntryAndAdvancePosition(bigramEntryPos);
+    if (outBigramPos) {
+        // Lookup target PtNode position.
+        *outBigramPos = mTerminalPositionLookupTable->getTerminalPtNodePosition(
+                bigramEntry.getTargetTerminalId());
+    }
+    if (outProbability) {
+        if (bigramEntry.hasHistoricalInfo()) {
+            *outProbability =
+                    ForgettingCurveUtils::decodeProbability(bigramEntry.getHistoricalInfo());
+        } else {
+            *outProbability = bigramEntry.getProbability();
+        }
+    }
+    if (outHasNext) {
+        *outHasNext = bigramEntry.hasNext();
+    }
+}
+
+bool Ver4BigramListPolicy::addNewEntry(const int terminalId, const int newTargetTerminalId,
+        const int newProbability, const int timestamp, bool *const outAddedNewEntry) {
+    if (outAddedNewEntry) {
+        *outAddedNewEntry = false;
+    }
+    const int bigramListPos = mBigramDictContent->getBigramListHeadPos(terminalId);
+    if (bigramListPos == NOT_A_DICT_POS) {
+        // Updating PtNode doesn't have a bigram list.
+        // Create new bigram list.
+        if (!mBigramDictContent->createNewBigramList(terminalId)) {
+            return false;
+        }
+        const BigramEntry newBigramEntry(false /* hasNext */, NOT_A_PROBABILITY,
+                newTargetTerminalId);
+        const BigramEntry bigramEntryToWrite = createUpdatedBigramEntryFrom(&newBigramEntry,
+                newProbability, timestamp);
+        // Write an entry.
+        const int writingPos =  mBigramDictContent->getBigramListHeadPos(terminalId);
+        if (!mBigramDictContent->writeBigramEntry(&bigramEntryToWrite, writingPos)) {
+            return false;
+        }
+        if (outAddedNewEntry) {
+            *outAddedNewEntry = true;
+        }
+        return true;
+    }
+
+    const int entryPosToUpdate = getEntryPosToUpdate(newTargetTerminalId, bigramListPos);
+    if (entryPosToUpdate != NOT_A_DICT_POS) {
+        // Overwrite existing entry.
+        const BigramEntry originalBigramEntry =
+                mBigramDictContent->getBigramEntry(entryPosToUpdate);
+        if (!originalBigramEntry.isValid()) {
+            // Reuse invalid entry.
+            if (outAddedNewEntry) {
+                *outAddedNewEntry = true;
+            }
+        }
+        const BigramEntry updatedBigramEntry =
+                originalBigramEntry.updateTargetTerminalIdAndGetEntry(newTargetTerminalId);
+        const BigramEntry bigramEntryToWrite = createUpdatedBigramEntryFrom(
+                &updatedBigramEntry, newProbability, timestamp);
+        return mBigramDictContent->writeBigramEntry(&bigramEntryToWrite, entryPosToUpdate);
+    }
+
+    // Add new entry to the bigram list.
+    // Create new bigram list.
+    if (!mBigramDictContent->createNewBigramList(terminalId)) {
+        return false;
+    }
+    // Write new entry at a head position of the bigram list.
+    int writingPos = mBigramDictContent->getBigramListHeadPos(terminalId);
+    const BigramEntry newBigramEntry(true /* hasNext */, NOT_A_PROBABILITY, newTargetTerminalId);
+    const BigramEntry bigramEntryToWrite = createUpdatedBigramEntryFrom(
+            &newBigramEntry, newProbability, timestamp);
+    if (!mBigramDictContent->writeBigramEntryAndAdvancePosition(&bigramEntryToWrite, &writingPos)) {
+        return false;
+    }
+    if (outAddedNewEntry) {
+        *outAddedNewEntry = true;
+    }
+    // Append existing entries by copying.
+    return mBigramDictContent->copyBigramList(bigramListPos, writingPos);
+}
+
+bool Ver4BigramListPolicy::removeEntry(const int terminalId, const int targetTerminalId) {
+    const int bigramListPos = mBigramDictContent->getBigramListHeadPos(terminalId);
+    if (bigramListPos == NOT_A_DICT_POS) {
+        // Bigram list doesn't exist.
+        return false;
+    }
+    const int entryPosToUpdate = getEntryPosToUpdate(targetTerminalId, bigramListPos);
+    if (entryPosToUpdate == NOT_A_DICT_POS) {
+        // Bigram entry doesn't exist.
+        return false;
+    }
+    const BigramEntry bigramEntry = mBigramDictContent->getBigramEntry(entryPosToUpdate);
+    if (targetTerminalId != bigramEntry.getTargetTerminalId()) {
+        // Bigram entry doesn't exist.
+        return false;
+    }
+    // Remove bigram entry by marking it as invalid entry and overwriting the original entry.
+    const BigramEntry updatedBigramEntry = bigramEntry.getInvalidatedEntry();
+    return mBigramDictContent->writeBigramEntry(&updatedBigramEntry, entryPosToUpdate);
+}
+
+bool Ver4BigramListPolicy::updateAllBigramEntriesAndDeleteUselessEntries(const int terminalId,
+        int *const outBigramCount) {
+    const int bigramListPos = mBigramDictContent->getBigramListHeadPos(terminalId);
+    if (bigramListPos == NOT_A_DICT_POS) {
+        // Bigram list doesn't exist.
+        return true;
+    }
+    bool hasNext = true;
+    int readingPos = bigramListPos;
+    while (hasNext) {
+        const int entryPos = readingPos;
+        const BigramEntry bigramEntry =
+                mBigramDictContent->getBigramEntryAndAdvancePosition(&readingPos);
+        hasNext = bigramEntry.hasNext();
+        if (!bigramEntry.isValid()) {
+            continue;
+        }
+        const int targetPtNodePos = mTerminalPositionLookupTable->getTerminalPtNodePosition(
+                bigramEntry.getTargetTerminalId());
+        if (targetPtNodePos == NOT_A_DICT_POS) {
+            // Invalidate bigram entry.
+            const BigramEntry updatedBigramEntry = bigramEntry.getInvalidatedEntry();
+            if (!mBigramDictContent->writeBigramEntry(&updatedBigramEntry, entryPos)) {
+                return false;
+            }
+        } else if (bigramEntry.hasHistoricalInfo()) {
+            const HistoricalInfo historicalInfo = ForgettingCurveUtils::createHistoricalInfoToSave(
+                    bigramEntry.getHistoricalInfo());
+            if (ForgettingCurveUtils::needsToKeep(&historicalInfo)) {
+                const BigramEntry updatedBigramEntry =
+                        bigramEntry.updateHistoricalInfoAndGetEntry(&historicalInfo);
+                if (!mBigramDictContent->writeBigramEntry(&updatedBigramEntry, entryPos)) {
+                    return false;
+                }
+                *outBigramCount += 1;
+            } else {
+                // Remove entry.
+                const BigramEntry updatedBigramEntry = bigramEntry.getInvalidatedEntry();
+                if (!mBigramDictContent->writeBigramEntry(&updatedBigramEntry, entryPos)) {
+                    return false;
+                }
+            }
+        } else {
+            *outBigramCount += 1;
+        }
+    }
+    return true;
+}
+
+int Ver4BigramListPolicy::getBigramEntryConut(const int terminalId) {
+    const int bigramListPos = mBigramDictContent->getBigramListHeadPos(terminalId);
+    if (bigramListPos == NOT_A_DICT_POS) {
+        // Bigram list doesn't exist.
+        return 0;
+    }
+    int bigramCount = 0;
+    bool hasNext = true;
+    int readingPos = bigramListPos;
+    while (hasNext) {
+        const BigramEntry bigramEntry =
+                mBigramDictContent->getBigramEntryAndAdvancePosition(&readingPos);
+        hasNext = bigramEntry.hasNext();
+        if (bigramEntry.isValid()) {
+            bigramCount++;
+        }
+    }
+    return bigramCount;
+}
+
+int Ver4BigramListPolicy::getEntryPosToUpdate(const int targetTerminalIdToFind,
+        const int bigramListPos) const {
+    bool hasNext = true;
+    int invalidEntryPos = NOT_A_DICT_POS;
+    int readingPos = bigramListPos;
+    while (hasNext) {
+        const int entryPos = readingPos;
+        const BigramEntry bigramEntry =
+                mBigramDictContent->getBigramEntryAndAdvancePosition(&readingPos);
+        hasNext = bigramEntry.hasNext();
+        if (bigramEntry.getTargetTerminalId() == targetTerminalIdToFind) {
+            // Entry with same target is found.
+            return entryPos;
+        } else if (!bigramEntry.isValid()) {
+            // Invalid entry that can be reused is found.
+            invalidEntryPos = entryPos;
+        }
+    }
+    return invalidEntryPos;
+}
+
+const BigramEntry Ver4BigramListPolicy::createUpdatedBigramEntryFrom(
+        const BigramEntry *const originalBigramEntry, const int newProbability,
+        const int timestamp) const {
+    // TODO: Consolidate historical info and probability.
+    if (mHeaderPolicy->hasHistoricalInfoOfWords()) {
+        const HistoricalInfo updatedHistoricalInfo =
+                ForgettingCurveUtils::createUpdatedHistoricalInfo(
+                        originalBigramEntry->getHistoricalInfo(), newProbability, timestamp);
+        return originalBigramEntry->updateHistoricalInfoAndGetEntry(&updatedHistoricalInfo);
+    } else {
+        return originalBigramEntry->updateProbabilityAndGetEntry(newProbability);
+    }
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h b/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h
new file mode 100644
index 0000000..5b6c5a1
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_BIGRAM_LIST_POLICY_H
+#define LATINIME_VER4_BIGRAM_LIST_POLICY_H
+
+#include "defines.h"
+#include "suggest/core/policy/dictionary_bigrams_structure_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/bigram_entry.h"
+
+namespace latinime {
+
+class BigramDictContent;
+class HeaderPolicy;
+class TerminalPositionLookupTable;
+
+class Ver4BigramListPolicy : public DictionaryBigramsStructurePolicy {
+ public:
+    Ver4BigramListPolicy(BigramDictContent *const bigramDictContent,
+            const TerminalPositionLookupTable *const terminalPositionLookupTable,
+            const HeaderPolicy *const headerPolicy)
+            : mBigramDictContent(bigramDictContent),
+              mTerminalPositionLookupTable(terminalPositionLookupTable),
+              mHeaderPolicy(headerPolicy) {}
+
+    void getNextBigram(int *const outBigramPos, int *const outProbability,
+            bool *const outHasNext, int *const bigramEntryPos) const;
+
+    void skipAllBigrams(int *const pos) const {
+        // Do nothing because we don't need to skip bigram lists in ver4 dictionaries.
+    }
+
+    bool addNewEntry(const int terminalId, const int newTargetTerminalId, const int newProbability,
+            const int timestamp, bool *const outAddedNewEntry);
+
+    bool removeEntry(const int terminalId, const int targetTerminalId);
+
+    bool updateAllBigramEntriesAndDeleteUselessEntries(const int terminalId,
+            int *const outBigramCount);
+
+    int getBigramEntryConut(const int terminalId);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4BigramListPolicy);
+
+    int getEntryPosToUpdate(const int targetTerminalIdToFind, const int bigramListPos) const;
+
+    const BigramEntry createUpdatedBigramEntryFrom(const BigramEntry *const originalBigramEntry,
+            const int newProbability, const int timestamp) const;
+
+    BigramDictContent *const mBigramDictContent;
+    const TerminalPositionLookupTable *const mTerminalPositionLookupTable;
+    const HeaderPolicy *const mHeaderPolicy;
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_BIGRAM_LIST_POLICY_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp b/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp
deleted file mode 100644
index ff80dd2..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp
+++ /dev/null
@@ -1,53 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h"
-
-#include <stdint.h>
-
-#include "defines.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_policy.h"
-#include "suggest/policyimpl/dictionary/utils/format_utils.h"
-#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
-
-namespace latinime {
-
-/* static */ DictionaryStructureWithBufferPolicy *DictionaryStructureWithBufferPolicyFactory
-        ::newDictionaryStructureWithBufferPolicy(const char *const path, const int bufOffset,
-                const int size, const bool isUpdatable) {
-    // Allocated buffer in MmapedBuffer::openBuffer() will be freed in the destructor of
-    // impl classes of DictionaryStructureWithBufferPolicy.
-    const MmappedBuffer *const mmapedBuffer = MmappedBuffer::openBuffer(path, bufOffset, size,
-            isUpdatable);
-    if (!mmapedBuffer) {
-        return 0;
-    }
-    switch (FormatUtils::detectFormatVersion(mmapedBuffer->getBuffer(),
-            mmapedBuffer->getBufferSize())) {
-        case FormatUtils::VERSION_2:
-            return new PatriciaTriePolicy(mmapedBuffer);
-        case FormatUtils::VERSION_3:
-            return new DynamicPatriciaTriePolicy(mmapedBuffer);
-        default:
-            AKLOGE("DICT: dictionary format is unknown, bad magic number");
-            delete mmapedBuffer;
-            ASSERT(false);
-            return 0;
-    }
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
deleted file mode 100644
index 5724c5d..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
+++ /dev/null
@@ -1,191 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h"
-
-#include "suggest/core/policy/dictionary_header_structure_policy.h"
-#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
-
-namespace latinime {
-
-bool DynamicPatriciaTrieGcEventListeners
-        ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
-                ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                        const int *const nodeCodePoints) {
-    // PtNode is useless when the PtNode is not a terminal and doesn't have any not useless
-    // children.
-    bool isUselessPtNode = !node->isTerminal();
-    if (node->isTerminal() && mIsDecayingDict) {
-        const int newProbability =
-                ForgettingCurveUtils::getEncodedProbabilityToSave(node->getProbability(),
-                        mHeaderPolicy);
-        int writingPos = node->getProbabilityFieldPos();
-        // Update probability.
-        if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(
-                mBuffer, newProbability, &writingPos)) {
-            return false;
-        }
-        if (!ForgettingCurveUtils::isValidEncodedProbability(newProbability)) {
-            isUselessPtNode = true;
-        }
-    }
-    if (mChildrenValue > 0) {
-        isUselessPtNode = false;
-    } else if (node->isTerminal()) {
-        // Remove children as all children are useless.
-        int writingPos = node->getChildrenPosFieldPos();
-        if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(
-                mBuffer, NOT_A_DICT_POS /* childrenPosition */, &writingPos)) {
-            return false;
-        }
-    }
-    if (isUselessPtNode) {
-        // Current PtNode is no longer needed. Mark it as deleted.
-        if (!mWritingHelper->markNodeAsDeleted(node)) {
-            return false;
-        }
-    } else {
-        mValueStack.back() += 1;
-        if (node->isTerminal()) {
-            mValidUnigramCount += 1;
-        }
-    }
-    return true;
-}
-
-bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateBigramProbability
-        ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints) {
-    if (!node->isDeleted()) {
-        int pos = node->getBigramsPos();
-        if (pos != NOT_A_DICT_POS) {
-            int bigramEntryCount = 0;
-            if (!mBigramPolicy->updateAllBigramEntriesAndDeleteUselessEntries(&pos,
-                    &bigramEntryCount)) {
-                return false;
-            }
-            mValidBigramEntryCount += bigramEntryCount;
-        }
-    }
-    return true;
-}
-
-// Writes dummy PtNode array size when the head of PtNode array is read.
-bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-        ::onDescend(const int ptNodeArrayPos) {
-    mValidPtNodeCount = 0;
-    int writingPos = mBufferToWrite->getTailPosition();
-    mDictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.insert(
-            DynamicPatriciaTrieWritingHelper::PtNodeArrayPositionRelocationMap::value_type(
-                    ptNodeArrayPos, writingPos));
-    // Writes dummy PtNode array size because arrays can have a forward link or needles PtNodes.
-    // This field will be updated later in onReadingPtNodeArrayTail() with actual PtNode count.
-    mPtNodeArraySizeFieldPos = writingPos;
-    return DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(
-            mBufferToWrite, 0 /* arraySize */, &writingPos);
-}
-
-// Write PtNode array terminal and actual PtNode array size.
-bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-        ::onReadingPtNodeArrayTail() {
-    int writingPos = mBufferToWrite->getTailPosition();
-    // Write PtNode array terminal.
-    if (!DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(
-            mBufferToWrite, NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
-        return false;
-    }
-    // Write actual PtNode array size.
-    if (!DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(
-            mBufferToWrite, mValidPtNodeCount, &mPtNodeArraySizeFieldPos)) {
-        return false;
-    }
-    return true;
-}
-
-// Write valid PtNode to buffer and memorize mapping from the old position to the new position.
-bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-        ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints) {
-    if (node->isDeleted()) {
-        // Current PtNode is not written in new buffer because it has been deleted.
-        mDictPositionRelocationMap->mPtNodePositionRelocationMap.insert(
-                DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap::value_type(
-                        node->getHeadPos(), NOT_A_DICT_POS));
-        return true;
-    }
-    int writingPos = mBufferToWrite->getTailPosition();
-    mDictPositionRelocationMap->mPtNodePositionRelocationMap.insert(
-            DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap::value_type(
-                    node->getHeadPos(), writingPos));
-    mValidPtNodeCount++;
-    // Writes current PtNode.
-    return mWritingHelper->writePtNodeToBufferByCopyingPtNodeInfo(mBufferToWrite, node,
-            node->getParentPos(), nodeCodePoints, node->getCodePointCount(),
-            node->getProbability(), &writingPos);
-}
-
-bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateAllPositionFields
-        ::onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints) {
-    // Updates parent position.
-    int parentPos = node->getParentPos();
-    if (parentPos != NOT_A_DICT_POS) {
-        DynamicPatriciaTrieWritingHelper::PtNodePositionRelocationMap::const_iterator it =
-                mDictPositionRelocationMap->mPtNodePositionRelocationMap.find(parentPos);
-        if (it != mDictPositionRelocationMap->mPtNodePositionRelocationMap.end()) {
-            parentPos = it->second;
-        }
-    }
-    int writingPos = node->getHeadPos() + DynamicPatriciaTrieWritingUtils::NODE_FLAG_FIELD_SIZE;
-    // Write updated parent offset.
-    if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(mBufferToWrite,
-            parentPos, node->getHeadPos(), &writingPos)) {
-        return false;
-    }
-
-    // Updates children position.
-    int childrenPos = node->getChildrenPos();
-    if (childrenPos != NOT_A_DICT_POS) {
-        DynamicPatriciaTrieWritingHelper::PtNodeArrayPositionRelocationMap::const_iterator it =
-                mDictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.find(childrenPos);
-        if (it != mDictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.end()) {
-            childrenPos = it->second;
-        }
-    }
-    writingPos = node->getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBufferToWrite,
-            childrenPos, &writingPos)) {
-        return false;
-    }
-
-    // Updates bigram target PtNode positions in the bigram list.
-    int bigramsPos = node->getBigramsPos();
-    if (bigramsPos != NOT_A_DICT_POS) {
-        int bigramEntryCount;
-        if (!mBigramPolicy->updateAllBigramTargetPtNodePositions(&bigramsPos,
-                &mDictPositionRelocationMap->mPtNodePositionRelocationMap, &bigramEntryCount)) {
-            return false;
-        }
-        mBigramCount += bigramEntryCount;
-    }
-    if (node->isTerminal()) {
-        mUnigramCount++;
-    }
-
-    return true;
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
deleted file mode 100644
index 9755120..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
+++ /dev/null
@@ -1,197 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_GC_EVENT_LISTENERS_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_GC_EVENT_LISTENERS_H
-
-#include <vector>
-
-#include "defines.h"
-#include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h"
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-#include "utils/hash_map_compat.h"
-
-namespace latinime {
-
-class DictionaryHeaderStructurePolicy;
-
-class DynamicPatriciaTrieGcEventListeners {
- public:
-    // Updates all PtNodes that can be reached from the root. Checks if each PtNode is useless or
-    // not and marks useless PtNodes as deleted. Such deleted PtNodes will be discarded in the GC.
-    // TODO: Concatenate non-terminal PtNodes.
-    class TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
-        : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
-     public:
-        TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
-                const DictionaryHeaderStructurePolicy *const headerPolicy,
-                DynamicPatriciaTrieWritingHelper *const writingHelper,
-                BufferWithExtendableBuffer *const buffer, const bool isDecayingDict)
-                : mHeaderPolicy(headerPolicy), mWritingHelper(writingHelper), mBuffer(buffer),
-                  mIsDecayingDict(isDecayingDict), mValueStack(), mChildrenValue(0),
-                  mValidUnigramCount(0) {}
-
-        ~TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted() {};
-
-        bool onAscend() {
-            if (mValueStack.empty()) {
-                return false;
-            }
-            mChildrenValue = mValueStack.back();
-            mValueStack.pop_back();
-            return true;
-        }
-
-        bool onDescend(const int ptNodeArrayPos) {
-            mValueStack.push_back(0);
-            mChildrenValue = 0;
-            return true;
-        }
-
-        bool onReadingPtNodeArrayTail() { return true; }
-
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints);
-
-        int getValidUnigramCount() const {
-            return mValidUnigramCount;
-        }
-
-     private:
-        DISALLOW_IMPLICIT_CONSTRUCTORS(
-                TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted);
-
-        const DictionaryHeaderStructurePolicy *const mHeaderPolicy;
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
-        BufferWithExtendableBuffer *const mBuffer;
-        const bool mIsDecayingDict;
-        std::vector<int> mValueStack;
-        int mChildrenValue;
-        int mValidUnigramCount;
-    };
-
-    // Updates all bigram entries that are held by valid PtNodes. This removes useless bigram
-    // entries.
-    class TraversePolicyToUpdateBigramProbability
-            : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
-     public:
-        TraversePolicyToUpdateBigramProbability(
-                DynamicBigramListPolicy *const bigramPolicy)
-                : mBigramPolicy(bigramPolicy), mValidBigramEntryCount(0) {}
-
-        bool onAscend() { return true; }
-
-        bool onDescend(const int ptNodeArrayPos) { return true; }
-
-        bool onReadingPtNodeArrayTail() { return true; }
-
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints);
-
-        int getValidBigramEntryCount() const {
-            return mValidBigramEntryCount;
-        }
-
-     private:
-        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateBigramProbability);
-
-        DynamicBigramListPolicy *const mBigramPolicy;
-        int mValidBigramEntryCount;
-    };
-
-    class TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-            : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
-     public:
-        TraversePolicyToPlaceAndWriteValidPtNodesToBuffer(
-                DynamicPatriciaTrieWritingHelper *const writingHelper,
-                BufferWithExtendableBuffer *const bufferToWrite,
-                DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
-                        dictPositionRelocationMap)
-                : mWritingHelper(writingHelper), mBufferToWrite(bufferToWrite),
-                  mDictPositionRelocationMap(dictPositionRelocationMap), mValidPtNodeCount(0),
-                  mPtNodeArraySizeFieldPos(NOT_A_DICT_POS) {};
-
-        bool onAscend() { return true; }
-
-        bool onDescend(const int ptNodeArrayPos);
-
-        bool onReadingPtNodeArrayTail();
-
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints);
-
-     private:
-        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToPlaceAndWriteValidPtNodesToBuffer);
-
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
-        BufferWithExtendableBuffer *const mBufferToWrite;
-        DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
-                mDictPositionRelocationMap;
-        int mValidPtNodeCount;
-        int mPtNodeArraySizeFieldPos;
-    };
-
-    class TraversePolicyToUpdateAllPositionFields
-            : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
-     public:
-        TraversePolicyToUpdateAllPositionFields(
-                DynamicPatriciaTrieWritingHelper *const writingHelper,
-                DynamicBigramListPolicy *const bigramPolicy,
-                BufferWithExtendableBuffer *const bufferToWrite,
-                const DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
-                        dictPositionRelocationMap)
-                : mWritingHelper(writingHelper), mBigramPolicy(bigramPolicy),
-                  mBufferToWrite(bufferToWrite),
-                  mDictPositionRelocationMap(dictPositionRelocationMap), mUnigramCount(0),
-                  mBigramCount(0) {};
-
-        bool onAscend() { return true; }
-
-        bool onDescend(const int ptNodeArrayPos) { return true; }
-
-        bool onReadingPtNodeArrayTail() { return true; }
-
-        bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints);
-
-        int getUnigramCount() const {
-            return mUnigramCount;
-        }
-
-        int getBigramCount() const {
-            return mBigramCount;
-        }
-
-     private:
-        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateAllPositionFields);
-
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
-        DynamicBigramListPolicy *const mBigramPolicy;
-        BufferWithExtendableBuffer *const mBufferToWrite;
-        const DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
-                mDictPositionRelocationMap;
-        int mUnigramCount;
-        int mBigramCount;
-    };
-
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieGcEventListeners);
-};
-} // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_GC_EVENT_LISTENERS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.cpp
deleted file mode 100644
index 2fa3111..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.cpp
+++ /dev/null
@@ -1,124 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h"
-
-#include "suggest/core/policy/dictionary_bigrams_structure_policy.h"
-#include "suggest/core/policy/dictionary_shortcuts_structure_policy.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-
-namespace latinime {
-
-void DynamicPatriciaTrieNodeReader::fetchPtNodeInfoFromBufferAndProcessMovedPtNode(
-        const int ptNodePos, const int maxCodePointCount, int *const outCodePoints) {
-    if (ptNodePos < 0 || ptNodePos >= mBuffer->getTailPosition()) {
-        // Reading invalid position because of bug or broken dictionary.
-        AKLOGE("Fetching PtNode info from invalid dictionary position: %d, dictionary size: %d",
-                ptNodePos, mBuffer->getTailPosition());
-        ASSERT(false);
-        invalidatePtNodeInfo();
-        return;
-    }
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(ptNodePos);
-    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
-    int pos = ptNodePos;
-    mHeadPos = ptNodePos;
-    if (usesAdditionalBuffer) {
-        pos -= mBuffer->getOriginalBufferSize();
-    }
-    mFlags = PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
-    const int parentPosOffset =
-            DynamicPatriciaTrieReadingUtils::getParentPtNodePosOffsetAndAdvancePosition(dictBuf,
-                    &pos);
-    mParentPos = DynamicPatriciaTrieReadingUtils::getParentPtNodePos(parentPosOffset, mHeadPos);
-    if (outCodePoints != 0) {
-        mCodePointCount = PatriciaTrieReadingUtils::getCharsAndAdvancePosition(
-                dictBuf, mFlags, maxCodePointCount, outCodePoints, &pos);
-    } else {
-        mCodePointCount = PatriciaTrieReadingUtils::skipCharacters(
-                dictBuf, mFlags, MAX_WORD_LENGTH, &pos);
-    }
-    if (isTerminal()) {
-        mProbabilityFieldPos = pos;
-        if (usesAdditionalBuffer) {
-            mProbabilityFieldPos += mBuffer->getOriginalBufferSize();
-        }
-        mProbability = PatriciaTrieReadingUtils::readProbabilityAndAdvancePosition(dictBuf, &pos);
-    } else {
-        mProbabilityFieldPos = NOT_A_DICT_POS;
-        mProbability = NOT_A_PROBABILITY;
-    }
-    mChildrenPosFieldPos = pos;
-    if (usesAdditionalBuffer) {
-        mChildrenPosFieldPos += mBuffer->getOriginalBufferSize();
-    }
-    mChildrenPos = DynamicPatriciaTrieReadingUtils::readChildrenPositionAndAdvancePosition(
-            dictBuf, &pos);
-    if (usesAdditionalBuffer && mChildrenPos != NOT_A_DICT_POS) {
-        mChildrenPos += mBuffer->getOriginalBufferSize();
-    }
-    if (mSiblingPos == NOT_A_DICT_POS) {
-        if (DynamicPatriciaTrieReadingUtils::isMoved(mFlags)) {
-            mBigramLinkedNodePos = mChildrenPos;
-        } else {
-            mBigramLinkedNodePos = NOT_A_DICT_POS;
-        }
-    }
-    if (usesAdditionalBuffer) {
-        pos += mBuffer->getOriginalBufferSize();
-    }
-    if (PatriciaTrieReadingUtils::hasShortcutTargets(mFlags)) {
-        mShortcutPos = pos;
-        mShortcutsPolicy->skipAllShortcuts(&pos);
-    } else {
-        mShortcutPos = NOT_A_DICT_POS;
-    }
-    if (PatriciaTrieReadingUtils::hasBigrams(mFlags)) {
-        mBigramPos = pos;
-        mBigramsPolicy->skipAllBigrams(&pos);
-    } else {
-        mBigramPos = NOT_A_DICT_POS;
-    }
-    // Update siblingPos if needed.
-    if (mSiblingPos == NOT_A_DICT_POS) {
-        // Sibling position is the tail position of current node.
-        mSiblingPos = pos;
-    }
-    // Read destination node if the read node is a moved node.
-    if (DynamicPatriciaTrieReadingUtils::isMoved(mFlags)) {
-        // The destination position is stored at the same place as the parent position.
-        fetchPtNodeInfoFromBufferAndProcessMovedPtNode(mParentPos, maxCodePointCount,
-                outCodePoints);
-    }
-}
-
-void DynamicPatriciaTrieNodeReader::invalidatePtNodeInfo() {
-    mHeadPos = NOT_A_DICT_POS;
-    mFlags = 0;
-    mParentPos = NOT_A_DICT_POS;
-    mCodePointCount = 0;
-    mProbabilityFieldPos = NOT_A_DICT_POS;
-    mProbability = NOT_A_PROBABILITY;
-    mChildrenPosFieldPos = NOT_A_DICT_POS;
-    mChildrenPos = NOT_A_DICT_POS;
-    mBigramLinkedNodePos = NOT_A_DICT_POS;
-    mShortcutPos = NOT_A_DICT_POS;
-    mBigramPos = NOT_A_DICT_POS;
-    mSiblingPos = NOT_A_DICT_POS;
-}
-
-}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h
deleted file mode 100644
index 3b36d42..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h
+++ /dev/null
@@ -1,163 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_NODE_READER_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_NODE_READER_H
-
-#include <stdint.h>
-
-#include "defines.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
-
-namespace latinime {
-
-class BufferWithExtendableBuffer;
-class DictionaryBigramsStructurePolicy;
-class DictionaryShortcutsStructurePolicy;
-
-/*
- * This class is used for helping to read nodes of dynamic patricia trie. This class handles moved
- * node and reads node attributes.
- */
-class DynamicPatriciaTrieNodeReader {
- public:
-    DynamicPatriciaTrieNodeReader(const BufferWithExtendableBuffer *const buffer,
-            const DictionaryBigramsStructurePolicy *const bigramsPolicy,
-            const DictionaryShortcutsStructurePolicy *const shortcutsPolicy)
-            : mBuffer(buffer), mBigramsPolicy(bigramsPolicy),
-              mShortcutsPolicy(shortcutsPolicy), mHeadPos(NOT_A_DICT_POS), mFlags(0),
-              mParentPos(NOT_A_DICT_POS), mCodePointCount(0), mProbabilityFieldPos(NOT_A_DICT_POS),
-              mProbability(NOT_A_PROBABILITY), mChildrenPosFieldPos(NOT_A_DICT_POS),
-              mChildrenPos(NOT_A_DICT_POS), mBigramLinkedNodePos(NOT_A_DICT_POS),
-              mShortcutPos(NOT_A_DICT_POS),  mBigramPos(NOT_A_DICT_POS),
-              mSiblingPos(NOT_A_DICT_POS) {}
-
-    ~DynamicPatriciaTrieNodeReader() {}
-
-    // Reads PtNode information from dictionary buffer and updates members with the information.
-    AK_FORCE_INLINE void fetchNodeInfoInBufferFromPtNodePos(const int ptNodePos) {
-        fetchNodeInfoInBufferFromPtNodePosAndGetNodeCodePoints(ptNodePos ,
-                0 /* maxCodePointCount */, 0 /* outCodePoints */);
-    }
-
-    AK_FORCE_INLINE void fetchNodeInfoInBufferFromPtNodePosAndGetNodeCodePoints(
-            const int ptNodePos, const int maxCodePointCount, int *const outCodePoints) {
-        mSiblingPos = NOT_A_DICT_POS;
-        mBigramLinkedNodePos = NOT_A_DICT_POS;
-        fetchPtNodeInfoFromBufferAndProcessMovedPtNode(ptNodePos, maxCodePointCount, outCodePoints);
-    }
-
-    // HeadPos is different from NodePos when the current PtNode is a moved PtNode.
-    AK_FORCE_INLINE int getHeadPos() const {
-        return mHeadPos;
-    }
-
-    // Flags
-    AK_FORCE_INLINE bool isDeleted() const {
-        return DynamicPatriciaTrieReadingUtils::isDeleted(mFlags);
-    }
-
-    AK_FORCE_INLINE bool hasChildren() const {
-        return mChildrenPos != NOT_A_DICT_POS;
-    }
-
-    AK_FORCE_INLINE bool isTerminal() const {
-        return PatriciaTrieReadingUtils::isTerminal(mFlags);
-    }
-
-    AK_FORCE_INLINE bool isBlacklisted() const {
-        return PatriciaTrieReadingUtils::isBlacklisted(mFlags);
-    }
-
-    AK_FORCE_INLINE bool isNotAWord() const {
-        return PatriciaTrieReadingUtils::isNotAWord(mFlags);
-    }
-
-    // Parent node position
-    AK_FORCE_INLINE int getParentPos() const {
-        return mParentPos;
-    }
-
-    // Number of code points
-    AK_FORCE_INLINE uint8_t getCodePointCount() const {
-        return mCodePointCount;
-    }
-
-    // Probability
-    AK_FORCE_INLINE int getProbabilityFieldPos() const {
-        return mProbabilityFieldPos;
-    }
-
-    AK_FORCE_INLINE int getProbability() const {
-        return mProbability;
-    }
-
-    // Children PtNode array position
-    AK_FORCE_INLINE int getChildrenPosFieldPos() const {
-        return mChildrenPosFieldPos;
-    }
-
-    AK_FORCE_INLINE int getChildrenPos() const {
-        return mChildrenPos;
-    }
-
-    // Bigram linked node position.
-    AK_FORCE_INLINE int getBigramLinkedNodePos() const {
-        return mBigramLinkedNodePos;
-    }
-
-    // Shortcutlist position
-    AK_FORCE_INLINE int getShortcutPos() const {
-        return mShortcutPos;
-    }
-
-    // Bigrams position
-    AK_FORCE_INLINE int getBigramsPos() const {
-        return mBigramPos;
-    }
-
-    // Sibling node position
-    AK_FORCE_INLINE int getSiblingNodePos() const {
-        return mSiblingPos;
-    }
-
- private:
-    DISALLOW_COPY_AND_ASSIGN(DynamicPatriciaTrieNodeReader);
-
-    const BufferWithExtendableBuffer *const mBuffer;
-    const DictionaryBigramsStructurePolicy *const mBigramsPolicy;
-    const DictionaryShortcutsStructurePolicy *const mShortcutsPolicy;
-    int mHeadPos;
-    DynamicPatriciaTrieReadingUtils::NodeFlags mFlags;
-    int mParentPos;
-    uint8_t mCodePointCount;
-    int mProbabilityFieldPos;
-    int mProbability;
-    int mChildrenPosFieldPos;
-    int mChildrenPos;
-    int mBigramLinkedNodePos;
-    int mShortcutPos;
-    int mBigramPos;
-    int mSiblingPos;
-
-    void fetchPtNodeInfoFromBufferAndProcessMovedPtNode(const int ptNodePos,
-            const int maxCodePointCount, int *const outCodePoints);
-
-    void invalidatePtNodeInfo();
-};
-} // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_NODE_READER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
deleted file mode 100644
index 495b146..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
+++ /dev/null
@@ -1,380 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h"
-
-#include <cstdio>
-#include <cstring>
-#include <ctime>
-
-#include "defines.h"
-#include "suggest/core/dicnode/dic_node.h"
-#include "suggest/core/dicnode/dic_node_vector.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
-#include "suggest/policyimpl/dictionary/utils/probability_utils.h"
-
-namespace latinime {
-
-// Note that these are corresponding definitions in Java side in BinaryDictionaryTests and
-// BinaryDictionaryDecayingTests.
-const char *const DynamicPatriciaTriePolicy::UNIGRAM_COUNT_QUERY = "UNIGRAM_COUNT";
-const char *const DynamicPatriciaTriePolicy::BIGRAM_COUNT_QUERY = "BIGRAM_COUNT";
-const char *const DynamicPatriciaTriePolicy::MAX_UNIGRAM_COUNT_QUERY = "MAX_UNIGRAM_COUNT";
-const char *const DynamicPatriciaTriePolicy::MAX_BIGRAM_COUNT_QUERY = "MAX_BIGRAM_COUNT";
-const char *const DynamicPatriciaTriePolicy::SET_NEEDS_TO_DECAY_FOR_TESTING_QUERY =
-        "SET_NEEDS_TO_DECAY_FOR_TESTING";
-const int DynamicPatriciaTriePolicy::MAX_DICT_EXTENDED_REGION_SIZE = 1024 * 1024;
-const int DynamicPatriciaTriePolicy::MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS =
-        DynamicPatriciaTrieWritingHelper::MAX_DICTIONARY_SIZE - 1024;
-
-void DynamicPatriciaTriePolicy::createAndGetAllChildNodes(const DicNode *const dicNode,
-        DicNodeVector *const childDicNodes) const {
-    if (!dicNode->hasChildren()) {
-        return;
-    }
-    DynamicPatriciaTrieReadingHelper readingHelper(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    readingHelper.initWithPtNodeArrayPos(dicNode->getChildrenPos());
-    const DynamicPatriciaTrieNodeReader *const nodeReader = readingHelper.getNodeReader();
-    while (!readingHelper.isEnd()) {
-        bool isTerminal = nodeReader->isTerminal() && !nodeReader->isDeleted();
-        if (isTerminal && mHeaderPolicy.isDecayingDict()) {
-            // A DecayingDict may have a terminal PtNode that has a terminal DicNode whose
-            // probability is NOT_A_PROBABILITY. In such case, we don't want to treat it as a
-            // valid terminal DicNode.
-            isTerminal = getProbability(nodeReader->getProbability(), NOT_A_PROBABILITY)
-                    != NOT_A_PROBABILITY;
-        }
-        childDicNodes->pushLeavingChild(dicNode, nodeReader->getHeadPos(),
-                nodeReader->getChildrenPos(), nodeReader->getProbability(), isTerminal,
-                nodeReader->hasChildren(), nodeReader->isBlacklisted() || nodeReader->isNotAWord(),
-                nodeReader->getCodePointCount(), readingHelper.getMergedNodeCodePoints());
-        readingHelper.readNextSiblingNode();
-    }
-}
-
-int DynamicPatriciaTriePolicy::getCodePointsAndProbabilityAndReturnCodePointCount(
-        const int ptNodePos, const int maxCodePointCount, int *const outCodePoints,
-        int *const outUnigramProbability) const {
-    // This method traverses parent nodes from the terminal by following parent pointers; thus,
-    // node code points are stored in the buffer in the reverse order.
-    int reverseCodePoints[maxCodePointCount];
-    DynamicPatriciaTrieReadingHelper readingHelper(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    // First, read the terminal node and get its probability.
-    readingHelper.initWithPtNodePos(ptNodePos);
-    if (!readingHelper.isValidTerminalNode()) {
-        // Node at the ptNodePos is not a valid terminal node.
-        *outUnigramProbability = NOT_A_PROBABILITY;
-        return 0;
-    }
-    // Store terminal node probability.
-    *outUnigramProbability = readingHelper.getNodeReader()->getProbability();
-    // Then, following parent node link to the dictionary root and fetch node code points.
-    while (!readingHelper.isEnd()) {
-        if (readingHelper.getTotalCodePointCount() > maxCodePointCount) {
-            // The ptNodePos is not a valid terminal node position in the dictionary.
-            *outUnigramProbability = NOT_A_PROBABILITY;
-            return 0;
-        }
-        // Store node code points to buffer in the reverse order.
-        readingHelper.fetchMergedNodeCodePointsInReverseOrder(
-                readingHelper.getPrevTotalCodePointCount(), reverseCodePoints);
-        // Follow parent node toward the root node.
-        readingHelper.readParentNode();
-    }
-    if (readingHelper.isError()) {
-        // The node position or the dictionary is invalid.
-        *outUnigramProbability = NOT_A_PROBABILITY;
-        return 0;
-    }
-    // Reverse the stored code points to output them.
-    const int codePointCount = readingHelper.getTotalCodePointCount();
-    for (int i = 0; i < codePointCount; ++i) {
-        outCodePoints[i] = reverseCodePoints[codePointCount - i - 1];
-    }
-    return codePointCount;
-}
-
-int DynamicPatriciaTriePolicy::getTerminalNodePositionOfWord(const int *const inWord,
-        const int length, const bool forceLowerCaseSearch) const {
-    int searchCodePoints[length];
-    for (int i = 0; i < length; ++i) {
-        searchCodePoints[i] = forceLowerCaseSearch ? CharUtils::toLowerCase(inWord[i]) : inWord[i];
-    }
-    DynamicPatriciaTrieReadingHelper readingHelper(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    readingHelper.initWithPtNodeArrayPos(getRootPosition());
-    const DynamicPatriciaTrieNodeReader *const nodeReader = readingHelper.getNodeReader();
-    while (!readingHelper.isEnd()) {
-        const int matchedCodePointCount = readingHelper.getPrevTotalCodePointCount();
-        if (readingHelper.getTotalCodePointCount() > length
-                || !readingHelper.isMatchedCodePoint(0 /* index */,
-                        searchCodePoints[matchedCodePointCount])) {
-            // Current node has too many code points or its first code point is different from
-            // target code point. Skip this node and read the next sibling node.
-            readingHelper.readNextSiblingNode();
-            continue;
-        }
-        // Check following merged node code points.
-        const int nodeCodePointCount = nodeReader->getCodePointCount();
-        for (int j = 1; j < nodeCodePointCount; ++j) {
-            if (!readingHelper.isMatchedCodePoint(
-                    j, searchCodePoints[matchedCodePointCount + j])) {
-                // Different code point is found. The given word is not included in the dictionary.
-                return NOT_A_DICT_POS;
-            }
-        }
-        // All characters are matched.
-        if (length == readingHelper.getTotalCodePointCount()) {
-            // Terminal position is found.
-            return nodeReader->getHeadPos();
-        }
-        if (!nodeReader->hasChildren()) {
-            return NOT_A_DICT_POS;
-        }
-        // Advance to the children nodes.
-        readingHelper.readChildNode();
-    }
-    // If we already traversed the tree further than the word is long, there means
-    // there was no match (or we would have found it).
-    return NOT_A_DICT_POS;
-}
-
-int DynamicPatriciaTriePolicy::getProbability(const int unigramProbability,
-        const int bigramProbability) const {
-    if (mHeaderPolicy.isDecayingDict()) {
-        return ForgettingCurveUtils::getProbability(unigramProbability, bigramProbability);
-    } else {
-        if (unigramProbability == NOT_A_PROBABILITY) {
-            return NOT_A_PROBABILITY;
-        } else if (bigramProbability == NOT_A_PROBABILITY) {
-            return ProbabilityUtils::backoff(unigramProbability);
-        } else {
-            return ProbabilityUtils::computeProbabilityForBigram(unigramProbability,
-                    bigramProbability);
-        }
-    }
-}
-
-int DynamicPatriciaTriePolicy::getUnigramProbabilityOfPtNode(const int ptNodePos) const {
-    if (ptNodePos == NOT_A_DICT_POS) {
-        return NOT_A_PROBABILITY;
-    }
-    DynamicPatriciaTrieNodeReader nodeReader(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos);
-    if (nodeReader.isDeleted() || nodeReader.isBlacklisted() || nodeReader.isNotAWord()) {
-        return NOT_A_PROBABILITY;
-    }
-    return getProbability(nodeReader.getProbability(), NOT_A_PROBABILITY);
-}
-
-int DynamicPatriciaTriePolicy::getShortcutPositionOfPtNode(const int ptNodePos) const {
-    if (ptNodePos == NOT_A_DICT_POS) {
-        return NOT_A_DICT_POS;
-    }
-    DynamicPatriciaTrieNodeReader nodeReader(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos);
-    if (nodeReader.isDeleted()) {
-        return NOT_A_DICT_POS;
-    }
-    return nodeReader.getShortcutPos();
-}
-
-int DynamicPatriciaTriePolicy::getBigramsPositionOfPtNode(const int ptNodePos) const {
-    if (ptNodePos == NOT_A_DICT_POS) {
-        return NOT_A_DICT_POS;
-    }
-    DynamicPatriciaTrieNodeReader nodeReader(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos);
-    if (nodeReader.isDeleted()) {
-        return NOT_A_DICT_POS;
-    }
-    return nodeReader.getBigramsPos();
-}
-
-bool DynamicPatriciaTriePolicy::addUnigramWord(const int *const word, const int length,
-        const int probability) {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: addUnigramWord() is called for non-updatable dictionary.");
-        return false;
-    }
-    if (mBufferWithExtendableBuffer.getTailPosition()
-            >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
-        AKLOGE("The dictionary is too large to dynamically update.");
-        return false;
-    }
-    DynamicPatriciaTrieReadingHelper readingHelper(&mBufferWithExtendableBuffer,
-            getBigramsStructurePolicy(), getShortcutsStructurePolicy());
-    readingHelper.initWithPtNodeArrayPos(getRootPosition());
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, mHeaderPolicy.isDecayingDict());
-    bool addedNewUnigram = false;
-    if (writingHelper.addUnigramWord(&readingHelper, word, length, probability,
-            &addedNewUnigram)) {
-        if (addedNewUnigram) {
-            mUnigramCount++;
-        }
-        return true;
-    } else {
-        return false;
-    }
-}
-
-bool DynamicPatriciaTriePolicy::addBigramWords(const int *const word0, const int length0,
-        const int *const word1, const int length1, const int probability) {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: addBigramWords() is called for non-updatable dictionary.");
-        return false;
-    }
-    if (mBufferWithExtendableBuffer.getTailPosition()
-            >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
-        AKLOGE("The dictionary is too large to dynamically update.");
-        return false;
-    }
-    const int word0Pos = getTerminalNodePositionOfWord(word0, length0,
-            false /* forceLowerCaseSearch */);
-    if (word0Pos == NOT_A_DICT_POS) {
-        return false;
-    }
-    const int word1Pos = getTerminalNodePositionOfWord(word1, length1,
-            false /* forceLowerCaseSearch */);
-    if (word1Pos == NOT_A_DICT_POS) {
-        return false;
-    }
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, mHeaderPolicy.isDecayingDict());
-    bool addedNewBigram = false;
-    if (writingHelper.addBigramWords(word0Pos, word1Pos, probability, &addedNewBigram)) {
-        if (addedNewBigram) {
-            mBigramCount++;
-        }
-        return true;
-    } else {
-        return false;
-    }
-}
-
-bool DynamicPatriciaTriePolicy::removeBigramWords(const int *const word0, const int length0,
-        const int *const word1, const int length1) {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: removeBigramWords() is called for non-updatable dictionary.");
-        return false;
-    }
-    if (mBufferWithExtendableBuffer.getTailPosition()
-            >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
-        AKLOGE("The dictionary is too large to dynamically update.");
-        return false;
-    }
-    const int word0Pos = getTerminalNodePositionOfWord(word0, length0,
-            false /* forceLowerCaseSearch */);
-    if (word0Pos == NOT_A_DICT_POS) {
-        return false;
-    }
-    const int word1Pos = getTerminalNodePositionOfWord(word1, length1,
-            false /* forceLowerCaseSearch */);
-    if (word1Pos == NOT_A_DICT_POS) {
-        return false;
-    }
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, mHeaderPolicy.isDecayingDict());
-    if (writingHelper.removeBigramWords(word0Pos, word1Pos)) {
-        mBigramCount--;
-        return true;
-    } else {
-        return false;
-    }
-}
-
-void DynamicPatriciaTriePolicy::flush(const char *const filePath) {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: flush() is called for non-updatable dictionary.");
-        return;
-    }
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, false /* needsToDecay */);
-    writingHelper.writeToDictFile(filePath, &mHeaderPolicy, mUnigramCount, mBigramCount);
-}
-
-void DynamicPatriciaTriePolicy::flushWithGC(const char *const filePath) {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: flushWithGC() is called for non-updatable dictionary.");
-        return;
-    }
-    const bool needsToDecay = mHeaderPolicy.isDecayingDict()
-            && (mNeedsToDecayForTesting || ForgettingCurveUtils::needsToDecay(
-                    false /* mindsBlockByDecay */, mUnigramCount, mBigramCount, &mHeaderPolicy));
-    DynamicBigramListPolicy bigramListPolicyForGC(&mHeaderPolicy, &mBufferWithExtendableBuffer,
-            &mShortcutListPolicy, needsToDecay);
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &bigramListPolicyForGC, &mShortcutListPolicy, needsToDecay);
-    writingHelper.writeToDictFileWithGC(getRootPosition(), filePath, &mHeaderPolicy);
-    mNeedsToDecayForTesting = false;
-}
-
-bool DynamicPatriciaTriePolicy::needsToRunGC(const bool mindsBlockByGC) const {
-    if (!mBuffer->isUpdatable()) {
-        AKLOGI("Warning: needsToRunGC() is called for non-updatable dictionary.");
-        return false;
-    }
-    if (mBufferWithExtendableBuffer.isNearSizeLimit()) {
-        // Additional buffer size is near the limit.
-        return true;
-    } else if (mHeaderPolicy.getExtendedRegionSize()
-            + mBufferWithExtendableBuffer.getUsedAdditionalBufferSize()
-                    > MAX_DICT_EXTENDED_REGION_SIZE) {
-        // Total extended region size exceeds the limit.
-        return true;
-    } else if (mBufferWithExtendableBuffer.getTailPosition()
-            >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS
-                    && mBufferWithExtendableBuffer.getUsedAdditionalBufferSize() > 0) {
-        // Needs to reduce dictionary size.
-        return true;
-    } else if (mHeaderPolicy.isDecayingDict()) {
-        return mNeedsToDecayForTesting || ForgettingCurveUtils::needsToDecay(
-                mindsBlockByGC, mUnigramCount, mBigramCount, &mHeaderPolicy);
-    }
-    return false;
-}
-
-void DynamicPatriciaTriePolicy::getProperty(const char *const query, char *const outResult,
-        const int maxResultLength) {
-    if (strncmp(query, UNIGRAM_COUNT_QUERY, maxResultLength) == 0) {
-        snprintf(outResult, maxResultLength, "%d", mUnigramCount);
-    } else if (strncmp(query, BIGRAM_COUNT_QUERY, maxResultLength) == 0) {
-        snprintf(outResult, maxResultLength, "%d", mBigramCount);
-    } else if (strncmp(query, MAX_UNIGRAM_COUNT_QUERY, maxResultLength) == 0) {
-        snprintf(outResult, maxResultLength, "%d",
-                mHeaderPolicy.isDecayingDict() ? ForgettingCurveUtils::MAX_UNIGRAM_COUNT :
-                        static_cast<int>(DynamicPatriciaTrieWritingHelper::MAX_DICTIONARY_SIZE));
-    } else if (strncmp(query, MAX_BIGRAM_COUNT_QUERY, maxResultLength) == 0) {
-        snprintf(outResult, maxResultLength, "%d",
-                mHeaderPolicy.isDecayingDict() ? ForgettingCurveUtils::MAX_BIGRAM_COUNT :
-                        static_cast<int>(DynamicPatriciaTrieWritingHelper::MAX_DICTIONARY_SIZE));
-    } else if (strncmp(query, SET_NEEDS_TO_DECAY_FOR_TESTING_QUERY, maxResultLength) == 0) {
-        mNeedsToDecayForTesting = true;
-    }
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
deleted file mode 100644
index be97ee1..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
+++ /dev/null
@@ -1,121 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_POLICY_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_POLICY_H
-
-#include "defines.h"
-#include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
-#include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
-#include "suggest/policyimpl/dictionary/header/header_policy.h"
-#include "suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h"
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
-
-namespace latinime {
-
-class DicNode;
-class DicNodeVector;
-
-class DynamicPatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
- public:
-    DynamicPatriciaTriePolicy(const MmappedBuffer *const buffer)
-            : mBuffer(buffer), mHeaderPolicy(mBuffer->getBuffer(), buffer->getBufferSize()),
-              mBufferWithExtendableBuffer(mBuffer->getBuffer() + mHeaderPolicy.getSize(),
-                      mBuffer->getBufferSize() - mHeaderPolicy.getSize()),
-              mShortcutListPolicy(&mBufferWithExtendableBuffer),
-              mBigramListPolicy(&mHeaderPolicy, &mBufferWithExtendableBuffer, &mShortcutListPolicy,
-                      mHeaderPolicy.isDecayingDict()),
-              mUnigramCount(mHeaderPolicy.getUnigramCount()),
-              mBigramCount(mHeaderPolicy.getBigramCount()), mNeedsToDecayForTesting(false) {}
-
-    ~DynamicPatriciaTriePolicy() {
-        delete mBuffer;
-    }
-
-    AK_FORCE_INLINE int getRootPosition() const {
-        return 0;
-    }
-
-    void createAndGetAllChildNodes(const DicNode *const dicNode,
-            DicNodeVector *const childDicNodes) const;
-
-    int getCodePointsAndProbabilityAndReturnCodePointCount(
-            const int terminalPtNodePos, const int maxCodePointCount, int *const outCodePoints,
-            int *const outUnigramProbability) const;
-
-    int getTerminalNodePositionOfWord(const int *const inWord,
-            const int length, const bool forceLowerCaseSearch) const;
-
-    int getProbability(const int unigramProbability, const int bigramProbability) const;
-
-    int getUnigramProbabilityOfPtNode(const int ptNodePos) const;
-
-    int getShortcutPositionOfPtNode(const int ptNodePos) const;
-
-    int getBigramsPositionOfPtNode(const int ptNodePos) const;
-
-    const DictionaryHeaderStructurePolicy *getHeaderStructurePolicy() const {
-        return &mHeaderPolicy;
-    }
-
-    const DictionaryBigramsStructurePolicy *getBigramsStructurePolicy() const {
-        return &mBigramListPolicy;
-    }
-
-    const DictionaryShortcutsStructurePolicy *getShortcutsStructurePolicy() const {
-        return &mShortcutListPolicy;
-    }
-
-    bool addUnigramWord(const int *const word, const int length, const int probability);
-
-    bool addBigramWords(const int *const word0, const int length0, const int *const word1,
-            const int length1, const int probability);
-
-    bool removeBigramWords(const int *const word0, const int length0, const int *const word1,
-            const int length1);
-
-    void flush(const char *const filePath);
-
-    void flushWithGC(const char *const filePath);
-
-    bool needsToRunGC(const bool mindsBlockByGC) const;
-
-    void getProperty(const char *const query, char *const outResult,
-            const int maxResultLength);
-
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTriePolicy);
-
-    static const char *const UNIGRAM_COUNT_QUERY;
-    static const char *const BIGRAM_COUNT_QUERY;
-    static const char *const MAX_UNIGRAM_COUNT_QUERY;
-    static const char *const MAX_BIGRAM_COUNT_QUERY;
-    static const char *const SET_NEEDS_TO_DECAY_FOR_TESTING_QUERY;
-    static const int MAX_DICT_EXTENDED_REGION_SIZE;
-    static const int MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS;
-
-    const MmappedBuffer *const mBuffer;
-    const HeaderPolicy mHeaderPolicy;
-    BufferWithExtendableBuffer mBufferWithExtendableBuffer;
-    DynamicShortcutListPolicy mShortcutListPolicy;
-    DynamicBigramListPolicy mBigramListPolicy;
-    int mUnigramCount;
-    int mBigramCount;
-    int mNeedsToDecayForTesting;
-};
-} // namespace latinime
-#endif // LATINIME_DYNAMIC_PATRICIA_TRIE_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp
deleted file mode 100644
index f108c21..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.cpp
+++ /dev/null
@@ -1,239 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h"
-
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-
-namespace latinime {
-
-// To avoid infinite loop caused by invalid or malicious forward links.
-const int DynamicPatriciaTrieReadingHelper::MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP = 100000;
-const int DynamicPatriciaTrieReadingHelper::MAX_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP = 100000;
-const size_t DynamicPatriciaTrieReadingHelper::MAX_READING_STATE_STACK_SIZE = MAX_WORD_LENGTH;
-
-// Visits all PtNodes in post-order depth first manner.
-// For example, visits c -> b -> y -> x -> a for the following dictionary:
-// a _ b _ c
-//   \ x _ y
-bool DynamicPatriciaTrieReadingHelper::traverseAllPtNodesInPostorderDepthFirstManner(
-        TraversingEventListener *const listener) {
-    bool alreadyVisitedChildren = false;
-    // Descend from the root to the root PtNode array.
-    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
-        return false;
-    }
-    while (!isEnd()) {
-        if (!alreadyVisitedChildren) {
-            if (mNodeReader.hasChildren()) {
-                // Move to the first child.
-                if (!listener->onDescend(mNodeReader.getChildrenPos())) {
-                    return false;
-                }
-                pushReadingStateToStack();
-                readChildNode();
-            } else {
-                alreadyVisitedChildren = true;
-            }
-        } else {
-            if (!listener->onVisitingPtNode(&mNodeReader, mMergedNodeCodePoints)) {
-                return false;
-            }
-            readNextSiblingNode();
-            if (isEnd()) {
-                // All PtNodes in current linked PtNode arrays have been visited.
-                // Return to the parent.
-                if (!listener->onReadingPtNodeArrayTail()) {
-                    return false;
-                }
-                if (mReadingStateStack.size() <= 0) {
-                    break;
-                }
-                if (!listener->onAscend()) {
-                    return false;
-                }
-                popReadingStateFromStack();
-                alreadyVisitedChildren = true;
-            } else {
-                // Process sibling PtNode.
-                alreadyVisitedChildren = false;
-            }
-        }
-    }
-    // Ascend from the root PtNode array to the root.
-    if (!listener->onAscend()) {
-        return false;
-    }
-    return !isError();
-}
-
-// Visits all PtNodes in PtNode array level pre-order depth first manner, which is the same order
-// that PtNodes are written in the dictionary buffer.
-// For example, visits a -> b -> x -> c -> y for the following dictionary:
-// a _ b _ c
-//   \ x _ y
-bool DynamicPatriciaTrieReadingHelper::traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
-        TraversingEventListener *const listener) {
-    bool alreadyVisitedAllPtNodesInArray = false;
-    bool alreadyVisitedChildren = false;
-    // Descend from the root to the root PtNode array.
-    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
-        return false;
-    }
-    if (isEnd()) {
-        // Empty dictionary. Needs to notify the listener of the tail of empty PtNode array.
-        if (!listener->onReadingPtNodeArrayTail()) {
-            return false;
-        }
-    }
-    pushReadingStateToStack();
-    while (!isEnd()) {
-        if (alreadyVisitedAllPtNodesInArray) {
-            if (alreadyVisitedChildren) {
-                // Move to next sibling PtNode's children.
-                readNextSiblingNode();
-                if (isEnd()) {
-                    // Return to the parent PTNode.
-                    if (!listener->onAscend()) {
-                        return false;
-                    }
-                    if (mReadingStateStack.size() <= 0) {
-                        break;
-                    }
-                    popReadingStateFromStack();
-                    alreadyVisitedChildren = true;
-                    alreadyVisitedAllPtNodesInArray = true;
-                } else {
-                    alreadyVisitedChildren = false;
-                }
-            } else {
-                if (mNodeReader.hasChildren()) {
-                    // Move to the first child.
-                    if (!listener->onDescend(mNodeReader.getChildrenPos())) {
-                        return false;
-                    }
-                    pushReadingStateToStack();
-                    readChildNode();
-                    // Push state to return the head of PtNode array.
-                    pushReadingStateToStack();
-                    alreadyVisitedAllPtNodesInArray = false;
-                    alreadyVisitedChildren = false;
-                } else {
-                    alreadyVisitedChildren = true;
-                }
-            }
-        } else {
-            if (!listener->onVisitingPtNode(&mNodeReader, mMergedNodeCodePoints)) {
-                return false;
-            }
-            readNextSiblingNode();
-            if (isEnd()) {
-                if (!listener->onReadingPtNodeArrayTail()) {
-                    return false;
-                }
-                // Return to the head of current PtNode array.
-                popReadingStateFromStack();
-                alreadyVisitedAllPtNodesInArray = true;
-            }
-        }
-    }
-    popReadingStateFromStack();
-    // Ascend from the root PtNode array to the root.
-    if (!listener->onAscend()) {
-        return false;
-    }
-    return !isError();
-}
-
-// Read node array size and process empty node arrays. Nodes and arrays are counted up in this
-// method to avoid an infinite loop.
-void DynamicPatriciaTrieReadingHelper::nextPtNodeArray() {
-    if (mReadingState.mPos < 0 || mReadingState.mPos >= mBuffer->getTailPosition()) {
-        // Reading invalid position because of a bug or a broken dictionary.
-        AKLOGE("Reading PtNode array info from invalid dictionary position: %d, dict size: %d",
-                mReadingState.mPos, mBuffer->getTailPosition());
-        ASSERT(false);
-        mIsError = true;
-        mReadingState.mPos = NOT_A_DICT_POS;
-        return;
-    }
-    mReadingState.mPosOfLastPtNodeArrayHead = mReadingState.mPos;
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(mReadingState.mPos);
-    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        mReadingState.mPos -= mBuffer->getOriginalBufferSize();
-    }
-    mReadingState.mNodeCount = PatriciaTrieReadingUtils::getPtNodeArraySizeAndAdvancePosition(
-            dictBuf, &mReadingState.mPos);
-    if (usesAdditionalBuffer) {
-        mReadingState.mPos += mBuffer->getOriginalBufferSize();
-    }
-    // Count up nodes and node arrays to avoid infinite loop.
-    mReadingState.mTotalNodeCount += mReadingState.mNodeCount;
-    mReadingState.mNodeArrayCount++;
-    if (mReadingState.mNodeCount < 0
-            || mReadingState.mTotalNodeCount > MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP
-            || mReadingState.mNodeArrayCount > MAX_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP) {
-        // Invalid dictionary.
-        AKLOGI("Invalid dictionary. nodeCount: %d, totalNodeCount: %d, MAX_CHILD_COUNT: %d"
-                "nodeArrayCount: %d, MAX_NODE_ARRAY_COUNT: %d",
-                mReadingState.mNodeCount, mReadingState.mTotalNodeCount,
-                MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP, mReadingState.mNodeArrayCount,
-                MAX_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP);
-        ASSERT(false);
-        mIsError = true;
-        mReadingState.mPos = NOT_A_DICT_POS;
-        return;
-    }
-    if (mReadingState.mNodeCount == 0) {
-        // Empty node array. Try following forward link.
-        followForwardLink();
-    }
-}
-
-// Follow the forward link and read the next node array if exists.
-void DynamicPatriciaTrieReadingHelper::followForwardLink() {
-    if (mReadingState.mPos < 0 || mReadingState.mPos >= mBuffer->getTailPosition()) {
-        // Reading invalid position because of bug or broken dictionary.
-        AKLOGE("Reading forward link from invalid dictionary position: %d, dict size: %d",
-                mReadingState.mPos, mBuffer->getTailPosition());
-        ASSERT(false);
-        mIsError = true;
-        mReadingState.mPos = NOT_A_DICT_POS;
-        return;
-    }
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(mReadingState.mPos);
-    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        mReadingState.mPos -= mBuffer->getOriginalBufferSize();
-    }
-    const int forwardLinkPosition =
-            DynamicPatriciaTrieReadingUtils::getForwardLinkPosition(dictBuf, mReadingState.mPos);
-    if (usesAdditionalBuffer) {
-        mReadingState.mPos += mBuffer->getOriginalBufferSize();
-    }
-    mReadingState.mPosOfLastForwardLinkField = mReadingState.mPos;
-    if (DynamicPatriciaTrieReadingUtils::isValidForwardLinkPosition(forwardLinkPosition)) {
-        // Follow the forward link.
-        mReadingState.mPos += forwardLinkPosition;
-        nextPtNodeArray();
-    } else {
-        // All node arrays have been read.
-        mReadingState.mPos = NOT_A_DICT_POS;
-    }
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h
deleted file mode 100644
index a71c069..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h
+++ /dev/null
@@ -1,289 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_READING_HELPER_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_READING_HELPER_H
-
-#include <cstddef>
-#include <vector>
-
-#include "defines.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
-
-namespace latinime {
-
-class BufferWithExtendableBuffer;
-class DictionaryBigramsStructurePolicy;
-class DictionaryShortcutsStructurePolicy;
-
-/*
- * This class is used for traversing dynamic patricia trie. This class supports iterating nodes and
- * dealing with additional buffer. This class counts nodes and node arrays to avoid infinite loop.
- */
-class DynamicPatriciaTrieReadingHelper {
- public:
-    class TraversingEventListener {
-     public:
-        virtual ~TraversingEventListener() {};
-
-        // Returns whether the event handling was succeeded or not.
-        virtual bool onAscend() = 0;
-
-        // Returns whether the event handling was succeeded or not.
-        virtual bool onDescend(const int ptNodeArrayPos) = 0;
-
-        // Returns whether the event handling was succeeded or not.
-        virtual bool onReadingPtNodeArrayTail() = 0;
-
-        // Returns whether the event handling was succeeded or not.
-        virtual bool onVisitingPtNode(const DynamicPatriciaTrieNodeReader *const node,
-                const int *const nodeCodePoints) = 0;
-
-     protected:
-        TraversingEventListener() {};
-
-     private:
-        DISALLOW_COPY_AND_ASSIGN(TraversingEventListener);
-    };
-
-    DynamicPatriciaTrieReadingHelper(const BufferWithExtendableBuffer *const buffer,
-            const DictionaryBigramsStructurePolicy *const bigramsPolicy,
-            const DictionaryShortcutsStructurePolicy *const shortcutsPolicy)
-            : mIsError(false), mReadingState(), mBuffer(buffer),
-              mNodeReader(mBuffer, bigramsPolicy, shortcutsPolicy), mReadingStateStack() {}
-
-    ~DynamicPatriciaTrieReadingHelper() {}
-
-    AK_FORCE_INLINE bool isError() const {
-        return mIsError;
-    }
-
-    AK_FORCE_INLINE bool isEnd() const {
-        return mReadingState.mPos == NOT_A_DICT_POS;
-    }
-
-    // Initialize reading state with the head position of a PtNode array.
-    AK_FORCE_INLINE void initWithPtNodeArrayPos(const int ptNodeArrayPos) {
-        if (ptNodeArrayPos == NOT_A_DICT_POS) {
-            mReadingState.mPos = NOT_A_DICT_POS;
-        } else {
-            mIsError = false;
-            mReadingState.mPos = ptNodeArrayPos;
-            mReadingState.mPrevTotalCodePointCount = 0;
-            mReadingState.mTotalNodeCount = 0;
-            mReadingState.mNodeArrayCount = 0;
-            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
-            mReadingStateStack.clear();
-            nextPtNodeArray();
-            if (!isEnd()) {
-                fetchPtNodeInfo();
-            }
-        }
-    }
-
-    // Initialize reading state with the head position of a node.
-    AK_FORCE_INLINE void initWithPtNodePos(const int ptNodePos) {
-        if (ptNodePos == NOT_A_DICT_POS) {
-            mReadingState.mPos = NOT_A_DICT_POS;
-        } else {
-            mIsError = false;
-            mReadingState.mPos = ptNodePos;
-            mReadingState.mNodeCount = 1;
-            mReadingState.mPrevTotalCodePointCount = 0;
-            mReadingState.mTotalNodeCount = 1;
-            mReadingState.mNodeArrayCount = 1;
-            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
-            mReadingState.mPosOfLastPtNodeArrayHead = NOT_A_DICT_POS;
-            mReadingStateStack.clear();
-            fetchPtNodeInfo();
-        }
-    }
-
-    AK_FORCE_INLINE const DynamicPatriciaTrieNodeReader* getNodeReader() const {
-        return &mNodeReader;
-    }
-
-    AK_FORCE_INLINE bool isValidTerminalNode() const {
-        return !isEnd() && !mNodeReader.isDeleted() && mNodeReader.isTerminal();
-    }
-
-    AK_FORCE_INLINE bool isMatchedCodePoint(const int index, const int codePoint) const {
-        return mMergedNodeCodePoints[index] == codePoint;
-    }
-
-    // Return code point count exclude the last read node's code points.
-    AK_FORCE_INLINE int getPrevTotalCodePointCount() const {
-        return mReadingState.mPrevTotalCodePointCount;
-    }
-
-    // Return code point count include the last read node's code points.
-    AK_FORCE_INLINE int getTotalCodePointCount() const {
-        return mReadingState.mPrevTotalCodePointCount + mNodeReader.getCodePointCount();
-    }
-
-    AK_FORCE_INLINE void fetchMergedNodeCodePointsInReverseOrder(
-            const int index, int *const outCodePoints) const {
-        const int nodeCodePointCount = mNodeReader.getCodePointCount();
-        for (int i =  0; i < nodeCodePointCount; ++i) {
-            outCodePoints[index + i] = mMergedNodeCodePoints[nodeCodePointCount - 1 - i];
-        }
-    }
-
-    AK_FORCE_INLINE const int *getMergedNodeCodePoints() const {
-        return mMergedNodeCodePoints;
-    }
-
-    AK_FORCE_INLINE void readNextSiblingNode() {
-        mReadingState.mNodeCount -= 1;
-        mReadingState.mPos = mNodeReader.getSiblingNodePos();
-        if (mReadingState.mNodeCount <= 0) {
-            // All nodes in the current node array have been read.
-            followForwardLink();
-            if (!isEnd()) {
-                fetchPtNodeInfo();
-            }
-        } else {
-            fetchPtNodeInfo();
-        }
-    }
-
-    // Read the first child node of the current node.
-    AK_FORCE_INLINE void readChildNode() {
-        if (mNodeReader.hasChildren()) {
-            mReadingState.mPrevTotalCodePointCount += mNodeReader.getCodePointCount();
-            mReadingState.mTotalNodeCount = 0;
-            mReadingState.mNodeArrayCount = 0;
-            mReadingState.mPos = mNodeReader.getChildrenPos();
-            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
-            // Read children node array.
-            nextPtNodeArray();
-            if (!isEnd()) {
-                fetchPtNodeInfo();
-            }
-        } else {
-            mReadingState.mPos = NOT_A_DICT_POS;
-        }
-    }
-
-    // Read the parent node of the current node.
-    AK_FORCE_INLINE void readParentNode() {
-        if (mNodeReader.getParentPos() != NOT_A_DICT_POS) {
-            mReadingState.mPrevTotalCodePointCount += mNodeReader.getCodePointCount();
-            mReadingState.mTotalNodeCount = 1;
-            mReadingState.mNodeArrayCount = 1;
-            mReadingState.mNodeCount = 1;
-            mReadingState.mPos = mNodeReader.getParentPos();
-            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
-            mReadingState.mPosOfLastPtNodeArrayHead = NOT_A_DICT_POS;
-            fetchPtNodeInfo();
-        } else {
-            mReadingState.mPos = NOT_A_DICT_POS;
-        }
-    }
-
-    AK_FORCE_INLINE int getPosOfLastForwardLinkField() const {
-        return mReadingState.mPosOfLastForwardLinkField;
-    }
-
-    AK_FORCE_INLINE int getPosOfLastPtNodeArrayHead() const {
-        return mReadingState.mPosOfLastPtNodeArrayHead;
-    }
-
-    AK_FORCE_INLINE void reloadCurrentPtNodeInfo() {
-        if (!isEnd()) {
-            fetchPtNodeInfo();
-        }
-    }
-
-    bool traverseAllPtNodesInPostorderDepthFirstManner(TraversingEventListener *const listener);
-
-    bool traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
-            TraversingEventListener *const listener);
-
- private:
-    DISALLOW_COPY_AND_ASSIGN(DynamicPatriciaTrieReadingHelper);
-
-    class ReadingState {
-     public:
-        // Note that copy constructor and assignment operator are used for this class to use
-        // std::vector.
-        ReadingState() : mPos(NOT_A_DICT_POS), mNodeCount(0), mPrevTotalCodePointCount(0),
-                mTotalNodeCount(0), mNodeArrayCount(0), mPosOfLastForwardLinkField(NOT_A_DICT_POS),
-                mPosOfLastPtNodeArrayHead(NOT_A_DICT_POS) {}
-
-        int mPos;
-        // Node count of a node array.
-        int mNodeCount;
-        int mPrevTotalCodePointCount;
-        int mTotalNodeCount;
-        int mNodeArrayCount;
-        int mPosOfLastForwardLinkField;
-        int mPosOfLastPtNodeArrayHead;
-    };
-
-    static const int MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP;
-    static const int MAX_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP;
-    static const size_t MAX_READING_STATE_STACK_SIZE;
-
-    // TODO: Introduce error code to track what caused the error.
-    bool mIsError;
-    ReadingState mReadingState;
-    const BufferWithExtendableBuffer *const mBuffer;
-    DynamicPatriciaTrieNodeReader mNodeReader;
-    int mMergedNodeCodePoints[MAX_WORD_LENGTH];
-    std::vector<ReadingState> mReadingStateStack;
-
-    void nextPtNodeArray();
-
-    void followForwardLink();
-
-    AK_FORCE_INLINE void fetchPtNodeInfo() {
-        mNodeReader.fetchNodeInfoInBufferFromPtNodePosAndGetNodeCodePoints(mReadingState.mPos,
-                MAX_WORD_LENGTH, mMergedNodeCodePoints);
-        if (mNodeReader.getCodePointCount() <= 0) {
-            // Empty node is not allowed.
-            mIsError = true;
-            mReadingState.mPos = NOT_A_DICT_POS;
-        }
-    }
-
-    AK_FORCE_INLINE void pushReadingStateToStack() {
-        if (mReadingStateStack.size() > MAX_READING_STATE_STACK_SIZE) {
-            AKLOGI("Reading state stack overflow. Max size: %zd", MAX_READING_STATE_STACK_SIZE);
-            ASSERT(false);
-            mIsError = true;
-            mReadingState.mPos = NOT_A_DICT_POS;
-        } else {
-            mReadingStateStack.push_back(mReadingState);
-        }
-    }
-
-    AK_FORCE_INLINE void popReadingStateFromStack() {
-        if (mReadingStateStack.empty()) {
-            mReadingState.mPos = NOT_A_DICT_POS;
-        } else {
-            mReadingState = mReadingStateStack.back();
-            mReadingStateStack.pop_back();
-            if (!isEnd()) {
-                fetchPtNodeInfo();
-            }
-        }
-    }
-};
-} // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_READING_HELPER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
deleted file mode 100644
index 052558b..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
+++ /dev/null
@@ -1,558 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h"
-
-#include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_node_reader.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_helper.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h"
-#include "suggest/policyimpl/dictionary/header/header_policy.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
-#include "suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h"
-#include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
-#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
-#include "utils/hash_map_compat.h"
-
-namespace latinime {
-
-const int DynamicPatriciaTrieWritingHelper::CHILDREN_POSITION_FIELD_SIZE = 3;
-// TODO: Make MAX_DICTIONARY_SIZE 8MB.
-const size_t DynamicPatriciaTrieWritingHelper::MAX_DICTIONARY_SIZE = 2 * 1024 * 1024;
-
-bool DynamicPatriciaTrieWritingHelper::addUnigramWord(
-        DynamicPatriciaTrieReadingHelper *const readingHelper,
-        const int *const wordCodePoints, const int codePointCount, const int probability,
-        bool *const outAddedNewUnigram) {
-    int parentPos = NOT_A_DICT_POS;
-    while (!readingHelper->isEnd()) {
-        const int matchedCodePointCount = readingHelper->getPrevTotalCodePointCount();
-        if (!readingHelper->isMatchedCodePoint(0 /* index */,
-                wordCodePoints[matchedCodePointCount])) {
-            // The first code point is different from target code point. Skip this node and read
-            // the next sibling node.
-            readingHelper->readNextSiblingNode();
-            continue;
-        }
-        // Check following merged node code points.
-        const DynamicPatriciaTrieNodeReader *const nodeReader = readingHelper->getNodeReader();
-        const int nodeCodePointCount = nodeReader->getCodePointCount();
-        for (int j = 1; j < nodeCodePointCount; ++j) {
-            const int nextIndex = matchedCodePointCount + j;
-            if (nextIndex >= codePointCount || !readingHelper->isMatchedCodePoint(j,
-                    wordCodePoints[matchedCodePointCount + j])) {
-                *outAddedNewUnigram = true;
-                return reallocatePtNodeAndAddNewPtNodes(nodeReader,
-                        readingHelper->getMergedNodeCodePoints(), j,
-                        getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */,
-                                probability),
-                        wordCodePoints + matchedCodePointCount,
-                        codePointCount - matchedCodePointCount);
-            }
-        }
-        // All characters are matched.
-        if (codePointCount == readingHelper->getTotalCodePointCount()) {
-            return setPtNodeProbability(nodeReader, probability,
-                    readingHelper->getMergedNodeCodePoints(), outAddedNewUnigram);
-        }
-        if (!nodeReader->hasChildren()) {
-            *outAddedNewUnigram = true;
-            return createChildrenPtNodeArrayAndAChildPtNode(nodeReader,
-                    getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability),
-                    wordCodePoints + readingHelper->getTotalCodePointCount(),
-                    codePointCount - readingHelper->getTotalCodePointCount());
-        }
-        // Advance to the children nodes.
-        parentPos = nodeReader->getHeadPos();
-        readingHelper->readChildNode();
-    }
-    if (readingHelper->isError()) {
-        // The dictionary is invalid.
-        return false;
-    }
-    int pos = readingHelper->getPosOfLastForwardLinkField();
-    *outAddedNewUnigram = true;
-    return createAndInsertNodeIntoPtNodeArray(parentPos,
-            wordCodePoints + readingHelper->getPrevTotalCodePointCount(),
-            codePointCount - readingHelper->getPrevTotalCodePointCount(),
-            getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability), &pos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::addBigramWords(const int word0Pos, const int word1Pos,
-        const int probability, bool *const outAddedNewBigram) {
-    int mMergedNodeCodePoints[MAX_WORD_LENGTH];
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    nodeReader.fetchNodeInfoInBufferFromPtNodePosAndGetNodeCodePoints(word0Pos, MAX_WORD_LENGTH,
-            mMergedNodeCodePoints);
-    // Move node to add bigram entry.
-    const int newNodePos = mBuffer->getTailPosition();
-    if (!markNodeAsMovedAndSetPosition(&nodeReader, newNodePos, newNodePos)) {
-        return false;
-    }
-    int writingPos = newNodePos;
-    // Write a new PtNode using original PtNode's info to the tail of the dictionary in mBuffer.
-    if (!writePtNodeToBufferByCopyingPtNodeInfo(mBuffer, &nodeReader, nodeReader.getParentPos(),
-            mMergedNodeCodePoints, nodeReader.getCodePointCount(), nodeReader.getProbability(),
-            &writingPos)) {
-        return false;
-    }
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(newNodePos);
-    if (nodeReader.getBigramsPos() != NOT_A_DICT_POS) {
-        // Insert a new bigram entry into the existing bigram list.
-        int bigramListPos = nodeReader.getBigramsPos();
-        return mBigramPolicy->addNewBigramEntryToBigramList(word1Pos, probability, &bigramListPos,
-                outAddedNewBigram);
-    } else {
-        // The PtNode doesn't have a bigram list.
-        *outAddedNewBigram = true;
-        // First, Write a bigram entry at the tail position of the PtNode.
-        if (!mBigramPolicy->writeNewBigramEntry(word1Pos, probability, &writingPos)) {
-            return false;
-        }
-        // Then, Mark as the PtNode having bigram list in the flags.
-        const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
-                PatriciaTrieReadingUtils::createAndGetFlags(nodeReader.isBlacklisted(),
-                        nodeReader.isNotAWord(), nodeReader.getProbability() != NOT_A_PROBABILITY,
-                        nodeReader.getShortcutPos() != NOT_A_DICT_POS, true /* hasBigrams */,
-                        nodeReader.getCodePointCount() > 1, CHILDREN_POSITION_FIELD_SIZE);
-        writingPos = newNodePos;
-        // Write updated flags into the moved PtNode's flags field.
-        return DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
-                &writingPos);
-    }
-}
-
-// Remove a bigram relation from word0Pos to word1Pos.
-bool DynamicPatriciaTrieWritingHelper::removeBigramWords(const int word0Pos, const int word1Pos) {
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(word0Pos);
-    if (nodeReader.getBigramsPos() == NOT_A_DICT_POS) {
-        return false;
-    }
-    return mBigramPolicy->removeBigram(nodeReader.getBigramsPos(), word1Pos);
-}
-
-void DynamicPatriciaTrieWritingHelper::writeToDictFile(const char *const fileName,
-        const HeaderPolicy *const headerPolicy, const int unigramCount, const int bigramCount) {
-    BufferWithExtendableBuffer headerBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */);
-    const int extendedRegionSize = headerPolicy->getExtendedRegionSize() +
-            mBuffer->getUsedAdditionalBufferSize();
-    if (!headerPolicy->writeHeaderToBuffer(&headerBuffer, false /* updatesLastUpdatedTime */,
-            false /* updatesLastDecayedTime */, unigramCount, bigramCount, extendedRegionSize)) {
-        return;
-    }
-    DictFileWritingUtils::flushAllHeaderAndBodyToFile(fileName, &headerBuffer, mBuffer);
-}
-
-void DynamicPatriciaTrieWritingHelper::writeToDictFileWithGC(const int rootPtNodeArrayPos,
-        const char *const fileName, const HeaderPolicy *const headerPolicy) {
-    BufferWithExtendableBuffer newDictBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */,
-            MAX_DICTIONARY_SIZE);
-    int unigramCount = 0;
-    int bigramCount = 0;
-    if (mNeedsToDecay) {
-        ForgettingCurveUtils::sTimeKeeper.setCurrentTime();
-    }
-    if (!runGC(rootPtNodeArrayPos, headerPolicy, &newDictBuffer, &unigramCount, &bigramCount)) {
-        return;
-    }
-    BufferWithExtendableBuffer headerBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */);
-    if (!headerPolicy->writeHeaderToBuffer(&headerBuffer, true /* updatesLastUpdatedTime */,
-            mNeedsToDecay, unigramCount, bigramCount, 0 /* extendedRegionSize */)) {
-        return;
-    }
-    DictFileWritingUtils::flushAllHeaderAndBodyToFile(fileName, &headerBuffer, &newDictBuffer);
-}
-
-bool DynamicPatriciaTrieWritingHelper::markNodeAsDeleted(
-        const DynamicPatriciaTrieNodeReader *const nodeToUpdate) {
-    int pos = nodeToUpdate->getHeadPos();
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(pos);
-    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        pos -= mBuffer->getOriginalBufferSize();
-    }
-    // Read original flags
-    const PatriciaTrieReadingUtils::NodeFlags originalFlags =
-            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
-    const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
-            DynamicPatriciaTrieReadingUtils::updateAndGetFlags(originalFlags, false /* isMoved */,
-                    true /* isDeleted */);
-    int writingPos = nodeToUpdate->getHeadPos();
-    // Update flags.
-    return DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
-            &writingPos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::markNodeAsMovedAndSetPosition(
-        const DynamicPatriciaTrieNodeReader *const originalNode, const int movedPos,
-        const int bigramLinkedNodePos) {
-    int pos = originalNode->getHeadPos();
-    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(pos);
-    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
-    if (usesAdditionalBuffer) {
-        pos -= mBuffer->getOriginalBufferSize();
-    }
-    // Read original flags
-    const PatriciaTrieReadingUtils::NodeFlags originalFlags =
-            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
-    const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
-            DynamicPatriciaTrieReadingUtils::updateAndGetFlags(originalFlags, true /* isMoved */,
-                    false /* isDeleted */);
-    int writingPos = originalNode->getHeadPos();
-    // Update flags.
-    if (!DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
-            &writingPos)) {
-        return false;
-    }
-    // Update moved position, which is stored in the parent offset field.
-    if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(
-            mBuffer, movedPos, originalNode->getHeadPos(), &writingPos)) {
-        return false;
-    }
-    // Update bigram linked node position, which is stored in the children position field.
-    int childrenPosFieldPos = originalNode->getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(
-            mBuffer, bigramLinkedNodePos, &childrenPosFieldPos)) {
-        return false;
-    }
-    if (originalNode->hasChildren()) {
-        // Update children's parent position.
-        DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, mBigramPolicy, mShortcutPolicy);
-        const DynamicPatriciaTrieNodeReader *const nodeReader = readingHelper.getNodeReader();
-        readingHelper.initWithPtNodeArrayPos(originalNode->getChildrenPos());
-        while (!readingHelper.isEnd()) {
-            int parentOffsetFieldPos = nodeReader->getHeadPos()
-                    + DynamicPatriciaTrieWritingUtils::NODE_FLAG_FIELD_SIZE;
-            if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(
-                    mBuffer, bigramLinkedNodePos, nodeReader->getHeadPos(),
-                    &parentOffsetFieldPos)) {
-                // Parent offset cannot be written because of a bug or a broken dictionary; thus,
-                // we give up to update dictionary.
-                return false;
-            }
-            readingHelper.readNextSiblingNode();
-        }
-    }
-    return true;
-}
-
-// Write new PtNode at writingPos.
-bool DynamicPatriciaTrieWritingHelper::writePtNodeWithFullInfoToBuffer(
-        BufferWithExtendableBuffer *const bufferToWrite, const bool isBlacklisted,
-        const bool isNotAWord, const int parentPos, const int *const codePoints,
-        const int codePointCount, const int probability, const int childrenPos,
-        const int originalBigramListPos, const int originalShortcutListPos,
-        int *const writingPos) {
-    const int nodePos = *writingPos;
-    // Write dummy flags. The Node flags are updated with appropriate flags at the last step of the
-    // PtNode writing.
-    if (!DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(bufferToWrite,
-            0 /* nodeFlags */, writingPos)) {
-        return false;
-    }
-    // Calculate a parent offset and write the offset.
-    if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(bufferToWrite,
-            parentPos, nodePos, writingPos)) {
-        return false;
-    }
-    // Write code points
-    if (!DynamicPatriciaTrieWritingUtils::writeCodePointsAndAdvancePosition(bufferToWrite,
-            codePoints, codePointCount, writingPos)) {
-        return false;
-    }
-    // Write probability when the probability is a valid probability, which means this node is
-    // terminal.
-    if (probability != NOT_A_PROBABILITY) {
-        if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(bufferToWrite,
-                probability, writingPos)) {
-            return false;
-        }
-    }
-    // Write children position
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(bufferToWrite,
-            childrenPos, writingPos)) {
-        return false;
-    }
-    // Copy shortcut list when the originalShortcutListPos is valid dictionary position.
-    if (originalShortcutListPos != NOT_A_DICT_POS) {
-        int fromPos = originalShortcutListPos;
-        if (!mShortcutPolicy->copyAllShortcutsAndReturnIfSucceededOrNot(bufferToWrite, &fromPos,
-                writingPos)) {
-            return false;
-        }
-    }
-    // Copy bigram list when the originalBigramListPos is valid dictionary position.
-    int bigramCount = 0;
-    if (originalBigramListPos != NOT_A_DICT_POS) {
-        int fromPos = originalBigramListPos;
-        if (!mBigramPolicy->copyAllBigrams(bufferToWrite, &fromPos, writingPos, &bigramCount)) {
-            return false;
-        }
-    }
-    // Create node flags and write them.
-    PatriciaTrieReadingUtils::NodeFlags nodeFlags =
-            PatriciaTrieReadingUtils::createAndGetFlags(isBlacklisted, isNotAWord,
-                    probability != NOT_A_PROBABILITY /* isTerminal */,
-                    originalShortcutListPos != NOT_A_DICT_POS /* hasShortcutTargets */,
-                    bigramCount > 0 /* hasBigrams */, codePointCount > 1 /* hasMultipleChars */,
-                    CHILDREN_POSITION_FIELD_SIZE);
-    int flagsFieldPos = nodePos;
-    if (!DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(bufferToWrite, nodeFlags,
-            &flagsFieldPos)) {
-        return false;
-    }
-    return true;
-}
-
-bool DynamicPatriciaTrieWritingHelper::writePtNodeToBuffer(
-        BufferWithExtendableBuffer *const bufferToWrite, const int parentPos,
-        const int *const codePoints, const int codePointCount, const int probability,
-        int *const writingPos) {
-    return writePtNodeWithFullInfoToBuffer(bufferToWrite, false /* isBlacklisted */,
-            false /* isNotAWord */, parentPos, codePoints, codePointCount, probability,
-            NOT_A_DICT_POS /* childrenPos */, NOT_A_DICT_POS /* originalBigramsPos */,
-            NOT_A_DICT_POS /* originalShortcutPos */, writingPos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::writePtNodeToBufferByCopyingPtNodeInfo(
-        BufferWithExtendableBuffer *const bufferToWrite,
-        const DynamicPatriciaTrieNodeReader *const originalNode, const int parentPos,
-        const int *const codePoints, const int codePointCount, const int probability,
-        int *const writingPos) {
-    return writePtNodeWithFullInfoToBuffer(bufferToWrite, originalNode->isBlacklisted(),
-            originalNode->isNotAWord(), parentPos, codePoints, codePointCount, probability,
-            originalNode->getChildrenPos(), originalNode->getBigramsPos(),
-            originalNode->getShortcutPos(), writingPos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::createAndInsertNodeIntoPtNodeArray(const int parentPos,
-        const int *const nodeCodePoints, const int nodeCodePointCount, const int probability,
-        int *const forwardLinkFieldPos) {
-    const int newPtNodeArrayPos = mBuffer->getTailPosition();
-    if (!DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
-            newPtNodeArrayPos, forwardLinkFieldPos)) {
-        return false;
-    }
-    return createNewPtNodeArrayWithAChildPtNode(parentPos, nodeCodePoints, nodeCodePointCount,
-            probability);
-}
-
-bool DynamicPatriciaTrieWritingHelper::setPtNodeProbability(
-        const DynamicPatriciaTrieNodeReader *const originalPtNode, const int probability,
-        const int *const codePoints, bool *const outAddedNewUnigram) {
-    if (originalPtNode->isTerminal()) {
-        // Overwrites the probability.
-        *outAddedNewUnigram = false;
-        const int probabilityToWrite = getUpdatedProbability(originalPtNode->getProbability(),
-                probability);
-        int probabilityFieldPos = originalPtNode->getProbabilityFieldPos();
-        if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(mBuffer,
-                probabilityToWrite, &probabilityFieldPos)) {
-            return false;
-        }
-    } else {
-        // Make the node terminal and write the probability.
-        *outAddedNewUnigram = true;
-        int movedPos = mBuffer->getTailPosition();
-        if (!markNodeAsMovedAndSetPosition(originalPtNode, movedPos, movedPos)) {
-            return false;
-        }
-        if (!writePtNodeToBufferByCopyingPtNodeInfo(mBuffer, originalPtNode,
-                originalPtNode->getParentPos(), codePoints, originalPtNode->getCodePointCount(),
-                getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability),
-                &movedPos)) {
-            return false;
-        }
-    }
-    return true;
-}
-
-bool DynamicPatriciaTrieWritingHelper::createChildrenPtNodeArrayAndAChildPtNode(
-        const DynamicPatriciaTrieNodeReader *const parentNode, const int probability,
-        const int *const codePoints, const int codePointCount) {
-    const int newPtNodeArrayPos = mBuffer->getTailPosition();
-    int childrenPosFieldPos = parentNode->getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
-            newPtNodeArrayPos, &childrenPosFieldPos)) {
-        return false;
-    }
-    return createNewPtNodeArrayWithAChildPtNode(parentNode->getHeadPos(), codePoints,
-            codePointCount, probability);
-}
-
-bool DynamicPatriciaTrieWritingHelper::createNewPtNodeArrayWithAChildPtNode(
-        const int parentPtNodePos, const int *const nodeCodePoints, const int nodeCodePointCount,
-        const int probability) {
-    int writingPos = mBuffer->getTailPosition();
-    if (!DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(mBuffer,
-            1 /* arraySize */, &writingPos)) {
-        return false;
-    }
-    if (!writePtNodeToBuffer(mBuffer, parentPtNodePos, nodeCodePoints, nodeCodePointCount,
-            probability, &writingPos)) {
-        return false;
-    }
-    if (!DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
-            NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
-        return false;
-    }
-    return true;
-}
-
-// Returns whether the dictionary updating was succeeded or not.
-bool DynamicPatriciaTrieWritingHelper::reallocatePtNodeAndAddNewPtNodes(
-        const DynamicPatriciaTrieNodeReader *const reallocatingPtNode,
-        const int *const reallocatingPtNodeCodePoints, const int overlappingCodePointCount,
-        const int probabilityOfNewPtNode, const int *const newNodeCodePoints,
-        const int newNodeCodePointCount) {
-    // When addsExtraChild is true, split the reallocating PtNode and add new child.
-    // Reallocating PtNode: abcde, newNode: abcxy.
-    // abc (1st, not terminal) __ de (2nd)
-    //                         \_ xy (extra child, terminal)
-    // Otherwise, this method makes 1st part terminal and write probabilityOfNewPtNode.
-    // Reallocating PtNode: abcde, newNode: abc.
-    // abc (1st, terminal) __ de (2nd)
-    const bool addsExtraChild = newNodeCodePointCount > overlappingCodePointCount;
-    const int firstPartOfReallocatedPtNodePos = mBuffer->getTailPosition();
-    int writingPos = firstPartOfReallocatedPtNodePos;
-    // Write the 1st part of the reallocating node. The children position will be updated later
-    // with actual children position.
-    const int newProbability = addsExtraChild ? NOT_A_PROBABILITY : probabilityOfNewPtNode;
-    if (!writePtNodeToBuffer(mBuffer, reallocatingPtNode->getParentPos(),
-            reallocatingPtNodeCodePoints, overlappingCodePointCount, newProbability,
-            &writingPos)) {
-        return false;
-    }
-    const int actualChildrenPos = writingPos;
-    // Create new children PtNode array.
-    const size_t newPtNodeCount = addsExtraChild ? 2 : 1;
-    if (!DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(mBuffer,
-            newPtNodeCount, &writingPos)) {
-        return false;
-    }
-    // Write the 2nd part of the reallocating node.
-    const int secondPartOfReallocatedPtNodePos = writingPos;
-    if (!writePtNodeToBufferByCopyingPtNodeInfo(mBuffer, reallocatingPtNode,
-            firstPartOfReallocatedPtNodePos,
-            reallocatingPtNodeCodePoints + overlappingCodePointCount,
-            reallocatingPtNode->getCodePointCount() - overlappingCodePointCount,
-            reallocatingPtNode->getProbability(), &writingPos)) {
-        return false;
-    }
-    if (addsExtraChild) {
-        if (!writePtNodeToBuffer(mBuffer, firstPartOfReallocatedPtNodePos,
-                newNodeCodePoints + overlappingCodePointCount,
-                newNodeCodePointCount - overlappingCodePointCount, probabilityOfNewPtNode,
-                &writingPos)) {
-            return false;
-        }
-    }
-    if (!DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
-            NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
-        return false;
-    }
-    // Update original reallocatingPtNode as moved.
-    if (!markNodeAsMovedAndSetPosition(reallocatingPtNode, firstPartOfReallocatedPtNodePos,
-            secondPartOfReallocatedPtNodePos)) {
-        return false;
-    }
-    // Load node info. Information of the 1st part will be fetched.
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    nodeReader.fetchNodeInfoInBufferFromPtNodePos(firstPartOfReallocatedPtNodePos);
-    // Update children position.
-    int childrenPosFieldPos = nodeReader.getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
-            actualChildrenPos, &childrenPosFieldPos)) {
-        return false;
-    }
-    return true;
-}
-
-bool DynamicPatriciaTrieWritingHelper::runGC(const int rootPtNodeArrayPos,
-        const HeaderPolicy *const headerPolicy, BufferWithExtendableBuffer *const bufferToWrite,
-        int *const outUnigramCount, int *const outBigramCount) {
-    DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, mBigramPolicy, mShortcutPolicy);
-    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
-    DynamicPatriciaTrieGcEventListeners
-            ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
-                    traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
-                            headerPolicy, this, mBuffer, mNeedsToDecay);
-    if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
-            &traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted)) {
-        return false;
-    }
-    if (mNeedsToDecay && traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
-            .getValidUnigramCount() > ForgettingCurveUtils::MAX_UNIGRAM_COUNT_AFTER_GC) {
-        // TODO: Remove more unigrams.
-    }
-
-    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
-    DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateBigramProbability
-            traversePolicyToUpdateBigramProbability(mBigramPolicy);
-    if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
-            &traversePolicyToUpdateBigramProbability)) {
-        return false;
-    }
-    if (mNeedsToDecay && traversePolicyToUpdateBigramProbability.getValidBigramEntryCount()
-            > ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC) {
-        // TODO: Remove more bigrams.
-    }
-
-    // Mapping from positions in mBuffer to positions in bufferToWrite.
-    DictPositionRelocationMap dictPositionRelocationMap;
-    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
-    DynamicPatriciaTrieGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-            traversePolicyToPlaceAndWriteValidPtNodesToBuffer(this, bufferToWrite,
-                    &dictPositionRelocationMap);
-    if (!readingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
-            &traversePolicyToPlaceAndWriteValidPtNodesToBuffer)) {
-        return false;
-    }
-
-    // Create policy instance for the GCed dictionary.
-    DynamicShortcutListPolicy newDictShortcutPolicy(bufferToWrite);
-    DynamicBigramListPolicy newDictBigramPolicy(headerPolicy, bufferToWrite, &newDictShortcutPolicy,
-            mNeedsToDecay);
-    // Create reading helper for the GCed dictionary.
-    DynamicPatriciaTrieReadingHelper newDictReadingHelper(bufferToWrite, &newDictBigramPolicy,
-            &newDictShortcutPolicy);
-    newDictReadingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
-    DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateAllPositionFields
-            traversePolicyToUpdateAllPositionFields(this, &newDictBigramPolicy, bufferToWrite,
-                    &dictPositionRelocationMap);
-    if (!newDictReadingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
-            &traversePolicyToUpdateAllPositionFields)) {
-        return false;
-    }
-    *outUnigramCount = traversePolicyToUpdateAllPositionFields.getUnigramCount();
-    *outBigramCount = traversePolicyToUpdateAllPositionFields.getBigramCount();
-    return true;
-}
-
-int DynamicPatriciaTrieWritingHelper::getUpdatedProbability(const int originalProbability,
-        const int newProbability) {
-    if (mNeedsToDecay) {
-        return ForgettingCurveUtils::getUpdatedEncodedProbability(originalProbability,
-                newProbability);
-    } else {
-        return newProbability;
-    }
-}
-
-} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
deleted file mode 100644
index ca86647..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
+++ /dev/null
@@ -1,138 +0,0 @@
-/*
- * Copyright (C) 2013, The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_HELPER_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_HELPER_H
-
-#include <stdint.h>
-
-#include "defines.h"
-#include "utils/hash_map_compat.h"
-
-namespace latinime {
-
-class BufferWithExtendableBuffer;
-class DynamicBigramListPolicy;
-class DynamicPatriciaTrieNodeReader;
-class DynamicPatriciaTrieReadingHelper;
-class DynamicShortcutListPolicy;
-class HeaderPolicy;
-
-class DynamicPatriciaTrieWritingHelper {
- public:
-    typedef hash_map_compat<int, int> PtNodeArrayPositionRelocationMap;
-    typedef hash_map_compat<int, int> PtNodePositionRelocationMap;
-    struct DictPositionRelocationMap {
-     public:
-        DictPositionRelocationMap()
-                : mPtNodeArrayPositionRelocationMap(), mPtNodePositionRelocationMap() {}
-
-        PtNodeArrayPositionRelocationMap mPtNodeArrayPositionRelocationMap;
-        PtNodePositionRelocationMap mPtNodePositionRelocationMap;
-
-     private:
-        DISALLOW_COPY_AND_ASSIGN(DictPositionRelocationMap);
-    };
-
-    static const size_t MAX_DICTIONARY_SIZE;
-
-    DynamicPatriciaTrieWritingHelper(BufferWithExtendableBuffer *const buffer,
-            DynamicBigramListPolicy *const bigramPolicy,
-            DynamicShortcutListPolicy *const shortcutPolicy, const bool needsToDecay)
-            : mBuffer(buffer), mBigramPolicy(bigramPolicy), mShortcutPolicy(shortcutPolicy),
-              mNeedsToDecay(needsToDecay) {}
-
-    ~DynamicPatriciaTrieWritingHelper() {}
-
-    // Add a word to the dictionary. If the word already exists, update the probability.
-    bool addUnigramWord(DynamicPatriciaTrieReadingHelper *const readingHelper,
-            const int *const wordCodePoints, const int codePointCount, const int probability,
-            bool *const outAddedNewUnigram);
-
-    // Add a bigram relation from word0Pos to word1Pos.
-    bool addBigramWords(const int word0Pos, const int word1Pos, const int probability,
-            bool *const outAddedNewBigram);
-
-    // Remove a bigram relation from word0Pos to word1Pos.
-    bool removeBigramWords(const int word0Pos, const int word1Pos);
-
-    void writeToDictFile(const char *const fileName, const HeaderPolicy *const headerPolicy,
-            const int unigramCount, const int bigramCount);
-
-    void writeToDictFileWithGC(const int rootPtNodeArrayPos, const char *const fileName,
-            const HeaderPolicy *const headerPolicy);
-
-    // CAVEAT: This method must be called only from inner classes of
-    // DynamicPatriciaTrieGcEventListeners.
-    bool markNodeAsDeleted(const DynamicPatriciaTrieNodeReader *const nodeToUpdate);
-
-    // CAVEAT: This method must be called only from this class or inner classes of
-    // DynamicPatriciaTrieGcEventListeners.
-    bool writePtNodeToBufferByCopyingPtNodeInfo(BufferWithExtendableBuffer *const bufferToWrite,
-            const DynamicPatriciaTrieNodeReader *const originalNode, const int parentPos,
-            const int *const codePoints, const int codePointCount, const int probability,
-            int *const writingPos);
-
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieWritingHelper);
-
-    static const int CHILDREN_POSITION_FIELD_SIZE;
-
-    BufferWithExtendableBuffer *const mBuffer;
-    DynamicBigramListPolicy *const mBigramPolicy;
-    DynamicShortcutListPolicy *const mShortcutPolicy;
-    const bool mNeedsToDecay;
-
-    bool markNodeAsMovedAndSetPosition(const DynamicPatriciaTrieNodeReader *const nodeToUpdate,
-            const int movedPos, const int bigramLinkedNodePos);
-
-    bool writePtNodeWithFullInfoToBuffer(BufferWithExtendableBuffer *const bufferToWrite,
-            const bool isBlacklisted, const bool isNotAWord,
-            const int parentPos,  const int *const codePoints, const int codePointCount,
-            const int probability, const int childrenPos, const int originalBigramListPos,
-            const int originalShortcutListPos, int *const writingPos);
-
-    bool writePtNodeToBuffer(BufferWithExtendableBuffer *const bufferToWrite,
-            const int parentPos, const int *const codePoints, const int codePointCount,
-            const int probability, int *const writingPos);
-
-    bool createAndInsertNodeIntoPtNodeArray(const int parentPos, const int *const nodeCodePoints,
-            const int nodeCodePointCount, const int probability, int *const forwardLinkFieldPos);
-
-    bool setPtNodeProbability(const DynamicPatriciaTrieNodeReader *const originalNode,
-            const int probability, const int *const codePoints, bool *const outAddedNewUnigram);
-
-    bool createChildrenPtNodeArrayAndAChildPtNode(
-            const DynamicPatriciaTrieNodeReader *const parentNode, const int probability,
-            const int *const codePoints, const int codePointCount);
-
-    bool createNewPtNodeArrayWithAChildPtNode(const int parentPos, const int *const nodeCodePoints,
-            const int nodeCodePointCount, const int probability);
-
-    bool reallocatePtNodeAndAddNewPtNodes(
-            const DynamicPatriciaTrieNodeReader *const reallocatingPtNode,
-            const int *const reallocatingPtNodeCodePoints, const int overlappingCodePointCount,
-            const int probabilityOfNewPtNode, const int *const newNodeCodePoints,
-            const int newNodeCodePointCount);
-
-    bool runGC(const int rootPtNodeArrayPos, const HeaderPolicy *const headerPolicy,
-            BufferWithExtendableBuffer *const bufferToWrite, int *const outUnigramCount,
-            int *const outBigramCount);
-
-    int getUpdatedProbability(const int originalProbability, const int newProbability);
-};
-} // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_HELPER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
index eb072fb..be7a3c2 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
@@ -20,6 +20,8 @@
 
 // Note that these are corresponding definitions in Java side in FormatSpec.FileHeader.
 const char *const HeaderPolicy::MULTIPLE_WORDS_DEMOTION_RATE_KEY = "MULTIPLE_WORDS_DEMOTION_RATE";
+const char *const HeaderPolicy::REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY =
+        "REQUIRES_GERMAN_UMLAUT_PROCESSING";
 // TODO: Change attribute string to "IS_DECAYING_DICT".
 const char *const HeaderPolicy::IS_DECAYING_DICT_KEY = "USES_FORGETTING_CURVE";
 const char *const HeaderPolicy::LAST_UPDATED_TIME_KEY = "date";
@@ -27,6 +29,9 @@
 const char *const HeaderPolicy::UNIGRAM_COUNT_KEY = "UNIGRAM_COUNT";
 const char *const HeaderPolicy::BIGRAM_COUNT_KEY = "BIGRAM_COUNT";
 const char *const HeaderPolicy::EXTENDED_REGION_SIZE_KEY = "EXTENDED_REGION_SIZE";
+// Historical info is information that is needed to support decaying such as timestamp, level and
+// count.
+const char *const HeaderPolicy::HAS_HISTORICAL_INFO_KEY = "HAS_HISTORICAL_INFO";
 const int HeaderPolicy::DEFAULT_MULTIPLE_WORDS_DEMOTION_RATE = 100;
 const float HeaderPolicy::MULTIPLE_WORD_COST_MULTIPLIER_SCALE = 100.0f;
 
@@ -63,6 +68,11 @@
     return MULTIPLE_WORD_COST_MULTIPLIER_SCALE / static_cast<float>(demotionRate);
 }
 
+bool HeaderPolicy::readRequiresGermanUmlautProcessing() const {
+    return HeaderReadWriteUtils::readBoolAttributeValue(&mAttributeMap,
+            REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY, false);
+}
+
 bool HeaderPolicy::writeHeaderToBuffer(BufferWithExtendableBuffer *const bufferToWrite,
         const bool updatesLastUpdatedTime, const bool updatesLastDecayedTime,
         const int unigramCount, const int bigramCount, const int extendedRegionSize) const {
@@ -89,12 +99,12 @@
     if (updatesLastUpdatedTime) {
         // Set current time as a last updated time.
         HeaderReadWriteUtils::setIntAttribute(&attributeMapTowrite, LAST_UPDATED_TIME_KEY,
-                time(0));
+                TimeKeeper::peekCurrentTime());
     }
     if (updatesLastDecayedTime) {
         // Set current time as a last updated time.
         HeaderReadWriteUtils::setIntAttribute(&attributeMapTowrite, LAST_DECAYED_TIME_KEY,
-                time(0));
+                TimeKeeper::peekCurrentTime());
     }
     if (!HeaderReadWriteUtils::writeHeaderAttributes(bufferToWrite, &attributeMapTowrite,
             &writingPos)) {
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
index a9c7805..1208d2c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
@@ -17,37 +17,40 @@
 #ifndef LATINIME_HEADER_POLICY_H
 #define LATINIME_HEADER_POLICY_H
 
-#include <ctime>
 #include <stdint.h>
 
 #include "defines.h"
 #include "suggest/core/policy/dictionary_header_structure_policy.h"
 #include "suggest/policyimpl/dictionary/header/header_read_write_utils.h"
 #include "suggest/policyimpl/dictionary/utils/format_utils.h"
+#include "utils/time_keeper.h"
 
 namespace latinime {
 
 class HeaderPolicy : public DictionaryHeaderStructurePolicy {
  public:
     // Reads information from existing dictionary buffer.
-    HeaderPolicy(const uint8_t *const dictBuf, const int dictSize)
-            : mDictFormatVersion(FormatUtils::detectFormatVersion(dictBuf, dictSize)),
+    HeaderPolicy(const uint8_t *const dictBuf, const FormatUtils::FORMAT_VERSION formatVersion)
+            : mDictFormatVersion(formatVersion),
               mDictionaryFlags(HeaderReadWriteUtils::getFlags(dictBuf)),
               mSize(HeaderReadWriteUtils::getHeaderSize(dictBuf)),
               mAttributeMap(createAttributeMapAndReadAllAttributes(dictBuf)),
               mMultiWordCostMultiplier(readMultipleWordCostMultiplier()),
+              mRequiresGermanUmlautProcessing(readRequiresGermanUmlautProcessing()),
               mIsDecayingDict(HeaderReadWriteUtils::readBoolAttributeValue(&mAttributeMap,
                       IS_DECAYING_DICT_KEY, false /* defaultValue */)),
               mLastUpdatedTime(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
-                      LAST_UPDATED_TIME_KEY, time(0) /* defaultValue */)),
+                      LAST_UPDATED_TIME_KEY, TimeKeeper::peekCurrentTime() /* defaultValue */)),
               mLastDecayedTime(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
-                      LAST_DECAYED_TIME_KEY, time(0) /* defaultValue */)),
+                      LAST_DECAYED_TIME_KEY, TimeKeeper::peekCurrentTime() /* defaultValue */)),
               mUnigramCount(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
                       UNIGRAM_COUNT_KEY, 0 /* defaultValue */)),
               mBigramCount(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
                       BIGRAM_COUNT_KEY, 0 /* defaultValue */)),
               mExtendedRegionSize(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
-                      EXTENDED_REGION_SIZE_KEY, 0 /* defaultValue */)) {}
+                      EXTENDED_REGION_SIZE_KEY, 0 /* defaultValue */)),
+              mHasHistoricalInfoOfWords(HeaderReadWriteUtils::readBoolAttributeValue(
+                      &mAttributeMap, HAS_HISTORICAL_INFO_KEY, false /* defaultValue */)) {}
 
     // Constructs header information using an attribute map.
     HeaderPolicy(const FormatUtils::FORMAT_VERSION dictFormatVersion,
@@ -56,32 +59,57 @@
               mDictionaryFlags(HeaderReadWriteUtils::createAndGetDictionaryFlagsUsingAttributeMap(
                       attributeMap)), mSize(0), mAttributeMap(*attributeMap),
               mMultiWordCostMultiplier(readMultipleWordCostMultiplier()),
+              mRequiresGermanUmlautProcessing(readRequiresGermanUmlautProcessing()),
               mIsDecayingDict(HeaderReadWriteUtils::readBoolAttributeValue(&mAttributeMap,
                       IS_DECAYING_DICT_KEY, false /* defaultValue */)),
               mLastUpdatedTime(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
-                      LAST_UPDATED_TIME_KEY, time(0) /* defaultValue */)),
+                      LAST_UPDATED_TIME_KEY, TimeKeeper::peekCurrentTime() /* defaultValue */)),
               mLastDecayedTime(HeaderReadWriteUtils::readIntAttributeValue(&mAttributeMap,
-                      LAST_UPDATED_TIME_KEY, time(0) /* defaultValue */)),
-              mUnigramCount(0), mBigramCount(0), mExtendedRegionSize(0) {}
+                      LAST_UPDATED_TIME_KEY, TimeKeeper::peekCurrentTime() /* defaultValue */)),
+              mUnigramCount(0), mBigramCount(0), mExtendedRegionSize(0),
+              mHasHistoricalInfoOfWords(HeaderReadWriteUtils::readBoolAttributeValue(
+                      &mAttributeMap, HAS_HISTORICAL_INFO_KEY, false /* defaultValue */)) {}
+
+    // Temporary dummy header.
+    HeaderPolicy()
+            : mDictFormatVersion(FormatUtils::UNKNOWN_VERSION), mDictionaryFlags(0), mSize(0),
+              mAttributeMap(), mMultiWordCostMultiplier(0.0f),
+              mRequiresGermanUmlautProcessing(false), mIsDecayingDict(false),
+              mLastUpdatedTime(0), mLastDecayedTime(0), mUnigramCount(0), mBigramCount(0),
+              mExtendedRegionSize(0), mHasHistoricalInfoOfWords(false) {}
 
     ~HeaderPolicy() {}
 
+    virtual int getFormatVersionNumber() const {
+        // Conceptually this converts the symbolic value we use in the code into the
+        // hardcoded of the bytes in the file. But we want the constants to be the
+        // same so we use them for both here.
+        switch (mDictFormatVersion) {
+            case FormatUtils::VERSION_2:
+                return FormatUtils::VERSION_2;
+            case FormatUtils::VERSION_4:
+                return FormatUtils::VERSION_4;
+            default:
+                return FormatUtils::UNKNOWN_VERSION;
+        }
+    }
+
+    AK_FORCE_INLINE bool isValid() const {
+        // Decaying dictionary must have historical information.
+        if (!mIsDecayingDict) {
+            return true;
+        }
+        if (mHasHistoricalInfoOfWords) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
     AK_FORCE_INLINE int getSize() const {
         return mSize;
     }
 
-    AK_FORCE_INLINE bool supportsDynamicUpdate() const {
-        return HeaderReadWriteUtils::supportsDynamicUpdate(mDictionaryFlags);
-    }
-
-    AK_FORCE_INLINE bool requiresGermanUmlautProcessing() const {
-        return HeaderReadWriteUtils::requiresGermanUmlautProcessing(mDictionaryFlags);
-    }
-
-    AK_FORCE_INLINE bool requiresFrenchLigatureProcessing() const {
-        return HeaderReadWriteUtils::requiresFrenchLigatureProcessing(mDictionaryFlags);
-    }
-
     AK_FORCE_INLINE float getMultiWordCostMultiplier() const {
         return mMultiWordCostMultiplier;
     }
@@ -90,6 +118,10 @@
         return mIsDecayingDict;
     }
 
+    AK_FORCE_INLINE bool requiresGermanUmlautProcessing() const {
+        return mRequiresGermanUmlautProcessing;
+    }
+
     AK_FORCE_INLINE int getLastUpdatedTime() const {
         return mLastUpdatedTime;
     }
@@ -110,6 +142,10 @@
         return mExtendedRegionSize;
     }
 
+    AK_FORCE_INLINE bool hasHistoricalInfoOfWords() const {
+        return mHasHistoricalInfoOfWords;
+    }
+
     void readHeaderValueOrQuestionMark(const char *const key,
             int *outValue, int outValueSize) const;
 
@@ -118,15 +154,17 @@
             const int unigramCount, const int bigramCount, const int extendedRegionSize) const;
 
  private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(HeaderPolicy);
+    DISALLOW_COPY_AND_ASSIGN(HeaderPolicy);
 
     static const char *const MULTIPLE_WORDS_DEMOTION_RATE_KEY;
+    static const char *const REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY;
     static const char *const IS_DECAYING_DICT_KEY;
     static const char *const LAST_UPDATED_TIME_KEY;
     static const char *const LAST_DECAYED_TIME_KEY;
     static const char *const UNIGRAM_COUNT_KEY;
     static const char *const BIGRAM_COUNT_KEY;
     static const char *const EXTENDED_REGION_SIZE_KEY;
+    static const char *const HAS_HISTORICAL_INFO_KEY;
     static const int DEFAULT_MULTIPLE_WORDS_DEMOTION_RATE;
     static const float MULTIPLE_WORD_COST_MULTIPLIER_SCALE;
 
@@ -135,14 +173,17 @@
     const int mSize;
     HeaderReadWriteUtils::AttributeMap mAttributeMap;
     const float mMultiWordCostMultiplier;
+    const bool mRequiresGermanUmlautProcessing;
     const bool mIsDecayingDict;
     const int mLastUpdatedTime;
     const int mLastDecayedTime;
     const int mUnigramCount;
     const int mBigramCount;
     const int mExtendedRegionSize;
+    const bool mHasHistoricalInfoOfWords;
 
     float readMultipleWordCostMultiplier() const;
+    bool readRequiresGermanUmlautProcessing() const;
 
     static HeaderReadWriteUtils::AttributeMap createAttributeMapAndReadAllAttributes(
             const uint8_t *const dictBuf);
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.cpp
index 5ded8f6..6b45986 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.cpp
@@ -35,22 +35,6 @@
 const int HeaderReadWriteUtils::HEADER_SIZE_FIELD_SIZE = 4;
 
 const HeaderReadWriteUtils::DictionaryFlags HeaderReadWriteUtils::NO_FLAGS = 0;
-// Flags for special processing
-// Those *must* match the flags in makedict (FormatSpec#*_PROCESSING_FLAG) or
-// something very bad (like, the apocalypse) will happen. Please update both at the same time.
-const HeaderReadWriteUtils::DictionaryFlags
-        HeaderReadWriteUtils::GERMAN_UMLAUT_PROCESSING_FLAG = 0x1;
-const HeaderReadWriteUtils::DictionaryFlags
-        HeaderReadWriteUtils::SUPPORTS_DYNAMIC_UPDATE_FLAG = 0x2;
-const HeaderReadWriteUtils::DictionaryFlags
-        HeaderReadWriteUtils::FRENCH_LIGATURE_PROCESSING_FLAG = 0x4;
-
-// Note that these are corresponding definitions in Java side in FormatSpec.FileHeader.
-const char *const HeaderReadWriteUtils::SUPPORTS_DYNAMIC_UPDATE_KEY = "SUPPORTS_DYNAMIC_UPDATE";
-const char *const HeaderReadWriteUtils::REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY =
-        "REQUIRES_GERMAN_UMLAUT_PROCESSING";
-const char *const HeaderReadWriteUtils::REQUIRES_FRENCH_LIGATURE_PROCESSING_KEY =
-        "REQUIRES_FRENCH_LIGATURE_PROCESSING";
 
 /* static */ int HeaderReadWriteUtils::getHeaderSize(const uint8_t *const dictBuf) {
     // See the format of the header in the comment in
@@ -68,17 +52,7 @@
 /* static */ HeaderReadWriteUtils::DictionaryFlags
         HeaderReadWriteUtils::createAndGetDictionaryFlagsUsingAttributeMap(
                 const HeaderReadWriteUtils::AttributeMap *const attributeMap) {
-    const bool requiresGermanUmlautProcessing = readBoolAttributeValue(attributeMap,
-            REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY, false /* defaultValue */);
-    const bool requiresFrenchLigatureProcessing = readBoolAttributeValue(attributeMap,
-            REQUIRES_FRENCH_LIGATURE_PROCESSING_KEY, false /* defaultValue */);
-    const bool supportsDynamicUpdate = readBoolAttributeValue(attributeMap,
-            SUPPORTS_DYNAMIC_UPDATE_KEY, false /* defaultValue */);
-    DictionaryFlags dictflags = NO_FLAGS;
-    dictflags |= requiresGermanUmlautProcessing ? GERMAN_UMLAUT_PROCESSING_FLAG : 0;
-    dictflags |= requiresFrenchLigatureProcessing ? FRENCH_LIGATURE_PROCESSING_FLAG : 0;
-    dictflags |= supportsDynamicUpdate ? SUPPORTS_DYNAMIC_UPDATE_FLAG : 0;
-    return dictflags;
+    return NO_FLAGS;
 }
 
 /* static */ void HeaderReadWriteUtils::fetchAllHeaderAttributes(const uint8_t *const dictBuf,
@@ -115,8 +89,8 @@
         case FormatUtils::VERSION_2:
             // Version 2 dictionary writing is not supported.
             return false;
-        case FormatUtils::VERSION_3:
-            return buffer->writeUintAndAdvancePosition(3 /* data */,
+        case FormatUtils::VERSION_4:
+            return buffer->writeUintAndAdvancePosition(FormatUtils::VERSION_4 /* data */,
                     HEADER_DICTIONARY_VERSION_SIZE, writingPos);
         default:
             return false;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.h b/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.h
index 2259683..fc24bbd 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_read_write_utils.h
@@ -37,18 +37,6 @@
 
     static DictionaryFlags getFlags(const uint8_t *const dictBuf);
 
-    static AK_FORCE_INLINE bool supportsDynamicUpdate(const DictionaryFlags flags) {
-        return (flags & SUPPORTS_DYNAMIC_UPDATE_FLAG) != 0;
-    }
-
-    static AK_FORCE_INLINE bool requiresGermanUmlautProcessing(const DictionaryFlags flags) {
-        return (flags & GERMAN_UMLAUT_PROCESSING_FLAG) != 0;
-    }
-
-    static AK_FORCE_INLINE bool requiresFrenchLigatureProcessing(const DictionaryFlags flags) {
-        return (flags & FRENCH_LIGATURE_PROCESSING_FLAG) != 0;
-    }
-
     static AK_FORCE_INLINE int getHeaderOptionsPosition() {
         return HEADER_MAGIC_NUMBER_SIZE + HEADER_DICTIONARY_VERSION_SIZE + HEADER_FLAG_SIZE
                 + HEADER_SIZE_FIELD_SIZE;
@@ -101,17 +89,8 @@
     static const int HEADER_FLAG_SIZE;
     static const int HEADER_SIZE_FIELD_SIZE;
 
+    // Value for the "flags" field. It's unused at the moment.
     static const DictionaryFlags NO_FLAGS;
-    // Flags for special processing
-    // Those *must* match the flags in makedict (FormatSpec#*_PROCESSING_FLAGS) or
-    // something very bad (like, the apocalypse) will happen. Please update both at the same time.
-    static const DictionaryFlags GERMAN_UMLAUT_PROCESSING_FLAG;
-    static const DictionaryFlags SUPPORTS_DYNAMIC_UPDATE_FLAG;
-    static const DictionaryFlags FRENCH_LIGATURE_PROCESSING_FLAG;
-
-    static const char *const SUPPORTS_DYNAMIC_UPDATE_KEY;
-    static const char *const REQUIRES_GERMAN_UMLAUT_PROCESSING_KEY;
-    static const char *const REQUIRES_FRENCH_LIGATURE_PROCESSING_KEY;
 
     static void setIntAttributeInner(AttributeMap *const headerAttributes,
             const AttributeMap::key_type *const key, const int value);
diff --git a/native/jni/src/suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h b/native/jni/src/suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h
deleted file mode 100644
index bd3211f..0000000
--- a/native/jni/src/suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h
+++ /dev/null
@@ -1,123 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef LATINIME_DYNAMIC_SHORTCUT_LIST_POLICY_H
-#define LATINIME_DYNAMIC_SHORTCUT_LIST_POLICY_H
-
-#include <stdint.h>
-
-#include "defines.h"
-#include "suggest/core/policy/dictionary_shortcuts_structure_policy.h"
-#include "suggest/policyimpl/dictionary/shortcut/shortcut_list_reading_utils.h"
-#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
-
-namespace latinime {
-
-/*
- * This is a dynamic version of ShortcutListPolicy and supports an additional buffer.
- */
-class DynamicShortcutListPolicy : public DictionaryShortcutsStructurePolicy {
- public:
-    explicit DynamicShortcutListPolicy(const BufferWithExtendableBuffer *const buffer)
-            : mBuffer(buffer) {}
-
-    ~DynamicShortcutListPolicy() {}
-
-    int getStartPos(const int pos) const {
-        if (pos == NOT_A_DICT_POS) {
-            return NOT_A_DICT_POS;
-        }
-        return pos + ShortcutListReadingUtils::getShortcutListSizeFieldSize();
-    }
-
-    void getNextShortcut(const int maxCodePointCount, int *const outCodePoint,
-            int *const outCodePointCount, bool *const outIsWhitelist, bool *const outHasNext,
-            int *const pos) const {
-        const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*pos);
-        const uint8_t *const buffer = mBuffer->getBuffer(usesAdditionalBuffer);
-        if (usesAdditionalBuffer) {
-            *pos -= mBuffer->getOriginalBufferSize();
-        }
-        const ShortcutListReadingUtils::ShortcutFlags flags =
-                ShortcutListReadingUtils::getFlagsAndForwardPointer(buffer, pos);
-        if (outHasNext) {
-            *outHasNext = ShortcutListReadingUtils::hasNext(flags);
-        }
-        if (outIsWhitelist) {
-            *outIsWhitelist = ShortcutListReadingUtils::isWhitelist(flags);
-        }
-        if (outCodePoint) {
-            *outCodePointCount = ShortcutListReadingUtils::readShortcutTarget(
-                    buffer, maxCodePointCount, outCodePoint, pos);
-        }
-        if (usesAdditionalBuffer) {
-            *pos += mBuffer->getOriginalBufferSize();
-        }
-    }
-
-    void skipAllShortcuts(int *const pos) const {
-        const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*pos);
-        const uint8_t *const buffer = mBuffer->getBuffer(usesAdditionalBuffer);
-        if (usesAdditionalBuffer) {
-            *pos -= mBuffer->getOriginalBufferSize();
-        }
-        const int shortcutListSize = ShortcutListReadingUtils
-                ::getShortcutListSizeAndForwardPointer(buffer, pos);
-        *pos += shortcutListSize;
-        if (usesAdditionalBuffer) {
-            *pos += mBuffer->getOriginalBufferSize();
-        }
-    }
-
-    // Copy shortcuts from the shortcut list that starts at fromPos in mBuffer to toPos in
-    // bufferToWrite and advance these positions after the shortcut lists. This returns whether
-    // the copy was succeeded or not.
-    bool copyAllShortcutsAndReturnIfSucceededOrNot(BufferWithExtendableBuffer *const bufferToWrite,
-            int *const fromPos, int *const toPos) const {
-        const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(*fromPos);
-        if (usesAdditionalBuffer) {
-            *fromPos -= mBuffer->getOriginalBufferSize();
-        }
-        const int shortcutListSize = ShortcutListReadingUtils
-                ::getShortcutListSizeAndForwardPointer(mBuffer->getBuffer(usesAdditionalBuffer),
-                        fromPos);
-        // Copy shortcut list size.
-        if (!bufferToWrite->writeUintAndAdvancePosition(
-                shortcutListSize + ShortcutListReadingUtils::getShortcutListSizeFieldSize(),
-                ShortcutListReadingUtils::getShortcutListSizeFieldSize(), toPos)) {
-            return false;
-        }
-        // Copy shortcut list.
-        for (int i = 0; i < shortcutListSize; ++i) {
-            const uint8_t data = ByteArrayUtils::readUint8AndAdvancePosition(
-                    mBuffer->getBuffer(usesAdditionalBuffer), fromPos);
-            if (!bufferToWrite->writeUintAndAdvancePosition(data, 1 /* size */, toPos)) {
-                return false;
-            }
-        }
-        if (usesAdditionalBuffer) {
-            *fromPos += mBuffer->getOriginalBufferSize();
-        }
-        return true;
-    }
-
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicShortcutListPolicy);
-
-    const BufferWithExtendableBuffer *const mBuffer;
-};
-} // namespace latinime
-#endif // LATINIME_DYNAMIC_SHORTCUT_LIST_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h b/native/jni/src/suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h
new file mode 100644
index 0000000..ae863af
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_SHORTCUT_LIST_POLICY_H
+#define LATINIME_VER4_SHORTCUT_LIST_POLICY_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/core/policy/dictionary_shortcuts_structure_policy.h"
+#include "suggest/policyimpl/dictionary/shortcut/shortcut_list_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+
+namespace latinime {
+
+class Ver4ShortcutListPolicy : public DictionaryShortcutsStructurePolicy {
+ public:
+    Ver4ShortcutListPolicy(ShortcutDictContent *const shortcutDictContent,
+            const TerminalPositionLookupTable *const terminalPositionLookupTable)
+            : mShortcutDictContent(shortcutDictContent),
+              mTerminalPositionLookupTable(terminalPositionLookupTable) {}
+
+    ~Ver4ShortcutListPolicy() {}
+
+    int getStartPos(const int pos) const {
+        // The first shortcut entry is located at the head position of the shortcut list.
+        return pos;
+    }
+
+    void getNextShortcut(const int maxCodePointCount, int *const outCodePoint,
+            int *const outCodePointCount, bool *const outIsWhitelist, bool *const outHasNext,
+            int *const pos) const {
+        int probability = 0;
+        mShortcutDictContent->getShortcutEntryAndAdvancePosition(maxCodePointCount,
+                outCodePoint, outCodePointCount, &probability, outHasNext, pos);
+        if (outIsWhitelist) {
+            *outIsWhitelist = ShortcutListReadingUtils::isWhitelist(probability);
+        }
+    }
+
+    void skipAllShortcuts(int *const pos) const {
+        // Do nothing because we don't need to skip shortcut lists in ver4 dictionaries.
+    }
+
+    bool addNewShortcut(const int terminalId, const int *const codePoints, const int codePointCount,
+            const int probability) {
+        const int shortcutListPos = mShortcutDictContent->getShortcutListHeadPos(terminalId);
+        if (shortcutListPos == NOT_A_DICT_POS) {
+            // Create shortcut list.
+            if (!mShortcutDictContent->createNewShortcutList(terminalId)) {
+                AKLOGE("Cannot create new shortcut list. terminal id: %d", terminalId);
+                return false;
+            }
+            const int writingPos =  mShortcutDictContent->getShortcutListHeadPos(terminalId);
+            return mShortcutDictContent->writeShortcutEntry(codePoints, codePointCount, probability,
+                    false /* hasNext */, writingPos);
+        }
+        const int entryPos = mShortcutDictContent->findShortcutEntryAndGetPos(shortcutListPos,
+                codePoints, codePointCount);
+        if (entryPos == NOT_A_DICT_POS) {
+            // Add new entry to the shortcut list.
+            // Create new shortcut list.
+            if (!mShortcutDictContent->createNewShortcutList(terminalId)) {
+                AKLOGE("Cannot create new shortcut list. terminal id: %d", terminalId);
+                return false;
+            }
+            int writingPos =  mShortcutDictContent->getShortcutListHeadPos(terminalId);
+            if (!mShortcutDictContent->writeShortcutEntryAndAdvancePosition(codePoints,
+                    codePointCount, probability, true /* hasNext */, &writingPos)) {
+                AKLOGE("Cannot write shortcut entry. terminal id: %d, pos: %d", terminalId,
+                        writingPos);
+                return false;
+            }
+            return mShortcutDictContent->copyShortcutList(shortcutListPos, writingPos);
+        }
+        // Overwrite existing entry.
+        bool hasNext = false;
+        mShortcutDictContent->getShortcutEntry(MAX_WORD_LENGTH, 0 /* outCodePoint */,
+                0 /* outCodePointCount */ , 0 /* probability */, &hasNext, entryPos);
+        if (!mShortcutDictContent->writeShortcutEntry(codePoints,
+                codePointCount, probability, hasNext, entryPos)) {
+            AKLOGE("Cannot overwrite shortcut entry. terminal id: %d, pos: %d", terminalId,
+                    entryPos);
+            return false;
+        }
+        return true;
+    }
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4ShortcutListPolicy);
+
+    ShortcutDictContent *const mShortcutDictContent;
+    const TerminalPositionLookupTable *const mTerminalPositionLookupTable;
+};
+} // namespace latinime
+#endif // LATINIME_VER4_SHORTCUT_LIST_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp
new file mode 100644
index 0000000..c81c61d
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp
@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.h"
+
+#include <climits>
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h"
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
+#include "suggest/policyimpl/dictionary/utils/format_utils.h"
+#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
+
+namespace latinime {
+
+/* static */ DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+        DictionaryStructureWithBufferPolicyFactory
+                ::newDictionaryStructureWithBufferPolicy(const char *const path,
+                        const int bufOffset, const int size, const bool isUpdatable) {
+    if (FileUtils::existsDir(path)) {
+        // Given path represents a directory.
+        return newPolicyforDirectoryDict(path, isUpdatable);
+    } else {
+        if (isUpdatable) {
+            AKLOGE("One file dictionaries don't support updating. path: %s", path);
+            ASSERT(false);
+            return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+        }
+        return newPolicyforFileDict(path, bufOffset, size);
+    }
+}
+
+/* static */ DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+        DictionaryStructureWithBufferPolicyFactory::newPolicyforDirectoryDict(
+                const char *const path, const bool isUpdatable) {
+    const int headerFilePathBufSize = PATH_MAX + 1 /* terminator */;
+    char headerFilePath[headerFilePathBufSize];
+    getHeaderFilePathInDictDir(path, headerFilePathBufSize, headerFilePath);
+    // Allocated buffer in MmapedBuffer::openBuffer() will be freed in the destructor of
+    // MmappedBufferPtr if the instance has the responsibility.
+    MmappedBuffer::MmappedBufferPtr mmappedBuffer = MmappedBuffer::openBuffer(headerFilePath,
+            isUpdatable);
+    if (!mmappedBuffer.get()) {
+        return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+    }
+    switch (FormatUtils::detectFormatVersion(mmappedBuffer.get()->getBuffer(),
+            mmappedBuffer.get()->getBufferSize())) {
+        case FormatUtils::VERSION_2:
+            AKLOGE("Given path is a directory but the format is version 2. path: %s", path);
+            break;
+        case FormatUtils::VERSION_4: {
+            const int dictDirPathBufSize = strlen(headerFilePath) + 1 /* terminator */;
+            char dictPath[dictDirPathBufSize];
+            if (!FileUtils::getFilePathWithoutSuffix(headerFilePath,
+                    Ver4DictConstants::HEADER_FILE_EXTENSION, dictDirPathBufSize, dictPath)) {
+                AKLOGE("Dictionary file name is not valid as a ver4 dictionary. path: %s", path);
+                ASSERT(false);
+                return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+            }
+            const Ver4DictBuffers::Ver4DictBuffersPtr dictBuffers =
+                    Ver4DictBuffers::openVer4DictBuffers(dictPath, mmappedBuffer);
+            if (!dictBuffers.get()->isValid()) {
+                AKLOGE("DICT: The dictionary doesn't satisfy ver4 format requirements. path: %s",
+                        path);
+                ASSERT(false);
+                return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+            }
+            return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(
+                    new Ver4PatriciaTriePolicy(dictBuffers));
+        }
+        default:
+            AKLOGE("DICT: dictionary format is unknown, bad magic number. path: %s", path);
+            break;
+    }
+    ASSERT(false);
+    return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+}
+
+/* static */ DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+        DictionaryStructureWithBufferPolicyFactory::newPolicyforFileDict(
+                const char *const path, const int bufOffset, const int size) {
+    // Allocated buffer in MmapedBuffer::openBuffer() will be freed in the destructor of
+    // MmappedBufferPtr if the instance has the responsibility.
+    MmappedBuffer::MmappedBufferPtr mmappedBuffer = MmappedBuffer::openBuffer(path, bufOffset,
+            size, false /* isUpdatable */);
+    if (!mmappedBuffer.get()) {
+        return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+    }
+    switch (FormatUtils::detectFormatVersion(mmappedBuffer.get()->getBuffer(),
+            mmappedBuffer.get()->getBufferSize())) {
+        case FormatUtils::VERSION_2:
+            return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(
+                    new PatriciaTriePolicy(mmappedBuffer));
+        case FormatUtils::VERSION_4:
+            AKLOGE("Given path is a file but the format is version 4. path: %s", path);
+            break;
+        default:
+            AKLOGE("DICT: dictionary format is unknown, bad magic number. path: %s", path);
+            break;
+    }
+    ASSERT(false);
+    return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(0);
+}
+
+/* static */ void DictionaryStructureWithBufferPolicyFactory::getHeaderFilePathInDictDir(
+        const char *const dictDirPath, const int outHeaderFileBufSize,
+        char *const outHeaderFilePath) {
+    const int dictNameBufSize = strlen(dictDirPath) + 1 /* terminator */;
+    char dictName[dictNameBufSize];
+    FileUtils::getBasename(dictDirPath, dictNameBufSize, dictName);
+    snprintf(outHeaderFilePath, outHeaderFileBufSize, "%s/%s%s", dictDirPath,
+            dictName, Ver4DictConstants::HEADER_FILE_EXTENSION);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.h
similarity index 60%
rename from native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h
rename to native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.h
index 8cebc3b..45ab529 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.h
@@ -21,16 +21,27 @@
 
 #include "defines.h"
 #include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
+#include "utils/exclusive_ownership_pointer.h"
 
 namespace latinime {
 
 class DictionaryStructureWithBufferPolicyFactory {
  public:
-    static DictionaryStructureWithBufferPolicy *newDictionaryStructureWithBufferPolicy(
-            const char *const path, const int bufOffset, const int size, const bool isUpdatable);
+    static DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+            newDictionaryStructureWithBufferPolicy(const char *const path, const int bufOffset,
+                    const int size, const bool isUpdatable);
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DictionaryStructureWithBufferPolicyFactory);
+
+    static DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+            newPolicyforDirectoryDict(const char *const path, const bool isUpdatable);
+
+    static DictionaryStructureWithBufferPolicy::StructurePolicyPtr
+            newPolicyforFileDict(const char *const path, const int bufOffset, const int size);
+
+    static void getHeaderFilePathInDictDir(const char *const dirPath,
+            const int outHeaderFileBufSize, char *const outHeaderFilePath);
 };
 } // namespace latinime
 #endif // LATINIME_DICTIONARY_STRUCTURE_WITH_BUFFER_POLICY_FACTORY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.cpp
new file mode 100644
index 0000000..8f42df6
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.cpp
@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.h"
+
+#include "suggest/core/policy/dictionary_header_structure_policy.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h"
+
+namespace latinime {
+
+bool DynamicPtGcEventListeners
+        ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
+                ::onVisitingPtNode(const PtNodeParams *const ptNodeParams) {
+    // PtNode is useless when the PtNode is not a terminal and doesn't have any not useless
+    // children.
+    bool isUselessPtNode = !ptNodeParams->isTerminal();
+    if (ptNodeParams->isTerminal()) {
+        bool needsToKeepPtNode = true;
+        if (!mPtNodeWriter->updatePtNodeProbabilityAndGetNeedsToKeepPtNodeAfterGC(ptNodeParams,
+                &needsToKeepPtNode)) {
+            AKLOGE("Cannot update PtNode probability or get needs to keep PtNode after GC.");
+            return false;
+        }
+        if (!needsToKeepPtNode) {
+            isUselessPtNode = true;
+        }
+    }
+    if (mChildrenValue > 0) {
+        isUselessPtNode = false;
+    } else if (ptNodeParams->isTerminal()) {
+        // Remove children as all children are useless.
+        if (!mPtNodeWriter->updateChildrenPosition(ptNodeParams,
+                NOT_A_DICT_POS /* newChildrenPosition */)) {
+            return false;
+        }
+    }
+    if (isUselessPtNode) {
+        // Current PtNode is no longer needed. Mark it as deleted.
+        if (!mPtNodeWriter->markPtNodeAsDeleted(ptNodeParams)) {
+            return false;
+        }
+    } else {
+        mValueStack.back() += 1;
+        if (ptNodeParams->isTerminal()) {
+            mValidUnigramCount += 1;
+        }
+    }
+    return true;
+}
+
+bool DynamicPtGcEventListeners::TraversePolicyToUpdateBigramProbability
+        ::onVisitingPtNode(const PtNodeParams *const ptNodeParams) {
+    if (!ptNodeParams->isDeleted() && ptNodeParams->hasBigrams()) {
+        int bigramEntryCount = 0;
+        if (!mPtNodeWriter->updateAllBigramEntriesAndDeleteUselessEntries(ptNodeParams,
+                &bigramEntryCount)) {
+            return false;
+        }
+        mValidBigramEntryCount += bigramEntryCount;
+    }
+    return true;
+}
+
+// Writes dummy PtNode array size when the head of PtNode array is read.
+bool DynamicPtGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
+        ::onDescend(const int ptNodeArrayPos) {
+    mValidPtNodeCount = 0;
+    int writingPos = mBufferToWrite->getTailPosition();
+    mDictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.insert(
+            PtNodeWriter::PtNodeArrayPositionRelocationMap::value_type(ptNodeArrayPos, writingPos));
+    // Writes dummy PtNode array size because arrays can have a forward link or needles PtNodes.
+    // This field will be updated later in onReadingPtNodeArrayTail() with actual PtNode count.
+    mPtNodeArraySizeFieldPos = writingPos;
+    return DynamicPtWritingUtils::writePtNodeArraySizeAndAdvancePosition(
+            mBufferToWrite, 0 /* arraySize */, &writingPos);
+}
+
+// Write PtNode array terminal and actual PtNode array size.
+bool DynamicPtGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
+        ::onReadingPtNodeArrayTail() {
+    int writingPos = mBufferToWrite->getTailPosition();
+    // Write PtNode array terminal.
+    if (!DynamicPtWritingUtils::writeForwardLinkPositionAndAdvancePosition(
+            mBufferToWrite, NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
+        return false;
+    }
+    // Write actual PtNode array size.
+    if (!DynamicPtWritingUtils::writePtNodeArraySizeAndAdvancePosition(
+            mBufferToWrite, mValidPtNodeCount, &mPtNodeArraySizeFieldPos)) {
+        return false;
+    }
+    return true;
+}
+
+// Write valid PtNode to buffer and memorize mapping from the old position to the new position.
+bool DynamicPtGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
+        ::onVisitingPtNode(const PtNodeParams *const ptNodeParams) {
+    if (ptNodeParams->isDeleted()) {
+        // Current PtNode is not written in new buffer because it has been deleted.
+        mDictPositionRelocationMap->mPtNodePositionRelocationMap.insert(
+                PtNodeWriter::PtNodePositionRelocationMap::value_type(
+                        ptNodeParams->getHeadPos(), NOT_A_DICT_POS));
+        return true;
+    }
+    int writingPos = mBufferToWrite->getTailPosition();
+    mDictPositionRelocationMap->mPtNodePositionRelocationMap.insert(
+            PtNodeWriter::PtNodePositionRelocationMap::value_type(
+                    ptNodeParams->getHeadPos(), writingPos));
+    mValidPtNodeCount++;
+    // Writes current PtNode.
+    return mPtNodeWriter->writePtNodeAndAdvancePosition(ptNodeParams, &writingPos);
+}
+
+bool DynamicPtGcEventListeners::TraversePolicyToUpdateAllPositionFields
+        ::onVisitingPtNode(const PtNodeParams *const ptNodeParams) {
+    // Updates parent position.
+    int bigramCount = 0;
+    if (!mPtNodeWriter->updateAllPositionFields(ptNodeParams, mDictPositionRelocationMap,
+            &bigramCount)) {
+        return false;
+    }
+    mBigramCount += bigramCount;
+    if (ptNodeParams->isTerminal()) {
+        mUnigramCount++;
+    }
+    return true;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.h
new file mode 100644
index 0000000..d886775
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.h
@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DYNAMIC_PT_GC_EVENT_LISTENERS_H
+#define LATINIME_DYNAMIC_PT_GC_EVENT_LISTENERS_H
+
+#include <vector>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "utils/hash_map_compat.h"
+
+namespace latinime {
+
+class PtNodeParams;
+
+class DynamicPtGcEventListeners {
+ public:
+    // Updates all PtNodes that can be reached from the root. Checks if each PtNode is useless or
+    // not and marks useless PtNodes as deleted. Such deleted PtNodes will be discarded in the GC.
+    // TODO: Concatenate non-terminal PtNodes.
+    class TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
+        : public DynamicPtReadingHelper::TraversingEventListener {
+     public:
+        TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
+                PtNodeWriter *const ptNodeWriter)
+                : mPtNodeWriter(ptNodeWriter), mValueStack(), mChildrenValue(0),
+                  mValidUnigramCount(0) {}
+
+        ~TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted() {};
+
+        bool onAscend() {
+            if (mValueStack.empty()) {
+                return false;
+            }
+            mChildrenValue = mValueStack.back();
+            mValueStack.pop_back();
+            return true;
+        }
+
+        bool onDescend(const int ptNodeArrayPos) {
+            mValueStack.push_back(0);
+            mChildrenValue = 0;
+            return true;
+        }
+
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const PtNodeParams *const ptNodeParams);
+
+        int getValidUnigramCount() const {
+            return mValidUnigramCount;
+        }
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(
+                TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted);
+
+        PtNodeWriter *const mPtNodeWriter;
+        std::vector<int> mValueStack;
+        int mChildrenValue;
+        int mValidUnigramCount;
+    };
+
+    // Updates all bigram entries that are held by valid PtNodes. This removes useless bigram
+    // entries.
+    class TraversePolicyToUpdateBigramProbability
+            : public DynamicPtReadingHelper::TraversingEventListener {
+     public:
+        TraversePolicyToUpdateBigramProbability(PtNodeWriter *const ptNodeWriter)
+                : mPtNodeWriter(ptNodeWriter), mValidBigramEntryCount(0) {}
+
+        bool onAscend() { return true; }
+
+        bool onDescend(const int ptNodeArrayPos) { return true; }
+
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const PtNodeParams *const ptNodeParams);
+
+        int getValidBigramEntryCount() const {
+            return mValidBigramEntryCount;
+        }
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateBigramProbability);
+
+        PtNodeWriter *const mPtNodeWriter;
+        int mValidBigramEntryCount;
+    };
+
+    class TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
+            : public DynamicPtReadingHelper::TraversingEventListener {
+     public:
+        TraversePolicyToPlaceAndWriteValidPtNodesToBuffer(
+                PtNodeWriter *const ptNodeWriter, BufferWithExtendableBuffer *const bufferToWrite,
+                PtNodeWriter::DictPositionRelocationMap *const dictPositionRelocationMap)
+                : mPtNodeWriter(ptNodeWriter), mBufferToWrite(bufferToWrite),
+                  mDictPositionRelocationMap(dictPositionRelocationMap), mValidPtNodeCount(0),
+                  mPtNodeArraySizeFieldPos(NOT_A_DICT_POS) {};
+
+        bool onAscend() { return true; }
+
+        bool onDescend(const int ptNodeArrayPos);
+
+        bool onReadingPtNodeArrayTail();
+
+        bool onVisitingPtNode(const PtNodeParams *const ptNodeParams);
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToPlaceAndWriteValidPtNodesToBuffer);
+
+        PtNodeWriter *const mPtNodeWriter;
+        BufferWithExtendableBuffer *const mBufferToWrite;
+        PtNodeWriter::DictPositionRelocationMap *const mDictPositionRelocationMap;
+        int mValidPtNodeCount;
+        int mPtNodeArraySizeFieldPos;
+    };
+
+    class TraversePolicyToUpdateAllPositionFields
+            : public DynamicPtReadingHelper::TraversingEventListener {
+     public:
+        TraversePolicyToUpdateAllPositionFields(PtNodeWriter *const ptNodeWriter,
+                const PtNodeWriter::DictPositionRelocationMap *const dictPositionRelocationMap)
+                : mPtNodeWriter(ptNodeWriter),
+                  mDictPositionRelocationMap(dictPositionRelocationMap), mUnigramCount(0),
+                  mBigramCount(0) {};
+
+        bool onAscend() { return true; }
+
+        bool onDescend(const int ptNodeArrayPos) { return true; }
+
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const PtNodeParams *const ptNodeParams);
+
+        int getUnigramCount() const {
+            return mUnigramCount;
+        }
+
+        int getBigramCount() const {
+            return mBigramCount;
+        }
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateAllPositionFields);
+
+        PtNodeWriter *const mPtNodeWriter;
+        const PtNodeWriter::DictPositionRelocationMap *const mDictPositionRelocationMap;
+        int mUnigramCount;
+        int mBigramCount;
+    };
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPtGcEventListeners);
+};
+} // namespace latinime
+#endif /* LATINIME_DYNAMIC_PT_GC_EVENT_LISTENERS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.cpp
new file mode 100644
index 0000000..b918e07
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.cpp
@@ -0,0 +1,342 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
+
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
+#include "utils/char_utils.h"
+
+namespace latinime {
+
+// To avoid infinite loop caused by invalid or malicious forward links.
+const int DynamicPtReadingHelper::MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP = 100000;
+const int DynamicPtReadingHelper::MAX_PT_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP = 100000;
+const size_t DynamicPtReadingHelper::MAX_READING_STATE_STACK_SIZE = MAX_WORD_LENGTH;
+
+// Visits all PtNodes in post-order depth first manner.
+// For example, visits c -> b -> y -> x -> a for the following dictionary:
+// a _ b _ c
+//   \ x _ y
+bool DynamicPtReadingHelper::traverseAllPtNodesInPostorderDepthFirstManner(
+        TraversingEventListener *const listener) {
+    bool alreadyVisitedChildren = false;
+    // Descend from the root to the root PtNode array.
+    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
+        return false;
+    }
+    while (!isEnd()) {
+        const PtNodeParams ptNodeParams(getPtNodeParams());
+        if (!ptNodeParams.isValid()) {
+            break;
+        }
+        if (!alreadyVisitedChildren) {
+            if (ptNodeParams.hasChildren()) {
+                // Move to the first child.
+                if (!listener->onDescend(ptNodeParams.getChildrenPos())) {
+                    return false;
+                }
+                pushReadingStateToStack();
+                readChildNode(ptNodeParams);
+            } else {
+                alreadyVisitedChildren = true;
+            }
+        } else {
+            if (!listener->onVisitingPtNode(&ptNodeParams)) {
+                return false;
+            }
+            readNextSiblingNode(ptNodeParams);
+            if (isEnd()) {
+                // All PtNodes in current linked PtNode arrays have been visited.
+                // Return to the parent.
+                if (!listener->onReadingPtNodeArrayTail()) {
+                    return false;
+                }
+                if (mReadingStateStack.size() <= 0) {
+                    break;
+                }
+                if (!listener->onAscend()) {
+                    return false;
+                }
+                popReadingStateFromStack();
+                alreadyVisitedChildren = true;
+            } else {
+                // Process sibling PtNode.
+                alreadyVisitedChildren = false;
+            }
+        }
+    }
+    // Ascend from the root PtNode array to the root.
+    if (!listener->onAscend()) {
+        return false;
+    }
+    return !isError();
+}
+
+// Visits all PtNodes in PtNode array level pre-order depth first manner, which is the same order
+// that PtNodes are written in the dictionary buffer.
+// For example, visits a -> b -> x -> c -> y for the following dictionary:
+// a _ b _ c
+//   \ x _ y
+bool DynamicPtReadingHelper::traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+        TraversingEventListener *const listener) {
+    bool alreadyVisitedAllPtNodesInArray = false;
+    bool alreadyVisitedChildren = false;
+    // Descend from the root to the root PtNode array.
+    if (!listener->onDescend(getPosOfLastPtNodeArrayHead())) {
+        return false;
+    }
+    if (isEnd()) {
+        // Empty dictionary. Needs to notify the listener of the tail of empty PtNode array.
+        if (!listener->onReadingPtNodeArrayTail()) {
+            return false;
+        }
+    }
+    pushReadingStateToStack();
+    while (!isEnd()) {
+        const PtNodeParams ptNodeParams(getPtNodeParams());
+        if (!ptNodeParams.isValid()) {
+            break;
+        }
+        if (alreadyVisitedAllPtNodesInArray) {
+            if (alreadyVisitedChildren) {
+                // Move to next sibling PtNode's children.
+                readNextSiblingNode(ptNodeParams);
+                if (isEnd()) {
+                    // Return to the parent PTNode.
+                    if (!listener->onAscend()) {
+                        return false;
+                    }
+                    if (mReadingStateStack.size() <= 0) {
+                        break;
+                    }
+                    popReadingStateFromStack();
+                    alreadyVisitedChildren = true;
+                    alreadyVisitedAllPtNodesInArray = true;
+                } else {
+                    alreadyVisitedChildren = false;
+                }
+            } else {
+                if (ptNodeParams.hasChildren()) {
+                    // Move to the first child.
+                    if (!listener->onDescend(ptNodeParams.getChildrenPos())) {
+                        return false;
+                    }
+                    pushReadingStateToStack();
+                    readChildNode(ptNodeParams);
+                    // Push state to return the head of PtNode array.
+                    pushReadingStateToStack();
+                    alreadyVisitedAllPtNodesInArray = false;
+                    alreadyVisitedChildren = false;
+                } else {
+                    alreadyVisitedChildren = true;
+                }
+            }
+        } else {
+            if (!listener->onVisitingPtNode(&ptNodeParams)) {
+                return false;
+            }
+            readNextSiblingNode(ptNodeParams);
+            if (isEnd()) {
+                if (!listener->onReadingPtNodeArrayTail()) {
+                    return false;
+                }
+                // Return to the head of current PtNode array.
+                popReadingStateFromStack();
+                alreadyVisitedAllPtNodesInArray = true;
+            }
+        }
+    }
+    popReadingStateFromStack();
+    // Ascend from the root PtNode array to the root.
+    if (!listener->onAscend()) {
+        return false;
+    }
+    return !isError();
+}
+
+int DynamicPtReadingHelper::getCodePointsAndProbabilityAndReturnCodePointCount(
+        const int maxCodePointCount, int *const outCodePoints, int *const outUnigramProbability) {
+    // This method traverses parent nodes from the terminal by following parent pointers; thus,
+    // node code points are stored in the buffer in the reverse order.
+    int reverseCodePoints[maxCodePointCount];
+    const PtNodeParams terminalPtNodeParams(getPtNodeParams());
+    // First, read the terminal node and get its probability.
+    if (!isValidTerminalNode(terminalPtNodeParams)) {
+        // Node at the ptNodePos is not a valid terminal node.
+        *outUnigramProbability = NOT_A_PROBABILITY;
+        return 0;
+    }
+    // Store terminal node probability.
+    *outUnigramProbability = terminalPtNodeParams.getProbability();
+    // Then, following parent node link to the dictionary root and fetch node code points.
+    int totalCodePointCount = 0;
+    while (!isEnd()) {
+        const PtNodeParams ptNodeParams(getPtNodeParams());
+        totalCodePointCount = getTotalCodePointCount(ptNodeParams);
+        if (!ptNodeParams.isValid() || totalCodePointCount > maxCodePointCount) {
+            // The ptNodePos is not a valid terminal node position in the dictionary.
+            *outUnigramProbability = NOT_A_PROBABILITY;
+            return 0;
+        }
+        // Store node code points to buffer in the reverse order.
+        fetchMergedNodeCodePointsInReverseOrder(ptNodeParams, getPrevTotalCodePointCount(),
+                reverseCodePoints);
+        // Follow parent node toward the root node.
+        readParentNode(ptNodeParams);
+    }
+    if (isError()) {
+        // The node position or the dictionary is invalid.
+        *outUnigramProbability = NOT_A_PROBABILITY;
+        return 0;
+    }
+    // Reverse the stored code points to output them.
+    for (int i = 0; i < totalCodePointCount; ++i) {
+        outCodePoints[i] = reverseCodePoints[totalCodePointCount - i - 1];
+    }
+    return totalCodePointCount;
+}
+
+int DynamicPtReadingHelper::getTerminalPtNodePositionOfWord(const int *const inWord,
+        const int length, const bool forceLowerCaseSearch) {
+    int searchCodePoints[length];
+    for (int i = 0; i < length; ++i) {
+        searchCodePoints[i] = forceLowerCaseSearch ? CharUtils::toLowerCase(inWord[i]) : inWord[i];
+    }
+    while (!isEnd()) {
+        const PtNodeParams ptNodeParams(getPtNodeParams());
+        const int matchedCodePointCount = getPrevTotalCodePointCount();
+        if (getTotalCodePointCount(ptNodeParams) > length
+                || !isMatchedCodePoint(ptNodeParams, 0 /* index */,
+                        searchCodePoints[matchedCodePointCount])) {
+            // Current node has too many code points or its first code point is different from
+            // target code point. Skip this node and read the next sibling node.
+            readNextSiblingNode(ptNodeParams);
+            continue;
+        }
+        // Check following merged node code points.
+        const int nodeCodePointCount = ptNodeParams.getCodePointCount();
+        for (int j = 1; j < nodeCodePointCount; ++j) {
+            if (!isMatchedCodePoint(ptNodeParams, j, searchCodePoints[matchedCodePointCount + j])) {
+                // Different code point is found. The given word is not included in the dictionary.
+                return NOT_A_DICT_POS;
+            }
+        }
+        // All characters are matched.
+        if (length == getTotalCodePointCount(ptNodeParams)) {
+            if (!ptNodeParams.isTerminal()) {
+                return NOT_A_DICT_POS;
+            }
+            // Terminal position is found.
+            return ptNodeParams.getHeadPos();
+        }
+        if (!ptNodeParams.hasChildren()) {
+            return NOT_A_DICT_POS;
+        }
+        // Advance to the children nodes.
+        readChildNode(ptNodeParams);
+    }
+    // If we already traversed the tree further than the word is long, there means
+    // there was no match (or we would have found it).
+    return NOT_A_DICT_POS;
+}
+
+// Read node array size and process empty node arrays. Nodes and arrays are counted up in this
+// method to avoid an infinite loop.
+void DynamicPtReadingHelper::nextPtNodeArray() {
+    if (mReadingState.mPos < 0 || mReadingState.mPos >= mBuffer->getTailPosition()) {
+        // Reading invalid position because of a bug or a broken dictionary.
+        AKLOGE("Reading PtNode array info from invalid dictionary position: %d, dict size: %d",
+                mReadingState.mPos, mBuffer->getTailPosition());
+        ASSERT(false);
+        mIsError = true;
+        mReadingState.mPos = NOT_A_DICT_POS;
+        return;
+    }
+    mReadingState.mPosOfThisPtNodeArrayHead = mReadingState.mPos;
+    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(mReadingState.mPos);
+    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
+    if (usesAdditionalBuffer) {
+        mReadingState.mPos -= mBuffer->getOriginalBufferSize();
+    }
+    mReadingState.mRemainingPtNodeCountInThisArray =
+            PatriciaTrieReadingUtils::getPtNodeArraySizeAndAdvancePosition(dictBuf,
+                    &mReadingState.mPos);
+    if (usesAdditionalBuffer) {
+        mReadingState.mPos += mBuffer->getOriginalBufferSize();
+    }
+    // Count up nodes and node arrays to avoid infinite loop.
+    mReadingState.mTotalPtNodeIndexInThisArrayChain +=
+            mReadingState.mRemainingPtNodeCountInThisArray;
+    mReadingState.mPtNodeArrayIndexInThisArrayChain++;
+    if (mReadingState.mRemainingPtNodeCountInThisArray < 0
+            || mReadingState.mTotalPtNodeIndexInThisArrayChain
+                    > MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP
+            || mReadingState.mPtNodeArrayIndexInThisArrayChain
+                    > MAX_PT_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP) {
+        // Invalid dictionary.
+        AKLOGI("Invalid dictionary. nodeCount: %d, totalNodeCount: %d, MAX_CHILD_COUNT: %d"
+                "nodeArrayCount: %d, MAX_NODE_ARRAY_COUNT: %d",
+                mReadingState.mRemainingPtNodeCountInThisArray,
+                mReadingState.mTotalPtNodeIndexInThisArrayChain,
+                MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP,
+                mReadingState.mPtNodeArrayIndexInThisArrayChain,
+                MAX_PT_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP);
+        ASSERT(false);
+        mIsError = true;
+        mReadingState.mPos = NOT_A_DICT_POS;
+        return;
+    }
+    if (mReadingState.mRemainingPtNodeCountInThisArray == 0) {
+        // Empty node array. Try following forward link.
+        followForwardLink();
+    }
+}
+
+// Follow the forward link and read the next node array if exists.
+void DynamicPtReadingHelper::followForwardLink() {
+    if (mReadingState.mPos < 0 || mReadingState.mPos >= mBuffer->getTailPosition()) {
+        // Reading invalid position because of bug or broken dictionary.
+        AKLOGE("Reading forward link from invalid dictionary position: %d, dict size: %d",
+                mReadingState.mPos, mBuffer->getTailPosition());
+        ASSERT(false);
+        mIsError = true;
+        mReadingState.mPos = NOT_A_DICT_POS;
+        return;
+    }
+    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(mReadingState.mPos);
+    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
+    if (usesAdditionalBuffer) {
+        mReadingState.mPos -= mBuffer->getOriginalBufferSize();
+    }
+    const int forwardLinkPosition =
+            DynamicPtReadingUtils::getForwardLinkPosition(dictBuf, mReadingState.mPos);
+    if (usesAdditionalBuffer) {
+        mReadingState.mPos += mBuffer->getOriginalBufferSize();
+    }
+    mReadingState.mPosOfLastForwardLinkField = mReadingState.mPos;
+    if (DynamicPtReadingUtils::isValidForwardLinkPosition(forwardLinkPosition)) {
+        // Follow the forward link.
+        mReadingState.mPos += forwardLinkPosition;
+        nextPtNodeArray();
+    } else {
+        // All node arrays have been read.
+        mReadingState.mPos = NOT_A_DICT_POS;
+    }
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h
new file mode 100644
index 0000000..a694909
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h
@@ -0,0 +1,269 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DYNAMIC_PT_READING_HELPER_H
+#define LATINIME_DYNAMIC_PT_READING_HELPER_H
+
+#include <cstddef>
+#include <vector>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class DictionaryBigramsStructurePolicy;
+class DictionaryShortcutsStructurePolicy;
+
+/*
+ * This class is used for traversing dynamic patricia trie. This class supports iterating nodes and
+ * dealing with additional buffer. This class counts nodes and node arrays to avoid infinite loop.
+ */
+class DynamicPtReadingHelper {
+ public:
+    class TraversingEventListener {
+     public:
+        virtual ~TraversingEventListener() {};
+
+        // Returns whether the event handling was succeeded or not.
+        virtual bool onAscend() = 0;
+
+        // Returns whether the event handling was succeeded or not.
+        virtual bool onDescend(const int ptNodeArrayPos) = 0;
+
+        // Returns whether the event handling was succeeded or not.
+        virtual bool onReadingPtNodeArrayTail() = 0;
+
+        // Returns whether the event handling was succeeded or not.
+        virtual bool onVisitingPtNode(const PtNodeParams *const node) = 0;
+
+     protected:
+        TraversingEventListener() {};
+
+     private:
+        DISALLOW_COPY_AND_ASSIGN(TraversingEventListener);
+    };
+
+    DynamicPtReadingHelper(const BufferWithExtendableBuffer *const buffer,
+            const PtNodeReader *const ptNodeReader)
+            : mIsError(false), mReadingState(), mBuffer(buffer),
+              mPtNodeReader(ptNodeReader), mReadingStateStack() {}
+
+    ~DynamicPtReadingHelper() {}
+
+    AK_FORCE_INLINE bool isError() const {
+        return mIsError;
+    }
+
+    AK_FORCE_INLINE bool isEnd() const {
+        return mReadingState.mPos == NOT_A_DICT_POS;
+    }
+
+    // Initialize reading state with the head position of a PtNode array.
+    AK_FORCE_INLINE void initWithPtNodeArrayPos(const int ptNodeArrayPos) {
+        if (ptNodeArrayPos == NOT_A_DICT_POS) {
+            mReadingState.mPos = NOT_A_DICT_POS;
+        } else {
+            mIsError = false;
+            mReadingState.mPos = ptNodeArrayPos;
+            mReadingState.mTotalCodePointCountSinceInitialization = 0;
+            mReadingState.mTotalPtNodeIndexInThisArrayChain = 0;
+            mReadingState.mPtNodeArrayIndexInThisArrayChain = 0;
+            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
+            mReadingStateStack.clear();
+            nextPtNodeArray();
+        }
+    }
+
+    // Initialize reading state with the head position of a node.
+    AK_FORCE_INLINE void initWithPtNodePos(const int ptNodePos) {
+        if (ptNodePos == NOT_A_DICT_POS) {
+            mReadingState.mPos = NOT_A_DICT_POS;
+        } else {
+            mIsError = false;
+            mReadingState.mPos = ptNodePos;
+            mReadingState.mRemainingPtNodeCountInThisArray = 1;
+            mReadingState.mTotalCodePointCountSinceInitialization = 0;
+            mReadingState.mTotalPtNodeIndexInThisArrayChain = 1;
+            mReadingState.mPtNodeArrayIndexInThisArrayChain = 1;
+            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
+            mReadingState.mPosOfThisPtNodeArrayHead = NOT_A_DICT_POS;
+            mReadingStateStack.clear();
+        }
+    }
+
+    AK_FORCE_INLINE const PtNodeParams getPtNodeParams() const {
+        if (isEnd()) {
+            return PtNodeParams();
+        }
+        return mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(mReadingState.mPos);
+    }
+
+    AK_FORCE_INLINE bool isValidTerminalNode(const PtNodeParams &ptNodeParams) const {
+        return !isEnd() && !ptNodeParams.isDeleted() && ptNodeParams.isTerminal();
+    }
+
+    AK_FORCE_INLINE bool isMatchedCodePoint(const PtNodeParams &ptNodeParams, const int index,
+            const int codePoint) const {
+        return ptNodeParams.getCodePoints()[index] == codePoint;
+    }
+
+    // Return code point count exclude the last read node's code points.
+    AK_FORCE_INLINE int getPrevTotalCodePointCount() const {
+        return mReadingState.mTotalCodePointCountSinceInitialization;
+    }
+
+    // Return code point count include the last read node's code points.
+    AK_FORCE_INLINE int getTotalCodePointCount(const PtNodeParams &ptNodeParams) const {
+        return mReadingState.mTotalCodePointCountSinceInitialization
+                + ptNodeParams.getCodePointCount();
+    }
+
+    AK_FORCE_INLINE void fetchMergedNodeCodePointsInReverseOrder(const PtNodeParams &ptNodeParams,
+            const int index, int *const outCodePoints) const {
+        const int nodeCodePointCount = ptNodeParams.getCodePointCount();
+        const int *const nodeCodePoints = ptNodeParams.getCodePoints();
+        for (int i =  0; i < nodeCodePointCount; ++i) {
+            outCodePoints[index + i] = nodeCodePoints[nodeCodePointCount - 1 - i];
+        }
+    }
+
+    AK_FORCE_INLINE void readNextSiblingNode(const PtNodeParams &ptNodeParams) {
+        mReadingState.mRemainingPtNodeCountInThisArray -= 1;
+        mReadingState.mPos = ptNodeParams.getSiblingNodePos();
+        if (mReadingState.mRemainingPtNodeCountInThisArray <= 0) {
+            // All nodes in the current node array have been read.
+            followForwardLink();
+        }
+    }
+
+    // Read the first child node of the current node.
+    AK_FORCE_INLINE void readChildNode(const PtNodeParams &ptNodeParams) {
+        if (ptNodeParams.hasChildren()) {
+            mReadingState.mTotalCodePointCountSinceInitialization +=
+                    ptNodeParams.getCodePointCount();
+            mReadingState.mTotalPtNodeIndexInThisArrayChain = 0;
+            mReadingState.mPtNodeArrayIndexInThisArrayChain = 0;
+            mReadingState.mPos = ptNodeParams.getChildrenPos();
+            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
+            // Read children node array.
+            nextPtNodeArray();
+        } else {
+            mReadingState.mPos = NOT_A_DICT_POS;
+        }
+    }
+
+    // Read the parent node of the current node.
+    AK_FORCE_INLINE void readParentNode(const PtNodeParams &ptNodeParams) {
+        if (ptNodeParams.getParentPos() != NOT_A_DICT_POS) {
+            mReadingState.mTotalCodePointCountSinceInitialization +=
+                    ptNodeParams.getCodePointCount();
+            mReadingState.mTotalPtNodeIndexInThisArrayChain = 1;
+            mReadingState.mPtNodeArrayIndexInThisArrayChain = 1;
+            mReadingState.mRemainingPtNodeCountInThisArray = 1;
+            mReadingState.mPos = ptNodeParams.getParentPos();
+            mReadingState.mPosOfLastForwardLinkField = NOT_A_DICT_POS;
+            mReadingState.mPosOfThisPtNodeArrayHead = NOT_A_DICT_POS;
+        } else {
+            mReadingState.mPos = NOT_A_DICT_POS;
+        }
+    }
+
+    AK_FORCE_INLINE int getPosOfLastForwardLinkField() const {
+        return mReadingState.mPosOfLastForwardLinkField;
+    }
+
+    AK_FORCE_INLINE int getPosOfLastPtNodeArrayHead() const {
+        return mReadingState.mPosOfThisPtNodeArrayHead;
+    }
+
+    bool traverseAllPtNodesInPostorderDepthFirstManner(TraversingEventListener *const listener);
+
+    bool traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+            TraversingEventListener *const listener);
+
+    int getCodePointsAndProbabilityAndReturnCodePointCount(const int maxCodePointCount,
+            int *const outCodePoints, int *const outUnigramProbability);
+
+    int getTerminalPtNodePositionOfWord(const int *const inWord, const int length,
+            const bool forceLowerCaseSearch);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(DynamicPtReadingHelper);
+
+    // This class encapsulates the reading state of a position in the dictionary. It points at a
+    // specific PtNode in the dictionary.
+    class PtNodeReadingState {
+     public:
+        // Note that copy constructor and assignment operator are used for this class to use
+        // std::vector.
+        PtNodeReadingState() : mPos(NOT_A_DICT_POS), mRemainingPtNodeCountInThisArray(0),
+                mTotalCodePointCountSinceInitialization(0), mTotalPtNodeIndexInThisArrayChain(0),
+                mPtNodeArrayIndexInThisArrayChain(0), mPosOfLastForwardLinkField(NOT_A_DICT_POS),
+                mPosOfThisPtNodeArrayHead(NOT_A_DICT_POS) {}
+
+        int mPos;
+        // Remaining node count in the current array.
+        int mRemainingPtNodeCountInThisArray;
+        int mTotalCodePointCountSinceInitialization;
+        // Counter of PtNodes used to avoid infinite loops caused by broken or malicious links.
+        int mTotalPtNodeIndexInThisArrayChain;
+        // Counter of PtNode arrays used to avoid infinite loops caused by cyclic links of empty
+        // PtNode arrays.
+        int mPtNodeArrayIndexInThisArrayChain;
+        int mPosOfLastForwardLinkField;
+        int mPosOfThisPtNodeArrayHead;
+    };
+
+    static const int MAX_CHILD_COUNT_TO_AVOID_INFINITE_LOOP;
+    static const int MAX_PT_NODE_ARRAY_COUNT_TO_AVOID_INFINITE_LOOP;
+    static const size_t MAX_READING_STATE_STACK_SIZE;
+
+    // TODO: Introduce error code to track what caused the error.
+    bool mIsError;
+    PtNodeReadingState mReadingState;
+    const BufferWithExtendableBuffer *const mBuffer;
+    const PtNodeReader *const mPtNodeReader;
+    std::vector<PtNodeReadingState> mReadingStateStack;
+
+    void nextPtNodeArray();
+
+    void followForwardLink();
+
+    AK_FORCE_INLINE void pushReadingStateToStack() {
+        if (mReadingStateStack.size() > MAX_READING_STATE_STACK_SIZE) {
+            AKLOGI("Reading state stack overflow. Max size: %zd", MAX_READING_STATE_STACK_SIZE);
+            ASSERT(false);
+            mIsError = true;
+            mReadingState.mPos = NOT_A_DICT_POS;
+        } else {
+            mReadingStateStack.push_back(mReadingState);
+        }
+    }
+
+    AK_FORCE_INLINE void popReadingStateFromStack() {
+        if (mReadingStateStack.empty()) {
+            mReadingState.mPos = NOT_A_DICT_POS;
+        } else {
+            mReadingState = mReadingStateStack.back();
+            mReadingStateStack.pop_back();
+        }
+    }
+};
+} // namespace latinime
+#endif /* LATINIME_DYNAMIC_PT_READING_HELPER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.cpp
similarity index 64%
rename from native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.cpp
rename to native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.cpp
index d68446d..3586b50 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.cpp
@@ -14,38 +14,38 @@
  * limitations under the License.
  */
 
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
 
 #include "defines.h"
 #include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
 
 namespace latinime {
 
-typedef DynamicPatriciaTrieReadingUtils DptReadingUtils;
-
-const DptReadingUtils::NodeFlags DptReadingUtils::MASK_MOVED = 0xC0;
-const DptReadingUtils::NodeFlags DptReadingUtils::FLAG_IS_NOT_MOVED = 0xC0;
-const DptReadingUtils::NodeFlags DptReadingUtils::FLAG_IS_MOVED = 0x40;
-const DptReadingUtils::NodeFlags DptReadingUtils::FLAG_IS_DELETED = 0x80;
+const DynamicPtReadingUtils::NodeFlags DynamicPtReadingUtils::MASK_MOVED = 0xC0;
+const DynamicPtReadingUtils::NodeFlags DynamicPtReadingUtils::FLAG_IS_NOT_MOVED = 0xC0;
+const DynamicPtReadingUtils::NodeFlags DynamicPtReadingUtils::FLAG_IS_MOVED = 0x40;
+const DynamicPtReadingUtils::NodeFlags DynamicPtReadingUtils::FLAG_IS_DELETED = 0x80;
+const DynamicPtReadingUtils::NodeFlags DynamicPtReadingUtils::FLAG_WILL_BECOME_NON_TERMINAL = 0x00;
 
 // TODO: Make DICT_OFFSET_ZERO_OFFSET = 0.
 // Currently, DICT_OFFSET_INVALID is 0 in Java side but offset can be 0 during GC. So, the maximum
 // value of offsets, which is 0x7FFFFF is used to represent 0 offset.
-const int DptReadingUtils::DICT_OFFSET_INVALID = 0;
-const int DptReadingUtils::DICT_OFFSET_ZERO_OFFSET = 0x7FFFFF;
+const int DynamicPtReadingUtils::DICT_OFFSET_INVALID = 0;
+const int DynamicPtReadingUtils::DICT_OFFSET_ZERO_OFFSET = 0x7FFFFF;
 
-/* static */ int DptReadingUtils::getForwardLinkPosition(const uint8_t *const buffer,
+/* static */ int DynamicPtReadingUtils::getForwardLinkPosition(const uint8_t *const buffer,
         const int pos) {
     int linkAddressPos = pos;
     return ByteArrayUtils::readSint24AndAdvancePosition(buffer, &linkAddressPos);
 }
 
-/* static */ int DptReadingUtils::getParentPtNodePosOffsetAndAdvancePosition(
+/* static */ int DynamicPtReadingUtils::getParentPtNodePosOffsetAndAdvancePosition(
         const uint8_t *const buffer, int *const pos) {
     return ByteArrayUtils::readSint24AndAdvancePosition(buffer, pos);
 }
 
-/* static */ int DptReadingUtils::getParentPtNodePos(const int parentOffset, const int ptNodePos) {
+/* static */ int DynamicPtReadingUtils::getParentPtNodePos(const int parentOffset,
+        const int ptNodePos) {
     if (parentOffset == DICT_OFFSET_INVALID) {
         return NOT_A_DICT_POS;
     } else if (parentOffset == DICT_OFFSET_ZERO_OFFSET) {
@@ -55,7 +55,7 @@
     }
 }
 
-/* static */ int DptReadingUtils::readChildrenPositionAndAdvancePosition(
+/* static */ int DynamicPtReadingUtils::readChildrenPositionAndAdvancePosition(
         const uint8_t *const buffer, int *const pos) {
     const int base = *pos;
     const int offset = ByteArrayUtils::readSint24AndAdvancePosition(buffer, pos);
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h
similarity index 72%
rename from native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h
rename to native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h
index 67c3cc5..89ae12c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_READING_UTILS_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_READING_UTILS_H
+#ifndef LATINIME_DYNAMIC_PT_READING_UTILS_H
+#define LATINIME_DYNAMIC_PT_READING_UTILS_H
 
 #include <stdint.h>
 
@@ -23,7 +23,7 @@
 
 namespace latinime {
 
-class DynamicPatriciaTrieReadingUtils {
+class DynamicPtReadingUtils {
  public:
     typedef uint8_t NodeFlags;
 
@@ -54,22 +54,30 @@
         return FLAG_IS_DELETED == (MASK_MOVED & flags);
     }
 
+    static AK_FORCE_INLINE bool willBecomeNonTerminal(const NodeFlags flags) {
+        return FLAG_WILL_BECOME_NON_TERMINAL == (MASK_MOVED & flags);
+    }
+
     static AK_FORCE_INLINE NodeFlags updateAndGetFlags(const NodeFlags originalFlags,
-            const bool isMoved, const bool isDeleted) {
+            const bool isMoved, const bool isDeleted, const bool willBecomeNonTerminal) {
         NodeFlags flags = originalFlags;
+        flags = willBecomeNonTerminal ?
+                ((flags & (~MASK_MOVED)) | FLAG_WILL_BECOME_NON_TERMINAL) : flags;
         flags = isMoved ? ((flags & (~MASK_MOVED)) | FLAG_IS_MOVED) : flags;
         flags = isDeleted ? ((flags & (~MASK_MOVED)) | FLAG_IS_DELETED) : flags;
-        flags = (!isMoved && !isDeleted) ? ((flags & (~MASK_MOVED)) | FLAG_IS_NOT_MOVED) : flags;
+        flags = (!isMoved && !isDeleted && !willBecomeNonTerminal) ?
+                ((flags & (~MASK_MOVED)) | FLAG_IS_NOT_MOVED) : flags;
         return flags;
     }
 
  private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieReadingUtils);
+    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPtReadingUtils);
 
     static const NodeFlags MASK_MOVED;
     static const NodeFlags FLAG_IS_NOT_MOVED;
     static const NodeFlags FLAG_IS_MOVED;
     static const NodeFlags FLAG_IS_DELETED;
+    static const NodeFlags FLAG_WILL_BECOME_NON_TERMINAL;
 };
 } // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_READING_UTILS_H */
+#endif /* LATINIME_DYNAMIC_PT_READING_UTILS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.cpp
new file mode 100644
index 0000000..2457b49
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.cpp
@@ -0,0 +1,294 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.h"
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+const int DynamicPtUpdatingHelper::CHILDREN_POSITION_FIELD_SIZE = 3;
+
+bool DynamicPtUpdatingHelper::addUnigramWord(
+        DynamicPtReadingHelper *const readingHelper,
+        const int *const wordCodePoints, const int codePointCount, const int probability,
+        const bool isNotAWord, const bool isBlacklisted, const int timestamp,
+        bool *const outAddedNewUnigram) {
+    int parentPos = NOT_A_DICT_POS;
+    while (!readingHelper->isEnd()) {
+        const PtNodeParams ptNodeParams(readingHelper->getPtNodeParams());
+        if (!ptNodeParams.isValid()) {
+            break;
+        }
+        const int matchedCodePointCount = readingHelper->getPrevTotalCodePointCount();
+        if (!readingHelper->isMatchedCodePoint(ptNodeParams, 0 /* index */,
+                wordCodePoints[matchedCodePointCount])) {
+            // The first code point is different from target code point. Skip this node and read
+            // the next sibling node.
+            readingHelper->readNextSiblingNode(ptNodeParams);
+            continue;
+        }
+        // Check following merged node code points.
+        const int nodeCodePointCount = ptNodeParams.getCodePointCount();
+        for (int j = 1; j < nodeCodePointCount; ++j) {
+            const int nextIndex = matchedCodePointCount + j;
+            if (nextIndex >= codePointCount || !readingHelper->isMatchedCodePoint(ptNodeParams, j,
+                    wordCodePoints[matchedCodePointCount + j])) {
+                *outAddedNewUnigram = true;
+                return reallocatePtNodeAndAddNewPtNodes(&ptNodeParams, j, isNotAWord, isBlacklisted,
+                        probability, timestamp, wordCodePoints + matchedCodePointCount,
+                        codePointCount - matchedCodePointCount);
+            }
+        }
+        // All characters are matched.
+        if (codePointCount == readingHelper->getTotalCodePointCount(ptNodeParams)) {
+            return setPtNodeProbability(&ptNodeParams, isNotAWord, isBlacklisted, probability,
+                    timestamp, outAddedNewUnigram);
+        }
+        if (!ptNodeParams.hasChildren()) {
+            *outAddedNewUnigram = true;
+            return createChildrenPtNodeArrayAndAChildPtNode(&ptNodeParams,
+                    isNotAWord, isBlacklisted, probability, timestamp,
+                    wordCodePoints + readingHelper->getTotalCodePointCount(ptNodeParams),
+                    codePointCount - readingHelper->getTotalCodePointCount(ptNodeParams));
+        }
+        // Advance to the children nodes.
+        parentPos = ptNodeParams.getHeadPos();
+        readingHelper->readChildNode(ptNodeParams);
+    }
+    if (readingHelper->isError()) {
+        // The dictionary is invalid.
+        return false;
+    }
+    int pos = readingHelper->getPosOfLastForwardLinkField();
+    *outAddedNewUnigram = true;
+    return createAndInsertNodeIntoPtNodeArray(parentPos,
+            wordCodePoints + readingHelper->getPrevTotalCodePointCount(),
+            codePointCount - readingHelper->getPrevTotalCodePointCount(),
+            isNotAWord, isBlacklisted, probability, timestamp, &pos);
+}
+
+bool DynamicPtUpdatingHelper::addBigramWords(const int word0Pos, const int word1Pos,
+        const int probability, const int timestamp, bool *const outAddedNewBigram) {
+    const PtNodeParams sourcePtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word0Pos));
+    const PtNodeParams targetPtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word1Pos));
+    return mPtNodeWriter->addNewBigramEntry(&sourcePtNodeParams, &targetPtNodeParams, probability,
+            timestamp, outAddedNewBigram);
+}
+
+// Remove a bigram relation from word0Pos to word1Pos.
+bool DynamicPtUpdatingHelper::removeBigramWords(const int word0Pos, const int word1Pos) {
+    const PtNodeParams sourcePtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word0Pos));
+    const PtNodeParams targetPtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word1Pos));
+    return mPtNodeWriter->removeBigramEntry(&sourcePtNodeParams, &targetPtNodeParams);
+}
+
+bool DynamicPtUpdatingHelper::addShortcutTarget(const int wordPos,
+        const int *const targetCodePoints, const int targetCodePointCount,
+        const int shortcutProbability) {
+    const PtNodeParams ptNodeParams(mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(wordPos));
+    return mPtNodeWriter->addShortcutTarget(&ptNodeParams, targetCodePoints, targetCodePointCount,
+            shortcutProbability);
+}
+
+bool DynamicPtUpdatingHelper::createAndInsertNodeIntoPtNodeArray(const int parentPos,
+        const int *const nodeCodePoints, const int nodeCodePointCount,
+        const bool isNotAWord, const bool isBlacklisted, const int probability,
+        const int timestamp,  int *const forwardLinkFieldPos) {
+    const int newPtNodeArrayPos = mBuffer->getTailPosition();
+    if (!DynamicPtWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
+            newPtNodeArrayPos, forwardLinkFieldPos)) {
+        return false;
+    }
+    return createNewPtNodeArrayWithAChildPtNode(parentPos, nodeCodePoints, nodeCodePointCount,
+            isNotAWord, isBlacklisted, probability, timestamp);
+}
+
+bool DynamicPtUpdatingHelper::setPtNodeProbability(
+        const PtNodeParams *const originalPtNodeParams, const bool isNotAWord,
+        const bool isBlacklisted, const int probability, const int timestamp,
+        bool *const outAddedNewUnigram) {
+    if (originalPtNodeParams->isTerminal()) {
+        // Overwrites the probability.
+        *outAddedNewUnigram = false;
+        return mPtNodeWriter->updatePtNodeProbability(originalPtNodeParams, probability, timestamp);
+    } else {
+        // Make the node terminal and write the probability.
+        *outAddedNewUnigram = true;
+        const int movedPos = mBuffer->getTailPosition();
+        int writingPos = movedPos;
+        const PtNodeParams ptNodeParamsToWrite(getUpdatedPtNodeParams(originalPtNodeParams,
+                isNotAWord, isBlacklisted, true /* isTerminal */,
+                originalPtNodeParams->getParentPos(), originalPtNodeParams->getCodePointCount(),
+                originalPtNodeParams->getCodePoints(), probability));
+        if (!mPtNodeWriter->writeNewTerminalPtNodeAndAdvancePosition(&ptNodeParamsToWrite,
+                timestamp, &writingPos)) {
+            return false;
+        }
+        if (!mPtNodeWriter->markPtNodeAsMoved(originalPtNodeParams, movedPos, movedPos)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool DynamicPtUpdatingHelper::createChildrenPtNodeArrayAndAChildPtNode(
+        const PtNodeParams *const parentPtNodeParams, const bool isNotAWord,
+        const bool isBlacklisted, const int probability, const int timestamp,
+        const int *const codePoints, const int codePointCount) {
+    const int newPtNodeArrayPos = mBuffer->getTailPosition();
+    if (!mPtNodeWriter->updateChildrenPosition(parentPtNodeParams, newPtNodeArrayPos)) {
+        return false;
+    }
+    return createNewPtNodeArrayWithAChildPtNode(parentPtNodeParams->getHeadPos(), codePoints,
+            codePointCount, isNotAWord, isBlacklisted, probability, timestamp);
+}
+
+bool DynamicPtUpdatingHelper::createNewPtNodeArrayWithAChildPtNode(
+        const int parentPtNodePos, const int *const nodeCodePoints, const int nodeCodePointCount,
+        const bool isNotAWord, const bool isBlacklisted, const int probability,
+        const int timestamp) {
+    int writingPos = mBuffer->getTailPosition();
+    if (!DynamicPtWritingUtils::writePtNodeArraySizeAndAdvancePosition(mBuffer,
+            1 /* arraySize */, &writingPos)) {
+        return false;
+    }
+    const PtNodeParams ptNodeParamsToWrite(getPtNodeParamsForNewPtNode(
+            isNotAWord, isBlacklisted, true /* isTerminal */,
+            parentPtNodePos, nodeCodePointCount, nodeCodePoints, probability));
+    if (!mPtNodeWriter->writeNewTerminalPtNodeAndAdvancePosition(&ptNodeParamsToWrite, timestamp,
+            &writingPos)) {
+        return false;
+    }
+    if (!DynamicPtWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
+            NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
+        return false;
+    }
+    return true;
+}
+
+// Returns whether the dictionary updating was succeeded or not.
+bool DynamicPtUpdatingHelper::reallocatePtNodeAndAddNewPtNodes(
+        const PtNodeParams *const reallocatingPtNodeParams, const int overlappingCodePointCount,
+        const bool isNotAWord, const bool isBlacklisted, const int probabilityOfNewPtNode,
+        const int timestamp, const int *const newNodeCodePoints, const int newNodeCodePointCount) {
+    // When addsExtraChild is true, split the reallocating PtNode and add new child.
+    // Reallocating PtNode: abcde, newNode: abcxy.
+    // abc (1st, not terminal) __ de (2nd)
+    //                         \_ xy (extra child, terminal)
+    // Otherwise, this method makes 1st part terminal and write probabilityOfNewPtNode.
+    // Reallocating PtNode: abcde, newNode: abc.
+    // abc (1st, terminal) __ de (2nd)
+    const bool addsExtraChild = newNodeCodePointCount > overlappingCodePointCount;
+    const int firstPartOfReallocatedPtNodePos = mBuffer->getTailPosition();
+    int writingPos = firstPartOfReallocatedPtNodePos;
+    // Write the 1st part of the reallocating node. The children position will be updated later
+    // with actual children position.
+    if (addsExtraChild) {
+        const PtNodeParams ptNodeParamsToWrite(getPtNodeParamsForNewPtNode(
+                false /* isNotAWord */, false /* isBlacklisted */, false /* isTerminal */,
+                reallocatingPtNodeParams->getParentPos(), overlappingCodePointCount,
+                reallocatingPtNodeParams->getCodePoints(), NOT_A_PROBABILITY));
+        if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&ptNodeParamsToWrite, &writingPos)) {
+            return false;
+        }
+    } else {
+        const PtNodeParams ptNodeParamsToWrite(getPtNodeParamsForNewPtNode(
+                isNotAWord, isBlacklisted, true /* isTerminal */,
+                reallocatingPtNodeParams->getParentPos(), overlappingCodePointCount,
+                reallocatingPtNodeParams->getCodePoints(), probabilityOfNewPtNode));
+        if (!mPtNodeWriter->writeNewTerminalPtNodeAndAdvancePosition(&ptNodeParamsToWrite,
+                timestamp, &writingPos)) {
+            return false;
+        }
+    }
+    const int actualChildrenPos = writingPos;
+    // Create new children PtNode array.
+    const size_t newPtNodeCount = addsExtraChild ? 2 : 1;
+    if (!DynamicPtWritingUtils::writePtNodeArraySizeAndAdvancePosition(mBuffer,
+            newPtNodeCount, &writingPos)) {
+        return false;
+    }
+    // Write the 2nd part of the reallocating node.
+    const int secondPartOfReallocatedPtNodePos = writingPos;
+    const PtNodeParams childPartPtNodeParams(getUpdatedPtNodeParams(reallocatingPtNodeParams,
+            reallocatingPtNodeParams->isNotAWord(), reallocatingPtNodeParams->isBlacklisted(),
+            reallocatingPtNodeParams->isTerminal(), firstPartOfReallocatedPtNodePos,
+            reallocatingPtNodeParams->getCodePointCount() - overlappingCodePointCount,
+            reallocatingPtNodeParams->getCodePoints() + overlappingCodePointCount,
+            reallocatingPtNodeParams->getProbability()));
+    if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&childPartPtNodeParams, &writingPos)) {
+        return false;
+    }
+    if (addsExtraChild) {
+        const PtNodeParams extraChildPtNodeParams(getPtNodeParamsForNewPtNode(
+                isNotAWord, isBlacklisted, true /* isTerminal */,
+                firstPartOfReallocatedPtNodePos, newNodeCodePointCount - overlappingCodePointCount,
+                newNodeCodePoints + overlappingCodePointCount, probabilityOfNewPtNode));
+        if (!mPtNodeWriter->writeNewTerminalPtNodeAndAdvancePosition(&extraChildPtNodeParams,
+                timestamp, &writingPos)) {
+            return false;
+        }
+    }
+    if (!DynamicPtWritingUtils::writeForwardLinkPositionAndAdvancePosition(mBuffer,
+            NOT_A_DICT_POS /* forwardLinkPos */, &writingPos)) {
+        return false;
+    }
+    // Update original reallocating PtNode as moved.
+    if (!mPtNodeWriter->markPtNodeAsMoved(reallocatingPtNodeParams, firstPartOfReallocatedPtNodePos,
+            secondPartOfReallocatedPtNodePos)) {
+        return false;
+    }
+    // Load node info. Information of the 1st part will be fetched.
+    const PtNodeParams ptNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(firstPartOfReallocatedPtNodePos));
+    // Update children position.
+    return mPtNodeWriter->updateChildrenPosition(&ptNodeParams, actualChildrenPos);
+}
+
+const PtNodeParams DynamicPtUpdatingHelper::getUpdatedPtNodeParams(
+        const PtNodeParams *const originalPtNodeParams, const bool isNotAWord,
+        const bool isBlacklisted, const bool isTerminal, const int parentPos,
+        const int codePointCount, const int *const codePoints, const int probability) const {
+    const PatriciaTrieReadingUtils::NodeFlags flags = PatriciaTrieReadingUtils::createAndGetFlags(
+            isBlacklisted, isNotAWord, isTerminal, originalPtNodeParams->hasShortcutTargets(),
+            originalPtNodeParams->hasBigrams(), codePointCount > 1 /* hasMultipleChars */,
+            CHILDREN_POSITION_FIELD_SIZE);
+    return PtNodeParams(originalPtNodeParams, flags, parentPos, codePointCount, codePoints,
+            probability);
+}
+
+const PtNodeParams DynamicPtUpdatingHelper::getPtNodeParamsForNewPtNode(
+        const bool isNotAWord, const bool isBlacklisted, const bool isTerminal,
+        const int parentPos, const int codePointCount, const int *const codePoints,
+        const int probability) const {
+    const PatriciaTrieReadingUtils::NodeFlags flags = PatriciaTrieReadingUtils::createAndGetFlags(
+            isBlacklisted, isNotAWord, isTerminal, false /* hasShortcutTargets */,
+            false /* hasBigrams */, codePointCount > 1 /* hasMultipleChars */,
+            CHILDREN_POSITION_FIELD_SIZE);
+    return PtNodeParams(flags, parentPos, codePointCount, codePoints, probability);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.h
new file mode 100644
index 0000000..71f4730
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.h
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DYNAMIC_PT_UPDATING_HELPER_H
+#define LATINIME_DYNAMIC_PT_UPDATING_HELPER_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "utils/hash_map_compat.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class DynamicPtReadingHelper;
+class PtNodeReader;
+class PtNodeWriter;
+
+class DynamicPtUpdatingHelper {
+ public:
+    DynamicPtUpdatingHelper(BufferWithExtendableBuffer *const buffer,
+            const PtNodeReader *const ptNodeReader, PtNodeWriter *const ptNodeWriter)
+            : mBuffer(buffer), mPtNodeReader(ptNodeReader), mPtNodeWriter(ptNodeWriter) {}
+
+    ~DynamicPtUpdatingHelper() {}
+
+    // Add a word to the dictionary. If the word already exists, update the probability.
+    bool addUnigramWord(DynamicPtReadingHelper *const readingHelper,
+            const int *const wordCodePoints, const int codePointCount, const int probability,
+            const bool isNotAWord, const bool isBlacklisted, const int timestamp,
+            bool *const outAddedNewUnigram);
+
+    // Add a bigram relation from word0Pos to word1Pos.
+    bool addBigramWords(const int word0Pos, const int word1Pos, const int probability,
+            const int timestamp, bool *const outAddedNewBigram);
+
+    // Remove a bigram relation from word0Pos to word1Pos.
+    bool removeBigramWords(const int word0Pos, const int word1Pos);
+
+    // Add a shortcut target.
+    bool addShortcutTarget(const int wordPos, const int *const targetCodePoints,
+            const int targetCodePointCount, const int shortcutProbability);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPtUpdatingHelper);
+
+    static const int CHILDREN_POSITION_FIELD_SIZE;
+
+    BufferWithExtendableBuffer *const mBuffer;
+    const PtNodeReader *const mPtNodeReader;
+    PtNodeWriter *const mPtNodeWriter;
+
+    bool createAndInsertNodeIntoPtNodeArray(const int parentPos, const int *const nodeCodePoints,
+            const int nodeCodePointCount, const bool isNotAWord, const bool isBlacklisted,
+            const int probability, const int timestamp, int *const forwardLinkFieldPos);
+
+    bool setPtNodeProbability(const PtNodeParams *const originalPtNodeParams, const bool isNotAWord,
+            const bool isBlacklisted, const int probability, const int timestamp,
+            bool *const outAddedNewUnigram);
+
+    bool createChildrenPtNodeArrayAndAChildPtNode(const PtNodeParams *const parentPtNodeParams,
+            const bool isNotAWord, const bool isBlacklisted, const int probability,
+            const int timestamp, const int *const codePoints, const int codePointCount);
+
+    bool createNewPtNodeArrayWithAChildPtNode(const int parentPos, const int *const nodeCodePoints,
+            const int nodeCodePointCount, const bool isNotAWord, const bool isBlacklisted,
+            const int probability, const int timestamp);
+
+    bool reallocatePtNodeAndAddNewPtNodes(
+            const PtNodeParams *const reallocatingPtNodeParams, const int overlappingCodePointCount,
+            const bool isNotAWord, const bool isBlacklisted, const int probabilityOfNewPtNode,
+            const int timestamp, const int *const newNodeCodePoints,
+            const int newNodeCodePointCount);
+
+    const PtNodeParams getUpdatedPtNodeParams(const PtNodeParams *const originalPtNodeParams,
+            const bool isNotAWord, const bool isBlacklisted, const bool isTerminal,
+            const int parentPos, const int codePointCount,
+            const int *const codePoints, const int probability) const;
+
+    const PtNodeParams getPtNodeParamsForNewPtNode(const bool isNotAWord, const bool isBlacklisted,
+            const bool isTerminal, const int parentPos,
+            const int codePointCount, const int *const codePoints, const int probability) const;
+};
+} // namespace latinime
+#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_UPDATING_HELPER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.cpp
similarity index 61%
rename from native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.cpp
rename to native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.cpp
index 30ff10c..ebbdc2e 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
 
 #include <cstddef>
 #include <cstdlib>
@@ -24,19 +24,18 @@
 
 namespace latinime {
 
-const size_t DynamicPatriciaTrieWritingUtils::MAX_PTNODE_ARRAY_SIZE_TO_USE_SMALL_SIZE_FIELD = 0x7F;
-const size_t DynamicPatriciaTrieWritingUtils::MAX_PTNODE_ARRAY_SIZE = 0x7FFF;
-const int DynamicPatriciaTrieWritingUtils::SMALL_PTNODE_ARRAY_SIZE_FIELD_SIZE = 1;
-const int DynamicPatriciaTrieWritingUtils::LARGE_PTNODE_ARRAY_SIZE_FIELD_SIZE = 2;
-const int DynamicPatriciaTrieWritingUtils::LARGE_PTNODE_ARRAY_SIZE_FIELD_SIZE_FLAG = 0x8000;
-const int DynamicPatriciaTrieWritingUtils::DICT_OFFSET_FIELD_SIZE = 3;
-const int DynamicPatriciaTrieWritingUtils::MAX_DICT_OFFSET_VALUE = 0x7FFFFF;
-const int DynamicPatriciaTrieWritingUtils::MIN_DICT_OFFSET_VALUE = -0x7FFFFF;
-const int DynamicPatriciaTrieWritingUtils::DICT_OFFSET_NEGATIVE_FLAG = 0x800000;
-const int DynamicPatriciaTrieWritingUtils::PROBABILITY_FIELD_SIZE = 1;
-const int DynamicPatriciaTrieWritingUtils::NODE_FLAG_FIELD_SIZE = 1;
+const size_t DynamicPtWritingUtils::MAX_PTNODE_ARRAY_SIZE_TO_USE_SMALL_SIZE_FIELD = 0x7F;
+const size_t DynamicPtWritingUtils::MAX_PTNODE_ARRAY_SIZE = 0x7FFF;
+const int DynamicPtWritingUtils::SMALL_PTNODE_ARRAY_SIZE_FIELD_SIZE = 1;
+const int DynamicPtWritingUtils::LARGE_PTNODE_ARRAY_SIZE_FIELD_SIZE = 2;
+const int DynamicPtWritingUtils::LARGE_PTNODE_ARRAY_SIZE_FIELD_SIZE_FLAG = 0x8000;
+const int DynamicPtWritingUtils::DICT_OFFSET_FIELD_SIZE = 3;
+const int DynamicPtWritingUtils::MAX_DICT_OFFSET_VALUE = 0x7FFFFF;
+const int DynamicPtWritingUtils::MIN_DICT_OFFSET_VALUE = -0x7FFFFF;
+const int DynamicPtWritingUtils::DICT_OFFSET_NEGATIVE_FLAG = 0x800000;
+const int DynamicPtWritingUtils::NODE_FLAG_FIELD_SIZE = 1;
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeEmptyDictionary(
+/* static */ bool DynamicPtWritingUtils::writeEmptyDictionary(
         BufferWithExtendableBuffer *const buffer, const int rootPos) {
     int writingPos = rootPos;
     if (!writePtNodeArraySizeAndAdvancePosition(buffer, 0 /* arraySize */, &writingPos)) {
@@ -46,13 +45,13 @@
             &writingPos);
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeForwardLinkPositionAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writeForwardLinkPositionAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer, const int forwardLinkPos,
         int *const forwardLinkFieldPos) {
     return writeDictOffset(buffer, forwardLinkPos, (*forwardLinkFieldPos), forwardLinkFieldPos);
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writePtNodeArraySizeAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writePtNodeArraySizeAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer, const size_t arraySize,
         int *const arraySizeFieldPos) {
     // Currently, all array size field to be created has LARGE_PTNODE_ARRAY_SIZE_FIELD_SIZE to
@@ -74,20 +73,20 @@
     }
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writeFlagsAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer,
-        const DynamicPatriciaTrieReadingUtils::NodeFlags nodeFlags, int *const nodeFlagsFieldPos) {
+        const DynamicPtReadingUtils::NodeFlags nodeFlags, int *const nodeFlagsFieldPos) {
     return buffer->writeUintAndAdvancePosition(nodeFlags, NODE_FLAG_FIELD_SIZE, nodeFlagsFieldPos);
 }
 
 // Note that parentOffset is offset from node's head position.
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writeParentPosOffsetAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer, const int parentPos, const int basePos,
         int *const parentPosFieldPos) {
     return writeDictOffset(buffer, parentPos, basePos, parentPosFieldPos);
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeCodePointsAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writeCodePointsAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer, const int *const codePoints,
         const int codePointCount, int *const codePointFieldPos) {
     if (codePointCount <= 0) {
@@ -101,34 +100,20 @@
             hasMultipleCodePoints, codePointFieldPos);
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(
-        BufferWithExtendableBuffer *const buffer, const int probability,
-        int *const probabilityFieldPos) {
-    if (probability < 0 || probability > MAX_PROBABILITY) {
-        AKLOGI("probability cannot be written because the probability is invalid: %d",
-                probability);
-        ASSERT(false);
-        return false;
-    }
-    return buffer->writeUintAndAdvancePosition(probability, PROBABILITY_FIELD_SIZE,
-            probabilityFieldPos);
-}
-
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(
+/* static */ bool DynamicPtWritingUtils::writeChildrenPositionAndAdvancePosition(
         BufferWithExtendableBuffer *const buffer, const int childrenPosition,
         int *const childrenPositionFieldPos) {
     return writeDictOffset(buffer, childrenPosition, (*childrenPositionFieldPos),
             childrenPositionFieldPos);
 }
 
-/* static */ bool DynamicPatriciaTrieWritingUtils::writeDictOffset(
-        BufferWithExtendableBuffer *const buffer, const int targetPos, const int basePos,
-        int *const offsetFieldPos) {
+/* static */ bool DynamicPtWritingUtils::writeDictOffset(BufferWithExtendableBuffer *const buffer,
+        const int targetPos, const int basePos, int *const offsetFieldPos) {
     int offset = targetPos - basePos;
     if (targetPos == NOT_A_DICT_POS) {
-        offset = DynamicPatriciaTrieReadingUtils::DICT_OFFSET_INVALID;
+        offset = DynamicPtReadingUtils::DICT_OFFSET_INVALID;
     } else if (offset == 0) {
-        offset = DynamicPatriciaTrieReadingUtils::DICT_OFFSET_ZERO_OFFSET;
+        offset = DynamicPtReadingUtils::DICT_OFFSET_ZERO_OFFSET;
     }
     if (offset > MAX_DICT_OFFSET_VALUE || offset < MIN_DICT_OFFSET_VALUE) {
         AKLOGI("offset cannot be written because the offset is too large or too small: %d",
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h
similarity index 78%
rename from native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h
rename to native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h
index af76bc6..362fbd1 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h
@@ -14,19 +14,19 @@
  * limitations under the License.
  */
 
-#ifndef LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_UTILS_H
-#define LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_UTILS_H
+#ifndef LATINIME_DYNAMIC_PT_WRITING_UTILS_H
+#define LATINIME_DYNAMIC_PT_WRITING_UTILS_H
 
 #include <cstddef>
 
 #include "defines.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
 
 namespace latinime {
 
 class BufferWithExtendableBuffer;
 
-class DynamicPatriciaTrieWritingUtils {
+class DynamicPtWritingUtils {
  public:
     static const int NODE_FLAG_FIELD_SIZE;
 
@@ -39,8 +39,15 @@
     static bool writePtNodeArraySizeAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
             const size_t arraySize, int *const arraySizeFieldPos);
 
+    static bool writeFlags(BufferWithExtendableBuffer *const buffer,
+            const DynamicPtReadingUtils::NodeFlags nodeFlags,
+            const int nodeFlagsFieldPos) {
+        int writingPos = nodeFlagsFieldPos;
+        return writeFlagsAndAdvancePosition(buffer, nodeFlags, &writingPos);
+    }
+
     static bool writeFlagsAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
-            const DynamicPatriciaTrieReadingUtils::NodeFlags nodeFlags,
+            const DynamicPtReadingUtils::NodeFlags nodeFlags,
             int *const nodeFlagsFieldPos);
 
     static bool writeParentPosOffsetAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
@@ -49,14 +56,11 @@
     static bool writeCodePointsAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
             const int *const codePoints, const int codePointCount, int *const codePointFieldPos);
 
-    static bool writeProbabilityAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
-            const int probability, int *const probabilityFieldPos);
-
     static bool writeChildrenPositionAndAdvancePosition(BufferWithExtendableBuffer *const buffer,
             const int childrenPosition, int *const childrenPositionFieldPos);
 
  private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieWritingUtils);
+    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPtWritingUtils);
 
     static const size_t MAX_PTNODE_ARRAY_SIZE_TO_USE_SMALL_SIZE_FIELD;
     static const size_t MAX_PTNODE_ARRAY_SIZE;
@@ -67,10 +71,9 @@
     static const int MAX_DICT_OFFSET_VALUE;
     static const int MIN_DICT_OFFSET_VALUE;
     static const int DICT_OFFSET_NEGATIVE_FLAG;
-    static const int PROBABILITY_FIELD_SIZE;
 
     static bool writeDictOffset(BufferWithExtendableBuffer *const buffer, const int targetPos,
             const int basePos, int *const offsetFieldPos);
 };
 } // namespace latinime
-#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_WRITING_UTILS_H */
+#endif /* LATINIME_DYNAMIC_PT_WRITING_UTILS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h
new file mode 100644
index 0000000..84731eb
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h
@@ -0,0 +1,229 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_PT_NODE_PARAMS_H
+#define LATINIME_PT_NODE_PARAMS_H
+
+#include <cstring>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+
+namespace latinime {
+
+// This class has information of a PtNode. This class is immutable.
+class PtNodeParams {
+ public:
+    // Invalid PtNode.
+    PtNodeParams() : mHeadPos(NOT_A_DICT_POS), mFlags(0), mParentPos(NOT_A_DICT_POS),
+            mCodePointCount(0), mCodePoints(), mTerminalIdFieldPos(NOT_A_DICT_POS),
+            mTerminalId(Ver4DictConstants::NOT_A_TERMINAL_ID), mProbabilityFieldPos(NOT_A_DICT_POS),
+            mProbability(NOT_A_PROBABILITY), mChildrenPosFieldPos(NOT_A_DICT_POS),
+            mChildrenPos(NOT_A_DICT_POS), mBigramLinkedNodePos(NOT_A_DICT_POS),
+            mShortcutPos(NOT_A_DICT_POS), mBigramPos(NOT_A_DICT_POS),
+            mSiblingPos(NOT_A_DICT_POS) {}
+
+    PtNodeParams(const PtNodeParams& ptNodeParams)
+            : mHeadPos(ptNodeParams.mHeadPos), mFlags(ptNodeParams.mFlags),
+              mParentPos(ptNodeParams.mParentPos), mCodePointCount(ptNodeParams.mCodePointCount),
+              mCodePoints(), mTerminalIdFieldPos(ptNodeParams.mTerminalIdFieldPos),
+              mTerminalId(ptNodeParams.mTerminalId),
+              mProbabilityFieldPos(ptNodeParams.mProbabilityFieldPos),
+              mProbability(ptNodeParams.mProbability),
+              mChildrenPosFieldPos(ptNodeParams.mChildrenPosFieldPos),
+              mChildrenPos(ptNodeParams.mChildrenPos),
+              mBigramLinkedNodePos(ptNodeParams.mBigramLinkedNodePos),
+              mShortcutPos(ptNodeParams.mShortcutPos), mBigramPos(ptNodeParams.mBigramPos),
+              mSiblingPos(ptNodeParams.mSiblingPos) {
+        memcpy(mCodePoints, ptNodeParams.getCodePoints(), sizeof(int) * mCodePointCount);
+    }
+
+    // PtNode with a terminal id.
+    PtNodeParams(const int headPos, const PatriciaTrieReadingUtils::NodeFlags flags,
+            const int parentPos, const int codePointCount, const int *const codePoints,
+            const int terminalIdFieldPos, const int terminalId, const int probability,
+            const int childrenPosFieldPos, const int childrenPos, const int siblingPos)
+            : mHeadPos(headPos), mFlags(flags), mParentPos(parentPos),
+              mCodePointCount(codePointCount), mCodePoints(),
+              mTerminalIdFieldPos(terminalIdFieldPos), mTerminalId(terminalId),
+              mProbabilityFieldPos(NOT_A_DICT_POS), mProbability(probability),
+              mChildrenPosFieldPos(childrenPosFieldPos), mChildrenPos(childrenPos),
+              mBigramLinkedNodePos(NOT_A_DICT_POS), mShortcutPos(terminalId),
+              mBigramPos(terminalId), mSiblingPos(siblingPos) {
+        memcpy(mCodePoints, codePoints, sizeof(int) * mCodePointCount);
+    }
+
+    // Construct new params by updating existing PtNode params.
+    PtNodeParams(const PtNodeParams *const ptNodeParams,
+            const PatriciaTrieReadingUtils::NodeFlags flags, const int parentPos,
+            const int codePointCount, const int *const codePoints, const int probability)
+            : mHeadPos(ptNodeParams->getHeadPos()), mFlags(flags), mParentPos(parentPos),
+              mCodePointCount(codePointCount), mCodePoints(),
+              mTerminalIdFieldPos(ptNodeParams->getTerminalIdFieldPos()),
+              mTerminalId(ptNodeParams->getTerminalId()),
+              mProbabilityFieldPos(ptNodeParams->getProbabilityFieldPos()),
+              mProbability(probability),
+              mChildrenPosFieldPos(ptNodeParams->getChildrenPosFieldPos()),
+              mChildrenPos(ptNodeParams->getChildrenPos()),
+              mBigramLinkedNodePos(ptNodeParams->getBigramLinkedNodePos()),
+              mShortcutPos(ptNodeParams->getShortcutPos()),
+              mBigramPos(ptNodeParams->getBigramsPos()),
+              mSiblingPos(ptNodeParams->getSiblingNodePos()) {
+        memcpy(mCodePoints, codePoints, sizeof(int) * mCodePointCount);
+    }
+
+    PtNodeParams(const PatriciaTrieReadingUtils::NodeFlags flags, const int parentPos,
+            const int codePointCount, const int *const codePoints, const int probability)
+            : mHeadPos(NOT_A_DICT_POS), mFlags(flags), mParentPos(parentPos),
+              mCodePointCount(codePointCount), mCodePoints(),
+              mTerminalIdFieldPos(NOT_A_DICT_POS),
+              mTerminalId(Ver4DictConstants::NOT_A_TERMINAL_ID),
+              mProbabilityFieldPos(NOT_A_DICT_POS), mProbability(probability),
+              mChildrenPosFieldPos(NOT_A_DICT_POS), mChildrenPos(NOT_A_DICT_POS),
+              mBigramLinkedNodePos(NOT_A_DICT_POS), mShortcutPos(NOT_A_DICT_POS),
+              mBigramPos(NOT_A_DICT_POS), mSiblingPos(NOT_A_DICT_POS) {
+        memcpy(mCodePoints, codePoints, sizeof(int) * mCodePointCount);
+    }
+
+    AK_FORCE_INLINE bool isValid() const {
+        return mCodePointCount > 0;
+    }
+
+    // Head position of the PtNode
+    AK_FORCE_INLINE int getHeadPos() const {
+        return mHeadPos;
+    }
+
+    // Flags
+    AK_FORCE_INLINE bool isDeleted() const {
+        return DynamicPtReadingUtils::isDeleted(mFlags);
+    }
+
+    AK_FORCE_INLINE bool willBecomeNonTerminal() const {
+        return DynamicPtReadingUtils::willBecomeNonTerminal(mFlags);
+    }
+
+    AK_FORCE_INLINE bool hasChildren() const {
+        return mChildrenPos != NOT_A_DICT_POS;
+    }
+
+    AK_FORCE_INLINE bool isTerminal() const {
+        return PatriciaTrieReadingUtils::isTerminal(mFlags);
+    }
+
+    AK_FORCE_INLINE bool isBlacklisted() const {
+        return PatriciaTrieReadingUtils::isBlacklisted(mFlags);
+    }
+
+    AK_FORCE_INLINE bool isNotAWord() const {
+        return PatriciaTrieReadingUtils::isNotAWord(mFlags);
+    }
+
+    AK_FORCE_INLINE bool hasBigrams() const {
+        return PatriciaTrieReadingUtils::hasBigrams(mFlags);
+    }
+
+    AK_FORCE_INLINE bool hasShortcutTargets() const {
+        return PatriciaTrieReadingUtils::hasShortcutTargets(mFlags);
+    }
+
+    // Parent node position
+    AK_FORCE_INLINE int getParentPos() const {
+        return mParentPos;
+    }
+
+    // Number of code points
+    AK_FORCE_INLINE uint8_t getCodePointCount() const {
+        return mCodePointCount;
+    }
+
+    AK_FORCE_INLINE const int *getCodePoints() const {
+        return mCodePoints;
+    }
+
+    // Probability
+    AK_FORCE_INLINE int getTerminalIdFieldPos() const {
+        return mTerminalIdFieldPos;
+    }
+
+    AK_FORCE_INLINE int getTerminalId() const {
+        return mTerminalId;
+    }
+
+    // Probability
+    AK_FORCE_INLINE int getProbabilityFieldPos() const {
+        return mProbabilityFieldPos;
+    }
+
+    AK_FORCE_INLINE int getProbability() const {
+        return mProbability;
+    }
+
+    // Children PtNode array position
+    AK_FORCE_INLINE int getChildrenPosFieldPos() const {
+        return mChildrenPosFieldPos;
+    }
+
+    AK_FORCE_INLINE int getChildrenPos() const {
+        return mChildrenPos;
+    }
+
+    // Bigram linked node position.
+    AK_FORCE_INLINE int getBigramLinkedNodePos() const {
+        return mBigramLinkedNodePos;
+    }
+
+    // Shortcutlist position
+    AK_FORCE_INLINE int getShortcutPos() const {
+        return mShortcutPos;
+    }
+
+    // Bigrams position
+    AK_FORCE_INLINE int getBigramsPos() const {
+        return mBigramPos;
+    }
+
+    // Sibling node position
+    AK_FORCE_INLINE int getSiblingNodePos() const {
+        return mSiblingPos;
+    }
+
+ private:
+    // This class have a public copy constructor to be used as a return value.
+
+    // Disallowing the assignment operator.
+    PtNodeParams &operator=(PtNodeParams &ptNodeParams);
+
+    const int mHeadPos;
+    const PatriciaTrieReadingUtils::NodeFlags mFlags;
+    const int mParentPos;
+    const uint8_t mCodePointCount;
+    int mCodePoints[MAX_WORD_LENGTH];
+    const int mTerminalIdFieldPos;
+    const int mTerminalId;
+    const int mProbabilityFieldPos;
+    const int mProbability;
+    const int mChildrenPosFieldPos;
+    const int mChildrenPos;
+    const int mBigramLinkedNodePos;
+    const int mShortcutPos;
+    const int mBigramPos;
+    const int mSiblingPos;
+};
+} // namespace latinime
+#endif /* LATINIME_PT_NODE_PARAMS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h
new file mode 100644
index 0000000..c6b2a8b
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_PT_NODE_READER_H
+#define LATINIME_PT_NODE_READER_H
+
+#include "defines.h"
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+
+namespace latinime {
+
+// Interface class used to read PtNode information.
+class PtNodeReader {
+ public:
+    virtual ~PtNodeReader() {}
+    virtual const PtNodeParams fetchNodeInfoInBufferFromPtNodePos(const int ptNodePos) const = 0;
+
+ protected:
+    PtNodeReader() {};
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(PtNodeReader);
+};
+} // namespace latinime
+#endif /* LATINIME_PT_NODE_READER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h
new file mode 100644
index 0000000..84dd687
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_PT_NODE_WRITER_H
+#define LATINIME_PT_NODE_WRITER_H
+
+#include "defines.h"
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "utils/hash_map_compat.h"
+
+namespace latinime {
+
+// Interface class used to write PtNode information.
+class PtNodeWriter {
+ public:
+    typedef hash_map_compat<int, int> PtNodeArrayPositionRelocationMap;
+    typedef hash_map_compat<int, int> PtNodePositionRelocationMap;
+    struct DictPositionRelocationMap {
+     public:
+        DictPositionRelocationMap()
+                : mPtNodeArrayPositionRelocationMap(), mPtNodePositionRelocationMap() {}
+
+        PtNodeArrayPositionRelocationMap mPtNodeArrayPositionRelocationMap;
+        PtNodePositionRelocationMap mPtNodePositionRelocationMap;
+
+     private:
+        DISALLOW_COPY_AND_ASSIGN(DictPositionRelocationMap);
+    };
+
+    virtual ~PtNodeWriter() {}
+
+    virtual bool markPtNodeAsDeleted(const PtNodeParams *const toBeUpdatedPtNodeParams) = 0;
+
+    virtual bool markPtNodeAsMoved(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int movedPos, const int bigramLinkedNodePos) = 0;
+
+    virtual bool markPtNodeAsWillBecomeNonTerminal(
+            const PtNodeParams *const toBeUpdatedPtNodeParams) = 0;
+
+    virtual bool updatePtNodeProbability(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int probability, const int timestamp) = 0;
+
+    virtual bool updatePtNodeProbabilityAndGetNeedsToKeepPtNodeAfterGC(
+            const PtNodeParams *const toBeUpdatedPtNodeParams,
+            bool *const outNeedsToKeepPtNode) = 0;
+
+    virtual bool updateChildrenPosition(const PtNodeParams *const toBeUpdatedPtNodeParams,
+                const int newChildrenPosition) = 0;
+
+    virtual bool writePtNodeAndAdvancePosition(const PtNodeParams *const ptNodeParams,
+            int *const ptNodeWritingPos) = 0;
+
+    virtual bool writeNewTerminalPtNodeAndAdvancePosition(const PtNodeParams *const ptNodeParams,
+            const int timestamp, int *const ptNodeWritingPos) = 0;
+
+    virtual bool addNewBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam, const int probability, const int timestamp,
+            bool *const outAddedNewBigram) = 0;
+
+    virtual bool removeBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam) = 0;
+
+    virtual bool updateAllBigramEntriesAndDeleteUselessEntries(
+            const PtNodeParams *const sourcePtNodeParams, int *const outBigramEntryCount) = 0;
+
+    virtual bool updateAllPositionFields(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const DictPositionRelocationMap *const dictPositionRelocationMap,
+            int *const outBigramEntryCount) = 0;
+
+    virtual bool addShortcutTarget(const PtNodeParams *const ptNodeParams,
+            const int *const targetCodePoints, const int targetCodePointCount,
+            const int shortcutProbability) = 0;
+
+ protected:
+    PtNodeWriter() {};
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(PtNodeWriter);
+};
+} // namespace latinime
+#endif /* LATINIME_PT_NODE_WRITER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
similarity index 95%
rename from native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.cpp
rename to native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
index 8a84bd2..960c1b9 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.cpp
@@ -15,22 +15,22 @@
  */
 
 
-#include "suggest/policyimpl/dictionary/patricia_trie_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h"
 
 #include "defines.h"
 #include "suggest/core/dicnode/dic_node.h"
 #include "suggest/core/dicnode/dic_node_vector.h"
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
 #include "suggest/policyimpl/dictionary/utils/probability_utils.h"
 
 namespace latinime {
 
-void PatriciaTriePolicy::createAndGetAllChildNodes(const DicNode *const dicNode,
+void PatriciaTriePolicy::createAndGetAllChildDicNodes(const DicNode *const dicNode,
         DicNodeVector *const childDicNodes) const {
     if (!dicNode->hasChildren()) {
         return;
     }
-    int nextPos = dicNode->getChildrenPos();
+    int nextPos = dicNode->getChildrenPtNodeArrayPos();
     if (nextPos < 0 || nextPos >= mDictBufferSize) {
         AKLOGE("Children PtNode array position is invalid. pos: %d, dict size: %d",
                 nextPos, mDictBufferSize);
@@ -52,14 +52,14 @@
 
 // This retrieves code points and the probability of the word by its terminal position.
 // Due to the fact that words are ordered in the dictionary in a strict breadth-first order,
-// it is possible to check for this with advantageous complexity. For each node, we search
+// it is possible to check for this with advantageous complexity. For each PtNode array, we search
 // for PtNodes with children and compare the children position with the position we look for.
 // When we shoot the position we look for, it means the word we look for is in the children
 // of the previous PtNode. The only tricky part is the fact that if we arrive at the end of a
 // PtNode array with the last PtNode's children position still less than what we are searching for,
 // we must descend the last PtNode's children (for example, if the word we are searching for starts
 // with a z, it's the last PtNode of the root array, so all children addresses will be smaller
-// than the position we look for, and we have to descend the z node).
+// than the position we look for, and we have to descend the z PtNode).
 /* Parameters :
  * ptNodePos: the byte position of the terminal PtNode of the word we are searching for (this is
  *   what is stored as the "bigram position" in each bigram)
@@ -74,9 +74,9 @@
     int pos = getRootPosition();
     int wordPos = 0;
     // One iteration of the outer loop iterates through PtNode arrays. As stated above, we will
-    // only traverse nodes that are actually a part of the terminal we are searching, so each time
-    // we enter this loop we are one depth level further than last time.
-    // The only reason we count nodes is because we want to reduce the probability of infinite
+    // only traverse PtNodes that are actually a part of the terminal we are searching, so each
+    // time we enter this loop we are one depth level further than last time.
+    // The only reason we count PtNodes is because we want to reduce the probability of infinite
     // looping in case there is a bug. Since we know there is an upper bound to the depth we are
     // supposed to traverse, it does not hurt to count iterations.
     for (int loopCount = maxCodePointCount; loopCount > 0; --loopCount) {
@@ -140,8 +140,9 @@
                     found = true;
                 } else if (1 >= ptNodeCount) {
                     // However if we are on the LAST PtNode of this array, and we have NOT shot the
-                    // position we should descend THIS node. So we trick the lastCandidatePtNodePos
-                    // so that we will descend this PtNode, not the previous one.
+                    // position we should descend THIS PtNode. So we trick the
+                    // lastCandidatePtNodePos so that we will descend this PtNode, not the previous
+                    // one.
                     lastCandidatePtNodePos = startPos;
                     found = true;
                 } else {
@@ -149,7 +150,7 @@
                     found = false;
                 }
             } else {
-                // Even if we don't have children here, we could still be on the last PtNode of /
+                // Even if we don't have children here, we could still be on the last PtNode of
                 // this array. If this is the case, we should descend the last PtNode that had
                 // children, and their position is already in lastCandidatePtNodePos.
                 found = (1 >= ptNodeCount);
@@ -230,9 +231,9 @@
     return 0;
 }
 
-// This function gets the position of the terminal node of the exact matching word in the
+// This function gets the position of the terminal PtNode of the exact matching word in the
 // dictionary. If no match is found, it returns NOT_A_DICT_POS.
-int PatriciaTriePolicy::getTerminalNodePositionOfWord(const int *const inWord,
+int PatriciaTriePolicy::getTerminalPtNodePositionOfWord(const int *const inWord,
         const int length, const bool forceLowerCaseSearch) const {
     int pos = getRootPosition();
     int wordPos = 0;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h
similarity index 78%
rename from native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h
rename to native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h
index 0f8662a..2adafd2 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h
@@ -24,6 +24,7 @@
 #include "suggest/policyimpl/dictionary/bigram/bigram_list_policy.h"
 #include "suggest/policyimpl/dictionary/header/header_policy.h"
 #include "suggest/policyimpl/dictionary/shortcut/shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/utils/format_utils.h"
 #include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
 
 namespace latinime {
@@ -33,28 +34,26 @@
 
 class PatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
  public:
-    PatriciaTriePolicy(const MmappedBuffer *const buffer)
-            : mBuffer(buffer), mHeaderPolicy(mBuffer->getBuffer(), buffer->getBufferSize()),
-              mDictRoot(mBuffer->getBuffer() + mHeaderPolicy.getSize()),
-              mDictBufferSize(mBuffer->getBufferSize() - mHeaderPolicy.getSize()),
+    PatriciaTriePolicy(const MmappedBuffer::MmappedBufferPtr &mmappedBuffer)
+            : mMmappedBuffer(mmappedBuffer),
+              mHeaderPolicy(mMmappedBuffer.get()->getBuffer(), FormatUtils::VERSION_2),
+              mDictRoot(mMmappedBuffer.get()->getBuffer() + mHeaderPolicy.getSize()),
+              mDictBufferSize(mMmappedBuffer.get()->getBufferSize()
+                      - mHeaderPolicy.getSize()),
               mBigramListPolicy(mDictRoot), mShortcutListPolicy(mDictRoot) {}
 
-    ~PatriciaTriePolicy() {
-        delete mBuffer;
-    }
-
     AK_FORCE_INLINE int getRootPosition() const {
         return 0;
     }
 
-    void createAndGetAllChildNodes(const DicNode *const dicNode,
+    void createAndGetAllChildDicNodes(const DicNode *const dicNode,
             DicNodeVector *const childDicNodes) const;
 
     int getCodePointsAndProbabilityAndReturnCodePointCount(
             const int terminalNodePos, const int maxCodePointCount, int *const outCodePoints,
             int *const outUnigramProbability) const;
 
-    int getTerminalNodePositionOfWord(const int *const inWord,
+    int getTerminalPtNodePositionOfWord(const int *const inWord,
             const int length, const bool forceLowerCaseSearch) const;
 
     int getProbability(const int unigramProbability, const int bigramProbability) const;
@@ -77,14 +76,17 @@
         return &mShortcutListPolicy;
     }
 
-    bool addUnigramWord(const int *const word, const int length, const int probability) {
+    bool addUnigramWord(const int *const word, const int length, const int probability,
+            const int *const shortcutTargetCodePoints, const int shortcutLength,
+            const int shortcutProbability, const bool isNotAWord, const bool isBlacklisted,
+            const int timestamp) {
         // This method should not be called for non-updatable dictionary.
         AKLOGI("Warning: addUnigramWord() is called for non-updatable dictionary.");
         return false;
     }
 
     bool addBigramWords(const int *const word0, const int length0, const int *const word1,
-            const int length1, const int probability) {
+            const int length1, const int probability, const int timestamp) {
         // This method should not be called for non-updatable dictionary.
         AKLOGI("Warning: addBigramWords() is called for non-updatable dictionary.");
         return false;
@@ -113,7 +115,7 @@
         return false;
     }
 
-    void getProperty(const char *const query, char *const outResult,
+    void getProperty(const char *const query, const int queryLength, char *const outResult,
             const int maxResultLength) {
         // getProperty is not supported for this class.
         if (maxResultLength > 0) {
@@ -121,10 +123,16 @@
         }
     }
 
+    const UnigramProperty getUnigramProperty(const int *const codePoints,
+            const int codePointCount) const {
+        // getUnigramProperty is not supported.
+        return UnigramProperty();
+    }
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(PatriciaTriePolicy);
 
-    const MmappedBuffer *const mBuffer;
+    const MmappedBuffer::MmappedBufferPtr mMmappedBuffer;
     const HeaderPolicy mHeaderPolicy;
     const uint8_t *const mDictRoot;
     const int mDictBufferSize;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.cpp
similarity index 98%
rename from native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.cpp
rename to native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.cpp
index 7df5581..82b3593 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "suggest/policyimpl/dictionary/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
 
 #include "defines.h"
 #include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
diff --git a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h
similarity index 99%
rename from native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.h
rename to native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h
index 8420ee9..b28f583 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_reading_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h
@@ -23,6 +23,7 @@
 
 namespace latinime {
 
+// TODO: Move to pt_common
 class PatriciaTrieReadingUtils {
  public:
     typedef uint8_t NodeFlags;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.cpp
new file mode 100644
index 0000000..cb9d450
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.cpp
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h"
+
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+const BigramEntry BigramDictContent::getBigramEntryAndAdvancePosition(
+        int *const bigramEntryPos) const {
+    const BufferWithExtendableBuffer *const bigramListBuffer = getContentBuffer();
+    const int bigramFlags = bigramListBuffer->readUintAndAdvancePosition(
+            Ver4DictConstants::BIGRAM_FLAGS_FIELD_SIZE, bigramEntryPos);
+    const bool hasNext = (bigramFlags & Ver4DictConstants::BIGRAM_HAS_NEXT_MASK) != 0;
+    int probability = NOT_A_PROBABILITY;
+    int timestamp = NOT_A_TIMESTAMP;
+    int level = 0;
+    int count = 0;
+    if (mHasHistoricalInfo) {
+        probability = bigramListBuffer->readUintAndAdvancePosition(
+                Ver4DictConstants::PROBABILITY_SIZE, bigramEntryPos);
+        timestamp = bigramListBuffer->readUintAndAdvancePosition(
+                Ver4DictConstants::TIME_STAMP_FIELD_SIZE, bigramEntryPos);
+        level = bigramListBuffer->readUintAndAdvancePosition(
+                Ver4DictConstants::WORD_LEVEL_FIELD_SIZE, bigramEntryPos);
+        count = bigramListBuffer->readUintAndAdvancePosition(
+                Ver4DictConstants::WORD_COUNT_FIELD_SIZE, bigramEntryPos);
+    } else {
+        probability = bigramFlags & Ver4DictConstants::BIGRAM_PROBABILITY_MASK;
+    }
+    const int encodedTargetTerminalId = bigramListBuffer->readUintAndAdvancePosition(
+            Ver4DictConstants::BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE, bigramEntryPos);
+    const int targetTerminalId =
+            (encodedTargetTerminalId == Ver4DictConstants::INVALID_BIGRAM_TARGET_TERMINAL_ID) ?
+                    Ver4DictConstants::NOT_A_TERMINAL_ID : encodedTargetTerminalId;
+    if (mHasHistoricalInfo) {
+        const HistoricalInfo historicalInfo(timestamp, level, count);
+        return BigramEntry(hasNext, probability, &historicalInfo, targetTerminalId);
+    } else {
+        return BigramEntry(hasNext, probability, targetTerminalId);
+    }
+}
+
+bool BigramDictContent::writeBigramEntryAndAdvancePosition(
+        const BigramEntry *const bigramEntryToWrite, int *const entryWritingPos) {
+    BufferWithExtendableBuffer *const bigramListBuffer = getWritableContentBuffer();
+    const int bigramFlags = createAndGetBigramFlags(
+            mHasHistoricalInfo ? 0 : bigramEntryToWrite->getProbability(),
+            bigramEntryToWrite->hasNext());
+    if (!bigramListBuffer->writeUintAndAdvancePosition(bigramFlags,
+            Ver4DictConstants::BIGRAM_FLAGS_FIELD_SIZE, entryWritingPos)) {
+        AKLOGE("Cannot write bigram flags. pos: %d, flags: %x", *entryWritingPos, bigramFlags);
+        return false;
+    }
+    if (mHasHistoricalInfo) {
+        if (!bigramListBuffer->writeUintAndAdvancePosition(bigramEntryToWrite->getProbability(),
+                Ver4DictConstants::PROBABILITY_SIZE, entryWritingPos)) {
+            AKLOGE("Cannot write bigram probability. pos: %d, probability: %d", *entryWritingPos,
+                    bigramEntryToWrite->getProbability());
+            return false;
+        }
+        const HistoricalInfo *const historicalInfo = bigramEntryToWrite->getHistoricalInfo();
+        if (!bigramListBuffer->writeUintAndAdvancePosition(historicalInfo->getTimeStamp(),
+                Ver4DictConstants::TIME_STAMP_FIELD_SIZE, entryWritingPos)) {
+            AKLOGE("Cannot write bigram timestamps. pos: %d, timestamp: %d", *entryWritingPos,
+                    historicalInfo->getTimeStamp());
+            return false;
+        }
+        if (!bigramListBuffer->writeUintAndAdvancePosition(historicalInfo->getLevel(),
+                Ver4DictConstants::WORD_LEVEL_FIELD_SIZE, entryWritingPos)) {
+            AKLOGE("Cannot write bigram level. pos: %d, level: %d", *entryWritingPos,
+                    historicalInfo->getLevel());
+            return false;
+        }
+        if (!bigramListBuffer->writeUintAndAdvancePosition(historicalInfo->getCount(),
+                Ver4DictConstants::WORD_COUNT_FIELD_SIZE, entryWritingPos)) {
+            AKLOGE("Cannot write bigram count. pos: %d, count: %d", *entryWritingPos,
+                    historicalInfo->getCount());
+            return false;
+        }
+    }
+    const int targetTerminalIdToWrite =
+            (bigramEntryToWrite->getTargetTerminalId() == Ver4DictConstants::NOT_A_TERMINAL_ID) ?
+                    Ver4DictConstants::INVALID_BIGRAM_TARGET_TERMINAL_ID :
+                            bigramEntryToWrite->getTargetTerminalId();
+    if (!bigramListBuffer->writeUintAndAdvancePosition(targetTerminalIdToWrite,
+            Ver4DictConstants::BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE, entryWritingPos)) {
+        AKLOGE("Cannot write bigram target terminal id. pos: %d, target terminal id: %d",
+                *entryWritingPos, bigramEntryToWrite->getTargetTerminalId());
+        return false;
+    }
+    return true;
+}
+
+bool BigramDictContent::copyBigramList(const int bigramListPos, const int toPos) {
+    int readingPos = bigramListPos;
+    int writingPos = toPos;
+    bool hasNext = true;
+    while (hasNext) {
+        const BigramEntry bigramEntry = getBigramEntryAndAdvancePosition(&readingPos);
+        hasNext = bigramEntry.hasNext();
+        if (!writeBigramEntryAndAdvancePosition(&bigramEntry, &writingPos)) {
+            AKLOGE("Cannot write bigram entry to copy. pos: %d", writingPos);
+            return false;
+        }
+    }
+    return true;
+}
+
+bool BigramDictContent::runGC(const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+        const BigramDictContent *const originalBigramDictContent,
+        int *const outBigramEntryCount) {
+    for (TerminalPositionLookupTable::TerminalIdMap::const_iterator it = terminalIdMap->begin();
+            it != terminalIdMap->end(); ++it) {
+        const int originalBigramListPos =
+                originalBigramDictContent->getBigramListHeadPos(it->first);
+        if (originalBigramListPos == NOT_A_DICT_POS) {
+            // This terminal does not have a bigram list.
+            continue;
+        }
+        const int bigramListPos = getContentBuffer()->getTailPosition();
+        int bigramEntryCount = 0;
+        // Copy bigram list with GC from original content.
+        if (!runGCBigramList(originalBigramListPos, originalBigramDictContent, bigramListPos,
+                terminalIdMap, &bigramEntryCount)) {
+            AKLOGE("Cannot complete GC for the bigram list. original pos: %d, pos: %d",
+                    originalBigramListPos, bigramListPos);
+            return false;
+        }
+        if (bigramEntryCount == 0) {
+            // All bigram entries are useless. This terminal does not have a bigram list.
+            continue;
+        }
+        *outBigramEntryCount += bigramEntryCount;
+        // Set bigram list position to the lookup table.
+        if (!getUpdatableAddressLookupTable()->set(it->second, bigramListPos)) {
+            AKLOGE("Cannot set bigram list position. terminal id: %d, pos: %d",
+                    it->second, bigramListPos);
+            return false;
+        }
+    }
+    return true;
+}
+
+// Returns whether GC for the bigram list was succeeded or not.
+bool BigramDictContent::runGCBigramList(const int bigramListPos,
+        const BigramDictContent *const sourceBigramDictContent, const int toPos,
+        const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+        int *const outEntrycount) {
+    bool hasNext = true;
+    int readingPos = bigramListPos;
+    int writingPos = toPos;
+    int lastEntryPos = NOT_A_DICT_POS;
+    while (hasNext) {
+        const BigramEntry originalBigramEntry =
+                sourceBigramDictContent->getBigramEntryAndAdvancePosition(&readingPos);
+        hasNext = originalBigramEntry.hasNext();
+        if (originalBigramEntry.getTargetTerminalId() == Ver4DictConstants::NOT_A_TERMINAL_ID) {
+            continue;
+        }
+        TerminalPositionLookupTable::TerminalIdMap::const_iterator it =
+                terminalIdMap->find(originalBigramEntry.getTargetTerminalId());
+        if (it == terminalIdMap->end()) {
+            // Target word has been removed.
+            continue;
+        }
+        lastEntryPos = hasNext ? writingPos : NOT_A_DICT_POS;
+        const BigramEntry updatedBigramEntry =
+                originalBigramEntry.updateTargetTerminalIdAndGetEntry(it->second);
+        if (!writeBigramEntryAndAdvancePosition(&updatedBigramEntry, &writingPos)) {
+            AKLOGE("Cannot write bigram entry to run GC. pos: %d", writingPos);
+            return false;
+        }
+        *outEntrycount += 1;
+    }
+    if (lastEntryPos != NOT_A_DICT_POS) {
+        // Update has next flag in the last written entry.
+        const BigramEntry bigramEntry = getBigramEntry(lastEntryPos).updateHasNextAndGetEntry(
+                false /* hasNext */);
+        if (!writeBigramEntry(&bigramEntry, lastEntryPos)) {
+            AKLOGE("Cannot write bigram entry to set hasNext flag after GC. pos: %d", writingPos);
+            return false;
+        }
+    }
+    return true;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h
new file mode 100644
index 0000000..ba2a052
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_BIGRAM_DICT_CONTENT_H
+#define LATINIME_BIGRAM_DICT_CONTENT_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/bigram_entry.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+
+namespace latinime {
+
+class BigramDictContent : public SparseTableDictContent {
+ public:
+    BigramDictContent(const char *const dictPath, const bool hasHistoricalInfo,
+            const bool isUpdatable)
+            : SparseTableDictContent(dictPath,
+                      Ver4DictConstants::BIGRAM_LOOKUP_TABLE_FILE_EXTENSION,
+                      Ver4DictConstants::BIGRAM_CONTENT_TABLE_FILE_EXTENSION,
+                      Ver4DictConstants::BIGRAM_FILE_EXTENSION, isUpdatable,
+                      Ver4DictConstants::BIGRAM_ADDRESS_TABLE_BLOCK_SIZE,
+                      Ver4DictConstants::BIGRAM_ADDRESS_TABLE_DATA_SIZE),
+              mHasHistoricalInfo(hasHistoricalInfo) {}
+
+    BigramDictContent(const bool hasHistoricalInfo)
+            : SparseTableDictContent(Ver4DictConstants::BIGRAM_ADDRESS_TABLE_BLOCK_SIZE,
+                      Ver4DictConstants::BIGRAM_ADDRESS_TABLE_DATA_SIZE),
+              mHasHistoricalInfo(hasHistoricalInfo) {}
+
+    const BigramEntry getBigramEntry(const int bigramEntryPos) const {
+        int readingPos = bigramEntryPos;
+        return getBigramEntryAndAdvancePosition(&readingPos);
+    }
+
+    const BigramEntry getBigramEntryAndAdvancePosition(int *const bigramEntryPos) const;
+
+    // Returns head position of bigram list for a PtNode specified by terminalId.
+    int getBigramListHeadPos(const int terminalId) const {
+        const SparseTable *const addressLookupTable = getAddressLookupTable();
+        if (!addressLookupTable->contains(terminalId)) {
+            return NOT_A_DICT_POS;
+        }
+        return addressLookupTable->get(terminalId);
+    }
+
+    bool writeBigramEntry(const BigramEntry *const bigramEntryToWrite, const int entryWritingPos) {
+        int writingPos = entryWritingPos;
+        return writeBigramEntryAndAdvancePosition(bigramEntryToWrite, &writingPos);
+    }
+
+    bool writeBigramEntryAndAdvancePosition(const BigramEntry *const bigramEntryToWrite,
+            int *const entryWritingPos);
+
+    bool createNewBigramList(const int terminalId) {
+        const int bigramListPos = getContentBuffer()->getTailPosition();
+        return getUpdatableAddressLookupTable()->set(terminalId, bigramListPos);
+    }
+
+    bool copyBigramList(const int bigramListPos, const int toPos);
+
+    bool flushToFile(const char *const dictPath) const {
+        return flush(dictPath, Ver4DictConstants::BIGRAM_LOOKUP_TABLE_FILE_EXTENSION,
+                Ver4DictConstants::BIGRAM_CONTENT_TABLE_FILE_EXTENSION,
+                Ver4DictConstants::BIGRAM_FILE_EXTENSION);
+    }
+
+    bool runGC(const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+            const BigramDictContent *const originalBigramDictContent,
+            int *const outBigramEntryCount);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(BigramDictContent);
+
+    int createAndGetBigramFlags(const int probability, const bool hasNext) const {
+        return (probability & Ver4DictConstants::BIGRAM_PROBABILITY_MASK)
+                | (hasNext ? Ver4DictConstants::BIGRAM_HAS_NEXT_MASK : 0);
+    }
+
+    bool runGCBigramList(const int bigramListPos,
+            const BigramDictContent *const sourceBigramDictContent, const int toPos,
+            const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+            int *const outEntryCount);
+
+    bool mHasHistoricalInfo;
+};
+} // namespace latinime
+#endif /* LATINIME_BIGRAM_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_entry.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_entry.h
new file mode 100644
index 0000000..2b0cbd9
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/bigram_entry.h
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_BIGRAM_ENTRY_H
+#define LATINIME_BIGRAM_ENTRY_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/historical_info.h"
+
+namespace latinime {
+
+class BigramEntry {
+ public:
+    BigramEntry(const BigramEntry& bigramEntry)
+            : mHasNext(bigramEntry.mHasNext), mProbability(bigramEntry.mProbability),
+              mHistoricalInfo(), mTargetTerminalId(bigramEntry.mTargetTerminalId) {}
+
+    // Entry with historical information.
+    BigramEntry(const bool hasNext, const int probability, const int targetTerminalId)
+            : mHasNext(hasNext), mProbability(probability), mHistoricalInfo(),
+              mTargetTerminalId(targetTerminalId) {}
+
+    // Entry with historical information.
+    BigramEntry(const bool hasNext, const int probability,
+            const HistoricalInfo *const historicalInfo, const int targetTerminalId)
+            : mHasNext(hasNext), mProbability(probability), mHistoricalInfo(*historicalInfo),
+              mTargetTerminalId(targetTerminalId) {}
+
+    const BigramEntry getInvalidatedEntry() const {
+        return updateTargetTerminalIdAndGetEntry(Ver4DictConstants::NOT_A_TERMINAL_ID);
+    }
+
+    const BigramEntry updateHasNextAndGetEntry(const bool hasNext) const {
+        return BigramEntry(hasNext, mProbability, &mHistoricalInfo, mTargetTerminalId);
+    }
+
+    const BigramEntry updateTargetTerminalIdAndGetEntry(const int newTargetTerminalId) const {
+        return BigramEntry(mHasNext, mProbability, &mHistoricalInfo, newTargetTerminalId);
+    }
+
+    const BigramEntry updateProbabilityAndGetEntry(const int probability) const {
+        return BigramEntry(mHasNext, probability, &mHistoricalInfo, mTargetTerminalId);
+    }
+
+    const BigramEntry updateHistoricalInfoAndGetEntry(
+            const HistoricalInfo *const historicalInfo) const {
+        return BigramEntry(mHasNext, mProbability, historicalInfo, mTargetTerminalId);
+    }
+
+    bool isValid() const {
+        return mTargetTerminalId != Ver4DictConstants::NOT_A_TERMINAL_ID;
+    }
+
+    bool hasNext() const {
+        return mHasNext;
+    }
+
+    int getProbability() const {
+        return mProbability;
+    }
+
+    bool hasHistoricalInfo() const {
+        return mHistoricalInfo.isValid();
+    }
+
+    const HistoricalInfo *getHistoricalInfo() const {
+        return &mHistoricalInfo;
+    }
+
+    int getTargetTerminalId() const {
+        return mTargetTerminalId;
+    }
+
+ private:
+    // Copy constructor is public to use this class as a type of return value.
+    DISALLOW_DEFAULT_CONSTRUCTOR(BigramEntry);
+    DISALLOW_ASSIGNMENT_OPERATOR(BigramEntry);
+
+    const bool mHasNext;
+    const int mProbability;
+    const HistoricalInfo mHistoricalInfo;
+    const int mTargetTerminalId;
+};
+} // namespace latinime
+#endif /* LATINIME_BIGRAM_ENTRY_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dict_content.h
new file mode 100644
index 0000000..0c2f470
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dict_content.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DICT_CONTENT_H
+#define LATINIME_DICT_CONTENT_H
+
+#include "defines.h"
+
+namespace latinime {
+
+class DictContent {
+ public:
+    virtual ~DictContent() {}
+    virtual bool isValid() const = 0;
+
+ protected:
+    DictContent() {}
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(DictContent);
+};
+} // namespace latinime
+#endif /* LATINIME_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.cpp
new file mode 100644
index 0000000..3b7c70e
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.cpp
@@ -0,0 +1,160 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h"
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+const ProbabilityEntry ProbabilityDictContent::getProbabilityEntry(const int terminalId) const {
+    if (terminalId < 0 || terminalId >= mSize) {
+        // This method can be called with invalid terminal id during GC.
+        return ProbabilityEntry(0 /* flags */, NOT_A_PROBABILITY);
+    }
+    const BufferWithExtendableBuffer *const buffer = getBuffer();
+    int entryPos = getEntryPos(terminalId);
+    const int flags = buffer->readUintAndAdvancePosition(
+            Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE, &entryPos);
+    const int probability = buffer->readUintAndAdvancePosition(
+            Ver4DictConstants::PROBABILITY_SIZE, &entryPos);
+    if (mHasHistoricalInfo) {
+        const int timestamp = buffer->readUintAndAdvancePosition(
+                Ver4DictConstants::TIME_STAMP_FIELD_SIZE, &entryPos);
+        const int level = buffer->readUintAndAdvancePosition(
+                Ver4DictConstants::WORD_LEVEL_FIELD_SIZE, &entryPos);
+        const int count = buffer->readUintAndAdvancePosition(
+                Ver4DictConstants::WORD_COUNT_FIELD_SIZE, &entryPos);
+        const HistoricalInfo historicalInfo(timestamp, level, count);
+        return ProbabilityEntry(flags, probability, &historicalInfo);
+    } else {
+        return ProbabilityEntry(flags, probability);
+    }
+}
+
+bool ProbabilityDictContent::setProbabilityEntry(const int terminalId,
+        const ProbabilityEntry *const probabilityEntry) {
+    if (terminalId < 0) {
+        return false;
+    }
+    const int entryPos = getEntryPos(terminalId);
+    if (terminalId >= mSize) {
+        ProbabilityEntry dummyEntry;
+        // Write new entry.
+        int writingPos = getBuffer()->getTailPosition();
+        while (writingPos <= entryPos) {
+            // Fulfilling with dummy entries until writingPos.
+            if (!writeEntry(&dummyEntry, writingPos)) {
+                AKLOGE("Cannot write dummy entry. pos: %d, mSize: %d", writingPos, mSize);
+                return false;
+            }
+            writingPos += getEntrySize();
+            mSize++;
+        }
+    }
+    return writeEntry(probabilityEntry, entryPos);
+}
+
+bool ProbabilityDictContent::flushToFile(const char *const dictPath) const {
+    if (getEntryPos(mSize) < getBuffer()->getTailPosition()) {
+        ProbabilityDictContent probabilityDictContentToWrite(mHasHistoricalInfo);
+        for (int i = 0; i < mSize; ++i) {
+            const ProbabilityEntry probabilityEntry = getProbabilityEntry(i);
+            if (!probabilityDictContentToWrite.setProbabilityEntry(i, &probabilityEntry)) {
+                AKLOGE("Cannot set probability entry in flushToFile. terminalId: %d", i);
+                return false;
+            }
+        }
+        return probabilityDictContentToWrite.flush(dictPath,
+                Ver4DictConstants::FREQ_FILE_EXTENSION);
+    } else {
+        return flush(dictPath, Ver4DictConstants::FREQ_FILE_EXTENSION);
+    }
+}
+
+bool ProbabilityDictContent::runGC(
+        const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+        const ProbabilityDictContent *const originalProbabilityDictContent) {
+    mSize = 0;
+    for (TerminalPositionLookupTable::TerminalIdMap::const_iterator it = terminalIdMap->begin();
+            it != terminalIdMap->end(); ++it) {
+        const ProbabilityEntry probabilityEntry =
+                originalProbabilityDictContent->getProbabilityEntry(it->first);
+        if (!setProbabilityEntry(it->second, &probabilityEntry)) {
+            AKLOGE("Cannot set probability entry in runGC. terminalId: %d", it->second);
+            return false;
+        }
+        mSize++;
+    }
+    return true;
+}
+
+int ProbabilityDictContent::getEntrySize() const {
+    if (mHasHistoricalInfo) {
+        return Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE
+                + Ver4DictConstants::PROBABILITY_SIZE
+                + Ver4DictConstants::TIME_STAMP_FIELD_SIZE
+                + Ver4DictConstants::WORD_LEVEL_FIELD_SIZE
+                + Ver4DictConstants::WORD_COUNT_FIELD_SIZE;
+    } else {
+        return Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE
+                + Ver4DictConstants::PROBABILITY_SIZE;
+    }
+}
+
+int ProbabilityDictContent::getEntryPos(const int terminalId) const {
+    return terminalId * getEntrySize();
+}
+
+bool ProbabilityDictContent::writeEntry(const ProbabilityEntry *const probabilityEntry,
+        const int entryPos) {
+    BufferWithExtendableBuffer *const bufferToWrite = getWritableBuffer();
+    int writingPos = entryPos;
+    if (!bufferToWrite->writeUintAndAdvancePosition(probabilityEntry->getFlags(),
+            Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE, &writingPos)) {
+        AKLOGE("Cannot write flags in probability dict content. pos: %d", writingPos);
+        return false;
+    }
+    if (!bufferToWrite->writeUintAndAdvancePosition(probabilityEntry->getProbability(),
+            Ver4DictConstants::PROBABILITY_SIZE, &writingPos)) {
+        AKLOGE("Cannot write probability in probability dict content. pos: %d", writingPos);
+        return false;
+    }
+    if (mHasHistoricalInfo) {
+        const HistoricalInfo *const historicalInfo = probabilityEntry->getHistoricalInfo();
+        if (!bufferToWrite->writeUintAndAdvancePosition(historicalInfo->getTimeStamp(),
+                Ver4DictConstants::TIME_STAMP_FIELD_SIZE, &writingPos)) {
+            AKLOGE("Cannot write timestamp in probability dict content. pos: %d", writingPos);
+            return false;
+        }
+        if (!bufferToWrite->writeUintAndAdvancePosition(historicalInfo->getLevel(),
+                Ver4DictConstants::WORD_LEVEL_FIELD_SIZE, &writingPos)) {
+            AKLOGE("Cannot write level in probability dict content. pos: %d", writingPos);
+            return false;
+        }
+        if (!bufferToWrite->writeUintAndAdvancePosition(historicalInfo->getCount(),
+                Ver4DictConstants::WORD_COUNT_FIELD_SIZE, &writingPos)) {
+            AKLOGE("Cannot write count in probability dict content. pos: %d", writingPos);
+            return false;
+        }
+    }
+    return true;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h
new file mode 100644
index 0000000..b065bc9
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_PROBABILITY_DICT_CONTENT_H
+#define LATINIME_PROBABILITY_DICT_CONTENT_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/single_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+class ProbabilityEntry;
+
+class ProbabilityDictContent : public SingleDictContent {
+ public:
+    ProbabilityDictContent(const char *const dictPath, const bool hasHistoricalInfo,
+            const bool isUpdatable)
+            : SingleDictContent(dictPath, Ver4DictConstants::FREQ_FILE_EXTENSION, isUpdatable),
+              mHasHistoricalInfo(hasHistoricalInfo),
+              mSize(getBuffer()->getTailPosition() / getEntrySize()) {}
+
+    ProbabilityDictContent(const bool hasHistoricalInfo)
+            : mHasHistoricalInfo(hasHistoricalInfo), mSize(0) {}
+
+    const ProbabilityEntry getProbabilityEntry(const int terminalId) const;
+
+    bool setProbabilityEntry(const int terminalId, const ProbabilityEntry *const probabilityEntry);
+
+    bool flushToFile(const char *const dictPath) const;
+
+    bool runGC(const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+            const ProbabilityDictContent *const originalProbabilityDictContent);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(ProbabilityDictContent);
+
+    int getEntrySize() const;
+
+    int getEntryPos(const int terminalId) const;
+
+    bool writeEntry(const ProbabilityEntry *const probabilityEntry, const int entryPos);
+
+    bool mHasHistoricalInfo;
+    int mSize;
+};
+} // namespace latinime
+#endif /* LATINIME_PROBABILITY_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h
new file mode 100644
index 0000000..36ba82b
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_PROBABILITY_ENTRY_H
+#define LATINIME_PROBABILITY_ENTRY_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/historical_info.h"
+
+namespace latinime {
+
+class ProbabilityEntry {
+ public:
+    ProbabilityEntry(const ProbabilityEntry &probabilityEntry)
+            : mFlags(probabilityEntry.mFlags), mProbability(probabilityEntry.mProbability),
+              mHistoricalInfo(probabilityEntry.mHistoricalInfo) {}
+
+    // Dummy entry
+    ProbabilityEntry()
+            : mFlags(0), mProbability(NOT_A_PROBABILITY), mHistoricalInfo() {}
+
+    // Entry without historical information
+    ProbabilityEntry(const int flags, const int probability)
+            : mFlags(flags), mProbability(probability), mHistoricalInfo() {}
+
+    // Entry with historical information.
+    ProbabilityEntry(const int flags, const int probability,
+            const HistoricalInfo *const historicalInfo)
+            : mFlags(flags), mProbability(probability), mHistoricalInfo(*historicalInfo) {}
+
+    const ProbabilityEntry createEntryWithUpdatedProbability(const int probability) const {
+        return ProbabilityEntry(mFlags, probability, &mHistoricalInfo);
+    }
+
+    const ProbabilityEntry createEntryWithUpdatedHistoricalInfo(
+            const HistoricalInfo *const historicalInfo) const {
+        return ProbabilityEntry(mFlags, mProbability, historicalInfo);
+    }
+
+    bool hasHistoricalInfo() const {
+        return mHistoricalInfo.isValid();
+    }
+
+    int getFlags() const {
+        return mFlags;
+    }
+
+    int getProbability() const {
+        return mProbability;
+    }
+
+    const HistoricalInfo *getHistoricalInfo() const {
+        return &mHistoricalInfo;
+    }
+
+ private:
+    // Copy constructor is public to use this class as a type of return value.
+    DISALLOW_ASSIGNMENT_OPERATOR(ProbabilityEntry);
+
+    const int mFlags;
+    const int mProbability;
+    const HistoricalInfo mHistoricalInfo;
+};
+} // namespace latinime
+#endif /* LATINIME_PROBABILITY_ENTRY_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.cpp
new file mode 100644
index 0000000..29972a4
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.cpp
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h"
+
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+void ShortcutDictContent::getShortcutEntryAndAdvancePosition(const int maxCodePointCount,
+        int *const outCodePoint, int *const outCodePointCount, int *const outProbability,
+        bool *const outhasNext, int *const shortcutEntryPos) const {
+    const BufferWithExtendableBuffer *const shortcutListBuffer = getContentBuffer();
+    const int shortcutFlags = shortcutListBuffer->readUintAndAdvancePosition(
+            Ver4DictConstants::SHORTCUT_FLAGS_FIELD_SIZE, shortcutEntryPos);
+    if (outProbability) {
+        *outProbability = shortcutFlags & Ver4DictConstants::SHORTCUT_PROBABILITY_MASK;
+    }
+    if (outhasNext) {
+        *outhasNext = shortcutFlags & Ver4DictConstants::SHORTCUT_HAS_NEXT_MASK;
+    }
+    if (outCodePoint && outCodePointCount) {
+        shortcutListBuffer->readCodePointsAndAdvancePosition(
+                maxCodePointCount, outCodePoint, outCodePointCount, shortcutEntryPos);
+    }
+}
+
+int ShortcutDictContent::getShortcutListHeadPos(const int terminalId) const {
+    const SparseTable *const addressLookupTable = getAddressLookupTable();
+    if (!addressLookupTable->contains(terminalId)) {
+        return NOT_A_DICT_POS;
+    }
+    return addressLookupTable->get(terminalId);
+}
+
+bool ShortcutDictContent::flushToFile(const char *const dictPath) const {
+    return flush(dictPath, Ver4DictConstants::SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION,
+            Ver4DictConstants::SHORTCUT_CONTENT_TABLE_FILE_EXTENSION,
+            Ver4DictConstants::SHORTCUT_FILE_EXTENSION);
+}
+
+bool ShortcutDictContent::runGC(
+        const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+        const ShortcutDictContent *const originalShortcutDictContent) {
+   for (TerminalPositionLookupTable::TerminalIdMap::const_iterator it = terminalIdMap->begin();
+           it != terminalIdMap->end(); ++it) {
+       const int originalShortcutListPos =
+               originalShortcutDictContent->getShortcutListHeadPos(it->first);
+       if (originalShortcutListPos == NOT_A_DICT_POS) {
+           continue;
+       }
+       const int shortcutListPos = getContentBuffer()->getTailPosition();
+       // Copy shortcut list from original content.
+       if (!copyShortcutListFromDictContent(originalShortcutListPos, originalShortcutDictContent,
+               shortcutListPos)) {
+           AKLOGE("Cannot copy shortcut list during GC. original pos: %d, pos: %d",
+                   originalShortcutListPos, shortcutListPos);
+           return false;
+       }
+       // Set shortcut list position to the lookup table.
+       if (!getUpdatableAddressLookupTable()->set(it->second, shortcutListPos)) {
+           AKLOGE("Cannot set shortcut list position. terminal id: %d, pos: %d",
+                   it->second, shortcutListPos);
+           return false;
+       }
+   }
+   return true;
+}
+
+bool ShortcutDictContent::createNewShortcutList(const int terminalId) {
+    const int shortcutListListPos = getContentBuffer()->getTailPosition();
+    return getUpdatableAddressLookupTable()->set(terminalId, shortcutListListPos);
+}
+
+bool ShortcutDictContent::copyShortcutList(const int shortcutListPos, const int toPos) {
+    return copyShortcutListFromDictContent(shortcutListPos, this, toPos);
+}
+
+bool ShortcutDictContent::copyShortcutListFromDictContent(const int shortcutListPos,
+        const ShortcutDictContent *const sourceShortcutDictContent, const int toPos) {
+    bool hasNext = true;
+    int readingPos = shortcutListPos;
+    int writingPos = toPos;
+    int codePoints[MAX_WORD_LENGTH];
+    while (hasNext) {
+        int probability = 0;
+        int codePointCount = 0;
+        sourceShortcutDictContent->getShortcutEntryAndAdvancePosition(MAX_WORD_LENGTH,
+                codePoints, &codePointCount, &probability, &hasNext, &readingPos);
+        if (!writeShortcutEntryAndAdvancePosition(codePoints, codePointCount, probability,
+                hasNext, &writingPos)) {
+            AKLOGE("Cannot write shortcut entry to copy. pos: %d", writingPos);
+            return false;
+        }
+    }
+    return true;
+}
+
+bool ShortcutDictContent::setProbability(const int probability, const int shortcutEntryPos) {
+    BufferWithExtendableBuffer *const shortcutListBuffer = getWritableContentBuffer();
+    const int shortcutFlags = shortcutListBuffer->readUint(
+            Ver4DictConstants::SHORTCUT_FLAGS_FIELD_SIZE, shortcutEntryPos);
+    const bool hasNext = shortcutFlags & Ver4DictConstants::SHORTCUT_HAS_NEXT_MASK;
+    const int shortcutFlagsToWrite = createAndGetShortcutFlags(probability, hasNext);
+    return shortcutListBuffer->writeUint(shortcutFlagsToWrite,
+            Ver4DictConstants::SHORTCUT_FLAGS_FIELD_SIZE, shortcutEntryPos);
+}
+
+bool ShortcutDictContent::writeShortcutEntryAndAdvancePosition(const int *const codePoint,
+        const int codePointCount, const int probability, const bool hasNext,
+        int *const shortcutEntryPos) {
+    BufferWithExtendableBuffer *const shortcutListBuffer = getWritableContentBuffer();
+    const int shortcutFlags = createAndGetShortcutFlags(probability, hasNext);
+    if (!shortcutListBuffer->writeUintAndAdvancePosition(shortcutFlags,
+            Ver4DictConstants::SHORTCUT_FLAGS_FIELD_SIZE, shortcutEntryPos)) {
+        AKLOGE("Cannot write shortcut flags. flags; %x, pos: %d", shortcutFlags, *shortcutEntryPos);
+        return false;
+    }
+    if (!shortcutListBuffer->writeCodePointsAndAdvancePosition(codePoint, codePointCount,
+            true /* writesTerminator */, shortcutEntryPos)) {
+        AKLOGE("Cannot write shortcut target code points. pos: %d", *shortcutEntryPos);
+        return false;
+    }
+    return true;
+}
+
+// Find a shortcut entry that has specified target and return its position.
+int ShortcutDictContent::findShortcutEntryAndGetPos(const int shortcutListPos,
+        const int *const targetCodePointsToFind, const int codePointCount) const {
+    bool hasNext = true;
+    int readingPos = shortcutListPos;
+    int targetCodePoints[MAX_WORD_LENGTH];
+    while (hasNext) {
+        const int entryPos = readingPos;
+        int probability = 0;
+        int targetCodePointCount = 0;
+        getShortcutEntryAndAdvancePosition(MAX_WORD_LENGTH, targetCodePoints, &targetCodePointCount,
+                &probability, &hasNext, &readingPos);
+        if (targetCodePointCount != codePointCount) {
+            continue;
+        }
+        bool matched = true;
+        for (int i = 0; i < codePointCount; ++i) {
+            if (targetCodePointsToFind[i] != targetCodePoints[i]) {
+                matched = false;
+                break;
+            }
+        }
+        if (matched) {
+            return entryPos;
+        }
+    }
+    return NOT_A_DICT_POS;
+}
+
+int ShortcutDictContent::createAndGetShortcutFlags(const int probability,
+        const bool hasNext) const {
+    return (probability & Ver4DictConstants::SHORTCUT_PROBABILITY_MASK)
+            | (hasNext ? Ver4DictConstants::SHORTCUT_HAS_NEXT_MASK : 0);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h
new file mode 100644
index 0000000..eaafc27
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_SHORTCUT_DICT_CONTENT_H
+#define LATINIME_SHORTCUT_DICT_CONTENT_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+
+namespace latinime {
+
+class ShortcutDictContent : public SparseTableDictContent {
+ public:
+    ShortcutDictContent(const char *const dictPath, const bool isUpdatable)
+            : SparseTableDictContent(dictPath,
+                      Ver4DictConstants::SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION,
+                      Ver4DictConstants::SHORTCUT_CONTENT_TABLE_FILE_EXTENSION,
+                      Ver4DictConstants::SHORTCUT_FILE_EXTENSION, isUpdatable,
+                      Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE,
+                      Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_DATA_SIZE) {}
+
+    ShortcutDictContent()
+            : SparseTableDictContent(Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE,
+                      Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_DATA_SIZE) {}
+
+    void getShortcutEntry(const int maxCodePointCount, int *const outCodePoint,
+            int *const outCodePointCount, int *const outProbability, bool *const outhasNext,
+            const int shortcutEntryPos) {
+        int readingPos = shortcutEntryPos;
+        return getShortcutEntryAndAdvancePosition(maxCodePointCount, outCodePoint,
+                outCodePointCount, outProbability, outhasNext, &readingPos);
+    }
+
+    void getShortcutEntryAndAdvancePosition(const int maxCodePointCount,
+            int *const outCodePoint, int *const outCodePointCount, int *const outProbability,
+            bool *const outhasNext, int *const shortcutEntryPos) const;
+
+   // Returns head position of shortcut list for a PtNode specified by terminalId.
+   int getShortcutListHeadPos(const int terminalId) const;
+
+   bool flushToFile(const char *const dictPath) const;
+
+   bool runGC(const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap,
+           const ShortcutDictContent *const originalShortcutDictContent);
+
+   bool createNewShortcutList(const int terminalId);
+
+   bool copyShortcutList(const int shortcutListPos, const int toPos);
+
+   bool setProbability(const int probability, const int shortcutEntryPos);
+
+   bool writeShortcutEntry(const int *const codePoint, const int codePointCount,
+           const int probability, const bool hasNext, const int shortcutEntryPos) {
+       int writingPos = shortcutEntryPos;
+       return writeShortcutEntryAndAdvancePosition(codePoint, codePointCount, probability,
+               hasNext, &writingPos);
+   }
+
+   bool writeShortcutEntryAndAdvancePosition(const int *const codePoint,
+           const int codePointCount, const int probability, const bool hasNext,
+           int *const shortcutEntryPos);
+
+   int findShortcutEntryAndGetPos(const int shortcutListPos,
+           const int *const targetCodePointsToFind, const int codePointCount) const;
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(ShortcutDictContent);
+
+    bool copyShortcutListFromDictContent(const int shortcutListPos,
+            const ShortcutDictContent *const sourceShortcutDictContent, const int toPos);
+
+    int createAndGetShortcutFlags(const int probability, const bool hasNext) const;
+};
+} // namespace latinime
+#endif /* LATINIME_SHORTCUT_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/single_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/single_dict_content.h
new file mode 100644
index 0000000..9064b7e
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/single_dict_content.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_SINGLE_DICT_CONTENT_H
+#define LATINIME_SINGLE_DICT_CONTENT_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
+
+namespace latinime {
+
+class SingleDictContent : public DictContent {
+ public:
+    SingleDictContent(const char *const dictPath, const char *const contentFileName,
+            const bool isUpdatable)
+            : mMmappedBuffer(MmappedBuffer::openBuffer(dictPath, contentFileName, isUpdatable)),
+              mExpandableContentBuffer(mMmappedBuffer.get() ? mMmappedBuffer.get()->getBuffer() : 0,
+                      mMmappedBuffer.get() ? mMmappedBuffer.get()->getBufferSize() : 0,
+                      BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+              mIsValid(mMmappedBuffer.get() != 0) {}
+
+    SingleDictContent()
+            : mMmappedBuffer(0), mExpandableContentBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+              mIsValid(true) {}
+
+    virtual ~SingleDictContent() {}
+
+    virtual bool isValid() const {
+        return mIsValid;
+    }
+
+    bool isNearSizeLimit() const {
+        return mExpandableContentBuffer.isNearSizeLimit();
+    }
+
+ protected:
+    BufferWithExtendableBuffer *getWritableBuffer() {
+        return &mExpandableContentBuffer;
+    }
+
+    const BufferWithExtendableBuffer *getBuffer() const {
+        return &mExpandableContentBuffer;
+    }
+
+    bool flush(const char *const dictPath, const char *const contentFileNameSuffix) const {
+        return DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath,
+                contentFileNameSuffix, &mExpandableContentBuffer);
+    }
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(SingleDictContent);
+
+    const MmappedBuffer::MmappedBufferPtr mMmappedBuffer;
+    BufferWithExtendableBuffer mExpandableContentBuffer;
+    const bool mIsValid;
+};
+} // namespace latinime
+#endif /* LATINIME_SINGLE_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.cpp
new file mode 100644
index 0000000..63c6ea3
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.cpp
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h"
+
+namespace latinime {
+
+bool SparseTableDictContent::flush(const char *const dictPath,
+        const char *const lookupTableFileNameSuffix, const char *const addressTableFileNameSuffix,
+        const char *const contentFileNameSuffix) const {
+    if (!DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath, lookupTableFileNameSuffix,
+            &mExpandableLookupTableBuffer)){
+        return false;
+    }
+    if (!DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath, addressTableFileNameSuffix,
+            &mExpandableAddressTableBuffer)) {
+        return false;
+    }
+    if (!DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath, contentFileNameSuffix,
+            &mExpandableContentBuffer)) {
+        return false;
+    }
+    return true;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h
new file mode 100644
index 0000000..a82e3f5
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/sparse_table_dict_content.h
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_SPARSE_TABLE_DICT_CONTENT_H
+#define LATINIME_SPARSE_TABLE_DICT_CONTENT_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/sparse_table.h"
+
+namespace latinime {
+
+// TODO: Support multiple contents.
+class SparseTableDictContent : public DictContent {
+ public:
+    AK_FORCE_INLINE SparseTableDictContent(const char *const dictPath,
+            const char *const lookupTableFileName, const char *const addressTableFileName,
+            const char *const contentFileName, const bool isUpdatable,
+            const int sparseTableBlockSize, const int sparseTableDataSize)
+            : mLookupTableBuffer(
+                      MmappedBuffer::openBuffer(dictPath, lookupTableFileName, isUpdatable)),
+              mAddressTableBuffer(
+                      MmappedBuffer::openBuffer(dictPath, addressTableFileName, isUpdatable)),
+              mContentBuffer(MmappedBuffer::openBuffer(dictPath, contentFileName, isUpdatable)),
+              mExpandableLookupTableBuffer(
+                      mLookupTableBuffer.get() ? mLookupTableBuffer.get()->getBuffer() : 0,
+                      mLookupTableBuffer.get() ? mLookupTableBuffer.get()->getBufferSize() : 0,
+                      BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+              mExpandableAddressTableBuffer(
+                      mAddressTableBuffer.get() ? mAddressTableBuffer.get()->getBuffer() : 0,
+                      mAddressTableBuffer.get() ? mAddressTableBuffer.get()->getBufferSize() : 0,
+                      BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+              mExpandableContentBuffer(mContentBuffer.get() ? mContentBuffer.get()->getBuffer() : 0,
+                      mContentBuffer.get() ? mContentBuffer.get()->getBufferSize() : 0,
+                      BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+              mAddressLookupTable(&mExpandableLookupTableBuffer, &mExpandableAddressTableBuffer,
+                      sparseTableBlockSize, sparseTableDataSize),
+              mIsValid(mLookupTableBuffer.get() != 0 && mAddressTableBuffer.get() != 0
+                      && mContentBuffer.get() != 0) {}
+
+    SparseTableDictContent(const int sparseTableBlockSize, const int sparseTableDataSize)
+            : mLookupTableBuffer(0), mAddressTableBuffer(0), mContentBuffer(0),
+              mExpandableLookupTableBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+              mExpandableAddressTableBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+              mExpandableContentBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+              mAddressLookupTable(&mExpandableLookupTableBuffer, &mExpandableAddressTableBuffer,
+                      sparseTableBlockSize, sparseTableDataSize), mIsValid(true) {}
+
+    virtual ~SparseTableDictContent() {}
+
+    virtual bool isValid() const {
+        return mIsValid;
+    }
+
+    bool isNearSizeLimit() const {
+        return mExpandableLookupTableBuffer.isNearSizeLimit()
+                || mExpandableAddressTableBuffer.isNearSizeLimit()
+                || mExpandableContentBuffer.isNearSizeLimit();
+    }
+
+ protected:
+    SparseTable *getUpdatableAddressLookupTable() {
+        return &mAddressLookupTable;
+    }
+
+    const SparseTable *getAddressLookupTable() const {
+        return &mAddressLookupTable;
+    }
+
+    BufferWithExtendableBuffer *getWritableContentBuffer() {
+        return &mExpandableContentBuffer;
+    }
+
+    const BufferWithExtendableBuffer *getContentBuffer() const {
+        return &mExpandableContentBuffer;
+    }
+
+    bool flush(const char *const dictDirPath, const char *const lookupTableFileName,
+            const char *const addressTableFileName, const char *const contentFileName) const;
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(SparseTableDictContent);
+
+    const MmappedBuffer::MmappedBufferPtr mLookupTableBuffer;
+    const MmappedBuffer::MmappedBufferPtr mAddressTableBuffer;
+    const MmappedBuffer::MmappedBufferPtr mContentBuffer;
+    BufferWithExtendableBuffer mExpandableLookupTableBuffer;
+    BufferWithExtendableBuffer mExpandableAddressTableBuffer;
+    BufferWithExtendableBuffer mExpandableContentBuffer;
+    SparseTable mAddressLookupTable;
+    const bool mIsValid;
+};
+} // namespace latinime
+#endif /* LATINIME_SPARSE_TABLE_DICT_CONTENT_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.cpp
new file mode 100644
index 0000000..0b17a00
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.cpp
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+int TerminalPositionLookupTable::getTerminalPtNodePosition(const int terminalId) const {
+    if (terminalId < 0 || terminalId >= mSize) {
+        return NOT_A_DICT_POS;
+    }
+    const int terminalPos = getBuffer()->readUint(
+            Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE, getEntryPos(terminalId));
+    return (terminalPos == Ver4DictConstants::NOT_A_TERMINAL_ADDRESS) ?
+            NOT_A_DICT_POS : terminalPos;
+}
+
+bool TerminalPositionLookupTable::setTerminalPtNodePosition(
+        const int terminalId, const int terminalPtNodePos) {
+    if (terminalId < 0) {
+        return NOT_A_DICT_POS;
+    }
+    while (terminalId >= mSize) {
+        // Write new entry.
+        if (!getWritableBuffer()->writeUint(Ver4DictConstants::NOT_A_TERMINAL_ADDRESS,
+                Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE, getEntryPos(mSize))) {
+            return false;
+        }
+        mSize++;
+    }
+    const int terminalPos = (terminalPtNodePos != NOT_A_DICT_POS) ?
+            terminalPtNodePos : Ver4DictConstants::NOT_A_TERMINAL_ADDRESS;
+    return getWritableBuffer()->writeUint(terminalPos,
+            Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE, getEntryPos(terminalId));
+}
+
+bool TerminalPositionLookupTable::flushToFile(const char *const dictPath) const {
+    // If the used buffer size is smaller than the actual buffer size, regenerate the lookup
+    // table and write the new table to the file.
+    if (getEntryPos(mSize) < getBuffer()->getTailPosition()) {
+        TerminalPositionLookupTable lookupTableToWrite;
+        for (int i = 0; i < mSize; ++i) {
+            const int terminalPtNodePosition = getTerminalPtNodePosition(i);
+            if (!lookupTableToWrite.setTerminalPtNodePosition(i, terminalPtNodePosition)) {
+                AKLOGE("Cannot set terminal position to lookupTableToWrite."
+                        " terminalId: %d, position: %d", i, terminalPtNodePosition);
+                return false;
+            }
+        }
+        return lookupTableToWrite.flush(dictPath,
+                Ver4DictConstants::TERMINAL_ADDRESS_TABLE_FILE_EXTENSION);
+    } else {
+        // We can simply use this lookup table because the buffer size has not been
+        // changed.
+        return flush(dictPath, Ver4DictConstants::TERMINAL_ADDRESS_TABLE_FILE_EXTENSION);
+    }
+}
+
+bool TerminalPositionLookupTable::runGCTerminalIds(TerminalIdMap *const terminalIdMap) {
+    int removedEntryCount = 0;
+    int nextNewTerminalId = 0;
+    for (int i = 0; i < mSize; ++i) {
+        const int terminalPos = getBuffer()->readUint(
+                Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE, getEntryPos(i));
+        if (terminalPos == Ver4DictConstants::NOT_A_TERMINAL_ADDRESS) {
+            // This entry is a garbage.
+            removedEntryCount++;
+        } else {
+            // Give a new terminal id to the entry.
+            if (!getWritableBuffer()->writeUint(terminalPos,
+                    Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE,
+                    getEntryPos(nextNewTerminalId))) {
+                return false;
+            }
+            // Memorize the mapping to the old terminal id to the new terminal id.
+            terminalIdMap->insert(TerminalIdMap::value_type(i, nextNewTerminalId));
+            nextNewTerminalId++;
+        }
+    }
+    mSize = nextNewTerminalId;
+    return true;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h
new file mode 100644
index 0000000..f73e227
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_TERMINAL_POSITION_LOOKUP_TABLE_H
+#define LATINIME_TERMINAL_POSITION_LOOKUP_TABLE_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/single_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "utils/hash_map_compat.h"
+
+namespace latinime {
+
+class TerminalPositionLookupTable : public SingleDictContent {
+ public:
+    typedef hash_map_compat<int, int> TerminalIdMap;
+
+    TerminalPositionLookupTable(const char *const dictPath, const bool isUpdatable)
+            : SingleDictContent(dictPath,
+                      Ver4DictConstants::TERMINAL_ADDRESS_TABLE_FILE_EXTENSION, isUpdatable),
+              mSize(getBuffer()->getTailPosition()
+                      / Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE) {}
+
+    TerminalPositionLookupTable() : mSize(0) {}
+
+    int getTerminalPtNodePosition(const int terminalId) const;
+
+    bool setTerminalPtNodePosition(const int terminalId, const int terminalPtNodePos);
+
+    int getNextTerminalId() const {
+        return mSize;
+    }
+
+    bool flushToFile(const char *const dictPath) const;
+
+    bool runGCTerminalIds(TerminalIdMap *const terminalIdMap);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(TerminalPositionLookupTable);
+
+    int getEntryPos(const int terminalId) const {
+        return terminalId * Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE;
+    }
+
+    int mSize;
+};
+} // namespace latinime
+#endif // LATINIME_TERMINAL_POSITION_LOOKUP_TABLE_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp
new file mode 100644
index 0000000..918c02b
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+
+#include <cerrno>
+#include <cstring>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
+
+namespace latinime {
+
+/* static */ Ver4DictBuffers::Ver4DictBuffersPtr Ver4DictBuffers::openVer4DictBuffers(
+        const char *const dictPath, const MmappedBuffer::MmappedBufferPtr &headerBuffer) {
+    const bool isUpdatable = headerBuffer.get() ? headerBuffer.get()->isUpdatable() : false;
+    // TODO: take only dictDirPath, and open both header and trie files in the constructor below
+    return Ver4DictBuffersPtr(new Ver4DictBuffers(dictPath, headerBuffer, isUpdatable));
+}
+
+bool Ver4DictBuffers::flushHeaderAndDictBuffers(const char *const dictDirPath,
+        const BufferWithExtendableBuffer *const headerBuffer) const {
+    // Create temporary directory.
+    const int tmpDirPathBufSize = FileUtils::getFilePathWithSuffixBufSize(dictDirPath,
+            DictFileWritingUtils::TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE);
+    char tmpDirPath[tmpDirPathBufSize];
+    FileUtils::getFilePathWithSuffix(dictDirPath,
+            DictFileWritingUtils::TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE, tmpDirPathBufSize,
+            tmpDirPath);
+    if (FileUtils::existsDir(tmpDirPath)) {
+        if (!FileUtils::removeDirAndFiles(tmpDirPath)) {
+            AKLOGE("Existing directory %s cannot be removed.", tmpDirPath);
+            ASSERT(false);
+            return false;
+        }
+    }
+    if (mkdir(tmpDirPath, S_IRWXU) == -1) {
+        AKLOGE("Cannot create directory: %s. errno: %d.", tmpDirPath, errno);
+        return false;
+    }
+    // Get dictionary base path.
+    const int dictNameBufSize = strlen(dictDirPath) + 1 /* terminator */;
+    char dictName[dictNameBufSize];
+    FileUtils::getBasename(dictDirPath, dictNameBufSize, dictName);
+    const int dictPathBufSize = FileUtils::getFilePathBufSize(tmpDirPath, dictName);
+    char dictPath[dictPathBufSize];
+    FileUtils::getFilePath(tmpDirPath, dictName, dictPathBufSize, dictPath);
+
+    // Write header file.
+    if (!DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath,
+            Ver4DictConstants::HEADER_FILE_EXTENSION, headerBuffer)) {
+        AKLOGE("Dictionary header file %s%s cannot be written.", tmpDirPath,
+                Ver4DictConstants::HEADER_FILE_EXTENSION);
+        return false;
+    }
+    // Write trie file.
+    if (!DictFileWritingUtils::flushBufferToFileWithSuffix(dictPath,
+            Ver4DictConstants::TRIE_FILE_EXTENSION, &mExpandableTrieBuffer)) {
+        AKLOGE("Dictionary trie file %s%s cannot be written.", tmpDirPath,
+                Ver4DictConstants::TRIE_FILE_EXTENSION);
+        return false;
+    }
+    // Write dictionary contents.
+    if (!mTerminalPositionLookupTable.flushToFile(dictPath)) {
+        AKLOGE("Terminal position lookup table cannot be written. %s", tmpDirPath);
+        return false;
+    }
+    if (!mProbabilityDictContent.flushToFile(dictPath)) {
+        AKLOGE("Probability dict content cannot be written. %s", tmpDirPath);
+        return false;
+    }
+    if (!mBigramDictContent.flushToFile(dictPath)) {
+        AKLOGE("Bigram dict content cannot be written. %s", tmpDirPath);
+        return false;
+    }
+    if (!mShortcutDictContent.flushToFile(dictPath)) {
+        AKLOGE("Shortcut dict content cannot be written. %s", tmpDirPath);
+        return false;
+    }
+    // Remove existing dictionary.
+    if (!FileUtils::removeDirAndFiles(dictDirPath)) {
+        AKLOGE("Existing directory %s cannot be removed.", dictDirPath);
+        ASSERT(false);
+        return false;
+    }
+    // Rename temporary directory.
+    if (rename(tmpDirPath, dictDirPath) != 0) {
+        AKLOGE("%s cannot be renamed to %s", tmpDirPath, dictDirPath);
+        ASSERT(false);
+        return false;
+    }
+    return true;
+}
+
+Ver4DictBuffers::Ver4DictBuffers(const char *const dictPath,
+        const MmappedBuffer::MmappedBufferPtr &headerBuffer, const bool isUpdatable)
+        : mHeaderBuffer(headerBuffer),
+          mDictBuffer(MmappedBuffer::openBuffer(dictPath,
+                  Ver4DictConstants::TRIE_FILE_EXTENSION, isUpdatable)),
+          mHeaderPolicy(headerBuffer.get()->getBuffer(), FormatUtils::VERSION_4),
+          mExpandableHeaderBuffer(headerBuffer.get()->getBuffer(), mHeaderPolicy.getSize(),
+                  BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+          mExpandableTrieBuffer(mDictBuffer.get()->getBuffer(),
+                  mDictBuffer.get()->getBufferSize(),
+                  BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE),
+          mTerminalPositionLookupTable(dictPath, isUpdatable),
+          mProbabilityDictContent(dictPath, mHeaderPolicy.hasHistoricalInfoOfWords(),
+                  isUpdatable),
+          mBigramDictContent(dictPath, mHeaderPolicy.hasHistoricalInfoOfWords(),
+                  isUpdatable),
+          mShortcutDictContent(dictPath, isUpdatable),
+          mIsUpdatable(isUpdatable) {}
+
+Ver4DictBuffers::Ver4DictBuffers(const HeaderPolicy *const headerPolicy)
+        : mHeaderBuffer(0), mDictBuffer(0), mHeaderPolicy(),
+          mExpandableHeaderBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+          mExpandableTrieBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
+          mTerminalPositionLookupTable(),
+          mProbabilityDictContent(headerPolicy->hasHistoricalInfoOfWords()),
+          mBigramDictContent(headerPolicy->hasHistoricalInfoOfWords()), mShortcutDictContent(),
+          mIsUpdatable(true) {}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h
new file mode 100644
index 0000000..a0c219e
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_DICT_BUFFER_H
+#define LATINIME_VER4_DICT_BUFFER_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/header/header_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/bigram_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/shortcut_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
+
+namespace latinime {
+
+class Ver4DictBuffers {
+ public:
+    typedef ExclusiveOwnershipPointer<Ver4DictBuffers> Ver4DictBuffersPtr;
+
+    static Ver4DictBuffersPtr openVer4DictBuffers(const char *const dictDirPath,
+            const MmappedBuffer::MmappedBufferPtr &headerBuffer);
+
+    static AK_FORCE_INLINE Ver4DictBuffersPtr createVer4DictBuffers(
+            const HeaderPolicy *const headerPolicy) {
+        return Ver4DictBuffersPtr(new Ver4DictBuffers(headerPolicy));
+    }
+
+    AK_FORCE_INLINE bool isValid() const {
+        return mDictBuffer.get() != 0 && mHeaderPolicy.isValid()
+                && mProbabilityDictContent.isValid() && mTerminalPositionLookupTable.isValid()
+                && mBigramDictContent.isValid() && mShortcutDictContent.isValid();
+    }
+
+    AK_FORCE_INLINE bool isNearSizeLimit() const {
+        return mExpandableTrieBuffer.isNearSizeLimit()
+                || mTerminalPositionLookupTable.isNearSizeLimit()
+                || mProbabilityDictContent.isNearSizeLimit()
+                || mBigramDictContent.isNearSizeLimit()
+                || mShortcutDictContent.isNearSizeLimit();
+    }
+
+    AK_FORCE_INLINE const HeaderPolicy *getHeaderPolicy() const {
+        return &mHeaderPolicy;
+    }
+
+    AK_FORCE_INLINE BufferWithExtendableBuffer *getWritableHeaderBuffer() {
+        return &mExpandableHeaderBuffer;
+    }
+
+    AK_FORCE_INLINE BufferWithExtendableBuffer *getWritableTrieBuffer() {
+        return &mExpandableTrieBuffer;
+    }
+
+    AK_FORCE_INLINE const BufferWithExtendableBuffer *getTrieBuffer() const {
+        return &mExpandableTrieBuffer;
+    }
+
+    AK_FORCE_INLINE TerminalPositionLookupTable *getMutableTerminalPositionLookupTable() {
+        return &mTerminalPositionLookupTable;
+    }
+
+    AK_FORCE_INLINE const TerminalPositionLookupTable *getTerminalPositionLookupTable() const {
+        return &mTerminalPositionLookupTable;
+    }
+
+    AK_FORCE_INLINE ProbabilityDictContent *getMutableProbabilityDictContent() {
+        return &mProbabilityDictContent;
+    }
+
+    AK_FORCE_INLINE const ProbabilityDictContent *getProbabilityDictContent() const {
+        return &mProbabilityDictContent;
+    }
+
+    AK_FORCE_INLINE BigramDictContent *getMutableBigramDictContent() {
+        return &mBigramDictContent;
+    }
+
+    AK_FORCE_INLINE const BigramDictContent *getBigramDictContent() const {
+        return &mBigramDictContent;
+    }
+
+    AK_FORCE_INLINE ShortcutDictContent *getMutableShortcutDictContent() {
+        return &mShortcutDictContent;
+    }
+
+    AK_FORCE_INLINE const ShortcutDictContent *getShortcutDictContent() const {
+        return &mShortcutDictContent;
+    }
+
+    AK_FORCE_INLINE bool isUpdatable() const {
+        return mIsUpdatable;
+    }
+
+    bool flush(const char *const dictDirPath) const {
+        return flushHeaderAndDictBuffers(dictDirPath, &mExpandableHeaderBuffer);
+    }
+
+    bool flushHeaderAndDictBuffers(const char *const dictDirPath,
+            const BufferWithExtendableBuffer *const headerBuffer) const;
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(Ver4DictBuffers);
+
+    Ver4DictBuffers(const char *const dictDirPath,
+            const MmappedBuffer::MmappedBufferPtr &headerBuffer, const bool isUpdatable);
+
+    Ver4DictBuffers(const HeaderPolicy *const headerPolicy);
+
+    const MmappedBuffer::MmappedBufferPtr mHeaderBuffer;
+    const MmappedBuffer::MmappedBufferPtr mDictBuffer;
+    const HeaderPolicy mHeaderPolicy;
+    BufferWithExtendableBuffer mExpandableHeaderBuffer;
+    BufferWithExtendableBuffer mExpandableTrieBuffer;
+    TerminalPositionLookupTable mTerminalPositionLookupTable;
+    ProbabilityDictContent mProbabilityDictContent;
+    BigramDictContent mBigramDictContent;
+    ShortcutDictContent mShortcutDictContent;
+    const int mIsUpdatable;
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_DICT_BUFFER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
new file mode 100644
index 0000000..34fecc2
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+
+namespace latinime {
+
+// These values MUST match the definitions in FormatSpec.java.
+const char *const Ver4DictConstants::TRIE_FILE_EXTENSION = ".trie";
+const char *const Ver4DictConstants::HEADER_FILE_EXTENSION = ".header";
+const char *const Ver4DictConstants::FREQ_FILE_EXTENSION = ".freq";
+// tat = Terminal Address Table
+const char *const Ver4DictConstants::TERMINAL_ADDRESS_TABLE_FILE_EXTENSION = ".tat";
+const char *const Ver4DictConstants::BIGRAM_FILE_EXTENSION = ".bigram_freq";
+const char *const Ver4DictConstants::BIGRAM_LOOKUP_TABLE_FILE_EXTENSION = ".bigram_lookup";
+const char *const Ver4DictConstants::BIGRAM_CONTENT_TABLE_FILE_EXTENSION = ".bigram_index_freq";
+const char *const Ver4DictConstants::SHORTCUT_FILE_EXTENSION = ".shortcut_shortcut";
+const char *const Ver4DictConstants::SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION = ".shortcut_lookup";
+const char *const Ver4DictConstants::SHORTCUT_CONTENT_TABLE_FILE_EXTENSION =
+        ".shortcut_index_shortcut";
+
+// Version 4 dictionary size is implicitly limited to 8MB due to 3-byte offsets.
+// TODO: Make MAX_DICTIONARY_SIZE 8MB.
+const int Ver4DictConstants::MAX_DICTIONARY_SIZE = 2 * 1024 * 1024;
+// Extended region size, which is not GCed region size in dict file + additional buffer size, is
+// limited to 1MB to prevent from inefficient traversing.
+const int Ver4DictConstants::MAX_DICT_EXTENDED_REGION_SIZE = 1 * 1024 * 1024;
+
+const int Ver4DictConstants::NOT_A_TERMINAL_ID = -1;
+const int Ver4DictConstants::PROBABILITY_SIZE = 1;
+const int Ver4DictConstants::FLAGS_IN_PROBABILITY_FILE_SIZE = 1;
+const int Ver4DictConstants::TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE = 3;
+const int Ver4DictConstants::NOT_A_TERMINAL_ADDRESS = 0;
+const int Ver4DictConstants::TERMINAL_ID_FIELD_SIZE = 4;
+const int Ver4DictConstants::TIME_STAMP_FIELD_SIZE = 4;
+const int Ver4DictConstants::WORD_LEVEL_FIELD_SIZE = 1;
+const int Ver4DictConstants::WORD_COUNT_FIELD_SIZE = 1;
+
+const int Ver4DictConstants::BIGRAM_ADDRESS_TABLE_BLOCK_SIZE = 4;
+const int Ver4DictConstants::BIGRAM_ADDRESS_TABLE_DATA_SIZE = 4;
+const int Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE = 16;
+const int Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_DATA_SIZE = 4;
+
+const int Ver4DictConstants::BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE = 3;
+// Unsigned int max value of BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE-byte is used for representing
+// invalid terminal ID in bigram lists.
+const int Ver4DictConstants::INVALID_BIGRAM_TARGET_TERMINAL_ID =
+        (1 << (BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE * 8)) - 1;
+const int Ver4DictConstants::BIGRAM_FLAGS_FIELD_SIZE = 1;
+const int Ver4DictConstants::BIGRAM_PROBABILITY_MASK = 0x0F;
+const int Ver4DictConstants::BIGRAM_HAS_NEXT_MASK = 0x80;
+const int Ver4DictConstants::BIGRAM_LARGE_PROBABILITY_FIELD_SIZE = 1;
+
+const int Ver4DictConstants::SHORTCUT_FLAGS_FIELD_SIZE = 1;
+const int Ver4DictConstants::SHORTCUT_PROBABILITY_MASK = 0x0F;
+const int Ver4DictConstants::SHORTCUT_HAS_NEXT_MASK = 0x80;
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
new file mode 100644
index 0000000..d6d22c5
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_DICT_CONSTANTS_H
+#define LATINIME_VER4_DICT_CONSTANTS_H
+
+#include "defines.h"
+
+namespace latinime {
+
+// TODO: Create PtConstants under the pt_common and move some constant values there.
+// Note that there are corresponding definitions in FormatSpec.java.
+class Ver4DictConstants {
+ public:
+    static const char *const TRIE_FILE_EXTENSION;
+    static const char *const HEADER_FILE_EXTENSION;
+    static const char *const FREQ_FILE_EXTENSION;
+    static const char *const TERMINAL_ADDRESS_TABLE_FILE_EXTENSION;
+    static const char *const BIGRAM_FILE_EXTENSION;
+    static const char *const BIGRAM_LOOKUP_TABLE_FILE_EXTENSION;
+    static const char *const BIGRAM_CONTENT_TABLE_FILE_EXTENSION;
+    static const char *const SHORTCUT_FILE_EXTENSION;
+    static const char *const SHORTCUT_LOOKUP_TABLE_FILE_EXTENSION;
+    static const char *const SHORTCUT_CONTENT_TABLE_FILE_EXTENSION;
+
+    static const int MAX_DICTIONARY_SIZE;
+    static const int MAX_DICT_EXTENDED_REGION_SIZE;
+
+    static const int NOT_A_TERMINAL_ID;
+    static const int PROBABILITY_SIZE;
+    static const int FLAGS_IN_PROBABILITY_FILE_SIZE;
+    static const int TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE;
+    static const int NOT_A_TERMINAL_ADDRESS;
+    static const int TERMINAL_ID_FIELD_SIZE;
+    static const int TIME_STAMP_FIELD_SIZE;
+    static const int WORD_LEVEL_FIELD_SIZE;
+    static const int WORD_COUNT_FIELD_SIZE;
+
+    static const int BIGRAM_ADDRESS_TABLE_BLOCK_SIZE;
+    static const int BIGRAM_ADDRESS_TABLE_DATA_SIZE;
+    static const int SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE;
+    static const int SHORTCUT_ADDRESS_TABLE_DATA_SIZE;
+
+    static const int BIGRAM_FLAGS_FIELD_SIZE;
+    static const int BIGRAM_TARGET_TERMINAL_ID_FIELD_SIZE;
+    static const int INVALID_BIGRAM_TARGET_TERMINAL_ID;
+    static const int BIGRAM_PROBABILITY_MASK;
+    static const int BIGRAM_HAS_NEXT_MASK;
+    // Used when bigram list has time stamp.
+    static const int BIGRAM_LARGE_PROBABILITY_FIELD_SIZE;
+
+    static const int SHORTCUT_FLAGS_FIELD_SIZE;
+    static const int SHORTCUT_PROBABILITY_MASK;
+    static const int SHORTCUT_HAS_NEXT_MASK;
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4DictConstants);
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_DICT_CONSTANTS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp
new file mode 100644
index 0000000..17fc948
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_dict_content.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+
+namespace latinime {
+
+const PtNodeParams Ver4PatriciaTrieNodeReader::fetchPtNodeInfoFromBufferAndProcessMovedPtNode(
+        const int ptNodePos, const int siblingNodePos) const {
+    if (ptNodePos < 0 || ptNodePos >= mBuffer->getTailPosition()) {
+        // Reading invalid position because of bug or broken dictionary.
+        AKLOGE("Fetching PtNode info from invalid dictionary position: %d, dictionary size: %d",
+                ptNodePos, mBuffer->getTailPosition());
+        ASSERT(false);
+        return PtNodeParams();
+    }
+    const bool usesAdditionalBuffer = mBuffer->isInAdditionalBuffer(ptNodePos);
+    const uint8_t *const dictBuf = mBuffer->getBuffer(usesAdditionalBuffer);
+    int pos = ptNodePos;
+    const int headPos = ptNodePos;
+    if (usesAdditionalBuffer) {
+        pos -= mBuffer->getOriginalBufferSize();
+    }
+    const PatriciaTrieReadingUtils::NodeFlags flags =
+            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
+    const int parentPosOffset =
+            DynamicPtReadingUtils::getParentPtNodePosOffsetAndAdvancePosition(
+                    dictBuf, &pos);
+    const int parentPos =
+            DynamicPtReadingUtils::getParentPtNodePos(parentPosOffset, headPos);
+    int codePoints[MAX_WORD_LENGTH];
+    const int codePonitCount = PatriciaTrieReadingUtils::getCharsAndAdvancePosition(
+            dictBuf, flags, MAX_WORD_LENGTH, codePoints, &pos);
+    int terminalIdFieldPos = NOT_A_DICT_POS;
+    int terminalId = Ver4DictConstants::NOT_A_TERMINAL_ID;
+    int probability = NOT_A_PROBABILITY;
+    if (PatriciaTrieReadingUtils::isTerminal(flags)) {
+        terminalIdFieldPos = pos;
+        if (usesAdditionalBuffer) {
+            terminalIdFieldPos += mBuffer->getOriginalBufferSize();
+        }
+        terminalId = Ver4PatriciaTrieReadingUtils::getTerminalIdAndAdvancePosition(dictBuf, &pos);
+        const ProbabilityEntry probabilityEntry =
+                mProbabilityDictContent->getProbabilityEntry(terminalId);
+        if (probabilityEntry.hasHistoricalInfo()) {
+            probability = ForgettingCurveUtils::decodeProbability(
+                    probabilityEntry.getHistoricalInfo());
+        } else {
+            probability = probabilityEntry.getProbability();
+        }
+    }
+    int childrenPosFieldPos = pos;
+    if (usesAdditionalBuffer) {
+        childrenPosFieldPos += mBuffer->getOriginalBufferSize();
+    }
+    int childrenPos = DynamicPtReadingUtils::readChildrenPositionAndAdvancePosition(
+            dictBuf, &pos);
+    if (usesAdditionalBuffer && childrenPos != NOT_A_DICT_POS) {
+        childrenPos += mBuffer->getOriginalBufferSize();
+    }
+    if (usesAdditionalBuffer) {
+        pos += mBuffer->getOriginalBufferSize();
+    }
+    // Sibling position is the tail position of original PtNode.
+    int newSiblingNodePos = (siblingNodePos == NOT_A_DICT_POS) ? pos : siblingNodePos;
+    // Read destination node if the read node is a moved node.
+    if (DynamicPtReadingUtils::isMoved(flags)) {
+        // The destination position is stored at the same place as the parent position.
+        return fetchPtNodeInfoFromBufferAndProcessMovedPtNode(parentPos, newSiblingNodePos);
+    } else {
+        return PtNodeParams(headPos, flags, parentPos, codePonitCount, codePoints,
+                terminalIdFieldPos, terminalId, probability, childrenPosFieldPos, childrenPos,
+                newSiblingNodePos);
+    }
+}
+
+}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h
new file mode 100644
index 0000000..9d93245
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_PATRICIA_TRIE_NODE_READER_H
+#define LATINIME_VER4_PATRICIA_TRIE_NODE_READER_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_reader.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class ProbabilityDictContent;
+
+/*
+ * This class is used for helping to read nodes of ver4 patricia trie. This class handles moved
+ * node and reads node attributes including probability form probabilityBuffer.
+ */
+class Ver4PatriciaTrieNodeReader : public PtNodeReader {
+ public:
+    Ver4PatriciaTrieNodeReader(const BufferWithExtendableBuffer *const buffer,
+            const ProbabilityDictContent *const probabilityDictContent)
+            : mBuffer(buffer), mProbabilityDictContent(probabilityDictContent) {}
+
+    ~Ver4PatriciaTrieNodeReader() {}
+
+    virtual const PtNodeParams fetchNodeInfoInBufferFromPtNodePos(const int ptNodePos) const {
+        return fetchPtNodeInfoFromBufferAndProcessMovedPtNode(ptNodePos,
+                NOT_A_DICT_POS /* siblingNodePos */);
+    }
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(Ver4PatriciaTrieNodeReader);
+
+    const BufferWithExtendableBuffer *const mBuffer;
+    const ProbabilityDictContent *const mProbabilityDictContent;
+
+    const PtNodeParams fetchPtNodeInfoFromBufferAndProcessMovedPtNode(const int ptNodePos,
+            const int siblingNodePos) const;
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_PATRICIA_TRIE_NODE_READER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.cpp
new file mode 100644
index 0000000..32576cf
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.cpp
@@ -0,0 +1,411 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h"
+
+#include "suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h"
+#include "suggest/policyimpl/dictionary/header/header_policy.h"
+#include "suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+
+namespace latinime {
+
+const int Ver4PatriciaTrieNodeWriter::CHILDREN_POSITION_FIELD_SIZE = 3;
+
+bool Ver4PatriciaTrieNodeWriter::markPtNodeAsDeleted(
+        const PtNodeParams *const toBeUpdatedPtNodeParams) {
+    int pos = toBeUpdatedPtNodeParams->getHeadPos();
+    const bool usesAdditionalBuffer = mTrieBuffer->isInAdditionalBuffer(pos);
+    const uint8_t *const dictBuf = mTrieBuffer->getBuffer(usesAdditionalBuffer);
+    if (usesAdditionalBuffer) {
+        pos -= mTrieBuffer->getOriginalBufferSize();
+    }
+    // Read original flags
+    const PatriciaTrieReadingUtils::NodeFlags originalFlags =
+            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
+    const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
+            DynamicPtReadingUtils::updateAndGetFlags(originalFlags, false /* isMoved */,
+                    true /* isDeleted */, false /* willBecomeNonTerminal */);
+    int writingPos = toBeUpdatedPtNodeParams->getHeadPos();
+    // Update flags.
+    if (!DynamicPtWritingUtils::writeFlagsAndAdvancePosition(mTrieBuffer, updatedFlags,
+            &writingPos)) {
+        return false;
+    }
+    if (toBeUpdatedPtNodeParams->isTerminal()) {
+        // The PtNode is a terminal. Delete entry from the terminal position lookup table.
+        return mBuffers->getMutableTerminalPositionLookupTable()->setTerminalPtNodePosition(
+                toBeUpdatedPtNodeParams->getTerminalId(), NOT_A_DICT_POS /* ptNodePos */);
+    } else {
+        return true;
+    }
+}
+
+bool Ver4PatriciaTrieNodeWriter::markPtNodeAsMoved(
+        const PtNodeParams *const toBeUpdatedPtNodeParams,
+        const int movedPos, const int bigramLinkedNodePos) {
+    int pos = toBeUpdatedPtNodeParams->getHeadPos();
+    const bool usesAdditionalBuffer = mTrieBuffer->isInAdditionalBuffer(pos);
+    const uint8_t *const dictBuf = mTrieBuffer->getBuffer(usesAdditionalBuffer);
+    if (usesAdditionalBuffer) {
+        pos -= mTrieBuffer->getOriginalBufferSize();
+    }
+    // Read original flags
+    const PatriciaTrieReadingUtils::NodeFlags originalFlags =
+            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
+    const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
+            DynamicPtReadingUtils::updateAndGetFlags(originalFlags, true /* isMoved */,
+                    false /* isDeleted */,  false /* willBecomeNonTerminal */);
+    int writingPos = toBeUpdatedPtNodeParams->getHeadPos();
+    // Update flags.
+    if (!DynamicPtWritingUtils::writeFlagsAndAdvancePosition(mTrieBuffer, updatedFlags,
+            &writingPos)) {
+        return false;
+    }
+    // Update moved position, which is stored in the parent offset field.
+    if (!DynamicPtWritingUtils::writeParentPosOffsetAndAdvancePosition(
+            mTrieBuffer, movedPos, toBeUpdatedPtNodeParams->getHeadPos(), &writingPos)) {
+        return false;
+    }
+    if (toBeUpdatedPtNodeParams->hasChildren()) {
+        // Update children's parent position.
+        mReadingHelper.initWithPtNodeArrayPos(toBeUpdatedPtNodeParams->getChildrenPos());
+        while (!mReadingHelper.isEnd()) {
+            const PtNodeParams childPtNodeParams(mReadingHelper.getPtNodeParams());
+            int parentOffsetFieldPos = childPtNodeParams.getHeadPos()
+                    + DynamicPtWritingUtils::NODE_FLAG_FIELD_SIZE;
+            if (!DynamicPtWritingUtils::writeParentPosOffsetAndAdvancePosition(
+                    mTrieBuffer, bigramLinkedNodePos, childPtNodeParams.getHeadPos(),
+                    &parentOffsetFieldPos)) {
+                // Parent offset cannot be written because of a bug or a broken dictionary; thus,
+                // we give up to update dictionary.
+                return false;
+            }
+            mReadingHelper.readNextSiblingNode(childPtNodeParams);
+        }
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieNodeWriter::markPtNodeAsWillBecomeNonTerminal(
+        const PtNodeParams *const toBeUpdatedPtNodeParams) {
+    int pos = toBeUpdatedPtNodeParams->getHeadPos();
+    const bool usesAdditionalBuffer = mTrieBuffer->isInAdditionalBuffer(pos);
+    const uint8_t *const dictBuf = mTrieBuffer->getBuffer(usesAdditionalBuffer);
+    if (usesAdditionalBuffer) {
+        pos -= mTrieBuffer->getOriginalBufferSize();
+    }
+    // Read original flags
+    const PatriciaTrieReadingUtils::NodeFlags originalFlags =
+            PatriciaTrieReadingUtils::getFlagsAndAdvancePosition(dictBuf, &pos);
+    const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
+            DynamicPtReadingUtils::updateAndGetFlags(originalFlags, false /* isMoved */,
+                    false /* isDeleted */, true /* willBecomeNonTerminal */);
+    if (!mBuffers->getMutableTerminalPositionLookupTable()->setTerminalPtNodePosition(
+            toBeUpdatedPtNodeParams->getTerminalId(), NOT_A_DICT_POS /* ptNodePos */)) {
+        AKLOGE("Cannot update terminal position lookup table. terminal id: %d",
+                toBeUpdatedPtNodeParams->getTerminalId());
+        return false;
+    }
+    // Update flags.
+    int writingPos = toBeUpdatedPtNodeParams->getHeadPos();
+    return DynamicPtWritingUtils::writeFlagsAndAdvancePosition(mTrieBuffer, updatedFlags,
+            &writingPos);
+}
+
+bool Ver4PatriciaTrieNodeWriter::updatePtNodeProbability(
+        const PtNodeParams *const toBeUpdatedPtNodeParams, const int newProbability,
+        const int timestamp) {
+    if (!toBeUpdatedPtNodeParams->isTerminal()) {
+        return false;
+    }
+    const ProbabilityEntry originalProbabilityEntry =
+            mBuffers->getProbabilityDictContent()->getProbabilityEntry(
+                    toBeUpdatedPtNodeParams->getTerminalId());
+    const ProbabilityEntry probabilityEntry = createUpdatedEntryFrom(&originalProbabilityEntry,
+            newProbability, timestamp);
+    return mBuffers->getMutableProbabilityDictContent()->setProbabilityEntry(
+            toBeUpdatedPtNodeParams->getTerminalId(), &probabilityEntry);
+}
+
+bool Ver4PatriciaTrieNodeWriter::updatePtNodeProbabilityAndGetNeedsToKeepPtNodeAfterGC(
+        const PtNodeParams *const toBeUpdatedPtNodeParams, bool *const outNeedsToKeepPtNode) {
+    if (!toBeUpdatedPtNodeParams->isTerminal()) {
+        AKLOGE("updatePtNodeProbabilityAndGetNeedsToSaveForGC is called for non-terminal PtNode.");
+        return false;
+    }
+    const ProbabilityEntry originalProbabilityEntry =
+            mBuffers->getProbabilityDictContent()->getProbabilityEntry(
+                    toBeUpdatedPtNodeParams->getTerminalId());
+    if (originalProbabilityEntry.hasHistoricalInfo()) {
+        const HistoricalInfo historicalInfo = ForgettingCurveUtils::createHistoricalInfoToSave(
+                originalProbabilityEntry.getHistoricalInfo());
+        const ProbabilityEntry probabilityEntry =
+                originalProbabilityEntry.createEntryWithUpdatedHistoricalInfo(&historicalInfo);
+        if (!mBuffers->getMutableProbabilityDictContent()->setProbabilityEntry(
+                toBeUpdatedPtNodeParams->getTerminalId(), &probabilityEntry)) {
+            AKLOGE("Cannot write updated probability entry. terminalId: %d",
+                    toBeUpdatedPtNodeParams->getTerminalId());
+            return false;
+        }
+        const bool isValid = ForgettingCurveUtils::needsToKeep(&historicalInfo);
+        if (!isValid) {
+            if (!markPtNodeAsWillBecomeNonTerminal(toBeUpdatedPtNodeParams)) {
+                AKLOGE("Cannot mark PtNode as willBecomeNonTerminal.");
+                return false;
+            }
+        }
+        *outNeedsToKeepPtNode = isValid;
+    } else {
+        // No need to update probability.
+        *outNeedsToKeepPtNode = true;
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieNodeWriter::updateChildrenPosition(
+        const PtNodeParams *const toBeUpdatedPtNodeParams, const int newChildrenPosition) {
+    int childrenPosFieldPos = toBeUpdatedPtNodeParams->getChildrenPosFieldPos();
+    return DynamicPtWritingUtils::writeChildrenPositionAndAdvancePosition(mTrieBuffer,
+            newChildrenPosition, &childrenPosFieldPos);
+}
+
+bool Ver4PatriciaTrieNodeWriter::updateTerminalId(const PtNodeParams *const toBeUpdatedPtNodeParams,
+        const int newTerminalId) {
+    return mTrieBuffer->writeUint(newTerminalId, Ver4DictConstants::TERMINAL_ID_FIELD_SIZE,
+            toBeUpdatedPtNodeParams->getTerminalIdFieldPos());
+}
+
+bool Ver4PatriciaTrieNodeWriter::writePtNodeAndAdvancePosition(
+        const PtNodeParams *const ptNodeParams, int *const ptNodeWritingPos) {
+    return writePtNodeAndGetTerminalIdAndAdvancePosition(ptNodeParams, 0 /* outTerminalId */,
+            ptNodeWritingPos);
+}
+
+
+bool Ver4PatriciaTrieNodeWriter::writeNewTerminalPtNodeAndAdvancePosition(
+        const PtNodeParams *const ptNodeParams, const int timestamp, int *const ptNodeWritingPos) {
+    int terminalId = Ver4DictConstants::NOT_A_TERMINAL_ID;
+    if (!writePtNodeAndGetTerminalIdAndAdvancePosition(ptNodeParams, &terminalId,
+            ptNodeWritingPos)) {
+        return false;
+    }
+    // Write probability.
+    ProbabilityEntry newProbabilityEntry;
+    const ProbabilityEntry probabilityEntryToWrite = createUpdatedEntryFrom(
+            &newProbabilityEntry, ptNodeParams->getProbability(), timestamp);
+    return mBuffers->getMutableProbabilityDictContent()->setProbabilityEntry(terminalId,
+            &probabilityEntryToWrite);
+}
+
+bool Ver4PatriciaTrieNodeWriter::addNewBigramEntry(
+        const PtNodeParams *const sourcePtNodeParams,
+        const PtNodeParams *const targetPtNodeParam, const int probability, const int timestamp,
+        bool *const outAddedNewBigram) {
+    if (!mBigramPolicy->addNewEntry(sourcePtNodeParams->getTerminalId(),
+            targetPtNodeParam->getTerminalId(), probability, timestamp, outAddedNewBigram)) {
+        AKLOGE("Cannot add new bigram entry. terminalId: %d, targetTerminalId: %d",
+                sourcePtNodeParams->getTerminalId(), targetPtNodeParam->getTerminalId());
+        return false;
+    }
+    if (!sourcePtNodeParams->hasBigrams()) {
+        // Update has bigrams flag.
+        return updatePtNodeFlags(sourcePtNodeParams->getHeadPos(),
+                sourcePtNodeParams->isBlacklisted(), sourcePtNodeParams->isNotAWord(),
+                sourcePtNodeParams->isTerminal(), sourcePtNodeParams->hasShortcutTargets(),
+                true /* hasBigrams */,
+                sourcePtNodeParams->getCodePointCount() > 1 /* hasMultipleChars */);
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieNodeWriter::removeBigramEntry(
+        const PtNodeParams *const sourcePtNodeParams, const PtNodeParams *const targetPtNodeParam) {
+    return mBigramPolicy->removeEntry(sourcePtNodeParams->getTerminalId(),
+            targetPtNodeParam->getTerminalId());
+}
+
+bool Ver4PatriciaTrieNodeWriter::updateAllBigramEntriesAndDeleteUselessEntries(
+            const PtNodeParams *const sourcePtNodeParams, int *const outBigramEntryCount) {
+    return mBigramPolicy->updateAllBigramEntriesAndDeleteUselessEntries(
+            sourcePtNodeParams->getTerminalId(), outBigramEntryCount);
+}
+
+bool Ver4PatriciaTrieNodeWriter::updateAllPositionFields(
+        const PtNodeParams *const toBeUpdatedPtNodeParams,
+        const DictPositionRelocationMap *const dictPositionRelocationMap,
+        int *const outBigramEntryCount) {
+    int parentPos = toBeUpdatedPtNodeParams->getParentPos();
+    if (parentPos != NOT_A_DICT_POS) {
+        PtNodeWriter::PtNodePositionRelocationMap::const_iterator it =
+                dictPositionRelocationMap->mPtNodePositionRelocationMap.find(parentPos);
+        if (it != dictPositionRelocationMap->mPtNodePositionRelocationMap.end()) {
+            parentPos = it->second;
+        }
+    }
+    int writingPos = toBeUpdatedPtNodeParams->getHeadPos()
+            + DynamicPtWritingUtils::NODE_FLAG_FIELD_SIZE;
+    // Write updated parent offset.
+    if (!DynamicPtWritingUtils::writeParentPosOffsetAndAdvancePosition(mTrieBuffer,
+            parentPos, toBeUpdatedPtNodeParams->getHeadPos(), &writingPos)) {
+        return false;
+    }
+
+    // Updates children position.
+    int childrenPos = toBeUpdatedPtNodeParams->getChildrenPos();
+    if (childrenPos != NOT_A_DICT_POS) {
+        PtNodeWriter::PtNodeArrayPositionRelocationMap::const_iterator it =
+                dictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.find(childrenPos);
+        if (it != dictPositionRelocationMap->mPtNodeArrayPositionRelocationMap.end()) {
+            childrenPos = it->second;
+        }
+    }
+    if (!updateChildrenPosition(toBeUpdatedPtNodeParams, childrenPos)) {
+        return false;
+    }
+
+    // Counts bigram entries.
+    if (outBigramEntryCount) {
+        *outBigramEntryCount = mBigramPolicy->getBigramEntryConut(
+                toBeUpdatedPtNodeParams->getTerminalId());
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieNodeWriter::addShortcutTarget(const PtNodeParams *const ptNodeParams,
+        const int *const targetCodePoints, const int targetCodePointCount,
+        const int shortcutProbability) {
+    if (!mShortcutPolicy->addNewShortcut(ptNodeParams->getTerminalId(),
+            targetCodePoints, targetCodePointCount, shortcutProbability)) {
+        AKLOGE("Cannot add new shortuct entry. terminalId: %d", ptNodeParams->getTerminalId());
+        return false;
+    }
+    if (!ptNodeParams->hasShortcutTargets()) {
+        // Update has shortcut targets flag.
+        return updatePtNodeFlags(ptNodeParams->getHeadPos(),
+                ptNodeParams->isBlacklisted(), ptNodeParams->isNotAWord(),
+                ptNodeParams->isTerminal(), true /* hasShortcutTargets */,
+                ptNodeParams->hasBigrams(),
+                ptNodeParams->getCodePointCount() > 1 /* hasMultipleChars */);
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieNodeWriter::updatePtNodeHasBigramsAndShortcutTargetsFlags(
+        const PtNodeParams *const ptNodeParams) {
+    const bool hasBigrams = mBuffers->getBigramDictContent()->getBigramListHeadPos(
+            ptNodeParams->getTerminalId()) != NOT_A_DICT_POS;
+    const bool hasShortcutTargets = mBuffers->getShortcutDictContent()->getShortcutListHeadPos(
+            ptNodeParams->getTerminalId()) != NOT_A_DICT_POS;
+    return updatePtNodeFlags(ptNodeParams->getHeadPos(), ptNodeParams->isBlacklisted(),
+            ptNodeParams->isNotAWord(), ptNodeParams->isTerminal(), hasShortcutTargets,
+            hasBigrams, ptNodeParams->getCodePointCount() > 1 /* hasMultipleChars */);
+}
+
+bool Ver4PatriciaTrieNodeWriter::writePtNodeAndGetTerminalIdAndAdvancePosition(
+        const PtNodeParams *const ptNodeParams, int *const outTerminalId,
+        int *const ptNodeWritingPos) {
+    const int nodePos = *ptNodeWritingPos;
+    // Write dummy flags. The Node flags are updated with appropriate flags at the last step of the
+    // PtNode writing.
+    if (!DynamicPtWritingUtils::writeFlagsAndAdvancePosition(mTrieBuffer,
+            0 /* nodeFlags */, ptNodeWritingPos)) {
+        return false;
+    }
+    // Calculate a parent offset and write the offset.
+    if (!DynamicPtWritingUtils::writeParentPosOffsetAndAdvancePosition(mTrieBuffer,
+            ptNodeParams->getParentPos(), nodePos, ptNodeWritingPos)) {
+        return false;
+    }
+    // Write code points
+    if (!DynamicPtWritingUtils::writeCodePointsAndAdvancePosition(mTrieBuffer,
+            ptNodeParams->getCodePoints(), ptNodeParams->getCodePointCount(), ptNodeWritingPos)) {
+        return false;
+    }
+    int terminalId = Ver4DictConstants::NOT_A_TERMINAL_ID;
+    if (!ptNodeParams->willBecomeNonTerminal()) {
+        if (ptNodeParams->getTerminalId() != Ver4DictConstants::NOT_A_TERMINAL_ID) {
+            terminalId = ptNodeParams->getTerminalId();
+        } else if (ptNodeParams->isTerminal()) {
+            // Write terminal information using a new terminal id.
+            // Get a new unused terminal id.
+            terminalId = mBuffers->getTerminalPositionLookupTable()->getNextTerminalId();
+        }
+    }
+    const int isTerminal = terminalId != Ver4DictConstants::NOT_A_TERMINAL_ID;
+    if (isTerminal) {
+        // Update the lookup table.
+        if (!mBuffers->getMutableTerminalPositionLookupTable()->setTerminalPtNodePosition(
+                terminalId, nodePos)) {
+            return false;
+        }
+        // Write terminal Id.
+        if (!mTrieBuffer->writeUintAndAdvancePosition(terminalId,
+                Ver4DictConstants::TERMINAL_ID_FIELD_SIZE, ptNodeWritingPos)) {
+            return false;
+        }
+        if (outTerminalId) {
+            *outTerminalId = terminalId;
+        }
+    }
+    // Write children position
+    if (!DynamicPtWritingUtils::writeChildrenPositionAndAdvancePosition(mTrieBuffer,
+            ptNodeParams->getChildrenPos(), ptNodeWritingPos)) {
+        return false;
+    }
+    return updatePtNodeFlags(nodePos, ptNodeParams->isBlacklisted(), ptNodeParams->isNotAWord(),
+            isTerminal, ptNodeParams->hasShortcutTargets(), ptNodeParams->hasBigrams(),
+            ptNodeParams->getCodePointCount() > 1 /* hasMultipleChars */);
+}
+
+const ProbabilityEntry Ver4PatriciaTrieNodeWriter::createUpdatedEntryFrom(
+        const ProbabilityEntry *const originalProbabilityEntry, const int newProbability,
+        const int timestamp) const {
+    // TODO: Consolidate historical info and probability.
+    if (mBuffers->getHeaderPolicy()->hasHistoricalInfoOfWords()) {
+        const HistoricalInfo updatedHistoricalInfo =
+                ForgettingCurveUtils::createUpdatedHistoricalInfo(
+                        originalProbabilityEntry->getHistoricalInfo(), newProbability, timestamp);
+        return originalProbabilityEntry->createEntryWithUpdatedHistoricalInfo(
+                &updatedHistoricalInfo);
+    } else {
+        return originalProbabilityEntry->createEntryWithUpdatedProbability(newProbability);
+    }
+}
+
+bool Ver4PatriciaTrieNodeWriter::updatePtNodeFlags(const int ptNodePos,
+        const bool isBlacklisted, const bool isNotAWord, const bool isTerminal,
+        const bool hasShortcutTargets, const bool hasBigrams, const bool hasMultipleChars) {
+    // Create node flags and write them.
+    PatriciaTrieReadingUtils::NodeFlags nodeFlags =
+            PatriciaTrieReadingUtils::createAndGetFlags(isBlacklisted, isNotAWord, isTerminal,
+                    hasShortcutTargets, hasBigrams, hasMultipleChars,
+                    CHILDREN_POSITION_FIELD_SIZE);
+    if (!DynamicPtWritingUtils::writeFlags(mTrieBuffer, nodeFlags, ptNodePos)) {
+        AKLOGE("Cannot write PtNode flags. flags: %x, pos: %d", nodeFlags, ptNodePos);
+        return false;
+    }
+    return true;
+}
+
+}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h
new file mode 100644
index 0000000..69576d8
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_PATRICIA_TRIE_NODE_WRITER_H
+#define LATINIME_VER4_PATRICIA_TRIE_NODE_WRITER_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_params.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class Ver4BigramListPolicy;
+class Ver4DictBuffers;
+class Ver4ShortcutListPolicy;
+
+/*
+ * This class is used for helping to writes nodes of ver4 patricia trie.
+ */
+class Ver4PatriciaTrieNodeWriter : public PtNodeWriter {
+ public:
+    Ver4PatriciaTrieNodeWriter(BufferWithExtendableBuffer *const trieBuffer,
+            Ver4DictBuffers *const buffers, const Ver4PatriciaTrieNodeReader *const ptNodeReader,
+            Ver4BigramListPolicy *const bigramPolicy, Ver4ShortcutListPolicy *const shortcutPolicy)
+            : mTrieBuffer(trieBuffer), mBuffers(buffers), mPtNodeReader(ptNodeReader),
+              mReadingHelper(mTrieBuffer, mPtNodeReader),
+              mBigramPolicy(bigramPolicy), mShortcutPolicy(shortcutPolicy) {}
+
+    virtual ~Ver4PatriciaTrieNodeWriter() {}
+
+    virtual bool markPtNodeAsDeleted(const PtNodeParams *const toBeUpdatedPtNodeParams);
+
+    virtual bool markPtNodeAsMoved(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int movedPos, const int bigramLinkedNodePos);
+
+    virtual bool markPtNodeAsWillBecomeNonTerminal(
+            const PtNodeParams *const toBeUpdatedPtNodeParams);
+
+    virtual bool updatePtNodeProbability(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int newProbability, const int timestamp);
+
+    virtual bool updatePtNodeProbabilityAndGetNeedsToKeepPtNodeAfterGC(
+            const PtNodeParams *const toBeUpdatedPtNodeParams, bool *const outNeedsToKeepPtNode);
+
+    virtual bool updateChildrenPosition(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int newChildrenPosition);
+
+    bool updateTerminalId(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int newTerminalId);
+
+    virtual bool writePtNodeAndAdvancePosition(const PtNodeParams *const ptNodeParams,
+            int *const ptNodeWritingPos);
+
+    virtual bool writeNewTerminalPtNodeAndAdvancePosition(const PtNodeParams *const ptNodeParams,
+            const int timestamp, int *const ptNodeWritingPos);
+
+    virtual bool addNewBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam, const int probability, const int timestamp,
+            bool *const outAddedNewBigram);
+
+    virtual bool removeBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam);
+
+    virtual bool updateAllBigramEntriesAndDeleteUselessEntries(
+            const PtNodeParams *const sourcePtNodeParams, int *const outBigramEntryCount);
+
+    virtual bool updateAllPositionFields(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const DictPositionRelocationMap *const dictPositionRelocationMap,
+            int *const outBigramEntryCount);
+
+    virtual bool addShortcutTarget(const PtNodeParams *const ptNodeParams,
+            const int *const targetCodePoints, const int targetCodePointCount,
+            const int shortcutProbability);
+
+    bool updatePtNodeHasBigramsAndShortcutTargetsFlags(const PtNodeParams *const ptNodeParams);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(Ver4PatriciaTrieNodeWriter);
+
+    bool writePtNodeAndGetTerminalIdAndAdvancePosition(
+            const PtNodeParams *const ptNodeParams, int *const outTerminalId,
+            int *const ptNodeWritingPos);
+
+    // Create updated probability entry using given probability and timestamp. In addition to the
+    // probability, this method updates historical information if needed.
+    const ProbabilityEntry createUpdatedEntryFrom(
+            const ProbabilityEntry *const originalProbabilityEntry, const int newProbability,
+            const int timestamp) const;
+
+    bool updatePtNodeFlags(const int ptNodePos, const bool isBlacklisted, const bool isNotAWord,
+            const bool isTerminal, const bool hasShortcutTargets, const bool hasBigrams,
+            const bool hasMultipleChars);
+
+    static const int CHILDREN_POSITION_FIELD_SIZE;
+
+    BufferWithExtendableBuffer *const mTrieBuffer;
+    Ver4DictBuffers *const mBuffers;
+    const Ver4PatriciaTrieNodeReader *const mPtNodeReader;
+    DynamicPtReadingHelper mReadingHelper;
+    Ver4BigramListPolicy *const mBigramPolicy;
+    Ver4ShortcutListPolicy *const mShortcutPolicy;
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_PATRICIA_TRIE_NODE_WRITER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
new file mode 100644
index 0000000..96bb812
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
@@ -0,0 +1,352 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h"
+
+#include <vector>
+
+#include "suggest/core/dicnode/dic_node.h"
+#include "suggest/core/dicnode/dic_node_vector.h"
+#include "suggest/core/dictionary/unigram_property.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+#include "suggest/policyimpl/dictionary/utils/probability_utils.h"
+
+namespace latinime {
+
+// Note that there are corresponding definitions in Java side in BinaryDictionaryTests and
+// BinaryDictionaryDecayingTests.
+const char *const Ver4PatriciaTriePolicy::UNIGRAM_COUNT_QUERY = "UNIGRAM_COUNT";
+const char *const Ver4PatriciaTriePolicy::BIGRAM_COUNT_QUERY = "BIGRAM_COUNT";
+const char *const Ver4PatriciaTriePolicy::MAX_UNIGRAM_COUNT_QUERY = "MAX_UNIGRAM_COUNT";
+const char *const Ver4PatriciaTriePolicy::MAX_BIGRAM_COUNT_QUERY = "MAX_BIGRAM_COUNT";
+const char *const Ver4PatriciaTriePolicy::SET_CURRENT_TIME_FOR_TESTING_QUERY_FORMAT =
+        "SET_CURRENT_TIME_FOR_TESTING:%d";
+const char *const Ver4PatriciaTriePolicy::GET_CURRENT_TIME_QUERY = "GET_CURRENT_TIME";
+const char *const Ver4PatriciaTriePolicy::QUIT_TIMEKEEPER_TEST_MODE_QUERY =
+        "QUIT_TIMEKEEPER_TEST_MODE";
+const int Ver4PatriciaTriePolicy::MARGIN_TO_REFUSE_DYNAMIC_OPERATIONS = 1024;
+const int Ver4PatriciaTriePolicy::MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS =
+        Ver4DictConstants::MAX_DICTIONARY_SIZE - MARGIN_TO_REFUSE_DYNAMIC_OPERATIONS;
+
+void Ver4PatriciaTriePolicy::createAndGetAllChildDicNodes(const DicNode *const dicNode,
+        DicNodeVector *const childDicNodes) const {
+    if (!dicNode->hasChildren()) {
+        return;
+    }
+    DynamicPtReadingHelper readingHelper(mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodeArrayPos(dicNode->getChildrenPtNodeArrayPos());
+    while (!readingHelper.isEnd()) {
+        const PtNodeParams ptNodeParams = readingHelper.getPtNodeParams();
+        if (!ptNodeParams.isValid()) {
+            break;
+        }
+        bool isTerminal = ptNodeParams.isTerminal() && !ptNodeParams.isDeleted();
+        if (isTerminal && mHeaderPolicy->isDecayingDict()) {
+            // A DecayingDict may have a terminal PtNode that has a terminal DicNode whose
+            // probability is NOT_A_PROBABILITY. In such case, we don't want to treat it as a
+            // valid terminal DicNode.
+            isTerminal = ptNodeParams.getProbability() != NOT_A_PROBABILITY;
+        }
+        childDicNodes->pushLeavingChild(dicNode, ptNodeParams.getHeadPos(),
+                ptNodeParams.getChildrenPos(), ptNodeParams.getProbability(), isTerminal,
+                ptNodeParams.hasChildren(),
+                ptNodeParams.isBlacklisted()
+                        || ptNodeParams.isNotAWord() /* isBlacklistedOrNotAWord */,
+                ptNodeParams.getCodePointCount(), ptNodeParams.getCodePoints());
+        readingHelper.readNextSiblingNode(ptNodeParams);
+    }
+}
+
+int Ver4PatriciaTriePolicy::getCodePointsAndProbabilityAndReturnCodePointCount(
+        const int ptNodePos, const int maxCodePointCount, int *const outCodePoints,
+        int *const outUnigramProbability) const {
+    DynamicPtReadingHelper readingHelper(mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodePos(ptNodePos);
+    return readingHelper.getCodePointsAndProbabilityAndReturnCodePointCount(
+            maxCodePointCount, outCodePoints, outUnigramProbability);
+}
+
+int Ver4PatriciaTriePolicy::getTerminalPtNodePositionOfWord(const int *const inWord,
+        const int length, const bool forceLowerCaseSearch) const {
+    DynamicPtReadingHelper readingHelper(mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodeArrayPos(getRootPosition());
+    return readingHelper.getTerminalPtNodePositionOfWord(inWord, length, forceLowerCaseSearch);
+}
+
+int Ver4PatriciaTriePolicy::getProbability(const int unigramProbability,
+        const int bigramProbability) const {
+    if (mHeaderPolicy->isDecayingDict()) {
+        // Both probabilities are encoded. Decode them and get probability.
+        return ForgettingCurveUtils::getProbability(unigramProbability, bigramProbability);
+    } else {
+        if (unigramProbability == NOT_A_PROBABILITY) {
+            return NOT_A_PROBABILITY;
+        } else if (bigramProbability == NOT_A_PROBABILITY) {
+            return ProbabilityUtils::backoff(unigramProbability);
+        } else {
+            // bigramProbability is a bigram probability delta.
+            return ProbabilityUtils::computeProbabilityForBigram(unigramProbability,
+                    bigramProbability);
+        }
+    }
+}
+
+int Ver4PatriciaTriePolicy::getUnigramProbabilityOfPtNode(const int ptNodePos) const {
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_PROBABILITY;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted() || ptNodeParams.isBlacklisted() || ptNodeParams.isNotAWord()) {
+        return NOT_A_PROBABILITY;
+    }
+    return getProbability(ptNodeParams.getProbability(), NOT_A_PROBABILITY);
+}
+
+int Ver4PatriciaTriePolicy::getShortcutPositionOfPtNode(const int ptNodePos) const {
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_DICT_POS;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted()) {
+        return NOT_A_DICT_POS;
+    }
+    return mBuffers.get()->getShortcutDictContent()->getShortcutListHeadPos(
+            ptNodeParams.getTerminalId());
+}
+
+int Ver4PatriciaTriePolicy::getBigramsPositionOfPtNode(const int ptNodePos) const {
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return NOT_A_DICT_POS;
+    }
+    const PtNodeParams ptNodeParams(mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos));
+    if (ptNodeParams.isDeleted()) {
+        return NOT_A_DICT_POS;
+    }
+    return mBuffers.get()->getBigramDictContent()->getBigramListHeadPos(
+            ptNodeParams.getTerminalId());
+}
+
+bool Ver4PatriciaTriePolicy::addUnigramWord(const int *const word, const int length,
+        const int probability, const int *const shortcutTargetCodePoints, const int shortcutLength,
+        const int shortcutProbability, const bool isNotAWord, const bool isBlacklisted,
+        const int timestamp) {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: addUnigramWord() is called for non-updatable dictionary.");
+        return false;
+    }
+    if (mDictBuffer->getTailPosition() >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
+        AKLOGE("The dictionary is too large to dynamically update. Dictionary size: %d",
+                mDictBuffer->getTailPosition());
+        return false;
+    }
+    DynamicPtReadingHelper readingHelper(mDictBuffer, &mNodeReader);
+    readingHelper.initWithPtNodeArrayPos(getRootPosition());
+    bool addedNewUnigram = false;
+    if (mUpdatingHelper.addUnigramWord(&readingHelper, word, length, probability, isNotAWord,
+            isBlacklisted, timestamp,  &addedNewUnigram)) {
+        if (addedNewUnigram) {
+            mUnigramCount++;
+        }
+        if (shortcutLength > 0) {
+            // Add shortcut target.
+            const int wordPos = getTerminalPtNodePositionOfWord(word, length,
+                    false /* forceLowerCaseSearch */);
+            if (wordPos == NOT_A_DICT_POS) {
+                AKLOGE("Cannot find terminal PtNode position to add shortcut target.");
+                return false;
+            }
+            if (!mUpdatingHelper.addShortcutTarget(wordPos, shortcutTargetCodePoints,
+                    shortcutLength, shortcutProbability)) {
+                AKLOGE("Cannot add new shortcut target. PtNodePos: %d, length: %d, probability: %d",
+                        wordPos, shortcutLength, shortcutProbability);
+                return false;
+            }
+        }
+        return true;
+    } else {
+        return false;
+    }
+}
+
+bool Ver4PatriciaTriePolicy::addBigramWords(const int *const word0, const int length0,
+        const int *const word1, const int length1, const int probability,
+        const int timestamp) {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: addBigramWords() is called for non-updatable dictionary.");
+        return false;
+    }
+    if (mDictBuffer->getTailPosition() >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
+        AKLOGE("The dictionary is too large to dynamically update. Dictionary size: %d",
+                mDictBuffer->getTailPosition());
+        return false;
+    }
+    const int word0Pos = getTerminalPtNodePositionOfWord(word0, length0,
+            false /* forceLowerCaseSearch */);
+    if (word0Pos == NOT_A_DICT_POS) {
+        return false;
+    }
+    const int word1Pos = getTerminalPtNodePositionOfWord(word1, length1,
+            false /* forceLowerCaseSearch */);
+    if (word1Pos == NOT_A_DICT_POS) {
+        return false;
+    }
+    bool addedNewBigram = false;
+    if (mUpdatingHelper.addBigramWords(word0Pos, word1Pos, probability, timestamp,
+            &addedNewBigram)) {
+        if (addedNewBigram) {
+            mBigramCount++;
+        }
+        return true;
+    } else {
+        return false;
+    }
+}
+
+bool Ver4PatriciaTriePolicy::removeBigramWords(const int *const word0, const int length0,
+        const int *const word1, const int length1) {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: addBigramWords() is called for non-updatable dictionary.");
+        return false;
+    }
+    if (mDictBuffer->getTailPosition() >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS) {
+        AKLOGE("The dictionary is too large to dynamically update. Dictionary size: %d",
+                mDictBuffer->getTailPosition());
+        return false;
+    }
+    const int word0Pos = getTerminalPtNodePositionOfWord(word0, length0,
+            false /* forceLowerCaseSearch */);
+    if (word0Pos == NOT_A_DICT_POS) {
+        return false;
+    }
+    const int word1Pos = getTerminalPtNodePositionOfWord(word1, length1,
+            false /* forceLowerCaseSearch */);
+    if (word1Pos == NOT_A_DICT_POS) {
+        return false;
+    }
+    if (mUpdatingHelper.removeBigramWords(word0Pos, word1Pos)) {
+        mBigramCount--;
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void Ver4PatriciaTriePolicy::flush(const char *const filePath) {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: flush() is called for non-updatable dictionary. filePath: %s", filePath);
+        return;
+    }
+    mWritingHelper.writeToDictFile(filePath, mUnigramCount, mBigramCount);
+}
+
+void Ver4PatriciaTriePolicy::flushWithGC(const char *const filePath) {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: flushWithGC() is called for non-updatable dictionary.");
+        return;
+    }
+    mWritingHelper.writeToDictFileWithGC(getRootPosition(), filePath);
+}
+
+bool Ver4PatriciaTriePolicy::needsToRunGC(const bool mindsBlockByGC) const {
+    if (!mBuffers.get()->isUpdatable()) {
+        AKLOGI("Warning: needsToRunGC() is called for non-updatable dictionary.");
+        return false;
+    }
+    if (mBuffers.get()->isNearSizeLimit()) {
+        // Additional buffer size is near the limit.
+        return true;
+    } else if (mHeaderPolicy->getExtendedRegionSize() + mDictBuffer->getUsedAdditionalBufferSize()
+            > Ver4DictConstants::MAX_DICT_EXTENDED_REGION_SIZE) {
+        // Total extended region size of the trie exceeds the limit.
+        return true;
+    } else if (mDictBuffer->getTailPosition() >= MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS
+            && mDictBuffer->getUsedAdditionalBufferSize() > 0) {
+        // Needs to reduce dictionary size.
+        return true;
+    } else if (mHeaderPolicy->isDecayingDict()) {
+        return ForgettingCurveUtils::needsToDecay(mindsBlockByGC, mUnigramCount, mBigramCount,
+                mHeaderPolicy);
+    }
+    return false;
+}
+
+void Ver4PatriciaTriePolicy::getProperty(const char *const query, const int queryLength,
+        char *const outResult, const int maxResultLength) {
+    const int compareLength = queryLength + 1 /* terminator */;
+    int timestamp = NOT_A_TIMESTAMP;
+    if (strncmp(query, UNIGRAM_COUNT_QUERY, compareLength) == 0) {
+        snprintf(outResult, maxResultLength, "%d", mUnigramCount);
+    } else if (strncmp(query, BIGRAM_COUNT_QUERY, compareLength) == 0) {
+        snprintf(outResult, maxResultLength, "%d", mBigramCount);
+    } else if (strncmp(query, MAX_UNIGRAM_COUNT_QUERY, compareLength) == 0) {
+        snprintf(outResult, maxResultLength, "%d",
+                mHeaderPolicy->isDecayingDict() ? ForgettingCurveUtils::MAX_UNIGRAM_COUNT :
+                        static_cast<int>(Ver4DictConstants::MAX_DICTIONARY_SIZE));
+    } else if (strncmp(query, MAX_BIGRAM_COUNT_QUERY, compareLength) == 0) {
+        snprintf(outResult, maxResultLength, "%d",
+                mHeaderPolicy->isDecayingDict() ? ForgettingCurveUtils::MAX_BIGRAM_COUNT :
+                        static_cast<int>(Ver4DictConstants::MAX_DICTIONARY_SIZE));
+    } else if (sscanf(query, SET_CURRENT_TIME_FOR_TESTING_QUERY_FORMAT, &timestamp) == 1) {
+        TimeKeeper::startTestModeWithForceCurrentTime(timestamp);
+    } else if (strncmp(query, GET_CURRENT_TIME_QUERY, compareLength) == 0) {
+        snprintf(outResult, maxResultLength, "%d", TimeKeeper::peekCurrentTime());
+    } else if (strncmp(query, QUIT_TIMEKEEPER_TEST_MODE_QUERY, compareLength) == 0) {
+        TimeKeeper::stopTestMode();
+    }
+}
+
+const UnigramProperty Ver4PatriciaTriePolicy::getUnigramProperty(const int *const codePoints,
+        const int codePointCount) const {
+    const int ptNodePos = getTerminalPtNodePositionOfWord(codePoints, codePointCount,
+            false /* forceLowerCaseSearch */);
+    if (ptNodePos == NOT_A_DICT_POS) {
+        AKLOGE("fetchUnigramProperty is called for invalid word.");
+        return UnigramProperty();
+    }
+    const PtNodeParams ptNodeParams = mNodeReader.fetchNodeInfoInBufferFromPtNodePos(ptNodePos);
+    const ProbabilityEntry probabilityEntry =
+            mBuffers.get()->getProbabilityDictContent()->getProbabilityEntry(
+                    ptNodeParams.getTerminalId());
+    const HistoricalInfo *const historicalInfo = probabilityEntry.getHistoricalInfo();
+    // Fetch shortcut information.
+    std::vector<std::vector<int> > shortcutTargets;
+    std::vector<int> shortcutProbabilities;
+    int shortcutPos = getShortcutPositionOfPtNode(ptNodePos);
+    if (shortcutPos != NOT_A_DICT_POS) {
+        int shortcutTarget[MAX_WORD_LENGTH];
+        const ShortcutDictContent *const shortcutDictContent =
+                mBuffers.get()->getShortcutDictContent();
+        bool hasNext = true;
+        while (hasNext) {
+            int shortcutTargetLength = 0;
+            int shortcutProbability = NOT_A_PROBABILITY;
+            shortcutDictContent->getShortcutEntryAndAdvancePosition(MAX_WORD_LENGTH, shortcutTarget,
+                    &shortcutTargetLength, &shortcutProbability, &hasNext, &shortcutPos);
+            std::vector<int> target(shortcutTarget, shortcutTarget + shortcutTargetLength);
+            shortcutTargets.push_back(target);
+            shortcutProbabilities.push_back(shortcutProbability);
+        }
+    }
+    return UnigramProperty(ptNodeParams.getCodePoints(), ptNodeParams.getCodePointCount(),
+            ptNodeParams.isNotAWord(), ptNodeParams.isBlacklisted(), ptNodeParams.hasBigrams(),
+            ptNodeParams.hasShortcutTargets(), ptNodeParams.getProbability(),
+            historicalInfo->getTimeStamp(), historicalInfo->getLevel(),
+            historicalInfo->getCount(), &shortcutTargets, &shortcutProbabilities);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h
new file mode 100644
index 0000000..8187b7a
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_PATRICIA_TRIE_POLICY_H
+#define LATINIME_VER4_PATRICIA_TRIE_POLICY_H
+
+#include "defines.h"
+#include "suggest/core/policy/dictionary_structure_with_buffer_policy.h"
+#include "suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h"
+#include "suggest/policyimpl/dictionary/header/header_policy.h"
+#include "suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_updating_helper.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+class DicNode;
+class DicNodeVector;
+
+// TODO: Implement.
+class Ver4PatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
+ public:
+    Ver4PatriciaTriePolicy(const Ver4DictBuffers::Ver4DictBuffersPtr &buffers)
+            : mBuffers(buffers), mHeaderPolicy(mBuffers.get()->getHeaderPolicy()),
+              mDictBuffer(mBuffers.get()->getWritableTrieBuffer()),
+              mBigramPolicy(mBuffers.get()->getMutableBigramDictContent(),
+                      mBuffers.get()->getTerminalPositionLookupTable(), mHeaderPolicy),
+              mShortcutPolicy(mBuffers.get()->getMutableShortcutDictContent(),
+                      mBuffers.get()->getTerminalPositionLookupTable()),
+              mNodeReader(mDictBuffer, mBuffers.get()->getProbabilityDictContent()),
+              mNodeWriter(mDictBuffer, mBuffers.get(), &mNodeReader, &mBigramPolicy,
+                      &mShortcutPolicy),
+              mUpdatingHelper(mDictBuffer, &mNodeReader, &mNodeWriter),
+              mWritingHelper(mBuffers.get()),
+              mUnigramCount(mHeaderPolicy->getUnigramCount()),
+              mBigramCount(mHeaderPolicy->getBigramCount()) {};
+
+    AK_FORCE_INLINE int getRootPosition() const {
+        return 0;
+    }
+
+    void createAndGetAllChildDicNodes(const DicNode *const dicNode,
+            DicNodeVector *const childDicNodes) const;
+
+    int getCodePointsAndProbabilityAndReturnCodePointCount(
+            const int terminalPtNodePos, const int maxCodePointCount, int *const outCodePoints,
+            int *const outUnigramProbability) const;
+
+    int getTerminalPtNodePositionOfWord(const int *const inWord,
+            const int length, const bool forceLowerCaseSearch) const;
+
+    int getProbability(const int unigramProbability, const int bigramProbability) const;
+
+    int getUnigramProbabilityOfPtNode(const int ptNodePos) const;
+
+    int getShortcutPositionOfPtNode(const int ptNodePos) const;
+
+    int getBigramsPositionOfPtNode(const int ptNodePos) const;
+
+    const DictionaryHeaderStructurePolicy *getHeaderStructurePolicy() const {
+        return mHeaderPolicy;
+    }
+
+    const DictionaryBigramsStructurePolicy *getBigramsStructurePolicy() const {
+        return &mBigramPolicy;
+    }
+
+    const DictionaryShortcutsStructurePolicy *getShortcutsStructurePolicy() const {
+        return &mShortcutPolicy;
+    }
+
+    bool addUnigramWord(const int *const word, const int length, const int probability,
+            const int *const shortcutTargetCodePoints, const int shortcutLength,
+            const int shortcutProbability, const bool isNotAWord, const bool isBlacklisted,
+            const int timestamp);
+
+    bool addBigramWords(const int *const word0, const int length0, const int *const word1,
+            const int length1, const int probability, const int timestamp);
+
+    bool removeBigramWords(const int *const word0, const int length0, const int *const word1,
+            const int length1);
+
+    void flush(const char *const filePath);
+
+    void flushWithGC(const char *const filePath);
+
+    bool needsToRunGC(const bool mindsBlockByGC) const;
+
+    void getProperty(const char *const query, const int queryLength, char *const outResult,
+            const int maxResultLength);
+
+    const UnigramProperty getUnigramProperty(const int *const codePoints,
+            const int codePointCount) const;
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4PatriciaTriePolicy);
+
+    static const char *const UNIGRAM_COUNT_QUERY;
+    static const char *const BIGRAM_COUNT_QUERY;
+    static const char *const MAX_UNIGRAM_COUNT_QUERY;
+    static const char *const MAX_BIGRAM_COUNT_QUERY;
+    static const char *const SET_CURRENT_TIME_FOR_TESTING_QUERY_FORMAT;
+    static const char *const GET_CURRENT_TIME_QUERY;
+    static const char *const QUIT_TIMEKEEPER_TEST_MODE_QUERY;
+    // When the dictionary size is near the maximum size, we have to refuse dynamic operations to
+    // prevent the dictionary from overflowing.
+    static const int MARGIN_TO_REFUSE_DYNAMIC_OPERATIONS;
+    static const int MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS;
+
+    Ver4DictBuffers::Ver4DictBuffersPtr mBuffers;
+    const HeaderPolicy *const mHeaderPolicy;
+    BufferWithExtendableBuffer *const mDictBuffer;
+    Ver4BigramListPolicy mBigramPolicy;
+    Ver4ShortcutListPolicy mShortcutPolicy;
+    Ver4PatriciaTrieNodeReader mNodeReader;
+    Ver4PatriciaTrieNodeWriter mNodeWriter;
+    DynamicPtUpdatingHelper mUpdatingHelper;
+    Ver4PatriciaTrieWritingHelper mWritingHelper;
+    int mUnigramCount;
+    int mBigramCount;
+};
+} // namespace latinime
+#endif // LATINIME_VER4_PATRICIA_TRIE_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp
new file mode 100644
index 0000000..254022d
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.cpp
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h"
+
+#include "suggest/policyimpl/dictionary/utils/byte_array_utils.h"
+
+namespace latinime {
+
+/* static */ int Ver4PatriciaTrieReadingUtils::getTerminalIdAndAdvancePosition(
+        const uint8_t *const buffer, int *pos) {
+    return ByteArrayUtils::readUint32AndAdvancePosition(buffer, pos);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h
new file mode 100644
index 0000000..e418c49
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_reading_utils.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_PATRICIA_TRIE_READING_UTILS_H
+#define LATINIME_VER4_PATRICIA_TRIE_READING_UTILS_H
+
+#include <stdint.h>
+
+#include "defines.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+
+class Ver4PatriciaTrieReadingUtils {
+ public:
+    static int getTerminalIdAndAdvancePosition(const uint8_t *const buffer,
+            int *const pos);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4PatriciaTrieReadingUtils);
+};
+} // namespace latinime
+#endif /* LATINIME_VER4_PATRICIA_TRIE_READING_UTILS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.cpp
new file mode 100644
index 0000000..4322763
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.cpp
@@ -0,0 +1,285 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.h"
+
+#include <cstring>
+#include <queue>
+
+#include "suggest/policyimpl/dictionary/bigram/ver4_bigram_list_policy.h"
+#include "suggest/policyimpl/dictionary/header/header_policy.h"
+#include "suggest/policyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_node_writer.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+
+namespace latinime {
+
+void Ver4PatriciaTrieWritingHelper::writeToDictFile(const char *const dictDirPath,
+        const int unigramCount, const int bigramCount) const {
+    const HeaderPolicy *const headerPolicy = mBuffers->getHeaderPolicy();
+    BufferWithExtendableBuffer headerBuffer(
+            BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE);
+    const int extendedRegionSize = headerPolicy->getExtendedRegionSize()
+            + mBuffers->getTrieBuffer()->getUsedAdditionalBufferSize();
+    if (!headerPolicy->writeHeaderToBuffer(&headerBuffer, false /* updatesLastUpdatedTime */,
+            false /* updatesLastDecayedTime */, unigramCount, bigramCount, extendedRegionSize)) {
+        AKLOGE("Cannot write header structure to buffer. updatesLastUpdatedTime: %d, "
+                "updatesLastDecayedTime: %d, unigramCount: %d, bigramCount: %d, "
+                "extendedRegionSize: %d", false, false, unigramCount, bigramCount,
+                extendedRegionSize);
+        return;
+    }
+    mBuffers->flushHeaderAndDictBuffers(dictDirPath, &headerBuffer);
+}
+
+void Ver4PatriciaTrieWritingHelper::writeToDictFileWithGC(const int rootPtNodeArrayPos,
+        const char *const dictDirPath) {
+    const HeaderPolicy *const headerPolicy = mBuffers->getHeaderPolicy();
+    Ver4DictBuffers::Ver4DictBuffersPtr dictBuffers(
+            Ver4DictBuffers::createVer4DictBuffers(headerPolicy));
+    int unigramCount = 0;
+    int bigramCount = 0;
+    if (!runGC(rootPtNodeArrayPos, headerPolicy, dictBuffers.get(), &unigramCount, &bigramCount)) {
+        return;
+    }
+    BufferWithExtendableBuffer headerBuffer(
+            BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE);
+    if (!headerPolicy->writeHeaderToBuffer(&headerBuffer, true /* updatesLastUpdatedTime */,
+            true /* updatesLastDecayedTime */, unigramCount, bigramCount,
+            0 /* extendedRegionSize */)) {
+        return;
+    }
+    dictBuffers.get()->flushHeaderAndDictBuffers(dictDirPath, &headerBuffer);
+}
+
+bool Ver4PatriciaTrieWritingHelper::runGC(const int rootPtNodeArrayPos,
+        const HeaderPolicy *const headerPolicy, Ver4DictBuffers *const buffersToWrite,
+        int *const outUnigramCount, int *const outBigramCount) {
+    Ver4PatriciaTrieNodeReader ptNodeReader(mBuffers->getTrieBuffer(),
+            mBuffers->getProbabilityDictContent());
+    Ver4BigramListPolicy bigramPolicy(mBuffers->getMutableBigramDictContent(),
+            mBuffers->getTerminalPositionLookupTable(), headerPolicy);
+    Ver4ShortcutListPolicy shortcutPolicy(mBuffers->getMutableShortcutDictContent(),
+            mBuffers->getTerminalPositionLookupTable());
+    Ver4PatriciaTrieNodeWriter ptNodeWriter(mBuffers->getWritableTrieBuffer(),
+            mBuffers, &ptNodeReader, &bigramPolicy, &shortcutPolicy);
+
+    DynamicPtReadingHelper readingHelper(mBuffers->getTrieBuffer(), &ptNodeReader);
+    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    DynamicPtGcEventListeners
+            ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
+                    traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
+                            &ptNodeWriter);
+    if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
+            &traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted)) {
+        return false;
+    }
+    const int unigramCount = traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
+            .getValidUnigramCount();
+    if (headerPolicy->isDecayingDict()
+            && unigramCount > ForgettingCurveUtils::MAX_UNIGRAM_COUNT_AFTER_GC) {
+        if (!truncateUnigrams(&ptNodeReader, &ptNodeWriter,
+                ForgettingCurveUtils::MAX_UNIGRAM_COUNT_AFTER_GC)) {
+            AKLOGE("Cannot remove unigrams. current: %d, max: %d", unigramCount,
+                    ForgettingCurveUtils::MAX_UNIGRAM_COUNT_AFTER_GC);
+            return false;
+        }
+    }
+
+    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    DynamicPtGcEventListeners::TraversePolicyToUpdateBigramProbability
+            traversePolicyToUpdateBigramProbability(&ptNodeWriter);
+    if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
+            &traversePolicyToUpdateBigramProbability)) {
+        return false;
+    }
+    const int bigramCount = traversePolicyToUpdateBigramProbability.getValidBigramEntryCount();
+    if (headerPolicy->isDecayingDict()
+            && bigramCount > ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC) {
+        if (!truncateBigrams(ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC)) {
+            AKLOGE("Cannot remove bigrams. current: %d, max: %d", bigramCount,
+                    ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC);
+            return false;
+        }
+    }
+
+    // Mapping from positions in mBuffer to positions in bufferToWrite.
+    PtNodeWriter::DictPositionRelocationMap dictPositionRelocationMap;
+    readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    Ver4PatriciaTrieNodeWriter ptNodeWriterForNewBuffers(buffersToWrite->getWritableTrieBuffer(),
+            buffersToWrite, &ptNodeReader, &bigramPolicy, &shortcutPolicy);
+    DynamicPtGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
+            traversePolicyToPlaceAndWriteValidPtNodesToBuffer(&ptNodeWriterForNewBuffers,
+                    buffersToWrite->getWritableTrieBuffer(), &dictPositionRelocationMap);
+    if (!readingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+            &traversePolicyToPlaceAndWriteValidPtNodesToBuffer)) {
+        return false;
+    }
+
+    // Create policy instances for the GCed dictionary.
+    Ver4PatriciaTrieNodeReader newPtNodeReader(buffersToWrite->getTrieBuffer(),
+            buffersToWrite->getProbabilityDictContent());
+    Ver4BigramListPolicy newBigramPolicy(buffersToWrite->getMutableBigramDictContent(),
+            buffersToWrite->getTerminalPositionLookupTable(), headerPolicy);
+    Ver4ShortcutListPolicy newShortcutPolicy(buffersToWrite->getMutableShortcutDictContent(),
+            buffersToWrite->getTerminalPositionLookupTable());
+    Ver4PatriciaTrieNodeWriter newPtNodeWriter(buffersToWrite->getWritableTrieBuffer(),
+            buffersToWrite, &newPtNodeReader, &newBigramPolicy, &newShortcutPolicy);
+    // Re-assign terminal IDs for valid terminal PtNodes.
+    TerminalPositionLookupTable::TerminalIdMap terminalIdMap;
+    if(!buffersToWrite->getMutableTerminalPositionLookupTable()->runGCTerminalIds(
+            &terminalIdMap)) {
+        return false;
+    }
+    // Run GC for probability dict content.
+    if (!buffersToWrite->getMutableProbabilityDictContent()->runGC(&terminalIdMap,
+            mBuffers->getProbabilityDictContent())) {
+        return false;
+    }
+    // Run GC for bigram dict content.
+    if(!buffersToWrite->getMutableBigramDictContent()->runGC(&terminalIdMap,
+            mBuffers->getBigramDictContent(), outBigramCount)) {
+        return false;
+    }
+    // Run GC for shortcut dict content.
+    if(!buffersToWrite->getMutableShortcutDictContent()->runGC(&terminalIdMap,
+            mBuffers->getShortcutDictContent())) {
+        return false;
+    }
+    DynamicPtReadingHelper newDictReadingHelper(buffersToWrite->getTrieBuffer(),
+            &newPtNodeReader);
+    newDictReadingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    DynamicPtGcEventListeners::TraversePolicyToUpdateAllPositionFields
+            traversePolicyToUpdateAllPositionFields(&newPtNodeWriter, &dictPositionRelocationMap);
+    if (!newDictReadingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
+            &traversePolicyToUpdateAllPositionFields)) {
+        return false;
+    }
+    newDictReadingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    TraversePolicyToUpdateAllPtNodeFlagsAndTerminalIds
+            traversePolicyToUpdateAllPtNodeFlagsAndTerminalIds(&newPtNodeWriter, &terminalIdMap);
+    if (!newDictReadingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
+            &traversePolicyToUpdateAllPtNodeFlagsAndTerminalIds)) {
+        return false;
+    }
+    *outUnigramCount = traversePolicyToUpdateAllPositionFields.getUnigramCount();
+    return true;
+}
+
+bool Ver4PatriciaTrieWritingHelper::truncateUnigrams(
+        const Ver4PatriciaTrieNodeReader *const ptNodeReader,
+        Ver4PatriciaTrieNodeWriter *const ptNodeWriter, const int maxUnigramCount) {
+    const TerminalPositionLookupTable *const terminalPosLookupTable =
+            mBuffers->getTerminalPositionLookupTable();
+    const int nextTerminalId = terminalPosLookupTable->getNextTerminalId();
+    std::priority_queue<DictProbability, std::vector<DictProbability>, DictProbabilityComparator>
+            priorityQueue;
+    for (int i = 0; i < nextTerminalId; ++i) {
+        const int terminalPos = terminalPosLookupTable->getTerminalPtNodePosition(i);
+        if (terminalPos == NOT_A_DICT_POS) {
+            continue;
+        }
+        const ProbabilityEntry probabilityEntry =
+                mBuffers->getProbabilityDictContent()->getProbabilityEntry(i);
+        const int probability = probabilityEntry.hasHistoricalInfo() ?
+                ForgettingCurveUtils::decodeProbability(probabilityEntry.getHistoricalInfo()) :
+                        probabilityEntry.getProbability();
+        priorityQueue.push(DictProbability(terminalPos, probability,
+                probabilityEntry.getHistoricalInfo()->getTimeStamp()));
+    }
+
+    // Delete unigrams.
+    while (static_cast<int>(priorityQueue.size()) > maxUnigramCount) {
+        const int ptNodePos = priorityQueue.top().getDictPos();
+        const PtNodeParams ptNodeParams =
+                ptNodeReader->fetchNodeInfoInBufferFromPtNodePos(ptNodePos);
+        if (!ptNodeWriter->markPtNodeAsWillBecomeNonTerminal(&ptNodeParams)) {
+            AKLOGE("Cannot mark PtNode as willBecomeNonterminal. PtNode pos: %d", ptNodePos);
+            return false;
+        }
+        priorityQueue.pop();
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieWritingHelper::truncateBigrams(const int maxBigramCount) {
+    const TerminalPositionLookupTable *const terminalPosLookupTable =
+            mBuffers->getTerminalPositionLookupTable();
+    const int nextTerminalId = terminalPosLookupTable->getNextTerminalId();
+    std::priority_queue<DictProbability, std::vector<DictProbability>, DictProbabilityComparator>
+            priorityQueue;
+    BigramDictContent *const bigramDictContent = mBuffers->getMutableBigramDictContent();
+    for (int i = 0; i < nextTerminalId; ++i) {
+        const int bigramListPos = bigramDictContent->getBigramListHeadPos(i);
+        if (bigramListPos == NOT_A_DICT_POS) {
+            continue;
+        }
+        bool hasNext = true;
+        int readingPos = bigramListPos;
+        while (hasNext) {
+            const int entryPos = readingPos;
+            const BigramEntry bigramEntry =
+                    bigramDictContent->getBigramEntryAndAdvancePosition(&readingPos);
+            hasNext = bigramEntry.hasNext();
+            if (!bigramEntry.isValid()) {
+                continue;
+            }
+            const int probability = bigramEntry.hasHistoricalInfo() ?
+                    ForgettingCurveUtils::decodeProbability(bigramEntry.getHistoricalInfo()) :
+                            bigramEntry.getProbability();
+            priorityQueue.push(DictProbability(entryPos, probability,
+                    bigramEntry.getHistoricalInfo()->getTimeStamp()));
+        }
+    }
+
+    // Delete bigrams.
+    while (static_cast<int>(priorityQueue.size()) > maxBigramCount) {
+        const int entryPos = priorityQueue.top().getDictPos();
+        const BigramEntry bigramEntry = bigramDictContent->getBigramEntry(entryPos);
+        const BigramEntry invalidatedBigramEntry = bigramEntry.getInvalidatedEntry();
+        if (!bigramDictContent->writeBigramEntry(&invalidatedBigramEntry, entryPos)) {
+            AKLOGE("Cannot write bigram entry to remove. pos: %d", entryPos);
+            return false;
+        }
+        priorityQueue.pop();
+    }
+    return true;
+}
+
+bool Ver4PatriciaTrieWritingHelper::TraversePolicyToUpdateAllPtNodeFlagsAndTerminalIds
+        ::onVisitingPtNode(const PtNodeParams *const ptNodeParams) {
+    if (!ptNodeParams->isTerminal()) {
+        return true;
+    }
+    TerminalPositionLookupTable::TerminalIdMap::const_iterator it =
+            mTerminalIdMap->find(ptNodeParams->getTerminalId());
+    if (it == mTerminalIdMap->end()) {
+        AKLOGE("terminal Id %d is not in the terminal position map. map size: %zd",
+                ptNodeParams->getTerminalId(), mTerminalIdMap->size());
+        return false;
+    }
+    if (!mPtNodeWriter->updateTerminalId(ptNodeParams, it->second)) {
+        AKLOGE("Cannot update terminal id. %d -> %d", it->first, it->second);
+    }
+    return mPtNodeWriter->updatePtNodeHasBigramsAndShortcutTargetsFlags(ptNodeParams);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.h
new file mode 100644
index 0000000..c3a155e
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_writing_helper.h
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_VER4_PATRICIA_TRIE_WRITING_HELPER_H
+#define LATINIME_VER4_PATRICIA_TRIE_WRITING_HELPER_H
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_gc_event_listeners.h"
+#include "suggest/policyimpl/dictionary/structure/v4/content/terminal_position_lookup_table.h"
+
+namespace latinime {
+
+class HeaderPolicy;
+class Ver4DictBuffers;
+class Ver4PatriciaTrieNodeReader;
+class Ver4PatriciaTrieNodeWriter;
+
+class Ver4PatriciaTrieWritingHelper {
+ public:
+    Ver4PatriciaTrieWritingHelper(Ver4DictBuffers *const buffers)
+            : mBuffers(buffers) {}
+
+    void writeToDictFile(const char *const dictDirPath, const int unigramCount,
+            const int bigramCount) const;
+
+    void writeToDictFileWithGC(const int rootPtNodeArrayPos, const char *const dictDirPath);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(Ver4PatriciaTrieWritingHelper);
+
+    class TraversePolicyToUpdateAllPtNodeFlagsAndTerminalIds
+            : public DynamicPtReadingHelper::TraversingEventListener {
+     public:
+        TraversePolicyToUpdateAllPtNodeFlagsAndTerminalIds(
+                Ver4PatriciaTrieNodeWriter *const ptNodeWriter,
+                const TerminalPositionLookupTable::TerminalIdMap *const terminalIdMap)
+                : mPtNodeWriter(ptNodeWriter), mTerminalIdMap(terminalIdMap) {}
+
+        bool onAscend() { return true; }
+
+        bool onDescend(const int ptNodeArrayPos) { return true; }
+
+        bool onReadingPtNodeArrayTail() { return true; }
+
+        bool onVisitingPtNode(const PtNodeParams *const ptNodeParams);
+
+     private:
+        DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateAllPtNodeFlagsAndTerminalIds);
+
+        Ver4PatriciaTrieNodeWriter *const mPtNodeWriter;
+        const TerminalPositionLookupTable::TerminalIdMap *const mTerminalIdMap;
+    };
+
+    // For truncateUnigrams() and truncateBigrams().
+    class DictProbability {
+     public:
+        DictProbability(const int dictPos, const int probability, const int timestamp)
+                : mDictPos(dictPos), mProbability(probability), mTimestamp(timestamp) {}
+
+        int getDictPos() const {
+            return mDictPos;
+        }
+
+        int getProbability() const {
+            return mProbability;
+        }
+
+        int getTimestamp() const {
+            return mTimestamp;
+        }
+
+     private:
+        DISALLOW_DEFAULT_CONSTRUCTOR(DictProbability);
+
+        int mDictPos;
+        int mProbability;
+        int mTimestamp;
+    };
+
+    // For truncateUnigrams() and truncateBigrams().
+    class DictProbabilityComparator {
+     public:
+        bool operator()(const DictProbability &left, const DictProbability &right) {
+            if (left.getProbability() != right.getProbability()) {
+                return left.getProbability() > right.getProbability();
+            }
+            if (left.getTimestamp() != right.getTimestamp()) {
+                return left.getTimestamp() < right.getTimestamp();
+            }
+            return left.getDictPos() > right.getDictPos();
+        }
+
+     private:
+        DISALLOW_ASSIGNMENT_OPERATOR(DictProbabilityComparator);
+    };
+
+    bool runGC(const int rootPtNodeArrayPos, const HeaderPolicy *const headerPolicy,
+            Ver4DictBuffers *const buffersToWrite, int *const outUnigramCount,
+            int *const outBigramCount);
+
+    bool truncateUnigrams(const Ver4PatriciaTrieNodeReader *const ptNodeReader,
+            Ver4PatriciaTrieNodeWriter *const ptNodeWriter, const int maxUnigramCount);
+
+    bool truncateBigrams(const int maxBigramCount);
+
+    Ver4DictBuffers *const mBuffers;
+};
+} // namespace latinime
+
+#endif /* LATINIME_VER4_PATRICIA_TRIE_WRITING_HELPER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.cpp
index f692882..259dae4 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.cpp
@@ -18,11 +18,42 @@
 
 namespace latinime {
 
-const size_t BufferWithExtendableBuffer::MAX_ADDITIONAL_BUFFER_SIZE = 1024 * 1024;
+const size_t BufferWithExtendableBuffer::DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE = 1024 * 1024;
 const int BufferWithExtendableBuffer::NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE = 90;
 // TODO: Needs to allocate larger memory corresponding to the current vector size.
 const size_t BufferWithExtendableBuffer::EXTEND_ADDITIONAL_BUFFER_SIZE_STEP = 128 * 1024;
 
+uint32_t BufferWithExtendableBuffer::readUint(const int size, const int pos) const {
+    const bool readingPosIsInAdditionalBuffer = isInAdditionalBuffer(pos);
+    const int posInBuffer = readingPosIsInAdditionalBuffer ? pos - mOriginalBufferSize : pos;
+    return ByteArrayUtils::readUint(getBuffer(readingPosIsInAdditionalBuffer), size, posInBuffer);
+}
+
+uint32_t BufferWithExtendableBuffer::readUintAndAdvancePosition(const int size,
+        int *const pos) const {
+    const int value = readUint(size, *pos);
+    *pos += size;
+    return value;
+}
+
+void BufferWithExtendableBuffer::readCodePointsAndAdvancePosition(const int maxCodePointCount,
+        int *const outCodePoints, int *outCodePointCount, int *const pos) const {
+    const bool readingPosIsInAdditionalBuffer = isInAdditionalBuffer(*pos);
+    if (readingPosIsInAdditionalBuffer) {
+        *pos -= mOriginalBufferSize;
+    }
+    *outCodePointCount = ByteArrayUtils::readStringAndAdvancePosition(
+            getBuffer(readingPosIsInAdditionalBuffer), maxCodePointCount, outCodePoints, pos);
+    if (readingPosIsInAdditionalBuffer) {
+        *pos += mOriginalBufferSize;
+    }
+}
+
+bool BufferWithExtendableBuffer::writeUint(const uint32_t data, const int size, const int pos) {
+    int writingPos = pos;
+    return writeUintAndAdvancePosition(data, size, &writingPos);
+}
+
 bool BufferWithExtendableBuffer::writeUintAndAdvancePosition(const uint32_t data, const int size,
         int *const pos) {
     if (!(size >= 1 && size <= 4)) {
@@ -46,7 +77,7 @@
 }
 
 bool BufferWithExtendableBuffer::writeCodePointsAndAdvancePosition(const int *const codePoints,
-        const int codePointCount, const bool writesTerminator ,int *const pos) {
+        const int codePointCount, const bool writesTerminator, int *const pos) {
     const size_t size = ByteArrayUtils::calculateRequiredByteCountToStoreCodePoints(
             codePoints, codePointCount, writesTerminator);
     if (!checkAndPrepareWriting(*pos, size)) {
@@ -100,4 +131,21 @@
     return true;
 }
 
+bool BufferWithExtendableBuffer::copy(const BufferWithExtendableBuffer *const sourceBuffer) {
+    int copyingPos = 0;
+    const int tailPos = sourceBuffer->getTailPosition();
+    const int maxDataChunkSize = sizeof(uint32_t);
+    while (copyingPos < tailPos) {
+        const int remainingSize = tailPos - copyingPos;
+        const int copyingSize = (remainingSize >= maxDataChunkSize) ?
+                maxDataChunkSize : remainingSize;
+        const uint32_t data = sourceBuffer->readUint(copyingSize, copyingPos);
+        if (!writeUint(data, copyingSize, copyingPos)) {
+            return false;
+        }
+        copyingPos += copyingSize;
+    }
+    return true;
+}
+
 }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h b/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h
index 9dc3482..76be165 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h
@@ -32,12 +32,20 @@
 // raw pointer but provides several methods that handle boundary checking for writing data.
 class BufferWithExtendableBuffer {
  public:
+    static const size_t DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE;
+
     BufferWithExtendableBuffer(uint8_t *const originalBuffer, const int originalBufferSize,
-            const int maxAdditionalBufferSize = MAX_ADDITIONAL_BUFFER_SIZE)
+            const int maxAdditionalBufferSize)
             : mOriginalBuffer(originalBuffer), mOriginalBufferSize(originalBufferSize),
               mAdditionalBuffer(EXTEND_ADDITIONAL_BUFFER_SIZE_STEP), mUsedAdditionalBufferSize(0),
               mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
 
+    // Without original buffer.
+    BufferWithExtendableBuffer(const int maxAdditionalBufferSize)
+            : mOriginalBuffer(0), mOriginalBufferSize(0),
+              mAdditionalBuffer(EXTEND_ADDITIONAL_BUFFER_SIZE_STEP), mUsedAdditionalBufferSize(0),
+              mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
+
     AK_FORCE_INLINE int getTailPosition() const {
         return mOriginalBufferSize + mUsedAdditionalBufferSize;
     }
@@ -63,6 +71,13 @@
         }
     }
 
+    uint32_t readUint(const int size, const int pos) const;
+
+    uint32_t readUintAndAdvancePosition(const int size, int *const pos) const;
+
+    void readCodePointsAndAdvancePosition(const int maxCodePointCount,
+            int *const outCodePoints, int *outCodePointCount, int *const pos) const;
+
     AK_FORCE_INLINE int getOriginalBufferSize() const {
         return mOriginalBufferSize;
     }
@@ -78,15 +93,18 @@
      * Writing is allowed for original buffer, already written region of additional buffer and the
      * tail of additional buffer.
      */
+    bool writeUint(const uint32_t data, const int size, const int pos);
+
     bool writeUintAndAdvancePosition(const uint32_t data, const int size, int *const pos);
 
     bool writeCodePointsAndAdvancePosition(const int *const codePoints, const int codePointCount,
             const bool writesTerminator, int *const pos);
 
+    bool copy(const BufferWithExtendableBuffer *const sourceBuffer);
+
  private:
     DISALLOW_COPY_AND_ASSIGN(BufferWithExtendableBuffer);
 
-    static const size_t MAX_ADDITIONAL_BUFFER_SIZE;
     static const int NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE;
     static const size_t EXTEND_ADDITIONAL_BUFFER_SIZE_STEP;
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/byte_array_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/byte_array_utils.h
index 0c15768..ebdd523 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/byte_array_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/byte_array_utils.h
@@ -114,6 +114,24 @@
         return buffer[(*pos)++];
     }
 
+    static AK_FORCE_INLINE int readUint(const uint8_t *const buffer,
+            const int size, const int pos) {
+        // size must be in 1 to 4.
+        ASSERT(size >= 1 && size <= 4);
+        switch (size) {
+            case 1:
+                return ByteArrayUtils::readUint8(buffer, pos);
+            case 2:
+                return ByteArrayUtils::readUint16(buffer, pos);
+            case 3:
+                return ByteArrayUtils::readUint24(buffer, pos);
+            case 4:
+                return ByteArrayUtils::readUint32(buffer, pos);
+            default:
+                return 0;
+        }
+    }
+
     /**
      * Code Point Reading
      *
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.cpp
index 994826f..442373b 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.cpp
@@ -17,12 +17,14 @@
 #include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
 
 #include <cstdio>
-#include <cstring>
 
 #include "suggest/policyimpl/dictionary/header/header_policy.h"
-#include "suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
 #include "suggest/policyimpl/dictionary/utils/format_utils.h"
+#include "utils/time_keeper.h"
 
 namespace latinime {
 
@@ -30,60 +32,81 @@
 
 /* static */ bool DictFileWritingUtils::createEmptyDictFile(const char *const filePath,
         const int dictVersion, const HeaderReadWriteUtils::AttributeMap *const attributeMap) {
+    TimeKeeper::setCurrentTime();
     switch (dictVersion) {
-        case 3:
-            return createEmptyV3DictFile(filePath, attributeMap);
+        case FormatUtils::VERSION_4:
+            return createEmptyV4DictFile(filePath, attributeMap);
         default:
-            // Only version 3 dictionary is supported for now.
+            AKLOGE("Cannot create dictionary %s because format version %d is not supported.",
+                    filePath, dictVersion);
             return false;
     }
 }
 
-/* static */ bool DictFileWritingUtils::createEmptyV3DictFile(const char *const filePath,
+/* static */ bool DictFileWritingUtils::createEmptyV4DictFile(const char *const dirPath,
         const HeaderReadWriteUtils::AttributeMap *const attributeMap) {
-    BufferWithExtendableBuffer headerBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */);
-    HeaderPolicy headerPolicy(FormatUtils::VERSION_3, attributeMap);
-    headerPolicy.writeHeaderToBuffer(&headerBuffer, true /* updatesLastUpdatedTime */,
-            true /* updatesLastDecayedTime */, 0 /* unigramCount */, 0 /* bigramCount */,
-            0 /* extendedRegionSize */);
-    BufferWithExtendableBuffer bodyBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */);
-    if (!DynamicPatriciaTrieWritingUtils::writeEmptyDictionary(&bodyBuffer, 0 /* rootPos */)) {
+    HeaderPolicy headerPolicy(FormatUtils::VERSION_4, attributeMap);
+    Ver4DictBuffers::Ver4DictBuffersPtr dictBuffers =
+            Ver4DictBuffers::createVer4DictBuffers(&headerPolicy);
+    headerPolicy.writeHeaderToBuffer(dictBuffers.get()->getWritableHeaderBuffer(),
+            true /* updatesLastUpdatedTime */, true /* updatesLastDecayedTime */,
+            0 /* unigramCount */, 0 /* bigramCount */, 0 /* extendedRegionSize */);
+    if (!DynamicPtWritingUtils::writeEmptyDictionary(
+            dictBuffers.get()->getWritableTrieBuffer(), 0 /* rootPos */)) {
+        AKLOGE("Empty ver4 dictionary structure cannot be created on memory.");
         return false;
     }
-    return flushAllHeaderAndBodyToFile(filePath, &headerBuffer, &bodyBuffer);
+    return dictBuffers.get()->flush(dirPath);
 }
 
 /* static */ bool DictFileWritingUtils::flushAllHeaderAndBodyToFile(const char *const filePath,
         BufferWithExtendableBuffer *const dictHeader, BufferWithExtendableBuffer *const dictBody) {
-    const int tmpFileNameBufSize = strlen(filePath)
-            + strlen(TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE) + 1 /* terminator */;
+    const int tmpFileNameBufSize = FileUtils::getFilePathWithSuffixBufSize(filePath,
+            TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE);
     // Name of a temporary file used for writing that is a connected string of original name and
     // TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE.
     char tmpFileName[tmpFileNameBufSize];
-    snprintf(tmpFileName, tmpFileNameBufSize, "%s%s", filePath,
-            TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE);
-    FILE *const file = fopen(tmpFileName, "wb");
+    FileUtils::getFilePathWithSuffix(filePath, TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE,
+            tmpFileNameBufSize, tmpFileName);
+    if (!DictFileWritingUtils::flushBufferToFile(tmpFileName, dictHeader)) {
+        AKLOGE("Dictionary header cannot be written to %s.", tmpFileName);
+        return false;
+    }
+    if (!DictFileWritingUtils::flushBufferToFile(tmpFileName, dictBody)) {
+        AKLOGE("Dictionary structure cannot be written to %s.", tmpFileName);
+        return false;
+    }
+    if (rename(tmpFileName, filePath) != 0) {
+        AKLOGE("Dictionary file %s cannot be renamed to %s", tmpFileName, filePath);;
+        return false;
+    }
+    return true;
+}
+
+/* static */ bool DictFileWritingUtils::flushBufferToFileWithSuffix(const char *const basePath,
+        const char *const suffix, const BufferWithExtendableBuffer *const buffer) {
+    const int filePathBufSize = FileUtils::getFilePathWithSuffixBufSize(basePath, suffix);
+    char filePath[filePathBufSize];
+    FileUtils::getFilePathWithSuffix(basePath, suffix, filePathBufSize, filePath);
+    return flushBufferToFile(filePath, buffer);
+}
+
+/* static */ bool DictFileWritingUtils::flushBufferToFile(const char *const filePath,
+        const BufferWithExtendableBuffer *const buffer) {
+    FILE *const file = fopen(filePath, "wb");
     if (!file) {
-        AKLOGE("Dictionary file %s cannnot be opened.", tmpFileName);
+        AKLOGE("File %s cannot be opened.", filePath);
         ASSERT(false);
         return false;
     }
-    // Write the dictionary header.
-    if (!writeBufferToFile(file, dictHeader)) {
-        remove(tmpFileName);
-        AKLOGE("Dictionary header cannnot be written. size: %d", dictHeader->getTailPosition());
-        ASSERT(false);
-        return false;
-    }
-    // Write the dictionary body.
-    if (!writeBufferToFile(file, dictBody)) {
-        remove(tmpFileName);
-        AKLOGE("Dictionary body cannnot be written. size: %d", dictBody->getTailPosition());
+    if (!writeBufferToFile(file, buffer)) {
+        remove(filePath);
+        AKLOGE("Buffer cannot be written to the file %s. size: %d", filePath,
+                buffer->getTailPosition());
         ASSERT(false);
         return false;
     }
     fclose(file);
-    rename(tmpFileName, filePath);
     return true;
 }
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h
index bd4ac66..bdf9fd6 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h
@@ -28,6 +28,8 @@
 
 class DictFileWritingUtils {
  public:
+    static const char *const TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE;
+
     static bool createEmptyDictFile(const char *const filePath, const int dictVersion,
             const HeaderReadWriteUtils::AttributeMap *const attributeMap);
 
@@ -35,14 +37,18 @@
             BufferWithExtendableBuffer *const dictHeader,
             BufferWithExtendableBuffer *const dictBody);
 
+    static bool flushBufferToFileWithSuffix(const char *const basePath, const char *const suffix,
+            const BufferWithExtendableBuffer *const buffer);
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DictFileWritingUtils);
 
-    static const char *const TEMP_FILE_SUFFIX_FOR_WRITING_DICT_FILE;
-
-    static bool createEmptyV3DictFile(const char *const filePath,
+    static bool createEmptyV4DictFile(const char *const filePath,
             const HeaderReadWriteUtils::AttributeMap *const attributeMap);
 
+    static bool flushBufferToFile(const char *const filePath,
+            const BufferWithExtendableBuffer *const buffer);
+
     static bool writeBufferToFile(FILE *const file,
             const BufferWithExtendableBuffer *const buffer);
 };
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.cpp
new file mode 100644
index 0000000..1f25cfa
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.cpp
@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
+
+#include <cstdio>
+#include <cstring>
+#include <dirent.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+namespace latinime {
+
+// Returns -1 on error.
+/* static */ int FileUtils::getFileSize(const char *const filePath) {
+    const int fd = open(filePath, O_RDONLY);
+    if (fd == -1) {
+        return -1;
+    }
+    struct stat statBuf;
+    if (fstat(fd, &statBuf) != 0) {
+        close(fd);
+        return -1;
+    }
+    close(fd);
+    return static_cast<int>(statBuf.st_size);
+}
+
+/* static */ bool FileUtils::existsDir(const char *const dirPath) {
+    DIR *const dir = opendir(dirPath);
+    if (dir == NULL) {
+        return false;
+    }
+    closedir(dir);
+    return true;
+}
+
+// Remove a directory and all files in the directory.
+/* static */ bool FileUtils::removeDirAndFiles(const char *const dirPath) {
+    DIR *const dir = opendir(dirPath);
+    if (dir == NULL) {
+        AKLOGE("Cannot open dir %s.", dirPath);
+        return true;
+    }
+    struct dirent *dirent;
+    while ((dirent = readdir(dir)) != NULL) {
+        if (dirent->d_type != DT_REG) {
+            continue;
+        }
+        const int filePathBufSize = getFilePathBufSize(dirPath, dirent->d_name);
+        char filePath[filePathBufSize];
+        getFilePath(dirPath, dirent->d_name, filePathBufSize, filePath);
+        if (remove(filePath) != 0) {
+            AKLOGE("Cannot remove file %s.", filePath);
+            closedir(dir);
+            return false;
+        }
+    }
+    closedir(dir);
+    if (remove(dirPath) != 0) {
+        AKLOGE("Cannot remove directory %s.", dirPath);
+        return false;
+    }
+    return true;
+}
+
+/* static */ int FileUtils::getFilePathWithSuffixBufSize(const char *const filePath,
+        const char *const suffix) {
+    return strlen(filePath) + strlen(suffix) + 1 /* terminator */;
+}
+
+/* static */ void FileUtils::getFilePathWithSuffix(const char *const filePath,
+        const char *const suffix, const int filePathBufSize, char *const outFilePath) {
+    snprintf(outFilePath, filePathBufSize, "%s%s", filePath, suffix);
+}
+
+/* static */ int FileUtils::getFilePathBufSize(const char *const dirPath,
+        const char *const fileName) {
+    return strlen(dirPath) + 1 /* '/' */ + strlen(fileName) + 1 /* terminator */;
+}
+
+/* static */ void FileUtils::getFilePath(const char *const dirPath, const char *const fileName,
+        const int filePathBufSize, char *const outFilePath) {
+    snprintf(outFilePath, filePathBufSize, "%s/%s", dirPath, fileName);
+}
+
+/* static */ bool FileUtils::getFilePathWithoutSuffix(const char *const filePath,
+        const char *const suffix, const int outDirPathBufSize, char *const outDirPath) {
+    const int filePathLength = strlen(filePath);
+    const int suffixLength = strlen(suffix);
+    if (filePathLength <= suffixLength) {
+        AKLOGE("File path length (%s:%d) is shorter that suffix length (%s:%d).",
+                filePath, filePathLength, suffix, suffixLength);
+        return false;
+    }
+    const int resultFilePathLength = filePathLength - suffixLength;
+    if (outDirPathBufSize <= resultFilePathLength) {
+        AKLOGE("outDirPathBufSize is too small. filePath: %s, suffix: %s, outDirPathBufSize: %d",
+                filePath, suffix, outDirPathBufSize);
+        return false;
+    }
+    if (strncmp(filePath + resultFilePathLength, suffix, suffixLength) != 0) {
+        AKLOGE("File Path %s does not have %s as a suffix", filePath, suffix);
+        return false;
+    }
+    snprintf(outDirPath, resultFilePathLength + 1 /* terminator */, "%s", filePath);
+    return true;
+}
+
+/* static */ void FileUtils::getDirPath(const char *const filePath, const int outDirPathBufSize,
+        char *const outDirPath) {
+    for (int i = strlen(filePath) - 1; i >= 0; --i) {
+        if (filePath[i] == '/') {
+            if (i >= outDirPathBufSize) {
+                AKLOGE("outDirPathBufSize is too small. filePath: %s, outDirPathBufSize: %d",
+                        filePath, outDirPathBufSize);
+                ASSERT(false);
+                return;
+            }
+            snprintf(outDirPath, i + 1 /* terminator */, "%s", filePath);
+            return;
+        }
+    }
+}
+
+/* static */ void FileUtils::getBasename(const char *const filePath,
+        const int outNameBufSize, char *const outName) {
+    const int filePathBufSize = strlen(filePath) + 1 /* terminator */;
+    char filePathBuf[filePathBufSize];
+    snprintf(filePathBuf, filePathBufSize, "%s", filePath);
+    const char *const baseName = basename(filePathBuf);
+    const int baseNameLength = strlen(baseName);
+    if (baseNameLength >= outNameBufSize) {
+        AKLOGE("outNameBufSize is too small. filePath: %s, outNameBufSize: %d",
+                filePath, outNameBufSize);
+        return;
+    }
+    snprintf(outName, baseNameLength + 1 /* terminator */, "%s", baseName);
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.h
new file mode 100644
index 0000000..3e84a303
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/file_utils.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_FILE_UTILS_H
+#define LATINIME_FILE_UTILS_H
+
+#include "defines.h"
+
+namespace latinime {
+
+class FileUtils {
+ public:
+    // Returns -1 on error.
+    static int getFileSize(const char *const filePath);
+
+    static bool existsDir(const char *const dirPath);
+
+    // Remove a directory and all files in the directory.
+    static bool removeDirAndFiles(const char *const dirPath);
+
+    static int getFilePathWithSuffixBufSize(const char *const filePath, const char *const suffix);
+
+    static void getFilePathWithSuffix(const char *const filePath, const char *const suffix,
+            const int filePathBufSize, char *const outFilePath);
+
+    static int getFilePathBufSize(const char *const dirPath, const char *const fileName);
+
+    static void getFilePath(const char *const dirPath, const char *const fileName,
+            const int filePathBufSize, char *const outFilePath);
+
+    // Returns whether the filePath have the suffix.
+    static bool getFilePathWithoutSuffix(const char *const filePath, const char *const suffix,
+            const int dirPathBufSize, char *const outDirPath);
+
+    static void getDirPath(const char *const filePath, const int dirPathBufSize,
+            char *const outDirPath);
+
+    static void getBasename(const char *const filePath, const int outNameBufSize,
+            char *const outName);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(FileUtils);
+};
+} // namespace latinime
+#endif /* LATINIME_FILE_UTILS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
index 1632fd0..4050ad3 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
@@ -14,14 +14,14 @@
  * limitations under the License.
  */
 
-#include <cmath>
-#include <ctime>
-#include <stdlib.h>
-
 #include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
 
+#include <cmath>
+#include <stdlib.h>
+
 #include "suggest/core/policy/dictionary_header_structure_policy.h"
 #include "suggest/policyimpl/dictionary/utils/probability_utils.h"
+#include "utils/time_keeper.h"
 
 namespace latinime {
 
@@ -31,76 +31,86 @@
 const int ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC = 10000;
 
 const int ForgettingCurveUtils::MAX_COMPUTED_PROBABILITY = 127;
-const int ForgettingCurveUtils::MAX_ENCODED_PROBABILITY = 15;
-const int ForgettingCurveUtils::MIN_VALID_ENCODED_PROBABILITY = 3;
-const int ForgettingCurveUtils::ENCODED_PROBABILITY_STEP = 1;
-// Currently, we try to decay each uni/bigram once every 2 hours. Accordingly, the expected
-// duration of the decay is approximately 66hours.
-const float ForgettingCurveUtils::MIN_PROBABILITY_TO_DECAY = 0.03f;
 const int ForgettingCurveUtils::DECAY_INTERVAL_SECONDS = 2 * 60 * 60;
 
-const ForgettingCurveUtils::ProbabilityTable ForgettingCurveUtils::sProbabilityTable;
-ForgettingCurveUtils::TimeKeeper ForgettingCurveUtils::sTimeKeeper;
+const int ForgettingCurveUtils::MAX_LEVEL = 3;
+const int ForgettingCurveUtils::MAX_COUNT = 3;
+const int ForgettingCurveUtils::MIN_VALID_LEVEL = 1;
+const int ForgettingCurveUtils::TIME_STEP_DURATION_IN_SECONDS = 6 * 60 * 60;
+const int ForgettingCurveUtils::MAX_ELAPSED_TIME_STEP_COUNT = 15;
+const int ForgettingCurveUtils::DISCARD_LEVEL_ZERO_ENTRY_TIME_STEP_COUNT_THRESHOLD = 14;
 
-void ForgettingCurveUtils::TimeKeeper::setCurrentTime() {
-    mCurrentTime = time(0);
+const ForgettingCurveUtils::ProbabilityTable ForgettingCurveUtils::sProbabilityTable;
+
+/* static */ const HistoricalInfo ForgettingCurveUtils::createUpdatedHistoricalInfo(
+        const HistoricalInfo *const originalHistoricalInfo,
+        const int newProbability, const int timestamp) {
+    if (newProbability != NOT_A_PROBABILITY && originalHistoricalInfo->getLevel() == 0) {
+        return HistoricalInfo(timestamp, MIN_VALID_LEVEL /* level */, 0 /* count */);
+    } else if (!originalHistoricalInfo->isValid()) {
+        // Initial information.
+        return HistoricalInfo(timestamp, 0 /* level */, 1 /* count */);
+    } else {
+        const int updatedCount = originalHistoricalInfo->getCount() + 1;
+        if (updatedCount > MAX_COUNT) {
+            // The count exceeds the max value the level can be incremented.
+            if (originalHistoricalInfo->getLevel() >= MAX_LEVEL) {
+                // The level is already max.
+                return HistoricalInfo(timestamp, originalHistoricalInfo->getLevel(),
+                        originalHistoricalInfo->getCount());
+            } else {
+                // Level up.
+                return HistoricalInfo(timestamp, originalHistoricalInfo->getLevel() + 1,
+                        0 /* count */);
+            }
+        } else {
+            return HistoricalInfo(timestamp, originalHistoricalInfo->getLevel(), updatedCount);
+        }
+    }
 }
 
-/* static */ int ForgettingCurveUtils::getProbability(const int encodedUnigramProbability,
-        const int encodedBigramProbability) {
-    if (encodedUnigramProbability == NOT_A_PROBABILITY) {
+/* static */ int ForgettingCurveUtils::decodeProbability(
+        const HistoricalInfo *const historicalInfo) {
+    const int elapsedTimeStepCount = getElapsedTimeStepCount(historicalInfo->getTimeStamp());
+    return sProbabilityTable.getProbability(historicalInfo->getLevel(),
+            min(max(elapsedTimeStepCount, 0), MAX_ELAPSED_TIME_STEP_COUNT));
+}
+
+/* static */ int ForgettingCurveUtils::getProbability(const int unigramProbability,
+        const int bigramProbability) {
+    if (unigramProbability == NOT_A_PROBABILITY) {
         return NOT_A_PROBABILITY;
-    } else if (encodedBigramProbability == NOT_A_PROBABILITY) {
-        return backoff(decodeProbability(encodedUnigramProbability));
+    } else if (bigramProbability == NOT_A_PROBABILITY) {
+        return min(backoff(unigramProbability), MAX_COMPUTED_PROBABILITY);
     } else {
-        const int unigramProbability = decodeProbability(encodedUnigramProbability);
-        const int bigramProbability = decodeProbability(encodedBigramProbability);
         return min(max(unigramProbability, bigramProbability), MAX_COMPUTED_PROBABILITY);
     }
 }
 
-// Caveat: Unlike getProbability(), this method doesn't assume special bigram probability encoding
-// (i.e. unigram probability + bigram probability delta).
-/* static */ int ForgettingCurveUtils::getUpdatedEncodedProbability(
-        const int originalEncodedProbability, const int newProbability) {
-    if (originalEncodedProbability == NOT_A_PROBABILITY) {
-        // The bigram relation is not in this dictionary.
-        if (newProbability == NOT_A_PROBABILITY) {
-            // The bigram target is not in other dictionaries.
-            return 0;
-        } else {
-            return MIN_VALID_ENCODED_PROBABILITY;
-        }
-    } else {
-        if (newProbability != NOT_A_PROBABILITY
-                && originalEncodedProbability < MIN_VALID_ENCODED_PROBABILITY) {
-            return MIN_VALID_ENCODED_PROBABILITY;
-        }
-        return min(originalEncodedProbability + ENCODED_PROBABILITY_STEP, MAX_ENCODED_PROBABILITY);
-    }
+/* static */ bool ForgettingCurveUtils::needsToKeep(const HistoricalInfo *const historicalInfo) {
+    return historicalInfo->getLevel() > 0
+            || getElapsedTimeStepCount(historicalInfo->getTimeStamp())
+                    < DISCARD_LEVEL_ZERO_ENTRY_TIME_STEP_COUNT_THRESHOLD;
 }
 
-/* static */ int ForgettingCurveUtils::isValidEncodedProbability(const int encodedProbability) {
-    return encodedProbability >= MIN_VALID_ENCODED_PROBABILITY;
-}
-
-/* static */ int ForgettingCurveUtils::getEncodedProbabilityToSave(const int encodedProbability,
-        const DictionaryHeaderStructurePolicy *const headerPolicy) {
-    const int elapsedTime = sTimeKeeper.peekCurrentTime() - headerPolicy->getLastDecayedTime();
-    const int decayIterationCount = max(elapsedTime / DECAY_INTERVAL_SECONDS, 1);
-    int currentEncodedProbability = max(min(encodedProbability, MAX_ENCODED_PROBABILITY), 0);
-    // TODO: Implement the decay in more proper way.
-    for (int i = 0; i < decayIterationCount; ++i) {
-        const float currentRate = static_cast<float>(currentEncodedProbability)
-                / static_cast<float>(MAX_ENCODED_PROBABILITY);
-        const float thresholdToDecay = (1.0f - MIN_PROBABILITY_TO_DECAY) * currentRate;
-        const float randValue = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
-        if (thresholdToDecay < randValue) {
-            currentEncodedProbability = max(currentEncodedProbability - ENCODED_PROBABILITY_STEP,
-                    0);
-        }
+/* static */ const HistoricalInfo ForgettingCurveUtils::createHistoricalInfoToSave(
+        const HistoricalInfo *const originalHistoricalInfo) {
+    if (originalHistoricalInfo->getTimeStamp() == NOT_A_TIMESTAMP) {
+        return HistoricalInfo();
     }
-    return currentEncodedProbability;
+    const int elapsedTimeStep = getElapsedTimeStepCount(originalHistoricalInfo->getTimeStamp());
+    if (elapsedTimeStep <= MAX_ELAPSED_TIME_STEP_COUNT) {
+        // No need to update historical info.
+        return *originalHistoricalInfo;
+    }
+    // Level down.
+    const int maxLevelDownAmonut = elapsedTimeStep / (MAX_ELAPSED_TIME_STEP_COUNT + 1);
+    const int levelDownAmount = (maxLevelDownAmonut >= originalHistoricalInfo->getLevel()) ?
+            originalHistoricalInfo->getLevel() : maxLevelDownAmonut;
+    const int adjustedTimestamp = originalHistoricalInfo->getTimeStamp() +
+            levelDownAmount * (MAX_ELAPSED_TIME_STEP_COUNT + 1) * TIME_STEP_DURATION_IN_SECONDS;
+    return HistoricalInfo(adjustedTimestamp,
+            originalHistoricalInfo->getLevel() - levelDownAmount, 0 /* count */);
 }
 
 /* static */ bool ForgettingCurveUtils::needsToDecay(const bool mindsBlockByDecay,
@@ -116,21 +126,14 @@
     if (mindsBlockByDecay) {
         return false;
     }
-    if (headerPolicy->getLastDecayedTime() + DECAY_INTERVAL_SECONDS < time(0)) {
+    if (headerPolicy->getLastDecayedTime() + DECAY_INTERVAL_SECONDS
+            < TimeKeeper::peekCurrentTime()) {
         // Time to decay.
         return true;
     }
     return false;
 }
 
-/* static */ int ForgettingCurveUtils::decodeProbability(const int encodedProbability) {
-    if (encodedProbability < MIN_VALID_ENCODED_PROBABILITY) {
-        return NOT_A_PROBABILITY;
-    } else {
-        return min(sProbabilityTable.getProbability(encodedProbability), MAX_ENCODED_PROBABILITY);
-    }
-}
-
 // See comments in ProbabilityUtils::backoff().
 /* static */ int ForgettingCurveUtils::backoff(const int unigramProbability) {
     if (unigramProbability == NOT_A_PROBABILITY) {
@@ -140,15 +143,29 @@
     }
 }
 
+/* static */ int ForgettingCurveUtils::getElapsedTimeStepCount(const int timestamp) {
+    return (TimeKeeper::peekCurrentTime() - timestamp) / TIME_STEP_DURATION_IN_SECONDS;
+}
+
 ForgettingCurveUtils::ProbabilityTable::ProbabilityTable() : mTable() {
-    // Table entry is as follows:
-    // 1, 1, 1, 2, 3, 5, 6, 9, 13, 18, 25, 34, 48, 66, 91, 127.
-    // Note that first MIN_VALID_ENCODED_PROBABILITY values are not used.
-    mTable.resize(MAX_ENCODED_PROBABILITY + 1);
-    for (int i = 0; i <= MAX_ENCODED_PROBABILITY; ++i) {
-        const int probability = static_cast<int>(powf(static_cast<float>(MAX_COMPUTED_PROBABILITY),
-                static_cast<float>(i) / static_cast<float>(MAX_ENCODED_PROBABILITY)));
-         mTable[i] = min(MAX_COMPUTED_PROBABILITY, max(0, probability));
+    mTable.resize(MAX_LEVEL + 1);
+    for (int level = 0; level <= MAX_LEVEL; ++level) {
+        mTable[level].resize(MAX_ELAPSED_TIME_STEP_COUNT + 1);
+        const float initialProbability =
+                static_cast<float>(MAX_COMPUTED_PROBABILITY / (1 << (MAX_LEVEL - level)));
+        for (int timeStepCount = 0; timeStepCount <= MAX_ELAPSED_TIME_STEP_COUNT; ++timeStepCount) {
+            if (level == 0) {
+                mTable[level][timeStepCount] = NOT_A_PROBABILITY;
+                continue;
+            }
+            const int elapsedTime = timeStepCount * TIME_STEP_DURATION_IN_SECONDS;
+            const float probability = initialProbability
+                    * powf(2.0f, -1.0f * static_cast<float>(elapsedTime)
+                            / static_cast<float>(TIME_STEP_DURATION_IN_SECONDS
+                                    * (MAX_ELAPSED_TIME_STEP_COUNT + 1)));
+            mTable[level][timeStepCount] =
+                    min(max(static_cast<int>(probability), 1), MAX_COMPUTED_PROBABILITY);
+        }
     }
 }
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
index 2ad4238..6ac8dc5 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
@@ -20,45 +20,33 @@
 #include <vector>
 
 #include "defines.h"
+#include "suggest/policyimpl/dictionary/utils/historical_info.h"
 
 namespace latinime {
 
 class DictionaryHeaderStructurePolicy;
 
-// TODO: Check the elapsed time and decrease the probability depending on the time. Time field is
-// required to introduced to each terminal PtNode and bigram entry.
 // TODO: Quit using bigram probability to indicate the delta.
 class ForgettingCurveUtils {
  public:
-    class TimeKeeper {
-     public:
-        TimeKeeper() : mCurrentTime(0) {}
-        void setCurrentTime();
-        int peekCurrentTime() const { return mCurrentTime; };
-
-     private:
-        DISALLOW_COPY_AND_ASSIGN(TimeKeeper);
-
-        int mCurrentTime;
-    };
-
     static const int MAX_UNIGRAM_COUNT;
     static const int MAX_UNIGRAM_COUNT_AFTER_GC;
     static const int MAX_BIGRAM_COUNT;
     static const int MAX_BIGRAM_COUNT_AFTER_GC;
 
-    static TimeKeeper sTimeKeeper;
+    static const HistoricalInfo createUpdatedHistoricalInfo(
+            const HistoricalInfo *const originalHistoricalInfo, const int newProbability,
+            const int timestamp);
+
+    static const HistoricalInfo createHistoricalInfoToSave(
+            const HistoricalInfo *const originalHistoricalInfo);
+
+    static int decodeProbability(const HistoricalInfo *const historicalInfo);
 
     static int getProbability(const int encodedUnigramProbability,
             const int encodedBigramProbability);
 
-    static int getUpdatedEncodedProbability(const int originalEncodedProbability,
-            const int newProbability);
-
-    static int isValidEncodedProbability(const int encodedProbability);
-
-    static int getEncodedProbabilityToSave(const int encodedProbability,
-            const DictionaryHeaderStructurePolicy *const headerPolicy);
+    static bool needsToKeep(const HistoricalInfo *const historicalInfo);
 
     static bool needsToDecay(const bool mindsBlockByDecay, const int unigramCount,
             const int bigramCount, const DictionaryHeaderStructurePolicy *const headerPolicy);
@@ -70,31 +58,32 @@
      public:
         ProbabilityTable();
 
-        int getProbability(const int encodedProbability) const {
-            if (encodedProbability < 0 || encodedProbability > static_cast<int>(mTable.size())) {
-                return NOT_A_PROBABILITY;
-            }
-            return mTable[encodedProbability];
+        int getProbability(const int level, const int elapsedTimeStepCount) const {
+            return mTable[level][elapsedTimeStepCount];
         }
 
      private:
         DISALLOW_COPY_AND_ASSIGN(ProbabilityTable);
 
-        std::vector<int> mTable;
+        std::vector<std::vector<int> > mTable;
     };
 
     static const int MAX_COMPUTED_PROBABILITY;
-    static const int MAX_ENCODED_PROBABILITY;
-    static const int MIN_VALID_ENCODED_PROBABILITY;
-    static const int ENCODED_PROBABILITY_STEP;
-    static const float MIN_PROBABILITY_TO_DECAY;
     static const int DECAY_INTERVAL_SECONDS;
 
+    static const int MAX_LEVEL;
+    static const int MAX_COUNT;
+    static const int MIN_VALID_LEVEL;
+    static const int TIME_STEP_DURATION_IN_SECONDS;
+    static const int MAX_ELAPSED_TIME_STEP_COUNT;
+    static const int DISCARD_LEVEL_ZERO_ENTRY_TIME_STEP_COUNT_THRESHOLD;
+    static const int HALF_LIFE_TIME_IN_SECONDS;
+
     static const ProbabilityTable sProbabilityTable;
 
-    static int decodeProbability(const int encodedProbability);
-
     static int backoff(const int unigramProbability);
+
+    static int getElapsedTimeStepCount(const int timestamp);
 };
 } // namespace latinime
 #endif /* LATINIME_FORGETTING_CURVE_UTILS_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.cpp
index 1d77d5c..cd3c403 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.cpp
@@ -41,10 +41,13 @@
             // Dictionary format version number (2 bytes)
             // Options (2 bytes)
             // Header size (4 bytes) : integer, big endian
-            if (ByteArrayUtils::readUint16(dict, 4) == 2) {
+            // Conceptually this converts the hardcoded value of the bytes in the file into
+            // the symbolic value we use in the code. But we want the constants to be the
+            // same so we use them for both here.
+            if (ByteArrayUtils::readUint16(dict, 4) == VERSION_2) {
                 return VERSION_2;
-            } else if (ByteArrayUtils::readUint16(dict, 4) == 3) {
-                return VERSION_3;
+            } else if (ByteArrayUtils::readUint16(dict, 4) == VERSION_4) {
+                return VERSION_4;
             } else {
                 return UNKNOWN_VERSION;
             }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.h
index 79ed0de..eb2227d 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/format_utils.h
@@ -29,9 +29,10 @@
 class FormatUtils {
  public:
     enum FORMAT_VERSION {
-        VERSION_2,
-        VERSION_3,
-        UNKNOWN_VERSION
+        // These MUST have the same values as the relevant constants in FormatSpec.java.
+        VERSION_2 = 2,
+        VERSION_4 = 400,
+        UNKNOWN_VERSION = -1
     };
 
     // 32 bit magic number is stored at the beginning of the dictionary header to reject
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/historical_info.h b/native/jni/src/suggest/policyimpl/dictionary/utils/historical_info.h
new file mode 100644
index 0000000..428ca86
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/historical_info.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_HISTORICAL_INFO_H
+#define LATINIME_HISTORICAL_INFO_H
+
+#include "defines.h"
+
+namespace latinime {
+
+class HistoricalInfo {
+ public:
+    // Invalid historical info.
+    HistoricalInfo()
+            : mTimestamp(NOT_A_TIMESTAMP), mLevel(0), mCount(0) {}
+
+    HistoricalInfo(const int timestamp, const int level, const int count)
+            : mTimestamp(timestamp), mLevel(level), mCount(count) {}
+
+    bool isValid() const {
+        return mTimestamp != NOT_A_TIMESTAMP;
+    }
+
+    int getTimeStamp() const {
+        return mTimestamp;
+    }
+
+    int getLevel() const {
+        return mLevel;
+    }
+
+    int getCount() const {
+        return mCount;
+    }
+
+ private:
+    // Copy constructor is public to use this class as a type of return value.
+    DISALLOW_ASSIGNMENT_OPERATOR(HistoricalInfo);
+
+    const int mTimestamp;
+    const int mLevel;
+    const int mCount;
+};
+} // namespace latinime
+#endif /* LATINIME_HISTORICAL_INFO_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp
new file mode 100644
index 0000000..e88d6e0
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
+
+#include <cerrno>
+#include <climits>
+#include <cstdio>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "suggest/policyimpl/dictionary/utils/file_utils.h"
+
+namespace latinime {
+
+/* static */ MmappedBuffer::MmappedBufferPtr MmappedBuffer::openBuffer(
+        const char *const path, const int bufferOffset, const int bufferSize,
+        const bool isUpdatable) {
+    const int mmapFd = open(path, O_RDONLY);
+    if (mmapFd < 0) {
+        AKLOGE("DICT: Can't open the source. path=%s errno=%d", path, errno);
+        return MmappedBufferPtr(0);
+    }
+    const int pagesize = sysconf(_SC_PAGESIZE);
+    const int offset = bufferOffset % pagesize;
+    int alignedOffset = bufferOffset - offset;
+    int alignedSize = bufferSize + offset;
+    const int protMode = isUpdatable ? PROT_READ | PROT_WRITE : PROT_READ;
+    void *const mmappedBuffer = mmap(0, alignedSize, protMode, MAP_PRIVATE, mmapFd,
+            alignedOffset);
+    if (mmappedBuffer == MAP_FAILED) {
+        AKLOGE("DICT: Can't mmap dictionary. errno=%d", errno);
+        close(mmapFd);
+        return MmappedBufferPtr(0);
+    }
+    uint8_t *const buffer = static_cast<uint8_t *>(mmappedBuffer) + offset;
+    if (!buffer) {
+        AKLOGE("DICT: buffer is null");
+        close(mmapFd);
+        return MmappedBufferPtr(0);
+    }
+    return MmappedBufferPtr(new MmappedBuffer(buffer, bufferSize, mmappedBuffer, alignedSize,
+            mmapFd, isUpdatable));
+}
+
+/* static */ MmappedBuffer::MmappedBufferPtr MmappedBuffer::openBuffer(
+        const char *const path, const bool isUpdatable) {
+    const int fileSize = FileUtils::getFileSize(path);
+    if (fileSize == -1) {
+        return MmappedBufferPtr(0);
+    } else if (fileSize == 0) {
+        return MmappedBufferPtr(new MmappedBuffer(isUpdatable));
+    } else {
+        return openBuffer(path, 0 /* bufferOffset */, fileSize, isUpdatable);
+    }
+}
+
+/* static */ MmappedBuffer::MmappedBufferPtr MmappedBuffer::openBuffer(
+        const char *const dirPath, const char *const fileName, const bool isUpdatable) {
+    const int filePathBufferSize = PATH_MAX + 1 /* terminator */;
+    char filePath[filePathBufferSize];
+    const int filePathLength = snprintf(filePath, filePathBufferSize, "%s%s", dirPath,
+            fileName);
+    if (filePathLength >= filePathBufferSize) {
+        return 0;
+    }
+    return openBuffer(filePath, isUpdatable);
+}
+
+MmappedBuffer::~MmappedBuffer() {
+    if (mAlignedSize == 0) {
+        return;
+    }
+    int ret = munmap(mMmappedBuffer, mAlignedSize);
+    if (ret != 0) {
+        AKLOGE("DICT: Failure in munmap. ret=%d errno=%d", ret, errno);
+    }
+    ret = close(mMmapFd);
+    if (ret != 0) {
+        AKLOGE("DICT: Failure in close. ret=%d errno=%d", ret, errno);
+    }
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
index 6b69116..73a733b 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
@@ -17,58 +17,27 @@
 #ifndef LATINIME_MMAPPED_BUFFER_H
 #define LATINIME_MMAPPED_BUFFER_H
 
-#include <cerrno>
-#include <fcntl.h>
 #include <stdint.h>
-#include <sys/mman.h>
-#include <unistd.h>
 
 #include "defines.h"
+#include "utils/exclusive_ownership_pointer.h"
 
 namespace latinime {
 
 class MmappedBuffer {
  public:
-    static MmappedBuffer* openBuffer(const char *const path, const int bufferOffset,
-            const int bufferSize, const bool isUpdatable) {
-        const int openMode = isUpdatable ? O_RDWR : O_RDONLY;
-        const int mmapFd = open(path, openMode);
-        if (mmapFd < 0) {
-            AKLOGE("DICT: Can't open the source. path=%s errno=%d", path, errno);
-            return 0;
-        }
-        const int pagesize = getpagesize();
-        const int offset = bufferOffset % pagesize;
-        int alignedOffset = bufferOffset - offset;
-        int alignedSize = bufferSize + offset;
-        const int protMode = isUpdatable ? PROT_READ | PROT_WRITE : PROT_READ;
-        void *const mmappedBuffer = mmap(0, alignedSize, protMode, MAP_PRIVATE, mmapFd,
-                alignedOffset);
-        if (mmappedBuffer == MAP_FAILED) {
-            AKLOGE("DICT: Can't mmap dictionary. errno=%d", errno);
-            close(mmapFd);
-            return 0;
-        }
-        uint8_t *const buffer = static_cast<uint8_t *>(mmappedBuffer) + offset;
-        if (!buffer) {
-            AKLOGE("DICT: buffer is null");
-            close(mmapFd);
-            return 0;
-        }
-        return new MmappedBuffer(buffer, bufferSize, mmappedBuffer, alignedSize, mmapFd,
-                isUpdatable);
-    }
+    typedef ExclusiveOwnershipPointer<MmappedBuffer> MmappedBufferPtr;
 
-    ~MmappedBuffer() {
-        int ret = munmap(mMmappedBuffer, mAlignedSize);
-        if (ret != 0) {
-            AKLOGE("DICT: Failure in munmap. ret=%d errno=%d", ret, errno);
-        }
-        ret = close(mMmapFd);
-        if (ret != 0) {
-            AKLOGE("DICT: Failure in close. ret=%d errno=%d", ret, errno);
-        }
-    }
+    static MmappedBufferPtr openBuffer(const char *const path,
+            const int bufferOffset, const int bufferSize, const bool isUpdatable);
+
+    // Mmap entire file.
+    static MmappedBufferPtr openBuffer(const char *const path, const bool isUpdatable);
+
+    static MmappedBufferPtr openBuffer(const char *const dirPath, const char *const fileName,
+            const bool isUpdatable);
+
+    ~MmappedBuffer();
 
     AK_FORCE_INLINE uint8_t *getBuffer() const {
         return mBuffer;
@@ -89,6 +58,11 @@
             : mBuffer(buffer), mBufferSize(bufferSize), mMmappedBuffer(mmappedBuffer),
               mAlignedSize(alignedSize), mMmapFd(mmapFd), mIsUpdatable(isUpdatable) {}
 
+    // Empty file. We have to handle an empty file as a valid part of a dictionary.
+    AK_FORCE_INLINE MmappedBuffer(const bool isUpdatable)
+            : mBuffer(0), mBufferSize(0), mMmappedBuffer(0), mAlignedSize(0), mMmapFd(0),
+              mIsUpdatable(isUpdatable) {}
+
     DISALLOW_IMPLICIT_CONSTRUCTORS(MmappedBuffer);
 
     uint8_t *const mBuffer;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.cpp
new file mode 100644
index 0000000..4ad82f9
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.cpp
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "suggest/policyimpl/dictionary/utils/sparse_table.h"
+
+namespace latinime {
+
+const int SparseTable::NOT_EXIST = -1;
+const int SparseTable::INDEX_SIZE = 4;
+
+bool SparseTable::contains(const int id) const {
+    const int readingPos = getPosInIndexTable(id);
+    if (id < 0 || mIndexTableBuffer->getTailPosition() <= readingPos) {
+        return false;
+    }
+    const int index = mIndexTableBuffer->readUint(INDEX_SIZE, readingPos);
+    return index != NOT_EXIST;
+}
+
+uint32_t SparseTable::get(const int id) const {
+    const int indexTableReadingPos = getPosInIndexTable(id);
+    const int index = mIndexTableBuffer->readUint(INDEX_SIZE, indexTableReadingPos);
+    const int contentTableReadingPos = getPosInContentTable(id, index);
+    return mContentTableBuffer->readUint(mDataSize, contentTableReadingPos);
+}
+
+bool SparseTable::set(const int id, const uint32_t value) {
+    const int posInIndexTable = getPosInIndexTable(id);
+    // Extends the index table if needed.
+    if (mIndexTableBuffer->getTailPosition() < posInIndexTable) {
+        int tailPos = mIndexTableBuffer->getTailPosition();
+        while(tailPos < posInIndexTable) {
+            if (!mIndexTableBuffer->writeUintAndAdvancePosition(NOT_EXIST, INDEX_SIZE, &tailPos)) {
+                AKLOGE("cannot extend index table. tailPos: %d to: %d", tailPos, posInIndexTable);
+                return false;
+            }
+        }
+    }
+    if (contains(id)) {
+        // The entry is already in the content table.
+        const int index = mIndexTableBuffer->readUint(INDEX_SIZE, posInIndexTable);
+        if (!mContentTableBuffer->writeUint(value, mDataSize, getPosInContentTable(id, index))) {
+            AKLOGE("cannot update value %d. pos: %d, tailPos: %d, mDataSize: %d", value,
+                    getPosInContentTable(id, index), mContentTableBuffer->getTailPosition(),
+                    mDataSize);
+            return false;
+        }
+        return true;
+    }
+    // The entry is not in the content table.
+    // Create new entry in the content table.
+    const int index = getIndexFromContentTablePos(mContentTableBuffer->getTailPosition());
+    if (!mIndexTableBuffer->writeUint(index, INDEX_SIZE, posInIndexTable)) {
+        AKLOGE("cannot write index %d. pos %d", index, posInIndexTable);
+        return false;
+    }
+    // Write a new block that containing the entry to be set.
+    int writingPos = getPosInContentTable(0 /* id */, index);
+    for (int i = 0; i < mBlockSize; ++i) {
+        if (!mContentTableBuffer->writeUintAndAdvancePosition(NOT_A_DICT_POS, mDataSize,
+                &writingPos)) {
+            AKLOGE("cannot write content table to extend. writingPos: %d, tailPos: %d, "
+                    "mDataSize: %d", writingPos, mContentTableBuffer->getTailPosition(), mDataSize);
+            return false;
+        }
+    }
+    return mContentTableBuffer->writeUint(value, mDataSize, getPosInContentTable(id, index));
+}
+
+int SparseTable::getIndexFromContentTablePos(const int contentTablePos) const {
+    return contentTablePos / mDataSize / mBlockSize;
+}
+
+int SparseTable::getPosInIndexTable(const int id) const {
+    return (id / mBlockSize) * INDEX_SIZE;
+}
+
+int SparseTable::getPosInContentTable(const int id, const int index) const {
+    const int offset = id % mBlockSize;
+    return (index * mBlockSize + offset) * mDataSize;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.h b/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.h
new file mode 100644
index 0000000..21c1675
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/sparse_table.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_SPARSE_TABLE_H
+#define LATINIME_SPARSE_TABLE_H
+
+#include <stdint.h>
+
+#include "defines.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+// Note that there is a corresponding implementation in SparseTable.java.
+// TODO: Support multiple content buffers.
+class SparseTable {
+ public:
+    SparseTable(BufferWithExtendableBuffer *const indexTableBuffer,
+            BufferWithExtendableBuffer *const contentTableBuffer, const int blockSize,
+            const int dataSize)
+            : mIndexTableBuffer(indexTableBuffer), mContentTableBuffer(contentTableBuffer),
+              mBlockSize(blockSize), mDataSize(dataSize) {}
+
+    bool contains(const int id) const;
+
+    uint32_t get(const int id) const;
+
+    bool set(const int id, const uint32_t value);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(SparseTable);
+
+    int getIndexFromContentTablePos(const int contentTablePos) const;
+
+    int getPosInIndexTable(const int id) const;
+
+    int getPosInContentTable(const int id, const int index) const;
+
+    static const int NOT_EXIST;
+    static const int INDEX_SIZE;
+
+    BufferWithExtendableBuffer *const mIndexTableBuffer;
+    BufferWithExtendableBuffer *const mContentTableBuffer;
+    const int mBlockSize;
+    const int mDataSize;
+};
+} // namespace latinime
+#endif /* LATINIME_SPARSE_TABLE_H */
diff --git a/native/jni/src/suggest/policyimpl/typing/typing_traversal.h b/native/jni/src/suggest/policyimpl/typing/typing_traversal.h
index 007c19e..fd0ac9e 100644
--- a/native/jni/src/suggest/policyimpl/typing/typing_traversal.h
+++ b/native/jni/src/suggest/policyimpl/typing/typing_traversal.h
@@ -81,7 +81,7 @@
             return false;
         }
         const int point0Index = dicNode->getInputIndex(0);
-        return dicNode->isTerminalWordNode()
+        return dicNode->isTerminalDicNode()
                 && traverseSession->getProximityInfoState(0)->
                         hasSpaceProximity(point0Index);
     }
@@ -96,7 +96,7 @@
         if (dicNode->isCompletion(inputSize)) {
             return false;
         }
-        if (!dicNode->isTerminalWordNode()) {
+        if (!dicNode->isTerminalDicNode()) {
             return false;
         }
         const int16_t pointIndex = dicNode->getInputIndex(0);
diff --git a/native/jni/src/suggest/policyimpl/typing/typing_weighting.cpp b/native/jni/src/suggest/policyimpl/typing/typing_weighting.cpp
index 5b6b5e8..54f65c7 100644
--- a/native/jni/src/suggest/policyimpl/typing/typing_weighting.cpp
+++ b/native/jni/src/suggest/policyimpl/typing/typing_weighting.cpp
@@ -23,39 +23,64 @@
 
 const TypingWeighting TypingWeighting::sInstance;
 
-ErrorType TypingWeighting::getErrorType(const CorrectionType correctionType,
+ErrorTypeUtils::ErrorType TypingWeighting::getErrorType(const CorrectionType correctionType,
         const DicTraverseSession *const traverseSession, const DicNode *const parentDicNode,
         const DicNode *const dicNode) const {
     switch (correctionType) {
         case CT_MATCH:
             if (isProximityDicNode(traverseSession, dicNode)) {
-                return ET_PROXIMITY_CORRECTION;
+                return ErrorTypeUtils::PROXIMITY_CORRECTION;
+            } else if (dicNode->isInDigraph()) {
+                return ErrorTypeUtils::MATCH_WITH_DIGRAPH;
             } else {
-                return ET_NOT_AN_ERROR;
+                // Compare the node code point with original primary code point on the keyboard.
+                const ProximityInfoState *const pInfoState =
+                        traverseSession->getProximityInfoState(0);
+                const int primaryOriginalCodePoint = pInfoState->getPrimaryOriginalCodePointAt(
+                        dicNode->getInputIndex(0));
+                const int nodeCodePoint = dicNode->getNodeCodePoint();
+                if (primaryOriginalCodePoint == nodeCodePoint) {
+                    // Node code point is same as original code point on the keyboard.
+                    return ErrorTypeUtils::NOT_AN_ERROR;
+                } else if (CharUtils::toLowerCase(primaryOriginalCodePoint) ==
+                        CharUtils::toLowerCase(nodeCodePoint)) {
+                    // Only cases of the code points are different.
+                    return ErrorTypeUtils::MATCH_WITH_CASE_ERROR;
+                } else if (CharUtils::toBaseCodePoint(primaryOriginalCodePoint) ==
+                        CharUtils::toBaseCodePoint(nodeCodePoint)) {
+                    // Node code point is a variant of original code point.
+                    return ErrorTypeUtils::MATCH_WITH_ACCENT_ERROR;
+                } else {
+                    // Node code point is a variant of original code point and the cases are also
+                    // different.
+                    return ErrorTypeUtils::MATCH_WITH_ACCENT_ERROR
+                            | ErrorTypeUtils::MATCH_WITH_CASE_ERROR;
+                }
             }
+            break;
         case CT_ADDITIONAL_PROXIMITY:
-            return ET_PROXIMITY_CORRECTION;
+            return  ErrorTypeUtils::PROXIMITY_CORRECTION;
         case CT_OMISSION:
             if (parentDicNode->canBeIntentionalOmission()) {
-                return ET_INTENTIONAL_OMISSION;
+                return ErrorTypeUtils::INTENTIONAL_OMISSION;
             } else {
-                return ET_EDIT_CORRECTION;
+                return ErrorTypeUtils::EDIT_CORRECTION;
             }
             break;
         case CT_SUBSTITUTION:
         case CT_INSERTION:
         case CT_TERMINAL_INSERTION:
         case CT_TRANSPOSITION:
-            return ET_EDIT_CORRECTION;
+            return ErrorTypeUtils::EDIT_CORRECTION;
         case CT_NEW_WORD_SPACE_OMISSION:
         case CT_NEW_WORD_SPACE_SUBSTITUTION:
-            return ET_NEW_WORD;
+            return ErrorTypeUtils::NEW_WORD;
         case CT_TERMINAL:
-            return ET_NOT_AN_ERROR;
+            return ErrorTypeUtils::NOT_AN_ERROR;
         case CT_COMPLETION:
-            return ET_COMPLETION;
+            return ErrorTypeUtils::COMPLETION;
         default:
-            return ET_NOT_AN_ERROR;
+            return ErrorTypeUtils::NOT_AN_ERROR;
     }
 }
 }  // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/typing/typing_weighting.h b/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
index 9f0a331..41314ef 100644
--- a/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
+++ b/native/jni/src/suggest/policyimpl/typing/typing_weighting.h
@@ -19,6 +19,7 @@
 
 #include "defines.h"
 #include "suggest/core/dicnode/dic_node_utils.h"
+#include "suggest/core/dictionary/error_type_utils.h"
 #include "suggest/core/layout/touch_position_correction_utils.h"
 #include "suggest/core/policy/weighting.h"
 #include "suggest/core/session/dic_traverse_session.h"
@@ -204,7 +205,7 @@
         return cost * traverseSession->getMultiWordCostMultiplier();
     }
 
-    ErrorType getErrorType(const CorrectionType correctionType,
+    ErrorTypeUtils::ErrorType getErrorType(const CorrectionType correctionType,
             const DicTraverseSession *const traverseSession,
             const DicNode *const parentDicNode, const DicNode *const dicNode) const;
 
diff --git a/native/jni/src/utils/exclusive_ownership_pointer.h b/native/jni/src/utils/exclusive_ownership_pointer.h
new file mode 100644
index 0000000..081802e
--- /dev/null
+++ b/native/jni/src/utils/exclusive_ownership_pointer.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_EXCLUSIVE_OWNERSHIP_POINTER_H
+#define LATINIME_EXCLUSIVE_OWNERSHIP_POINTER_H
+
+#include "defines.h"
+
+namespace latinime {
+
+template<class T>
+class ExclusiveOwnershipPointer {
+ public:
+    // This instance become an owner of the raw pointer.
+    AK_FORCE_INLINE ExclusiveOwnershipPointer(T *const rawPointer)
+            : mPointer(rawPointer),
+              mSharedOwnerPtr(new (ExclusiveOwnershipPointer<T> *)(this)) {}
+
+    // Move the ownership.
+    AK_FORCE_INLINE ExclusiveOwnershipPointer(const ExclusiveOwnershipPointer<T> &pointer)
+            : mPointer(pointer.mPointer), mSharedOwnerPtr(pointer.mSharedOwnerPtr) {
+        transferOwnership(&pointer);
+    }
+
+    AK_FORCE_INLINE ~ExclusiveOwnershipPointer() {
+        deletePointersIfHavingOwnership();
+    }
+
+    AK_FORCE_INLINE T *get() const {
+        return mPointer;
+    }
+
+ private:
+    // This class allows to copy and ensures only one instance has the ownership of the
+    // managed pointer.
+    DISALLOW_DEFAULT_CONSTRUCTOR(ExclusiveOwnershipPointer);
+    DISALLOW_ASSIGNMENT_OPERATOR(ExclusiveOwnershipPointer);
+
+    void transferOwnership(const ExclusiveOwnershipPointer<T> *const src) {
+        if (*mSharedOwnerPtr != src) {
+           AKLOGE("Failed to transfer the ownership because src is not the current owner."
+                   "src: %p, owner: %p", src, *mSharedOwnerPtr);
+           ASSERT(false);
+           return;
+        }
+        // Transfer the ownership from src to this instance.
+        *mSharedOwnerPtr = this;
+    }
+
+    void deletePointersIfHavingOwnership() {
+        if (mSharedOwnerPtr && *mSharedOwnerPtr == this) {
+            if (mPointer) {
+                if (DEBUG_DICT) {
+                    AKLOGI("Releasing pointer: %p", mPointer);
+                }
+                delete mPointer;
+            }
+            delete mSharedOwnerPtr;
+        }
+    }
+
+    T *mPointer;
+    // mSharedOwnerPtr points a shared memory space where the instance which has the ownership is
+    // stored.
+    ExclusiveOwnershipPointer<T> **mSharedOwnerPtr;
+};
+} // namespace latinime
+#endif /* LATINIME_EXCLUSIVE_OWNERSHIP_POINTER_H */
diff --git a/native/jni/src/utils/time_keeper.cpp b/native/jni/src/utils/time_keeper.cpp
new file mode 100644
index 0000000..0262840
--- /dev/null
+++ b/native/jni/src/utils/time_keeper.cpp
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "utils/time_keeper.h"
+
+#include <ctime>
+
+namespace latinime {
+
+int TimeKeeper::sCurrentTime;
+bool TimeKeeper::sSetForTesting;
+
+/* static  */ void TimeKeeper::setCurrentTime() {
+    if (!sSetForTesting) {
+        sCurrentTime = time(0);
+    }
+}
+
+/* static */ void TimeKeeper::startTestModeWithForceCurrentTime(const int currentTime) {
+    sCurrentTime = currentTime;
+    sSetForTesting = true;
+}
+
+/* static */ void TimeKeeper::stopTestMode() {
+    sSetForTesting = false;
+}
+
+} // namespace latinime
diff --git a/native/jni/src/utils/time_keeper.h b/native/jni/src/utils/time_keeper.h
new file mode 100644
index 0000000..d066757
--- /dev/null
+++ b/native/jni/src/utils/time_keeper.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2013, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_TIME_KEEPER_H
+#define LATINIME_TIME_KEEPER_H
+
+#include "defines.h"
+
+namespace latinime {
+
+class TimeKeeper {
+ public:
+    static void setCurrentTime();
+
+    static void startTestModeWithForceCurrentTime(const int currentTime);
+
+    static void stopTestMode();
+
+    static int peekCurrentTime() { return sCurrentTime; };
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(TimeKeeper);
+
+    static int sCurrentTime;
+    static bool sSetForTesting;
+};
+} // namespace latinime
+#endif /* LATINIME_TIME_KEEPER_H */