diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
index 167c691..c7b063d 100644
--- a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
@@ -145,21 +145,21 @@
      * Reads unigrams and bigrams from the binary file.
      * Doesn't make the memory representation of the dictionary.
      *
-     * @param buffer the buffer to read.
+     * @param reader the reader.
      * @param words the map to store the address as a key and the word as a value.
      * @param frequencies the map to store the address as a key and the frequency as a value.
      * @param bigrams the map to store the address as a key and the list of address as a value.
      * @throws IOException
      * @throws UnsupportedFormatException
      */
-    public static void readUnigramsAndBigramsBinary(final FusionDictionaryBufferInterface buffer,
+    public static void readUnigramsAndBigramsBinary(final BinaryDictReader reader,
             final Map<Integer, String> words, final Map<Integer, Integer> frequencies,
             final Map<Integer, ArrayList<PendingAttribute>> bigrams) throws IOException,
             UnsupportedFormatException {
         // Read header
-        final FileHeader header = BinaryDictInputOutput.readHeader(buffer);
-        readUnigramsAndBigramsBinaryInner(buffer, header.mHeaderSize, words, frequencies, bigrams,
-                header.mFormatOptions);
+        final FileHeader header = BinaryDictInputOutput.readHeader(reader.getBuffer());
+        readUnigramsAndBigramsBinaryInner(reader.getBuffer(), header.mHeaderSize, words,
+                frequencies, bigrams, header.mFormatOptions);
     }
 
     /**
diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictInputOutput.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictInputOutput.java
index e0874bb..504349a 100644
--- a/java/src/com/android/inputmethod/latin/makedict/BinaryDictInputOutput.java
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictInputOutput.java
@@ -66,6 +66,7 @@
         public void position(int newPosition);
         public void put(final byte b);
         public int limit();
+        @UsedForTesting
         public int capacity();
     }
 
@@ -1722,23 +1723,30 @@
      * FusionDictionary structure. The optional dict argument is an existing dictionary to
      * which words from the buffer should be added. If it is null, a new dictionary is created.
      *
-     * @param buffer the buffer to read.
+     * @param reader the reader.
      * @param dict an optional dictionary to add words to, or null.
      * @return the created (or merged) dictionary.
      */
     @UsedForTesting
-    public static FusionDictionary readDictionaryBinary(
-            final FusionDictionaryBufferInterface buffer, final FusionDictionary dict)
-                    throws IOException, UnsupportedFormatException {
+    public static FusionDictionary readDictionaryBinary(final BinaryDictReader reader,
+            final FusionDictionary dict) throws FileNotFoundException, IOException,
+            UnsupportedFormatException {
         // clear cache
         wordCache.clear();
 
+        // if the buffer has not been opened, open the buffer with bytebuffer.
+        if (reader.getBuffer() == null) reader.openBuffer(
+                new BinaryDictReader.FusionDictionaryBufferFromByteBufferFactory());
+        if (reader.getBuffer() == null) {
+            MakedictLog.e("Cannot open the buffer");
+        }
+
         // Read header
-        final FileHeader header = readHeader(buffer);
+        final FileHeader header = readHeader(reader.getBuffer());
 
         Map<Integer, Node> reverseNodeMapping = new TreeMap<Integer, Node>();
         Map<Integer, CharGroup> reverseGroupMapping = new TreeMap<Integer, CharGroup>();
-        final Node root = readNode(buffer, header.mHeaderSize, reverseNodeMapping,
+        final Node root = readNode(reader.getBuffer(), header.mHeaderSize, reverseNodeMapping,
                 reverseGroupMapping, header.mFormatOptions);
 
         FusionDictionary newDict = new FusionDictionary(root, header.mDictionaryOptions);
diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictReader.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictReader.java
new file mode 100644
index 0000000..57a5832
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictReader.java
@@ -0,0 +1,109 @@
+/*
+ * 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.
+ */
+
+package com.android.inputmethod.latin.makedict;
+
+import com.android.inputmethod.annotations.UsedForTesting;
+import com.android.inputmethod.latin.makedict.BinaryDictInputOutput.FusionDictionaryBufferInterface;
+import com.android.inputmethod.latin.utils.ByteArrayWrapper;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+
+public class BinaryDictReader {
+
+    public interface FusionDictionaryBufferFactory {
+        public FusionDictionaryBufferInterface getFusionDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException;
+    }
+
+    /**
+     * Creates FusionDictionaryBuffer from a ByteBuffer
+     */
+    public static final class FusionDictionaryBufferFromByteBufferFactory
+            implements FusionDictionaryBufferFactory {
+        @Override
+        public FusionDictionaryBufferInterface getFusionDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException {
+            FileInputStream inStream = null;
+            ByteBuffer buffer = null;
+            try {
+                inStream = new FileInputStream(file);
+                buffer = inStream.getChannel().map(FileChannel.MapMode.READ_ONLY,
+                        0, file.length());
+            } finally {
+                if (inStream != null) {
+                    inStream.close();
+                }
+            }
+            if (buffer != null) {
+                return new BinaryDictInputOutput.ByteBufferWrapper(buffer);
+            }
+            return null;
+        }
+    }
+
+    /**
+     * Creates FusionDictionaryBuffer from a byte array
+     */
+    public static final class FusionDictionaryBufferFromByteArrayFactory
+            implements FusionDictionaryBufferFactory {
+        @Override
+        public FusionDictionaryBufferInterface getFusionDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException {
+            FileInputStream inStream = null;
+            try {
+                inStream = new FileInputStream(file);
+                final byte[] array = new byte[(int) file.length()];
+                inStream.read(array);
+                return new ByteArrayWrapper(array);
+            } finally {
+                if (inStream != null) {
+                    inStream.close();
+                }
+            }
+        }
+    }
+
+    private final File mDictionaryBinaryFile;
+    private FusionDictionaryBufferInterface mFusionDictionaryBuffer;
+
+    public BinaryDictReader(final File file) {
+        mDictionaryBinaryFile = file;
+        mFusionDictionaryBuffer = null;
+    }
+
+    public void openBuffer(final FusionDictionaryBufferFactory factory)
+            throws FileNotFoundException, IOException {
+        mFusionDictionaryBuffer = factory.getFusionDictionaryBuffer(mDictionaryBinaryFile);
+    }
+
+    public FusionDictionaryBufferInterface getBuffer() {
+        return mFusionDictionaryBuffer;
+    }
+
+    @UsedForTesting
+    public FusionDictionaryBufferInterface openAndGetBuffer(
+            final FusionDictionaryBufferFactory factory)
+                    throws FileNotFoundException, IOException {
+        openBuffer(factory);
+        return getBuffer();
+    }
+}
diff --git a/java/src/com/android/inputmethod/latin/personalization/DynamicPredictionDictionaryBase.java b/java/src/com/android/inputmethod/latin/personalization/DynamicPredictionDictionaryBase.java
index a8600c0..065e00e 100644
--- a/java/src/com/android/inputmethod/latin/personalization/DynamicPredictionDictionaryBase.java
+++ b/java/src/com/android/inputmethod/latin/personalization/DynamicPredictionDictionaryBase.java
@@ -28,9 +28,9 @@
 import com.android.inputmethod.latin.LatinImeLogger;
 import com.android.inputmethod.latin.SuggestedWords.SuggestedWordInfo;
 import com.android.inputmethod.latin.WordComposer;
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
 import com.android.inputmethod.latin.settings.Settings;
-import com.android.inputmethod.latin.utils.ByteArrayWrapper;
 import com.android.inputmethod.latin.utils.CollectionUtils;
 import com.android.inputmethod.latin.utils.UserHistoryDictIOUtils;
 import com.android.inputmethod.latin.utils.UserHistoryDictIOUtils.BigramDictionaryInterface;
@@ -39,7 +39,6 @@
 import com.android.inputmethod.latin.utils.UserHistoryForgettingCurveUtils.ForgettingCurveParams;
 
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -234,27 +233,17 @@
         };
 
         // Load the dictionary from binary file
-        FileInputStream inStream = null;
+        final BinaryDictReader reader = new BinaryDictReader(
+                new File(getContext().getFilesDir(), fileName));
         try {
-            final File file = new File(getContext().getFilesDir(), fileName);
-            final byte[] buffer = new byte[(int)file.length()];
-            inStream = new FileInputStream(file);
-            inStream.read(buffer);
-            UserHistoryDictIOUtils.readDictionaryBinary(
-                    new ByteArrayWrapper(buffer), listener);
+            reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
+            UserHistoryDictIOUtils.readDictionaryBinary(reader, listener);
         } catch (FileNotFoundException e) {
             // This is an expected condition: we don't have a user history dictionary for this
             // language yet. It will be created sometime later.
         } catch (IOException e) {
             Log.e(TAG, "IOException on opening a bytebuffer", e);
         } finally {
-            if (inStream != null) {
-                try {
-                    inStream.close();
-                } catch (IOException e) {
-                    // do nothing
-                }
-            }
             if (PROFILE_SAVE_RESTORE) {
                 final long diff = System.currentTimeMillis() - now;
                 Log.d(TAG, "PROF: Load UserHistoryDictionary: "
diff --git a/java/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtils.java b/java/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtils.java
index d02f718..a0ad27c 100644
--- a/java/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtils.java
@@ -21,7 +21,7 @@
 import com.android.inputmethod.annotations.UsedForTesting;
 import com.android.inputmethod.latin.makedict.BinaryDictIOUtils;
 import com.android.inputmethod.latin.makedict.BinaryDictInputOutput;
-import com.android.inputmethod.latin.makedict.BinaryDictInputOutput.FusionDictionaryBufferInterface;
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
 import com.android.inputmethod.latin.makedict.FusionDictionary;
 import com.android.inputmethod.latin.makedict.FusionDictionary.Node;
@@ -118,13 +118,13 @@
     /**
      * Reads dictionary from file.
      */
-    public static void readDictionaryBinary(final FusionDictionaryBufferInterface buffer,
+    public static void readDictionaryBinary(final BinaryDictReader reader,
             final OnAddWordListener dict) {
         final Map<Integer, String> unigrams = CollectionUtils.newTreeMap();
         final Map<Integer, Integer> frequencies = CollectionUtils.newTreeMap();
         final Map<Integer, ArrayList<PendingAttribute>> bigrams = CollectionUtils.newTreeMap();
         try {
-            BinaryDictIOUtils.readUnigramsAndBigramsBinary(buffer, unigrams, frequencies,
+            BinaryDictIOUtils.readUnigramsAndBigramsBinary(reader, unigrams, frequencies,
                     bigrams);
         } catch (IOException e) {
             Log.e(TAG, "IO exception while reading file", e);
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOTests.java
index ef4ed33..e4b5ad2 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOTests.java
@@ -27,15 +27,13 @@
 import com.android.inputmethod.latin.makedict.FusionDictionary.CharGroup;
 import com.android.inputmethod.latin.makedict.FusionDictionary.Node;
 import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
-import com.android.inputmethod.latin.utils.ByteArrayWrapper;
 import com.android.inputmethod.latin.utils.CollectionUtils;
 
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.nio.ByteBuffer;
-import java.nio.channels.FileChannel;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -120,31 +118,13 @@
     /**
      * Makes new buffer according to BUFFER_TYPE.
      */
-    private FusionDictionaryBufferInterface getBuffer(final File file, final int bufferType) {
-        FileInputStream inStream = null;
-        try {
-            inStream = new FileInputStream(file);
-            if (bufferType == USE_BYTE_ARRAY) {
-                final byte[] array = new byte[(int)file.length()];
-                inStream.read(array);
-                return new ByteArrayWrapper(array);
-            } else if (bufferType == USE_BYTE_BUFFER){
-                final ByteBuffer buffer = inStream.getChannel().map(
-                        FileChannel.MapMode.READ_ONLY, 0, file.length());
-                return new BinaryDictInputOutput.ByteBufferWrapper(buffer);
-            }
-        } catch (IOException e) {
-            Log.e(TAG, "IOException while making buffer", e);
-        } finally {
-            if (inStream != null) {
-                try {
-                    inStream.close();
-                } catch (IOException e) {
-                    Log.e(TAG, "IOException while closing stream", e);
-                }
-            }
+    private void getBuffer(final BinaryDictReader reader, final int bufferType)
+            throws FileNotFoundException, IOException {
+        if (bufferType == USE_BYTE_BUFFER) {
+            reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteBufferFactory());
+        } else if (bufferType == USE_BYTE_ARRAY) {
+            reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
         }
-        return null;
     }
 
     /**
@@ -285,13 +265,14 @@
             final SparseArray<List<Integer>> bigrams, final Map<String, List<String>> shortcutMap,
             final int bufferType) {
         long now, diff = -1;
-        final FusionDictionaryBufferInterface buffer = getBuffer(file, bufferType);
-        assertNotNull(buffer);
+        final BinaryDictReader reader = new BinaryDictReader(file);
 
         FusionDictionary dict = null;
         try {
+            getBuffer(reader, bufferType);
+            assertNotNull(reader.getBuffer());
             now = System.currentTimeMillis();
-            dict = BinaryDictInputOutput.readDictionaryBinary(buffer, null);
+            dict = BinaryDictInputOutput.readDictionaryBinary(reader, null);
             diff  = System.currentTimeMillis() - now;
         } catch (IOException e) {
             Log.e(TAG, "IOException while reading dictionary", e);
@@ -421,11 +402,12 @@
         final Map<Integer, Integer> resultFreqs = CollectionUtils.newTreeMap();
 
         long now = -1, diff = -1;
-        final FusionDictionaryBufferInterface buffer = getBuffer(file, bufferType);
-        assertNotNull("Can't get buffer.", buffer);
+        final BinaryDictReader reader = new BinaryDictReader(file);
         try {
+            getBuffer(reader, bufferType);
+            assertNotNull("Can't get buffer.", reader.getBuffer());
             now = System.currentTimeMillis();
-            BinaryDictIOUtils.readUnigramsAndBigramsBinary(buffer, resultWords, resultFreqs,
+            BinaryDictIOUtils.readUnigramsAndBigramsBinary(reader, resultWords, resultFreqs,
                     resultBigrams);
             diff = System.currentTimeMillis() - now;
         } catch (IOException e) {
@@ -562,7 +544,16 @@
         addUnigrams(sWords.size(), dict, sWords, null /* shortcutMap */);
         timeWritingDictToFile(file, dict, VERSION3_WITH_DYNAMIC_UPDATE);
 
-        final FusionDictionaryBufferInterface buffer = getBuffer(file, USE_BYTE_ARRAY);
+        final BinaryDictReader reader = new BinaryDictReader(file);
+        FusionDictionaryBufferInterface buffer = null;
+        try {
+            buffer = reader.openAndGetBuffer(
+                    new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
+        } catch (IOException e) {
+            // ignore
+            Log.e(TAG, "IOException while opening the buffer", e);
+        }
+        assertNotNull("Can't get the buffer", buffer);
 
         try {
             // too long word
@@ -614,7 +605,16 @@
         addUnigrams(sWords.size(), dict, sWords, null /* shortcutMap */);
         timeWritingDictToFile(file, dict, VERSION3_WITH_DYNAMIC_UPDATE);
 
-        final FusionDictionaryBufferInterface buffer = getBuffer(file, USE_BYTE_ARRAY);
+        final BinaryDictReader reader = new BinaryDictReader(file);
+        FusionDictionaryBufferInterface buffer = null;
+        try {
+            buffer = reader.openAndGetBuffer(
+                    new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
+        } catch (IOException e) {
+            // ignore
+            Log.e(TAG, "IOException while opening the buffer", e);
+        }
+        assertNotNull("Can't get the buffer", buffer);
 
         try {
             MoreAsserts.assertNotEqual(FormatSpec.NOT_VALID_WORD,
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictReaderTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictReaderTests.java
new file mode 100644
index 0000000..5f6950a
--- /dev/null
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictReaderTests.java
@@ -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.
+ */
+
+package com.android.inputmethod.latin.makedict;
+
+import com.android.inputmethod.latin.makedict.BinaryDictInputOutput.FusionDictionaryBufferInterface;
+import com.android.inputmethod.latin.makedict.BinaryDictReader.FusionDictionaryBufferFactory;
+import com.android.inputmethod.latin.makedict.BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory;
+import com.android.inputmethod.latin.makedict.BinaryDictReader.FusionDictionaryBufferFromByteBufferFactory;
+
+import android.test.AndroidTestCase;
+import android.util.Log;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * Unit tests for BinaryDictReader
+ */
+public class BinaryDictReaderTests extends AndroidTestCase {
+    private static final String TAG = BinaryDictReaderTests.class.getSimpleName();
+
+    private final byte[] data = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+
+    // Utilities for testing
+    public void writeDataToFile(final File file) {
+        FileOutputStream outStream = null;
+        try {
+            outStream = new FileOutputStream(file);
+            outStream.write(data);
+        } catch (IOException e) {
+            fail ("Can't write data to the test file");
+        } finally {
+            if (outStream != null) {
+                try {
+                    outStream.close();
+                } catch (IOException e) {
+                    Log.e(TAG, "Failed to close the output stream", e);
+                }
+            }
+        }
+    }
+
+    @SuppressWarnings("null")
+    public void runTestOpenBuffer(final String testName,
+            final FusionDictionaryBufferFactory factory) {
+        File testFile = null;
+        try {
+            testFile = File.createTempFile(testName, ".tmp", getContext().getCacheDir());
+        } catch (IOException e) {
+            Log.e(TAG, "IOException while the creating temporary file", e);
+        }
+
+        assertNotNull(testFile);
+        final BinaryDictReader reader = new BinaryDictReader(testFile);
+        try {
+            reader.openBuffer(factory);
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to open the buffer", e);
+        }
+
+        writeDataToFile(testFile);
+
+        try {
+            reader.openBuffer(factory);
+        } catch (Exception e) {
+            Log.e(TAG, "Raised the exception while opening buffer", e);
+        }
+
+        assertEquals(testFile.length(), reader.getBuffer().capacity());
+    }
+
+    public void testOpenBufferWithByteBuffer() {
+        runTestOpenBuffer("testOpenBufferWithByteBuffer",
+                new FusionDictionaryBufferFromByteBufferFactory());
+    }
+
+    public void testOpenBufferWithByteArray() {
+        runTestOpenBuffer("testOpenBufferWithByteArray",
+                new FusionDictionaryBufferFromByteArrayFactory());
+    }
+
+    @SuppressWarnings("null")
+    public void runTestGetBuffer(final String testName,
+            final FusionDictionaryBufferFactory factory) {
+        File testFile = null;
+        try {
+            testFile = File.createTempFile(testName, ".tmp", getContext().getCacheDir());
+        } catch (IOException e) {
+            Log.e(TAG, "IOException while the creating temporary file", e);
+        }
+
+        final BinaryDictReader reader = new BinaryDictReader(testFile);
+
+        // the default return value of getBuffer() must be null.
+        assertNull("the default return value of getBuffer() is not null", reader.getBuffer());
+
+        writeDataToFile(testFile);
+        assertTrue(testFile.exists());
+        Log.d(TAG, "file length = " + testFile.length());
+
+        FusionDictionaryBufferInterface buffer = null;
+        try {
+            buffer = reader.openAndGetBuffer(factory);
+        } catch (IOException e) {
+            Log.e(TAG, "Failed to open and get the buffer", e);
+        }
+        assertNotNull("the buffer must not be null", buffer);
+
+        for (int i = 0; i < data.length; ++i) {
+            assertEquals(data[i], buffer.readUnsignedByte());
+        }
+    }
+
+    public void testGetBufferWithByteBuffer() {
+        runTestGetBuffer("testGetBufferWithByteBuffer",
+                new FusionDictionaryBufferFromByteBufferFactory());
+    }
+
+    public void testGetBufferWithByteArray() {
+        runTestGetBuffer("testGetBufferWithByteArray",
+                new FusionDictionaryBufferFromByteArrayFactory());
+    }
+}
diff --git a/tests/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtilsTests.java b/tests/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtilsTests.java
index b679839..ce62bf2 100644
--- a/tests/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/utils/UserHistoryDictIOUtilsTests.java
@@ -21,16 +21,15 @@
 import android.test.suitebuilder.annotation.LargeTest;
 import android.util.Log;
 
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FormatSpec;
 import com.android.inputmethod.latin.makedict.FusionDictionary;
 import com.android.inputmethod.latin.makedict.FusionDictionary.CharGroup;
 import com.android.inputmethod.latin.personalization.UserHistoryDictionaryBigramList;
-import com.android.inputmethod.latin.utils.ByteArrayWrapper;
 import com.android.inputmethod.latin.utils.UserHistoryDictIOUtils.BigramDictionaryInterface;
 import com.android.inputmethod.latin.utils.UserHistoryDictIOUtils.OnAddWordListener;
 
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -147,27 +146,15 @@
     }
 
     private void readDictFromFile(final File file, final OnAddWordListener listener) {
-        FileInputStream inStream = null;
-
+        final BinaryDictReader reader = new BinaryDictReader(file);
         try {
-            inStream = new FileInputStream(file);
-            final byte[] buffer = new byte[(int)file.length()];
-            inStream.read(buffer);
-
-            UserHistoryDictIOUtils.readDictionaryBinary(new ByteArrayWrapper(buffer), listener);
+            reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
         } catch (FileNotFoundException e) {
             Log.e(TAG, "file not found", e);
         } catch (IOException e) {
             Log.e(TAG, "IOException", e);
-        } finally {
-            if (inStream != null) {
-                try {
-                    inStream.close();
-                } catch (IOException e) {
-                    // do nothing
-                }
-            }
         }
+        UserHistoryDictIOUtils.readDictionaryBinary(reader, listener);
     }
 
     public void testGenerateFusionDictionary() {
diff --git a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
index c2c77d6..d0b460a 100644
--- a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
+++ b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
@@ -17,6 +17,7 @@
 package com.android.inputmethod.latin.dicttool;
 
 import com.android.inputmethod.latin.makedict.BinaryDictInputOutput;
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FusionDictionary;
 import com.android.inputmethod.latin.makedict.UnsupportedFormatException;
 
@@ -185,16 +186,15 @@
                     crash(filename, new RuntimeException(
                             filename + " does not seem to be a dictionary file"));
                 } else {
-                    final FileInputStream inStream = new FileInputStream(decodedSpec.mFile);
-                    final ByteBuffer buffer = inStream.getChannel().map(
-                            FileChannel.MapMode.READ_ONLY, 0, decodedSpec.mFile.length());
+                    final BinaryDictReader reader = new BinaryDictReader(decodedSpec.mFile);
+                    reader.openBuffer(
+                            new BinaryDictReader.FusionDictionaryBufferFromByteArrayFactory());
                     if (report) {
                         System.out.println("Format : Binary dictionary format");
                         System.out.println("Packaging : " + decodedSpec.describeChain());
                         System.out.println("Uncompressed size : " + decodedSpec.mFile.length());
                     }
-                    return BinaryDictInputOutput.readDictionaryBinary(
-                            new BinaryDictInputOutput.ByteBufferWrapper(buffer), null);
+                    return BinaryDictInputOutput.readDictionaryBinary(reader, null);
                 }
             }
         } catch (IOException e) {
diff --git a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
index cc890f6..9bce988 100644
--- a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
+++ b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
@@ -17,6 +17,7 @@
 package com.android.inputmethod.latin.dicttool;
 
 import com.android.inputmethod.latin.makedict.BinaryDictInputOutput;
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FormatSpec;
 import com.android.inputmethod.latin.makedict.FusionDictionary;
 import com.android.inputmethod.latin.makedict.MakedictLog;
@@ -265,24 +266,10 @@
      */
     private static FusionDictionary readBinaryFile(final String binaryFilename)
             throws FileNotFoundException, IOException, UnsupportedFormatException {
-        FileInputStream inStream = null;
-
-        try {
-            final File file = new File(binaryFilename);
-            inStream = new FileInputStream(file);
-            final ByteBuffer buffer = inStream.getChannel().map(
-                    FileChannel.MapMode.READ_ONLY, 0, file.length());
-            return BinaryDictInputOutput.readDictionaryBinary(
-                    new BinaryDictInputOutput.ByteBufferWrapper(buffer), null);
-        } finally {
-            if (inStream != null) {
-                try {
-                    inStream.close();
-                } catch (IOException e) {
-                    // do nothing
-                }
-            }
-        }
+        final File file = new File(binaryFilename);
+        final BinaryDictReader reader = new BinaryDictReader(file);
+        reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteBufferFactory());
+        return BinaryDictInputOutput.readDictionaryBinary(reader, null);
     }
 
     /**
diff --git a/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java b/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
index 554bd24..fb1cc84 100644
--- a/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
+++ b/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
@@ -17,6 +17,7 @@
 package com.android.inputmethod.latin.dicttool;
 
 import com.android.inputmethod.latin.makedict.BinaryDictInputOutput;
+import com.android.inputmethod.latin.makedict.BinaryDictReader;
 import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
 import com.android.inputmethod.latin.makedict.FusionDictionary;
 import com.android.inputmethod.latin.makedict.FusionDictionary.DictionaryOptions;
@@ -69,11 +70,9 @@
             assertEquals("Wrong decode spec", BinaryDictOffdeviceUtils.COMPRESSION, step);
         }
         assertEquals("Wrong decode spec", 3, decodeSpec.mDecoderSpec.size());
-        final FileInputStream inStream = new FileInputStream(decodeSpec.mFile);
-        final ByteBuffer buffer = inStream.getChannel().map(
-                FileChannel.MapMode.READ_ONLY, 0, decodeSpec.mFile.length());
-        final FusionDictionary resultDict = BinaryDictInputOutput.readDictionaryBinary(
-                new BinaryDictInputOutput.ByteBufferWrapper(buffer),
+        final BinaryDictReader reader = new BinaryDictReader(decodeSpec.mFile);
+        reader.openBuffer(new BinaryDictReader.FusionDictionaryBufferFromByteBufferFactory());
+        final FusionDictionary resultDict = BinaryDictInputOutput.readDictionaryBinary(reader,
                 null /* dict : an optional dictionary to add words to, or null */);
         assertEquals("Dictionary can't be read back correctly",
                 resultDict.findWordInTree(resultDict.mRoot, "foo").getFrequency(), TEST_FREQ);