diff --git a/java/res/drawable-hdpi/keyboard_popup_panel_background_holo.9.png b/java/res/drawable-hdpi/keyboard_popup_panel_background_holo.9.png
index dc2fc7d..f9dd3b8 100644
--- a/java/res/drawable-hdpi/keyboard_popup_panel_background_holo.9.png
+++ b/java/res/drawable-hdpi/keyboard_popup_panel_background_holo.9.png
Binary files differ
diff --git a/java/res/drawable-mdpi/keyboard_popup_panel_background_holo.9.png b/java/res/drawable-mdpi/keyboard_popup_panel_background_holo.9.png
index 441edc3..8965055 100644
--- a/java/res/drawable-mdpi/keyboard_popup_panel_background_holo.9.png
+++ b/java/res/drawable-mdpi/keyboard_popup_panel_background_holo.9.png
Binary files differ
diff --git a/java/res/drawable-xhdpi/keyboard_popup_panel_background_holo.9.png b/java/res/drawable-xhdpi/keyboard_popup_panel_background_holo.9.png
index dde1856..36df715 100644
--- a/java/res/drawable-xhdpi/keyboard_popup_panel_background_holo.9.png
+++ b/java/res/drawable-xhdpi/keyboard_popup_panel_background_holo.9.png
Binary files differ
diff --git a/java/res/drawable-xxhdpi/keyboard_popup_panel_background_holo.9.png b/java/res/drawable-xxhdpi/keyboard_popup_panel_background_holo.9.png
index ca576de..91d5d7f 100644
--- a/java/res/drawable-xxhdpi/keyboard_popup_panel_background_holo.9.png
+++ b/java/res/drawable-xxhdpi/keyboard_popup_panel_background_holo.9.png
Binary files differ
diff --git a/native/jni/Android.mk b/native/jni/Android.mk
index 3336880..35fa352 100644
--- a/native/jni/Android.mk
+++ b/native/jni/Android.mk
@@ -80,9 +80,11 @@
     $(addprefix suggest/policyimpl/dictionary/structure/v3/, \
         dynamic_patricia_trie_gc_event_listeners.cpp \
         dynamic_patricia_trie_node_reader.cpp \
+        dynamic_patricia_trie_node_writer.cpp \
         dynamic_patricia_trie_policy.cpp \
         dynamic_patricia_trie_reading_helper.cpp \
         dynamic_patricia_trie_reading_utils.cpp \
+        dynamic_patricia_trie_updating_helper.cpp \
         dynamic_patricia_trie_writing_helper.cpp \
         dynamic_patricia_trie_writing_utils.cpp) \
     $(addprefix suggest/policyimpl/dictionary/structure/v4/, \
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
index edc7b95..6a4cfee 100644
--- 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
@@ -86,6 +86,38 @@
         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;
     }
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..0f1e635
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/pt_common/pt_node_writer.h
@@ -0,0 +1,59 @@
+/*
+ * 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"
+
+namespace latinime {
+
+// Interface class used to write PtNode information.
+class PtNodeWriter {
+ public:
+    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 updatePtNodeProbability(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int probability) = 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 addNewBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam, const int probability,
+            bool *const outAddedNewBigram) = 0;
+
+    virtual bool removeBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam) = 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/structure/v3/dynamic_patricia_trie_gc_event_listeners.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.cpp
index db4e86d..a252c6f 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.cpp
@@ -18,6 +18,8 @@
 
 #include "suggest/core/policy/dictionary_header_structure_policy.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/v3/dynamic_patricia_trie_writing_utils.h"
 #include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
 
 namespace latinime {
@@ -54,7 +56,7 @@
     }
     if (isUselessPtNode) {
         // Current PtNode is no longer needed. Mark it as deleted.
-        if (!mWritingHelper->markNodeAsDeleted(ptNodeParams)) {
+        if (!mPtNodeWriter->markPtNodeAsDeleted(ptNodeParams)) {
             return false;
         }
     } else {
@@ -130,9 +132,7 @@
                     ptNodeParams->getHeadPos(), writingPos));
     mValidPtNodeCount++;
     // Writes current PtNode.
-    return mWritingHelper->writePtNodeToBufferByCopyingPtNodeInfo(mBufferToWrite, ptNodeParams,
-            ptNodeParams->getParentPos(), ptNodeParams->getCodePoints(),
-            ptNodeParams->getCodePointCount(), ptNodeParams->getProbability(), &writingPos);
+    return mPtNodeWriter->writePtNodeAndAdvancePosition(ptNodeParams, &writingPos);
 }
 
 bool DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateAllPositionFields
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.h
index cfe3c14..a0b3b4d 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_gc_event_listeners.h
@@ -23,13 +23,13 @@
 #include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_helper.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h"
-#include "suggest/policyimpl/dictionary/structure/v3/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 PtNodeWriter;
 class PtNodeParams;
 
 class DynamicPatriciaTrieGcEventListeners {
@@ -42,9 +42,9 @@
      public:
         TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
                 const DictionaryHeaderStructurePolicy *const headerPolicy,
-                DynamicPatriciaTrieWritingHelper *const writingHelper,
-                BufferWithExtendableBuffer *const buffer, const bool isDecayingDict)
-                : mHeaderPolicy(headerPolicy), mWritingHelper(writingHelper), mBuffer(buffer),
+                PtNodeWriter *const ptNodeWriter, BufferWithExtendableBuffer *const buffer,
+                const bool isDecayingDict)
+                : mHeaderPolicy(headerPolicy), mPtNodeWriter(ptNodeWriter), mBuffer(buffer),
                   mIsDecayingDict(isDecayingDict), mValueStack(), mChildrenValue(0),
                   mValidUnigramCount(0) {}
 
@@ -78,7 +78,7 @@
                 TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted);
 
         const DictionaryHeaderStructurePolicy *const mHeaderPolicy;
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
+        PtNodeWriter *const mPtNodeWriter;
         BufferWithExtendableBuffer *const mBuffer;
         const bool mIsDecayingDict;
         std::vector<int> mValueStack;
@@ -118,11 +118,10 @@
             : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
      public:
         TraversePolicyToPlaceAndWriteValidPtNodesToBuffer(
-                DynamicPatriciaTrieWritingHelper *const writingHelper,
-                BufferWithExtendableBuffer *const bufferToWrite,
+                PtNodeWriter *const ptNodeWriter, BufferWithExtendableBuffer *const bufferToWrite,
                 DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
                         dictPositionRelocationMap)
-                : mWritingHelper(writingHelper), mBufferToWrite(bufferToWrite),
+                : mPtNodeWriter(ptNodeWriter), mBufferToWrite(bufferToWrite),
                   mDictPositionRelocationMap(dictPositionRelocationMap), mValidPtNodeCount(0),
                   mPtNodeArraySizeFieldPos(NOT_A_DICT_POS) {};
 
@@ -137,7 +136,7 @@
      private:
         DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToPlaceAndWriteValidPtNodesToBuffer);
 
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
+        PtNodeWriter *const mPtNodeWriter;
         BufferWithExtendableBuffer *const mBufferToWrite;
         DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
                 mDictPositionRelocationMap;
@@ -149,13 +148,11 @@
             : 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),
+                : mBigramPolicy(bigramPolicy), mBufferToWrite(bufferToWrite),
                   mDictPositionRelocationMap(dictPositionRelocationMap), mUnigramCount(0),
                   mBigramCount(0) {};
 
@@ -178,7 +175,6 @@
      private:
         DISALLOW_IMPLICIT_CONSTRUCTORS(TraversePolicyToUpdateAllPositionFields);
 
-        DynamicPatriciaTrieWritingHelper *const mWritingHelper;
         DynamicBigramListPolicy *const mBigramPolicy;
         BufferWithExtendableBuffer *const mBufferToWrite;
         const DynamicPatriciaTrieWritingHelper::DictPositionRelocationMap *const
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.cpp
new file mode 100644
index 0000000..3b1e16c
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.cpp
@@ -0,0 +1,236 @@
+/*
+ * 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/v3/dynamic_patricia_trie_node_writer.h"
+
+#include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h"
+#include "suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h"
+#include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+
+namespace latinime {
+
+const int DynamicPatriciaTrieNodeWriter::CHILDREN_POSITION_FIELD_SIZE = 3;
+
+bool DynamicPatriciaTrieNodeWriter::markPtNodeAsDeleted(
+        const PtNodeParams *const toBeUpdatedPtNodeParams) {
+    int pos = toBeUpdatedPtNodeParams->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 = toBeUpdatedPtNodeParams->getHeadPos();
+    // Update flags.
+    return DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
+            &writingPos);
+}
+
+bool DynamicPatriciaTrieNodeWriter::markPtNodeAsMoved(
+        const PtNodeParams *const toBeUpdatedPtNodeParams,
+        const int movedPos, const int bigramLinkedNodePos) {
+    int pos = toBeUpdatedPtNodeParams->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 = toBeUpdatedPtNodeParams->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, toBeUpdatedPtNodeParams->getHeadPos(), &writingPos)) {
+        return false;
+    }
+    // Update bigram linked node position, which is stored in the children position field.
+    int childrenPosFieldPos = toBeUpdatedPtNodeParams->getChildrenPosFieldPos();
+    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(
+            mBuffer, bigramLinkedNodePos, &childrenPosFieldPos)) {
+        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()
+                    + DynamicPatriciaTrieWritingUtils::NODE_FLAG_FIELD_SIZE;
+            if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(
+                    mBuffer, 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 DynamicPatriciaTrieNodeWriter::updatePtNodeProbability(
+        const PtNodeParams *const toBeUpdatedPtNodeParams, const int newProbability) {
+    if (!toBeUpdatedPtNodeParams->isTerminal()) {
+        return false;
+    }
+    int probabilityFieldPos = toBeUpdatedPtNodeParams->getProbabilityFieldPos();
+    return DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(mBuffer,
+            newProbability, &probabilityFieldPos);
+}
+
+bool DynamicPatriciaTrieNodeWriter::updateChildrenPosition(
+        const PtNodeParams *const toBeUpdatedPtNodeParams, const int newChildrenPosition) {
+    int childrenPosFieldPos = toBeUpdatedPtNodeParams->getChildrenPosFieldPos();
+    return DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
+            newChildrenPosition, &childrenPosFieldPos);
+}
+
+bool DynamicPatriciaTrieNodeWriter::writePtNodeAndAdvancePosition(
+        const PtNodeParams *const ptNodeParams, 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 (!DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer,
+            0 /* nodeFlags */, ptNodeWritingPos)) {
+        return false;
+    }
+    // Calculate a parent offset and write the offset.
+    if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(mBuffer,
+            ptNodeParams->getParentPos(), nodePos, ptNodeWritingPos)) {
+        return false;
+    }
+    // Write code points
+    if (!DynamicPatriciaTrieWritingUtils::writeCodePointsAndAdvancePosition(mBuffer,
+            ptNodeParams->getCodePoints(), ptNodeParams->getCodePointCount(), ptNodeWritingPos)) {
+        return false;
+    }
+    // Write probability when the probability is a valid probability, which means this node is
+    // terminal.
+    if (ptNodeParams->getProbability() != NOT_A_PROBABILITY) {
+        if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(mBuffer,
+                ptNodeParams->getProbability(), ptNodeWritingPos)) {
+            return false;
+        }
+    }
+    // Write children position
+    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
+            ptNodeParams->getChildrenPos(), ptNodeWritingPos)) {
+        return false;
+    }
+    // Copy shortcut list when the originalShortcutListPos is valid dictionary position.
+    if (ptNodeParams->getShortcutPos() != NOT_A_DICT_POS) {
+        int fromPos = ptNodeParams->getShortcutPos();
+        if (!mShortcutPolicy->copyAllShortcutsAndReturnIfSucceededOrNot(mBuffer, &fromPos,
+                ptNodeWritingPos)) {
+            return false;
+        }
+    }
+    // Copy bigram list when the originalBigramListPos is valid dictionary position.
+    int bigramCount = 0;
+    if (ptNodeParams->getBigramsPos() != NOT_A_DICT_POS) {
+        int fromPos = ptNodeParams->getBigramsPos();
+        if (!mBigramPolicy->copyAllBigrams(mBuffer, &fromPos, ptNodeWritingPos, &bigramCount)) {
+            return false;
+        }
+    }
+    // Create node flags and write them.
+    PatriciaTrieReadingUtils::NodeFlags nodeFlags =
+            PatriciaTrieReadingUtils::createAndGetFlags(ptNodeParams->isBlacklisted(),
+                    ptNodeParams->isNotAWord(),
+                    ptNodeParams->getProbability() != NOT_A_PROBABILITY /* isTerminal */,
+                    ptNodeParams->getShortcutPos() != NOT_A_DICT_POS /* hasShortcutTargets */,
+                    bigramCount > 0 /* hasBigrams */,
+                    ptNodeParams->getCodePointCount() > 1 /* hasMultipleChars */,
+                    CHILDREN_POSITION_FIELD_SIZE);
+    int flagsFieldPos = nodePos;
+    if (!DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, nodeFlags,
+            &flagsFieldPos)) {
+        return false;
+    }
+    return true;
+}
+
+bool DynamicPatriciaTrieNodeWriter::addNewBigramEntry(
+        const PtNodeParams *const sourcePtNodeParams,
+        const PtNodeParams *const targetPtNodeParam, const int probability,
+        bool *const outAddedNewBigram) {
+    const int newNodePos = mBuffer->getTailPosition();
+    int writingPos = newNodePos;
+    // Write a new PtNode using original PtNode's info to the tail of the dictionary in mBuffer.
+    if (!writePtNodeAndAdvancePosition(sourcePtNodeParams, &writingPos)) {
+        return false;
+    }
+    if (!markPtNodeAsMoved(sourcePtNodeParams, newNodePos, newNodePos)) {
+        return false;
+    }
+    const PtNodeParams newPtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(newNodePos));
+    if (newPtNodeParams.getBigramsPos() != NOT_A_DICT_POS) {
+        // Insert a new bigram entry into the existing bigram list.
+        int bigramListPos = newPtNodeParams.getBigramsPos();
+        return mBigramPolicy->addNewBigramEntryToBigramList(targetPtNodeParam->getHeadPos(),
+                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(targetPtNodeParam->getHeadPos(), probability,
+                &writingPos)) {
+            return false;
+        }
+        // Then, Mark as the PtNode having bigram list in the flags.
+        const PatriciaTrieReadingUtils::NodeFlags updatedFlags =
+                PatriciaTrieReadingUtils::createAndGetFlags(newPtNodeParams.isBlacklisted(),
+                        newPtNodeParams.isNotAWord(),
+                        newPtNodeParams.getProbability() != NOT_A_PROBABILITY,
+                        newPtNodeParams.getShortcutPos() != NOT_A_DICT_POS, true /* hasBigrams */,
+                        newPtNodeParams.getCodePointCount() > 1, CHILDREN_POSITION_FIELD_SIZE);
+        writingPos = newNodePos;
+        // Write updated flags into the moved PtNode's flags field.
+        return DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
+                &writingPos);
+    }
+}
+
+bool DynamicPatriciaTrieNodeWriter::removeBigramEntry(
+        const PtNodeParams *const sourcePtNodeParams, const PtNodeParams *const targetPtNodeParam) {
+    if (sourcePtNodeParams->getBigramsPos() == NOT_A_DICT_POS) {
+        return false;
+    }
+    return mBigramPolicy->removeBigram(sourcePtNodeParams->getBigramsPos(),
+            targetPtNodeParam->getHeadPos());
+}
+
+}
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.h
new file mode 100644
index 0000000..87ed1b1
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.h
@@ -0,0 +1,82 @@
+/*
+ * 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_WRITER_H
+#define LATINIME_DYNAMIC_PATRICIA_TRIE_NODE_WRITER_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_writer.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_helper.h"
+
+namespace latinime {
+
+class BufferWithExtendableBuffer;
+class DynamicBigramListPolicy;
+class DynamicShortcutListPolicy;
+
+/*
+ * This class is used for helping to writes nodes of dynamic patricia trie.
+ */
+class DynamicPatriciaTrieNodeWriter : public PtNodeWriter {
+ public:
+    DynamicPatriciaTrieNodeWriter(BufferWithExtendableBuffer *const buffer,
+            const DynamicPatriciaTrieNodeReader *const ptNodeReader,
+            DynamicBigramListPolicy *const bigramPolicy,
+            DynamicShortcutListPolicy *const shortcutPolicy)
+            : mBuffer(buffer), mPtNodeReader(ptNodeReader), mReadingHelper(mBuffer, ptNodeReader),
+              mBigramPolicy(bigramPolicy), mShortcutPolicy(shortcutPolicy) {}
+
+    virtual ~DynamicPatriciaTrieNodeWriter() {}
+
+    virtual bool markPtNodeAsDeleted(const PtNodeParams *const toBeUpdatedPtNodeParams);
+
+    virtual bool markPtNodeAsMoved(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int movedPos, const int bigramLinkedNodePos);
+
+    virtual bool updatePtNodeProbability(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int newProbability);
+
+    virtual bool updateChildrenPosition(const PtNodeParams *const toBeUpdatedPtNodeParams,
+            const int newChildrenPosition);
+
+    virtual bool writePtNodeAndAdvancePosition(const PtNodeParams *const ptNodeParams,
+            int *const ptNodeWritingPos);
+
+    virtual bool addNewBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam, const int probability,
+            bool *const outAddedNewBigram);
+
+    virtual bool removeBigramEntry(const PtNodeParams *const sourcePtNodeParams,
+            const PtNodeParams *const targetPtNodeParam);
+
+ private:
+    DISALLOW_COPY_AND_ASSIGN(DynamicPatriciaTrieNodeWriter);
+
+    static const int CHILDREN_POSITION_FIELD_SIZE;
+
+    BufferWithExtendableBuffer *const mBuffer;
+    const DynamicPatriciaTrieNodeReader *const mPtNodeReader;
+    DynamicPatriciaTrieReadingHelper mReadingHelper;
+    DynamicBigramListPolicy *const mBigramPolicy;
+    DynamicShortcutListPolicy *const mShortcutPolicy;
+
+};
+} // namespace latinime
+#endif /* LATINIME_DYNAMIC_PATRICIA_TRIE_NODE_WRITER_H */
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.cpp
index 205d181..6b58f5f 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.cpp
@@ -27,6 +27,7 @@
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_helper.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_utils.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h"
 #include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
 #include "suggest/policyimpl/dictionary/utils/probability_utils.h"
@@ -152,10 +153,8 @@
     }
     DynamicPatriciaTrieReadingHelper readingHelper(&mBufferWithExtendableBuffer, &mNodeReader);
     readingHelper.initWithPtNodeArrayPos(getRootPosition());
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, mHeaderPolicy.isDecayingDict());
     bool addedNewUnigram = false;
-    if (writingHelper.addUnigramWord(&readingHelper, word, length, probability,
+    if (mUpdatingHelper.addUnigramWord(&readingHelper, word, length, probability,
             &addedNewUnigram)) {
         if (addedNewUnigram) {
             mUnigramCount++;
@@ -187,10 +186,8 @@
     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 (mUpdatingHelper.addBigramWords(word0Pos, word1Pos, probability, &addedNewBigram)) {
         if (addedNewBigram) {
             mBigramCount++;
         }
@@ -221,9 +218,7 @@
     if (word1Pos == NOT_A_DICT_POS) {
         return false;
     }
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, mHeaderPolicy.isDecayingDict());
-    if (writingHelper.removeBigramWords(word0Pos, word1Pos)) {
+    if (mUpdatingHelper.removeBigramWords(word0Pos, word1Pos)) {
         mBigramCount--;
         return true;
     } else {
@@ -236,8 +231,8 @@
         AKLOGI("Warning: flush() is called for non-updatable dictionary.");
         return;
     }
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &mBigramListPolicy, &mShortcutListPolicy, false /* needsToDecay */);
+    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer, &mNodeReader,
+            &mNodeWriter, &mBigramListPolicy, &mShortcutListPolicy, false /* needsToDecay */);
     writingHelper.writeToDictFile(filePath, &mHeaderPolicy, mUnigramCount, mBigramCount);
 }
 
@@ -251,8 +246,8 @@
                     false /* mindsBlockByDecay */, mUnigramCount, mBigramCount, &mHeaderPolicy));
     DynamicBigramListPolicy bigramListPolicyForGC(&mHeaderPolicy, &mBufferWithExtendableBuffer,
             &mShortcutListPolicy, needsToDecay);
-    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &bigramListPolicyForGC, &mShortcutListPolicy, needsToDecay);
+    DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer, &mNodeReader,
+            &mNodeWriter, &bigramListPolicyForGC, &mShortcutListPolicy, needsToDecay);
     writingHelper.writeToDictFileWithGC(getRootPosition(), filePath, &mHeaderPolicy);
     mNeedsToDecayForTesting = false;
 }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.h
index 7a81a9c..4546984 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_policy.h
@@ -23,6 +23,8 @@
 #include "suggest/policyimpl/dictionary/header/header_policy.h"
 #include "suggest/policyimpl/dictionary/shortcut/dynamic_shortcut_list_policy.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.h"
 #include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
 #include "suggest/policyimpl/dictionary/utils/format_utils.h"
 #include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
@@ -46,6 +48,10 @@
               mBigramListPolicy(&mHeaderPolicy, &mBufferWithExtendableBuffer, &mShortcutListPolicy,
                       mHeaderPolicy.isDecayingDict()),
               mNodeReader(&mBufferWithExtendableBuffer, &mBigramListPolicy, &mShortcutListPolicy),
+              mNodeWriter(&mBufferWithExtendableBuffer, &mNodeReader, &mBigramListPolicy,
+                      &mShortcutListPolicy),
+              mUpdatingHelper(&mBufferWithExtendableBuffer, &mNodeReader, &mNodeWriter,
+                      mHeaderPolicy.isDecayingDict()),
               mUnigramCount(mHeaderPolicy.getUnigramCount()),
               mBigramCount(mHeaderPolicy.getBigramCount()), mNeedsToDecayForTesting(false) {}
 
@@ -117,6 +123,8 @@
     DynamicShortcutListPolicy mShortcutListPolicy;
     DynamicBigramListPolicy mBigramListPolicy;
     DynamicPatriciaTrieNodeReader mNodeReader;
+    DynamicPatriciaTrieNodeWriter mNodeWriter;
+    DynamicPatriciaTrieUpdatingHelper mUpdatingHelper;
     int mUnigramCount;
     int mBigramCount;
     int mNeedsToDecayForTesting;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.cpp
new file mode 100644
index 0000000..cbc0d23
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.cpp
@@ -0,0 +1,279 @@
+/*
+ * 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/v3/dynamic_patricia_trie_updating_helper.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/structure/v3/dynamic_patricia_trie_reading_helper.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_utils.h"
+#include "suggest/policyimpl/dictionary/utils/buffer_with_extendable_buffer.h"
+#include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
+
+namespace latinime {
+
+const int DynamicPatriciaTrieUpdatingHelper::CHILDREN_POSITION_FIELD_SIZE = 3;
+
+bool DynamicPatriciaTrieUpdatingHelper::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 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,
+                        getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */,
+                                probability),
+                        wordCodePoints + matchedCodePointCount,
+                        codePointCount - matchedCodePointCount);
+            }
+        }
+        // All characters are matched.
+        if (codePointCount == readingHelper->getTotalCodePointCount(ptNodeParams)) {
+            return setPtNodeProbability(&ptNodeParams, probability, outAddedNewUnigram);
+        }
+        if (!ptNodeParams.hasChildren()) {
+            *outAddedNewUnigram = true;
+            return createChildrenPtNodeArrayAndAChildPtNode(&ptNodeParams,
+                    getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability),
+                    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(),
+            getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability), &pos);
+}
+
+bool DynamicPatriciaTrieUpdatingHelper::addBigramWords(const int word0Pos, const int word1Pos,
+        const int probability, bool *const outAddedNewBigram) {
+    const PtNodeParams sourcePtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word0Pos));
+    const PtNodeParams targetPtNodeParams(
+            mPtNodeReader->fetchNodeInfoInBufferFromPtNodePos(word1Pos));
+    return mPtNodeWriter->addNewBigramEntry(&sourcePtNodeParams, &targetPtNodeParams, probability,
+            outAddedNewBigram);
+}
+
+// Remove a bigram relation from word0Pos to word1Pos.
+bool DynamicPatriciaTrieUpdatingHelper::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 DynamicPatriciaTrieUpdatingHelper::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 DynamicPatriciaTrieUpdatingHelper::setPtNodeProbability(
+        const PtNodeParams *const originalPtNodeParams, const int probability,
+        bool *const outAddedNewUnigram) {
+    if (originalPtNodeParams->isTerminal()) {
+        // Overwrites the probability.
+        *outAddedNewUnigram = false;
+        const int probabilityToWrite = getUpdatedProbability(
+                originalPtNodeParams->getProbability(), probability);
+        return mPtNodeWriter->updatePtNodeProbability(originalPtNodeParams, probabilityToWrite);
+    } else {
+        // Make the node terminal and write the probability.
+        *outAddedNewUnigram = true;
+        const int movedPos = mBuffer->getTailPosition();
+        int writingPos = movedPos;
+        const PtNodeParams ptNodeParamsToWrite(getUpdatedPtNodeParams(originalPtNodeParams,
+                originalPtNodeParams->getParentPos(), originalPtNodeParams->getCodePointCount(),
+                originalPtNodeParams->getCodePoints(),
+                getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability)));
+        if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&ptNodeParamsToWrite, &writingPos)) {
+            return false;
+        }
+        if (!mPtNodeWriter->markPtNodeAsMoved(originalPtNodeParams, movedPos, movedPos)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool DynamicPatriciaTrieUpdatingHelper::createChildrenPtNodeArrayAndAChildPtNode(
+        const PtNodeParams *const parentPtNodeParams, const int probability,
+        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, probability);
+}
+
+bool DynamicPatriciaTrieUpdatingHelper::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;
+    }
+    const PtNodeParams ptNodeParamsToWrite(getPtNodeParamsForNewPtNode(
+            parentPtNodePos, nodeCodePointCount, nodeCodePoints, probability));
+    if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&ptNodeParamsToWrite, &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 DynamicPatriciaTrieUpdatingHelper::reallocatePtNodeAndAddNewPtNodes(
+        const PtNodeParams *const reallocatingPtNodeParams, 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;
+    const PtNodeParams ptNodeParamsToWrite(getPtNodeParamsForNewPtNode(
+            reallocatingPtNodeParams->getParentPos(), overlappingCodePointCount,
+            reallocatingPtNodeParams->getCodePoints(), newProbability));
+    if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&ptNodeParamsToWrite, &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;
+    const PtNodeParams childPartPtNodeParams(getUpdatedPtNodeParams(reallocatingPtNodeParams,
+            firstPartOfReallocatedPtNodePos,
+            reallocatingPtNodeParams->getCodePointCount() - overlappingCodePointCount,
+            reallocatingPtNodeParams->getCodePoints() + overlappingCodePointCount,
+            reallocatingPtNodeParams->getProbability()));
+    if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&childPartPtNodeParams, &writingPos)) {
+        return false;
+    }
+    if (addsExtraChild) {
+        const PtNodeParams extraChildPtNodeParams(getPtNodeParamsForNewPtNode(
+                firstPartOfReallocatedPtNodePos, newNodeCodePointCount - overlappingCodePointCount,
+                newNodeCodePoints + overlappingCodePointCount, probabilityOfNewPtNode));
+        if (!mPtNodeWriter->writePtNodeAndAdvancePosition(&extraChildPtNodeParams, &writingPos)) {
+            return false;
+        }
+    }
+    if (!DynamicPatriciaTrieWritingUtils::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);
+}
+
+int DynamicPatriciaTrieUpdatingHelper::getUpdatedProbability(const int originalProbability,
+        const int newProbability) const {
+    if (mNeedsToDecay) {
+        return ForgettingCurveUtils::getUpdatedEncodedProbability(originalProbability,
+                newProbability);
+    } else {
+        return newProbability;
+    }
+}
+
+const PtNodeParams DynamicPatriciaTrieUpdatingHelper::getUpdatedPtNodeParams(
+        const PtNodeParams *const originalPtNodeParams, const int parentPos,
+        const int codePointCount, const int *const codePoints, const int probability) const {
+    const PatriciaTrieReadingUtils::NodeFlags flags = PatriciaTrieReadingUtils::createAndGetFlags(
+            originalPtNodeParams->isBlacklisted(), originalPtNodeParams->isNotAWord(),
+            probability != NOT_A_PROBABILITY /* isTerminal */,
+            originalPtNodeParams->getShortcutPos() != NOT_A_DICT_POS /* hasShortcutTargets */,
+            originalPtNodeParams->getBigramsPos() != NOT_A_DICT_POS /* hasBigrams */,
+            codePointCount > 1 /* hasMultipleChars */, CHILDREN_POSITION_FIELD_SIZE);
+    return PtNodeParams(originalPtNodeParams, flags, parentPos, codePointCount, codePoints,
+            probability);
+}
+
+const PtNodeParams DynamicPatriciaTrieUpdatingHelper::getPtNodeParamsForNewPtNode(
+        const int parentPos, const int codePointCount, const int *const codePoints,
+        const int probability) const {
+    const PatriciaTrieReadingUtils::NodeFlags flags = PatriciaTrieReadingUtils::createAndGetFlags(
+            false /* isBlacklisted */, false /* isNotAWord */,
+            probability != NOT_A_PROBABILITY /* 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/v3/dynamic_patricia_trie_updating_helper.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.h
new file mode 100644
index 0000000..b9800cd
--- /dev/null
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_updating_helper.h
@@ -0,0 +1,93 @@
+/*
+ * 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_UPDATING_HELPER_H
+#define LATINIME_DYNAMIC_PATRICIA_TRIE_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 DynamicPatriciaTrieReadingHelper;
+class PtNodeReader;
+class PtNodeWriter;
+
+// TODO: Move to pt_common.
+class DynamicPatriciaTrieUpdatingHelper {
+ public:
+    DynamicPatriciaTrieUpdatingHelper(BufferWithExtendableBuffer *const buffer,
+            const PtNodeReader *const ptNodeReader, PtNodeWriter *const ptNodeWriter,
+            const bool needsToDecay)
+            : mBuffer(buffer), mPtNodeReader(ptNodeReader), mPtNodeWriter(ptNodeWriter),
+              mNeedsToDecay(needsToDecay) {}
+
+    ~DynamicPatriciaTrieUpdatingHelper() {}
+
+    // 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);
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTrieUpdatingHelper);
+
+    static const int CHILDREN_POSITION_FIELD_SIZE;
+
+    BufferWithExtendableBuffer *const mBuffer;
+    const PtNodeReader *const mPtNodeReader;
+    PtNodeWriter *const mPtNodeWriter;
+    const bool mNeedsToDecay;
+
+    bool createAndInsertNodeIntoPtNodeArray(const int parentPos, const int *const nodeCodePoints,
+            const int nodeCodePointCount, const int probability, int *const forwardLinkFieldPos);
+
+    bool setPtNodeProbability(const PtNodeParams *const originalPtNodeParams, const int probability,
+            bool *const outAddedNewUnigram);
+
+    bool createChildrenPtNodeArrayAndAChildPtNode(const PtNodeParams *const parentPtNodeParams,
+            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 PtNodeParams *const reallocatingPtNodeParams, const int overlappingCodePointCount,
+            const int probabilityOfNewPtNode, const int *const newNodeCodePoints,
+            const int newNodeCodePointCount);
+
+    int getUpdatedProbability(const int originalProbability, const int newProbability) const;
+
+    const PtNodeParams getUpdatedPtNodeParams(const PtNodeParams *const originalPtNodeParams,
+            const int parentPos, const int codePointCount, const int *const codePoints,
+            const int probability) const;
+
+    const PtNodeParams getPtNodeParamsForNewPtNode(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/structure/v3/dynamic_patricia_trie_writing_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.cpp
index 05caaeb..d97cec5 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.cpp
@@ -17,9 +17,12 @@
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h"
 
 #include "suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.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/structure/v3/dynamic_patricia_trie_gc_event_listeners.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_reader.h"
+#include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_node_writer.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_helper.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_reading_utils.h"
 #include "suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_utils.h"
@@ -31,122 +34,9 @@
 
 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 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,
-                        getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */,
-                                probability),
-                        wordCodePoints + matchedCodePointCount,
-                        codePointCount - matchedCodePointCount);
-            }
-        }
-        // All characters are matched.
-        if (codePointCount == readingHelper->getTotalCodePointCount(ptNodeParams)) {
-            return setPtNodeProbability(&ptNodeParams, probability, outAddedNewUnigram);
-        }
-        if (!ptNodeParams.hasChildren()) {
-            *outAddedNewUnigram = true;
-            return createChildrenPtNodeArrayAndAChildPtNode(&ptNodeParams,
-                    getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability),
-                    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(),
-            getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability), &pos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::addBigramWords(const int word0Pos, const int word1Pos,
-        const int probability, bool *const outAddedNewBigram) {
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    const PtNodeParams ptNodeParams(nodeReader.fetchNodeInfoInBufferFromPtNodePos(word0Pos));
-    // Move node to add bigram entry.
-    const int newNodePos = mBuffer->getTailPosition();
-    if (!markNodeAsMovedAndSetPosition(&ptNodeParams, 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, &ptNodeParams, ptNodeParams.getParentPos(),
-            ptNodeParams.getCodePoints(), ptNodeParams.getCodePointCount(),
-            ptNodeParams.getProbability(), &writingPos)) {
-        return false;
-    }
-    const PtNodeParams newPtNodeParams(nodeReader.fetchNodeInfoInBufferFromPtNodePos(newNodePos));
-    if (newPtNodeParams.getBigramsPos() != NOT_A_DICT_POS) {
-        // Insert a new bigram entry into the existing bigram list.
-        int bigramListPos = newPtNodeParams.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(newPtNodeParams.isBlacklisted(),
-                        newPtNodeParams.isNotAWord(),
-                        newPtNodeParams.getProbability() != NOT_A_PROBABILITY,
-                        newPtNodeParams.getShortcutPos() != NOT_A_DICT_POS, true /* hasBigrams */,
-                        newPtNodeParams.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);
-    const PtNodeParams ptNodeParams(nodeReader.fetchNodeInfoInBufferFromPtNodePos(word0Pos));
-    if (ptNodeParams.getBigramsPos() == NOT_A_DICT_POS) {
-        return false;
-    }
-    return mBigramPolicy->removeBigram(ptNodeParams.getBigramsPos(), word1Pos);
-}
-
 void DynamicPatriciaTrieWritingHelper::writeToDictFile(const char *const fileName,
         const HeaderPolicy *const headerPolicy, const int unigramCount, const int bigramCount) {
     BufferWithExtendableBuffer headerBuffer(
@@ -180,323 +70,17 @@
     DictFileWritingUtils::flushAllHeaderAndBodyToFile(fileName, &headerBuffer, &newDictBuffer);
 }
 
-bool DynamicPatriciaTrieWritingHelper::markNodeAsDeleted(
-        const PtNodeParams *const toBeUpdatedPtNodeParams) {
-    int pos = toBeUpdatedPtNodeParams->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 = toBeUpdatedPtNodeParams->getHeadPos();
-    // Update flags.
-    return DynamicPatriciaTrieWritingUtils::writeFlagsAndAdvancePosition(mBuffer, updatedFlags,
-            &writingPos);
-}
-
-bool DynamicPatriciaTrieWritingHelper::markNodeAsMovedAndSetPosition(
-        const PtNodeParams *const toBeUpdatedPtNodeParams, const int movedPos,
-        const int bigramLinkedNodePos) {
-    int pos = toBeUpdatedPtNodeParams->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 = toBeUpdatedPtNodeParams->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, toBeUpdatedPtNodeParams->getHeadPos(), &writingPos)) {
-        return false;
-    }
-    // Update bigram linked node position, which is stored in the children position field.
-    int childrenPosFieldPos = toBeUpdatedPtNodeParams->getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(
-            mBuffer, bigramLinkedNodePos, &childrenPosFieldPos)) {
-        return false;
-    }
-    if (toBeUpdatedPtNodeParams->hasChildren()) {
-        // Update children's parent position.
-        DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-        DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, &nodeReader);
-        readingHelper.initWithPtNodeArrayPos(toBeUpdatedPtNodeParams->getChildrenPos());
-        while (!readingHelper.isEnd()) {
-            const PtNodeParams childPtNodeParams(readingHelper.getPtNodeParams());
-            int parentOffsetFieldPos = childPtNodeParams.getHeadPos()
-                    + DynamicPatriciaTrieWritingUtils::NODE_FLAG_FIELD_SIZE;
-            if (!DynamicPatriciaTrieWritingUtils::writeParentPosOffsetAndAdvancePosition(
-                    mBuffer, 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;
-            }
-            readingHelper.readNextSiblingNode(childPtNodeParams);
-        }
-    }
-    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 PtNodeParams *const originalPtNodeParams, const int parentPos,
-        const int *const codePoints, const int codePointCount, const int probability,
-        int *const writingPos) {
-    return writePtNodeWithFullInfoToBuffer(bufferToWrite, originalPtNodeParams->isBlacklisted(),
-            originalPtNodeParams->isNotAWord(), parentPos, codePoints, codePointCount, probability,
-            originalPtNodeParams->getChildrenPos(), originalPtNodeParams->getBigramsPos(),
-            originalPtNodeParams->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 PtNodeParams *const originalPtNodeParams, const int probability,
-        bool *const outAddedNewUnigram) {
-    if (originalPtNodeParams->isTerminal()) {
-        // Overwrites the probability.
-        *outAddedNewUnigram = false;
-        const int probabilityToWrite = getUpdatedProbability(
-                originalPtNodeParams->getProbability(), probability);
-        int probabilityFieldPos = originalPtNodeParams->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(originalPtNodeParams, movedPos, movedPos)) {
-            return false;
-        }
-        if (!writePtNodeToBufferByCopyingPtNodeInfo(mBuffer, originalPtNodeParams,
-                originalPtNodeParams->getParentPos(), originalPtNodeParams->getCodePoints(),
-                originalPtNodeParams->getCodePointCount(),
-                getUpdatedProbability(NOT_A_PROBABILITY /* originalProbability */, probability),
-                &movedPos)) {
-            return false;
-        }
-    }
-    return true;
-}
-
-bool DynamicPatriciaTrieWritingHelper::createChildrenPtNodeArrayAndAChildPtNode(
-        const PtNodeParams *const parentPtNodeParams, const int probability,
-        const int *const codePoints, const int codePointCount) {
-    const int newPtNodeArrayPos = mBuffer->getTailPosition();
-    int childrenPosFieldPos = parentPtNodeParams->getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
-            newPtNodeArrayPos, &childrenPosFieldPos)) {
-        return false;
-    }
-    return createNewPtNodeArrayWithAChildPtNode(parentPtNodeParams->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 PtNodeParams *const reallocatingPtNodeParams, 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, reallocatingPtNodeParams->getParentPos(),
-            reallocatingPtNodeParams->getCodePoints(), 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, reallocatingPtNodeParams,
-            firstPartOfReallocatedPtNodePos,
-            reallocatingPtNodeParams->getCodePoints() + overlappingCodePointCount,
-            reallocatingPtNodeParams->getCodePointCount() - overlappingCodePointCount,
-            reallocatingPtNodeParams->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 reallocating PtNode as moved.
-    if (!markNodeAsMovedAndSetPosition(reallocatingPtNodeParams, firstPartOfReallocatedPtNodePos,
-            secondPartOfReallocatedPtNodePos)) {
-        return false;
-    }
-    // Load node info. Information of the 1st part will be fetched.
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    const PtNodeParams ptNodeParams(
-            nodeReader.fetchNodeInfoInBufferFromPtNodePos(firstPartOfReallocatedPtNodePos));
-    // Update children position.
-    int childrenPosFieldPos = ptNodeParams.getChildrenPosFieldPos();
-    if (!DynamicPatriciaTrieWritingUtils::writeChildrenPositionAndAdvancePosition(mBuffer,
-            actualChildrenPos, &childrenPosFieldPos)) {
-        return false;
-    }
-    return true;
-}
-
+// TODO: Make this method version independent.
 bool DynamicPatriciaTrieWritingHelper::runGC(const int rootPtNodeArrayPos,
         const HeaderPolicy *const headerPolicy, BufferWithExtendableBuffer *const bufferToWrite,
         int *const outUnigramCount, int *const outBigramCount) {
-    DynamicPatriciaTrieNodeReader nodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
-    DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, &nodeReader);
+    DynamicPatriciaTrieNodeReader ptNodeReader(mBuffer, mBigramPolicy, mShortcutPolicy);
+    DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, &ptNodeReader);
     readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
     DynamicPatriciaTrieGcEventListeners
             ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
                     traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
-                            headerPolicy, this, mBuffer, mNeedsToDecay);
+                            headerPolicy, mPtNodeWriter, mBuffer, mNeedsToDecay);
     if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
             &traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted)) {
         return false;
@@ -521,8 +105,10 @@
     // Mapping from positions in mBuffer to positions in bufferToWrite.
     DictPositionRelocationMap dictPositionRelocationMap;
     readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
+    DynamicPatriciaTrieNodeWriter newPtNodeWriter(bufferToWrite,
+            &ptNodeReader, mBigramPolicy, mShortcutPolicy);
     DynamicPatriciaTrieGcEventListeners::TraversePolicyToPlaceAndWriteValidPtNodesToBuffer
-            traversePolicyToPlaceAndWriteValidPtNodesToBuffer(this, bufferToWrite,
+            traversePolicyToPlaceAndWriteValidPtNodesToBuffer(&newPtNodeWriter, bufferToWrite,
                     &dictPositionRelocationMap);
     if (!readingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
             &traversePolicyToPlaceAndWriteValidPtNodesToBuffer)) {
@@ -539,7 +125,7 @@
     DynamicPatriciaTrieReadingHelper newDictReadingHelper(bufferToWrite, &newDictNodeReader);
     newDictReadingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
     DynamicPatriciaTrieGcEventListeners::TraversePolicyToUpdateAllPositionFields
-            traversePolicyToUpdateAllPositionFields(this, &newDictBigramPolicy, bufferToWrite,
+            traversePolicyToUpdateAllPositionFields(&newDictBigramPolicy, bufferToWrite,
                     &dictPositionRelocationMap);
     if (!newDictReadingHelper.traverseAllPtNodesInPtNodeArrayLevelPreorderDepthFirstManner(
             &traversePolicyToUpdateAllPositionFields)) {
@@ -550,14 +136,4 @@
     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/structure/v3/dynamic_patricia_trie_writing_helper.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h
index 5614cb3..7223dea 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v3/dynamic_patricia_trie_writing_helper.h
@@ -29,7 +29,8 @@
 class DynamicPatriciaTrieReadingHelper;
 class DynamicShortcutListPolicy;
 class HeaderPolicy;
-class PtNodeParams;
+class PtNodeReader;
+class PtNodeWriter;
 
 // TODO: Make it independent from a particular format and move to pt_common.
 class DynamicPatriciaTrieWritingHelper {
@@ -51,87 +52,34 @@
     static const size_t MAX_DICTIONARY_SIZE;
 
     DynamicPatriciaTrieWritingHelper(BufferWithExtendableBuffer *const buffer,
+            const PtNodeReader *const ptNodeReader, PtNodeWriter *const ptNodeWriter,
             DynamicBigramListPolicy *const bigramPolicy,
             DynamicShortcutListPolicy *const shortcutPolicy, const bool needsToDecay)
-            : mBuffer(buffer), mBigramPolicy(bigramPolicy), mShortcutPolicy(shortcutPolicy),
+            : mBuffer(buffer), mPtNodeReader(ptNodeReader), mPtNodeWriter(ptNodeWriter),
+              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 PtNodeParams *const toBeUpdatedPtNodeParams);
-
-    // CAVEAT: This method must be called only from this class or inner classes of
-    // DynamicPatriciaTrieGcEventListeners.
-    bool writePtNodeToBufferByCopyingPtNodeInfo(BufferWithExtendableBuffer *const bufferToWrite,
-            const PtNodeParams *const originalPtNodeParams, 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;
+    const PtNodeReader *const mPtNodeReader;
+    PtNodeWriter *const mPtNodeWriter;
     DynamicBigramListPolicy *const mBigramPolicy;
     DynamicShortcutListPolicy *const mShortcutPolicy;
     const bool mNeedsToDecay;
 
-    bool markNodeAsMovedAndSetPosition(const PtNodeParams *const toBeUpdatedPtNodeParams,
-            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 PtNodeParams *const originalPtNodeParams, const int probability,
-            bool *const outAddedNewUnigram);
-
-    bool createChildrenPtNodeArrayAndAChildPtNode(const PtNodeParams *const parentPtNodeParams,
-            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 PtNodeParams *const reallocatingPtNodeParams, 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 */