Merge remote-tracking branch 'goog/master' into mergescriptpackage

Conflicts:
	java/res/values-ca/strings.xml
	java/res/values-cs/strings.xml
	java/res/values-de/strings.xml
	java/res/values-es/strings.xml
	java/res/values-hr/strings.xml
	java/res/values-hu/strings.xml
	java/res/values-it/strings.xml
	java/res/values-lv/strings.xml
	java/res/values-nb/strings.xml
	java/res/values-nl/strings.xml
	java/res/values-pl/strings.xml
	java/res/values-pt/strings.xml
	java/res/values-ro/strings.xml
	java/res/values-ru/strings.xml
	java/res/values-sv/strings.xml
	java/res/values-sw/strings.xml
	java/res/values-tr/strings.xml
	java/res/values-uk/strings.xml
	java/res/values-zh-rCN/strings.xml
	java/res/values-zh-rTW/strings.xml
	java/src/com/android/inputmethod/latin/RichInputConnection.java

Change-Id: Iba00dd5b86cb16d72968bc7e40d75853845b6dcb

1 files changed, 816 insertions, 29 deletions

diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
index 7a1b9dcb7..ee0e9cd7e 100644
--- a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
@@ -16,21 +16,34 @@
 
 package com.android.inputmethod.latin.makedict;
 
+import com.android.inputmethod.annotations.UsedForTesting;
 import com.android.inputmethod.latin.Constants;
+import com.android.inputmethod.latin.makedict.BinaryDictInputOutput.CharEncoding;
 import com.android.inputmethod.latin.makedict.BinaryDictInputOutput.FusionDictionaryBufferInterface;
 import com.android.inputmethod.latin.makedict.FormatSpec.FileHeader;
 import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
 import com.android.inputmethod.latin.makedict.FusionDictionary.CharGroup;
+import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
 
 import java.io.IOException;
+import java.io.OutputStream;
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.Stack;
 
-public class BinaryDictIOUtils {
+public final class BinaryDictIOUtils {
     private static final boolean DBG = false;
+    private static final int MSB24 = 0x800000;
+    private static final int SINT24_MAX = 0x7FFFFF;
+    private static final int MAX_JUMPS = 10000;
 
-    private static class Position {
+    private BinaryDictIOUtils() {
+        // This utility class is not publicly instantiable.
+    }
+
+    private static final class Position {
         public static final int NOT_READ_GROUPCOUNT = -1;
 
         public int mAddress;
@@ -77,7 +90,10 @@ public class BinaryDictIOUtils {
                 p.mAddress += BinaryDictInputOutput.getGroupCountSize(p.mNumOfCharGroup);
                 p.mPosition = 0;
             }
-
+            if (p.mNumOfCharGroup == 0) {
+                stack.pop();
+                continue;
+            }
             CharGroupInfo info = BinaryDictInputOutput.readCharGroup(buffer,
                     p.mAddress - headerSize, formatOptions);
             for (int i = 0; i < info.mCharacters.length; ++i) {
@@ -85,20 +101,36 @@ public class BinaryDictIOUtils {
             }
             p.mPosition++;
 
-            if (info.mFrequency != FusionDictionary.CharGroup.NOT_A_TERMINAL) { // found word
+            final boolean isMovedGroup = BinaryDictInputOutput.isMovedGroup(info.mFlags,
+                    formatOptions);
+            final boolean isDeletedGroup = BinaryDictInputOutput.isDeletedGroup(info.mFlags,
+                    formatOptions);
+            if (!isMovedGroup && !isDeletedGroup
+                    && info.mFrequency != FusionDictionary.CharGroup.NOT_A_TERMINAL) {// found word
                 words.put(info.mOriginalAddress, new String(pushedChars, 0, index));
                 frequencies.put(info.mOriginalAddress, info.mFrequency);
                 if (info.mBigrams != null) bigrams.put(info.mOriginalAddress, info.mBigrams);
             }
 
             if (p.mPosition == p.mNumOfCharGroup) {
-                stack.pop();
+                if (formatOptions.mSupportsDynamicUpdate) {
+                    final int forwardLinkAddress = buffer.readUnsignedInt24();
+                    if (forwardLinkAddress != FormatSpec.NO_FORWARD_LINK_ADDRESS) {
+                        // the node has a forward link.
+                        p.mNumOfCharGroup = Position.NOT_READ_GROUPCOUNT;
+                        p.mAddress = forwardLinkAddress;
+                    } else {
+                        stack.pop();
+                    }
+                } else {
+                    stack.pop();
+                }
             } else {
                 // the node has more groups.
                 p.mAddress = buffer.position();
             }
 
-            if (BinaryDictInputOutput.hasChildrenAddress(info.mChildrenAddress)) {
+            if (!isMovedGroup && BinaryDictInputOutput.hasChildrenAddress(info.mChildrenAddress)) {
                 Position childrenPos = new Position(info.mChildrenAddress + headerSize, index);
                 stack.push(childrenPos);
             }
@@ -136,6 +168,7 @@ public class BinaryDictIOUtils {
      * @throws IOException
      * @throws UnsupportedFormatException
      */
+    @UsedForTesting
     public static int getTerminalPosition(final FusionDictionaryBufferInterface buffer,
             final String word) throws IOException, UnsupportedFormatException {
         if (word == null) return FormatSpec.NOT_VALID_WORD;
@@ -146,48 +179,802 @@ public class BinaryDictIOUtils {
         final int wordLen = word.codePointCount(0, word.length());
         for (int depth = 0; depth < Constants.Dictionary.MAX_WORD_LENGTH; ++depth) {
             if (wordPos >= wordLen) return FormatSpec.NOT_VALID_WORD;
-            int groupOffset = buffer.position() - header.mHeaderSize;
+
+            do {
+                final int charGroupCount = BinaryDictInputOutput.readCharGroupCount(buffer);
+                boolean foundNextCharGroup = false;
+                for (int i = 0; i < charGroupCount; ++i) {
+                    final int charGroupPos = buffer.position();
+                    final CharGroupInfo currentInfo = BinaryDictInputOutput.readCharGroup(buffer,
+                            buffer.position(), header.mFormatOptions);
+                    final boolean isMovedGroup =
+                            BinaryDictInputOutput.isMovedGroup(currentInfo.mFlags,
+                                    header.mFormatOptions);
+                    final boolean isDeletedGroup =
+                            BinaryDictInputOutput.isDeletedGroup(currentInfo.mFlags,
+                                    header.mFormatOptions);
+                    if (isMovedGroup) continue;
+                    boolean same = true;
+                    for (int p = 0, j = word.offsetByCodePoints(0, wordPos);
+                            p < currentInfo.mCharacters.length;
+                            ++p, j = word.offsetByCodePoints(j, 1)) {
+                        if (wordPos + p >= wordLen
+                                || word.codePointAt(j) != currentInfo.mCharacters[p]) {
+                            same = false;
+                            break;
+                        }
+                    }
+
+                    if (same) {
+                        // found the group matches the word.
+                        if (wordPos + currentInfo.mCharacters.length == wordLen) {
+                            if (currentInfo.mFrequency == CharGroup.NOT_A_TERMINAL
+                                    || isDeletedGroup) {
+                                return FormatSpec.NOT_VALID_WORD;
+                            } else {
+                                return charGroupPos;
+                            }
+                        }
+                        wordPos += currentInfo.mCharacters.length;
+                        if (currentInfo.mChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS) {
+                            return FormatSpec.NOT_VALID_WORD;
+                        }
+                        foundNextCharGroup = true;
+                        buffer.position(currentInfo.mChildrenAddress);
+                        break;
+                    }
+                }
+
+                // If we found the next char group, it is under the file pointer.
+                // But if not, we are at the end of this node so we expect to have
+                // a forward link address that we need to consult and possibly resume
+                // search on the next node in the linked list.
+                if (foundNextCharGroup) break;
+                if (!header.mFormatOptions.mSupportsDynamicUpdate) {
+                    return FormatSpec.NOT_VALID_WORD;
+                }
+
+                final int forwardLinkAddress = buffer.readUnsignedInt24();
+                if (forwardLinkAddress == FormatSpec.NO_FORWARD_LINK_ADDRESS) {
+                    return FormatSpec.NOT_VALID_WORD;
+                }
+                buffer.position(forwardLinkAddress);
+            } while(true);
+        }
+        return FormatSpec.NOT_VALID_WORD;
+    }
+
+    private static int markAsDeleted(final int flags) {
+        return (flags & (~FormatSpec.MASK_GROUP_ADDRESS_TYPE)) | FormatSpec.FLAG_IS_DELETED;
+    }
+
+    /**
+     * Delete the word from the binary file.
+     *
+     * @param buffer the buffer to write.
+     * @param word the word we delete
+     * @throws IOException
+     * @throws UnsupportedFormatException
+     */
+    @UsedForTesting
+    public static void deleteWord(final FusionDictionaryBufferInterface buffer,
+            final String word) throws IOException, UnsupportedFormatException {
+        buffer.position(0);
+        final FileHeader header = BinaryDictInputOutput.readHeader(buffer);
+        final int wordPosition = getTerminalPosition(buffer, word);
+        if (wordPosition == FormatSpec.NOT_VALID_WORD) return;
+
+        buffer.position(wordPosition);
+        final int flags = buffer.readUnsignedByte();
+        buffer.position(wordPosition);
+        buffer.put((byte)markAsDeleted(flags));
+    }
+
+    /**
+     * @return the size written, in bytes. Always 3 bytes.
+     */
+    private static int writeSInt24ToBuffer(final FusionDictionaryBufferInterface buffer,
+            final int value) {
+        final int absValue = Math.abs(value);
+        buffer.put((byte)(((value < 0 ? 0x80 : 0) | (absValue >> 16)) & 0xFF));
+        buffer.put((byte)((absValue >> 8) & 0xFF));
+        buffer.put((byte)(absValue & 0xFF));
+        return 3;
+    }
+
+    /**
+     * @return the size written, in bytes. Always 3 bytes.
+     */
+    private static int writeSInt24ToStream(final OutputStream destination, final int value)
+            throws IOException {
+        final int absValue = Math.abs(value);
+        destination.write((byte)(((value < 0 ? 0x80 : 0) | (absValue >> 16)) & 0xFF));
+        destination.write((byte)((absValue >> 8) & 0xFF));
+        destination.write((byte)(absValue & 0xFF));
+        return 3;
+    }
+
+    /**
+     * @return the size written, in bytes. 1, 2, or 3 bytes.
+     */
+    private static int writeVariableAddress(final OutputStream destination, final int value)
+            throws IOException {
+        switch (BinaryDictInputOutput.getByteSize(value)) {
+        case 1:
+            destination.write((byte)value);
+            break;
+        case 2:
+            destination.write((byte)(0xFF & (value >> 8)));
+            destination.write((byte)(0xFF & value));
+            break;
+        case 3:
+            destination.write((byte)(0xFF & (value >> 16)));
+            destination.write((byte)(0xFF & (value >> 8)));
+            destination.write((byte)(0xFF & value));
+            break;
+        }
+        return BinaryDictInputOutput.getByteSize(value);
+    }
+
+    /**
+     * Update a parent address in a CharGroup that is referred to by groupOriginAddress.
+     *
+     * @param buffer the buffer to write.
+     * @param groupOriginAddress the address of the group.
+     * @param newParentAddress the absolute address of the parent.
+     * @param formatOptions file format options.
+     */
+    public static void updateParentAddress(final FusionDictionaryBufferInterface buffer,
+            final int groupOriginAddress, final int newParentAddress,
+            final FormatOptions formatOptions) {
+        final int originalPosition = buffer.position();
+        buffer.position(groupOriginAddress);
+        if (!formatOptions.mSupportsDynamicUpdate) {
+            throw new RuntimeException("this file format does not support parent addresses");
+        }
+        final int flags = buffer.readUnsignedByte();
+        if (BinaryDictInputOutput.isMovedGroup(flags, formatOptions)) {
+            // if the group is moved, the parent address is stored in the destination group.
+            // We are guaranteed to process the destination group later, so there is no need to
+            // update anything here.
+            buffer.position(originalPosition);
+            return;
+        }
+        if (DBG) {
+            MakedictLog.d("update parent address flags=" + flags + ", " + groupOriginAddress);
+        }
+        final int parentOffset = newParentAddress - groupOriginAddress;
+        writeSInt24ToBuffer(buffer, parentOffset);
+        buffer.position(originalPosition);
+    }
+
+    private static void skipCharGroup(final FusionDictionaryBufferInterface buffer,
+            final FormatOptions formatOptions) {
+        final int flags = buffer.readUnsignedByte();
+        BinaryDictInputOutput.readParentAddress(buffer, formatOptions);
+        skipString(buffer, (flags & FormatSpec.FLAG_HAS_MULTIPLE_CHARS) != 0);
+        BinaryDictInputOutput.readChildrenAddress(buffer, flags, formatOptions);
+        if ((flags & FormatSpec.FLAG_IS_TERMINAL) != 0) buffer.readUnsignedByte();
+        if ((flags & FormatSpec.FLAG_HAS_SHORTCUT_TARGETS) != 0) {
+            final int shortcutsSize = buffer.readUnsignedShort();
+            buffer.position(buffer.position() + shortcutsSize
+                    - FormatSpec.GROUP_SHORTCUT_LIST_SIZE_SIZE);
+        }
+        if ((flags & FormatSpec.FLAG_HAS_BIGRAMS) != 0) {
+            int bigramCount = 0;
+            while (bigramCount++ < FormatSpec.MAX_BIGRAMS_IN_A_GROUP) {
+                final int bigramFlags = buffer.readUnsignedByte();
+                switch (bigramFlags & FormatSpec.MASK_ATTRIBUTE_ADDRESS_TYPE) {
+                    case FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE:
+                        buffer.readUnsignedByte();
+                        break;
+                    case FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES:
+                        buffer.readUnsignedShort();
+                        break;
+                    case FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES:
+                        buffer.readUnsignedInt24();
+                        break;
+                }
+                if ((bigramFlags & FormatSpec.FLAG_ATTRIBUTE_HAS_NEXT) == 0) break;
+            }
+            if (bigramCount >= FormatSpec.MAX_BIGRAMS_IN_A_GROUP) {
+                throw new RuntimeException("Too many bigrams in a group.");
+            }
+        }
+    }
+
+    /**
+     * Update parent addresses in a Node that is referred to by nodeOriginAddress.
+     *
+     * @param buffer the buffer to be modified.
+     * @param nodeOriginAddress the address of a modified Node.
+     * @param newParentAddress the address to be written.
+     * @param formatOptions file format options.
+     */
+    public static void updateParentAddresses(final FusionDictionaryBufferInterface buffer,
+            final int nodeOriginAddress, final int newParentAddress,
+            final FormatOptions formatOptions) {
+        final int originalPosition = buffer.position();
+        buffer.position(nodeOriginAddress);
+        do {
+            final int count = BinaryDictInputOutput.readCharGroupCount(buffer);
+            for (int i = 0; i < count; ++i) {
+                updateParentAddress(buffer, buffer.position(), newParentAddress, formatOptions);
+                skipCharGroup(buffer, formatOptions);
+            }
+            final int forwardLinkAddress = buffer.readUnsignedInt24();
+            buffer.position(forwardLinkAddress);
+        } while (formatOptions.mSupportsDynamicUpdate
+                && buffer.position() != FormatSpec.NO_FORWARD_LINK_ADDRESS);
+        buffer.position(originalPosition);
+    }
+
+    private static void skipString(final FusionDictionaryBufferInterface buffer,
+            final boolean hasMultipleChars) {
+        if (hasMultipleChars) {
+            int character = CharEncoding.readChar(buffer);
+            while (character != FormatSpec.INVALID_CHARACTER) {
+                character = CharEncoding.readChar(buffer);
+            }
+        } else {
+            CharEncoding.readChar(buffer);
+        }
+    }
+
+    /**
+     * Write a string to a stream.
+     *
+     * @param destination the stream to write.
+     * @param word the string to be written.
+     * @return the size written, in bytes.
+     * @throws IOException
+     */
+    private static int writeString(final OutputStream destination, final String word)
+            throws IOException {
+        int size = 0;
+        final int length = word.length();
+        for (int i = 0; i < length; i = word.offsetByCodePoints(i, 1)) {
+            final int codePoint = word.codePointAt(i);
+            if (CharEncoding.getCharSize(codePoint) == 1) {
+                destination.write((byte)codePoint);
+                size++;
+            } else {
+                destination.write((byte)(0xFF & (codePoint >> 16)));
+                destination.write((byte)(0xFF & (codePoint >> 8)));
+                destination.write((byte)(0xFF & codePoint));
+                size += 3;
+            }
+        }
+        destination.write((byte)FormatSpec.GROUP_CHARACTERS_TERMINATOR);
+        size += FormatSpec.GROUP_TERMINATOR_SIZE;
+        return size;
+    }
+
+    /**
+     * Update a children address in a CharGroup that is addressed by groupOriginAddress.
+     *
+     * @param buffer the buffer to write.
+     * @param groupOriginAddress the address of the group.
+     * @param newChildrenAddress the absolute address of the child.
+     * @param formatOptions file format options.
+     */
+    public static void updateChildrenAddress(final FusionDictionaryBufferInterface buffer,
+            final int groupOriginAddress, final int newChildrenAddress,
+            final FormatOptions formatOptions) {
+        final int originalPosition = buffer.position();
+        buffer.position(groupOriginAddress);
+        final int flags = buffer.readUnsignedByte();
+        final int parentAddress = BinaryDictInputOutput.readParentAddress(buffer, formatOptions);
+        skipString(buffer, (flags & FormatSpec.FLAG_HAS_MULTIPLE_CHARS) != 0);
+        if ((flags & FormatSpec.FLAG_IS_TERMINAL) != 0) buffer.readUnsignedByte();
+        final int childrenOffset = newChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS
+                ? FormatSpec.NO_CHILDREN_ADDRESS : newChildrenAddress - buffer.position();
+        writeSInt24ToBuffer(buffer, childrenOffset);
+        buffer.position(originalPosition);
+    }
+
+    /**
+     * Write a char group to an output stream.
+     * A char group is an in-memory representation of a node in trie.
+     * A char group info is an on-disk representation of a node.
+     *
+     * @param destination the stream to write.
+     * @param info the char group info to be written.
+     * @return the size written, in bytes.
+     */
+    public static int writeCharGroup(final OutputStream destination, final CharGroupInfo info)
+            throws IOException {
+        int size = FormatSpec.GROUP_FLAGS_SIZE;
+        destination.write((byte)info.mFlags);
+        final int parentOffset = info.mParentAddress == FormatSpec.NO_PARENT_ADDRESS ?
+                FormatSpec.NO_PARENT_ADDRESS : info.mParentAddress - info.mOriginalAddress;
+        size += writeSInt24ToStream(destination, parentOffset);
+
+        for (int i = 0; i < info.mCharacters.length; ++i) {
+            if (CharEncoding.getCharSize(info.mCharacters[i]) == 1) {
+                destination.write((byte)info.mCharacters[i]);
+                size++;
+            } else {
+                size += writeSInt24ToStream(destination, info.mCharacters[i]);
+            }
+        }
+        if (info.mCharacters.length > 1) {
+            destination.write((byte)FormatSpec.GROUP_CHARACTERS_TERMINATOR);
+            size++;
+        }
+
+        if ((info.mFlags & FormatSpec.FLAG_IS_TERMINAL) != 0) {
+            destination.write((byte)info.mFrequency);
+            size++;
+        }
+
+        if (DBG) {
+            MakedictLog.d("writeCharGroup origin=" + info.mOriginalAddress + ", size=" + size
+                    + ", child=" + info.mChildrenAddress + ", characters ="
+                    + new String(info.mCharacters, 0, info.mCharacters.length));
+        }
+        final int childrenOffset = info.mChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS ?
+                0 : info.mChildrenAddress - (info.mOriginalAddress + size);
+        writeSInt24ToStream(destination, childrenOffset);
+        size += FormatSpec.SIGNED_CHILDREN_ADDRESS_SIZE;
+
+        if (info.mShortcutTargets != null && info.mShortcutTargets.size() > 0) {
+            final int shortcutListSize =
+                    BinaryDictInputOutput.getShortcutListSize(info.mShortcutTargets);
+            destination.write((byte)(shortcutListSize >> 8));
+            destination.write((byte)(shortcutListSize & 0xFF));
+            size += 2;
+            final Iterator<WeightedString> shortcutIterator = info.mShortcutTargets.iterator();
+            while (shortcutIterator.hasNext()) {
+                final WeightedString target = shortcutIterator.next();
+                destination.write((byte)BinaryDictInputOutput.makeShortcutFlags(
+                        shortcutIterator.hasNext(), target.mFrequency));
+                size++;
+                size += writeString(destination, target.mWord);
+            }
+        }
+
+        if (info.mBigrams != null) {
+            // TODO: Consolidate this code with the code that computes the size of the bigram list
+            //        in BinaryDictionaryInputOutput#computeActualNodeSize
+            for (int i = 0; i < info.mBigrams.size(); ++i) {
+
+                final int bigramFrequency = info.mBigrams.get(i).mFrequency;
+                int bigramFlags = (i < info.mBigrams.size() - 1)
+                        ? FormatSpec.FLAG_ATTRIBUTE_HAS_NEXT : 0;
+                size++;
+                final int bigramOffset = info.mBigrams.get(i).mAddress - (info.mOriginalAddress
+                        + size);
+                bigramFlags |= (bigramOffset < 0) ? FormatSpec.FLAG_ATTRIBUTE_OFFSET_NEGATIVE : 0;
+                switch (BinaryDictInputOutput.getByteSize(bigramOffset)) {
+                case 1:
+                    bigramFlags |= FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_ONEBYTE;
+                    break;
+                case 2:
+                    bigramFlags |= FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES;
+                    break;
+                case 3:
+                    bigramFlags |= FormatSpec.FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES;
+                    break;
+                }
+                bigramFlags |= bigramFrequency & FormatSpec.FLAG_ATTRIBUTE_FREQUENCY;
+                destination.write((byte)bigramFlags);
+                size += writeVariableAddress(destination, Math.abs(bigramOffset));
+            }
+        }
+        return size;
+    }
+
+    @SuppressWarnings("unused")
+    private static void updateForwardLink(final FusionDictionaryBufferInterface buffer,
+            final int nodeOriginAddress, final int newNodeAddress,
+            final FormatOptions formatOptions) {
+        buffer.position(nodeOriginAddress);
+        int jumpCount = 0;
+        while (jumpCount++ < MAX_JUMPS) {
+            final int count = BinaryDictInputOutput.readCharGroupCount(buffer);
+            for (int i = 0; i < count; ++i) skipCharGroup(buffer, formatOptions);
+            final int forwardLinkAddress = buffer.readUnsignedInt24();
+            if (forwardLinkAddress == FormatSpec.NO_FORWARD_LINK_ADDRESS) {
+                buffer.position(buffer.position() - FormatSpec.FORWARD_LINK_ADDRESS_SIZE);
+                writeSInt24ToBuffer(buffer, newNodeAddress);
+                return;
+            }
+            buffer.position(forwardLinkAddress);
+        }
+        if (DBG && jumpCount >= MAX_JUMPS) {
+            throw new RuntimeException("too many jumps, probably a bug.");
+        }
+    }
+
+    /**
+     * Helper method to move a char group to the tail of the file.
+     */
+    private static int moveCharGroup(final OutputStream destination,
+            final FusionDictionaryBufferInterface buffer, final CharGroupInfo info,
+            final int nodeOriginAddress, final int oldGroupAddress,
+            final FormatOptions formatOptions) throws IOException {
+        updateParentAddress(buffer, oldGroupAddress, buffer.limit() + 1, formatOptions);
+        buffer.position(oldGroupAddress);
+        final int currentFlags = buffer.readUnsignedByte();
+        buffer.position(oldGroupAddress);
+        buffer.put((byte)(FormatSpec.FLAG_IS_MOVED | (currentFlags
+                & (~FormatSpec.MASK_MOVE_AND_DELETE_FLAG))));
+        int size = FormatSpec.GROUP_FLAGS_SIZE;
+        updateForwardLink(buffer, nodeOriginAddress, buffer.limit(), formatOptions);
+        size += writeNode(destination, new CharGroupInfo[] { info });
+        return size;
+    }
+
+    /**
+     * Compute the size of the char group.
+     */
+    private static int computeGroupSize(final CharGroupInfo info,
+            final FormatOptions formatOptions) {
+        int size = FormatSpec.GROUP_FLAGS_SIZE + FormatSpec.PARENT_ADDRESS_SIZE
+                + BinaryDictInputOutput.getGroupCharactersSize(info.mCharacters)
+                + BinaryDictInputOutput.getChildrenAddressSize(info.mFlags, formatOptions);
+        if ((info.mFlags & FormatSpec.FLAG_IS_TERMINAL) != 0) {
+            size += FormatSpec.GROUP_FREQUENCY_SIZE;
+        }
+        if (info.mShortcutTargets != null && !info.mShortcutTargets.isEmpty()) {
+            size += BinaryDictInputOutput.getShortcutListSize(info.mShortcutTargets);
+        }
+        if (info.mBigrams != null) {
+            for (final PendingAttribute attr : info.mBigrams) {
+                size += FormatSpec.GROUP_FLAGS_SIZE;
+                size += BinaryDictInputOutput.getByteSize(attr.mAddress);
+            }
+        }
+        return size;
+    }
+
+    /**
+     * Write a node to the stream.
+     *
+     * @param destination the stream to write.
+     * @param infos groups to be written.
+     * @return the size written, in bytes.
+     * @throws IOException
+     */
+    private static int writeNode(final OutputStream destination, final CharGroupInfo[] infos)
+            throws IOException {
+        int size = BinaryDictInputOutput.getGroupCountSize(infos.length);
+        switch (BinaryDictInputOutput.getGroupCountSize(infos.length)) {
+            case 1:
+                destination.write((byte)infos.length);
+                break;
+            case 2:
+                destination.write((byte)(infos.length >> 8));
+                destination.write((byte)(infos.length & 0xFF));
+                break;
+            default:
+                throw new RuntimeException("Invalid group count size.");
+        }
+        for (final CharGroupInfo info : infos) size += writeCharGroup(destination, info);
+        writeSInt24ToStream(destination, FormatSpec.NO_FORWARD_LINK_ADDRESS);
+        return size + FormatSpec.FORWARD_LINK_ADDRESS_SIZE;
+    }
+
+    /**
+     * Move a group that is referred to by oldGroupOrigin to the tail of the file.
+     * And set the children address to the byte after the group.
+     *
+     * @param nodeOrigin the address of the tail of the file.
+     * @param characters
+     * @param length
+     * @param flags
+     * @param frequency
+     * @param parentAddress
+     * @param shortcutTargets
+     * @param bigrams
+     * @param destination the stream representing the tail of the file.
+     * @param buffer the buffer representing the (constant-size) body of the file.
+     * @param oldNodeOrigin
+     * @param oldGroupOrigin
+     * @param formatOptions
+     * @return the size written, in bytes.
+     * @throws IOException
+     */
+    private static int moveGroup(final int nodeOrigin, final int[] characters, final int length,
+            final int flags, final int frequency, final int parentAddress,
+            final ArrayList<WeightedString> shortcutTargets,
+            final ArrayList<PendingAttribute> bigrams, final OutputStream destination,
+            final FusionDictionaryBufferInterface buffer, final int oldNodeOrigin,
+            final int oldGroupOrigin, final FormatOptions formatOptions) throws IOException {
+        int size = 0;
+        final int newGroupOrigin = nodeOrigin + 1;
+        final int[] writtenCharacters = Arrays.copyOfRange(characters, 0, length);
+        final CharGroupInfo tmpInfo = new CharGroupInfo(newGroupOrigin, -1 /* endAddress */,
+                flags, writtenCharacters, frequency, parentAddress, FormatSpec.NO_CHILDREN_ADDRESS,
+                shortcutTargets, bigrams);
+        size = computeGroupSize(tmpInfo, formatOptions);
+        final CharGroupInfo newInfo = new CharGroupInfo(newGroupOrigin, newGroupOrigin + size,
+                flags, writtenCharacters, frequency, parentAddress,
+                nodeOrigin + 1 + size + FormatSpec.FORWARD_LINK_ADDRESS_SIZE, shortcutTargets,
+                bigrams);
+        moveCharGroup(destination, buffer, newInfo, oldNodeOrigin, oldGroupOrigin, formatOptions);
+        return 1 + size + FormatSpec.FORWARD_LINK_ADDRESS_SIZE;
+    }
+
+    /**
+     * Insert a word into a binary dictionary.
+     *
+     * @param buffer
+     * @param destination
+     * @param word
+     * @param frequency
+     * @param bigramStrings
+     * @param shortcuts
+     * @throws IOException
+     * @throws UnsupportedFormatException
+     */
+    // TODO: Support batch insertion.
+    // TODO: Remove @UsedForTesting once UserHistoryDictionary is implemented by BinaryDictionary.
+    @UsedForTesting
+    public static void insertWord(final FusionDictionaryBufferInterface buffer,
+            final OutputStream destination, final String word, final int frequency,
+            final ArrayList<WeightedString> bigramStrings,
+            final ArrayList<WeightedString> shortcuts, final boolean isNotAWord,
+            final boolean isBlackListEntry)
+                    throws IOException, UnsupportedFormatException {
+        final ArrayList<PendingAttribute> bigrams = new ArrayList<PendingAttribute>();
+        if (bigramStrings != null) {
+            for (final WeightedString bigram : bigramStrings) {
+                int position = getTerminalPosition(buffer, bigram.mWord);
+                if (position == FormatSpec.NOT_VALID_WORD) {
+                    // TODO: figure out what is the correct thing to do here.
+                } else {
+                    bigrams.add(new PendingAttribute(bigram.mFrequency, position));
+                }
+            }
+        }
+
+        final boolean isTerminal = true;
+        final boolean hasBigrams = !bigrams.isEmpty();
+        final boolean hasShortcuts = shortcuts != null && !shortcuts.isEmpty();
+
+        // find the insert position of the word.
+        if (buffer.position() != 0) buffer.position(0);
+        final FileHeader header = BinaryDictInputOutput.readHeader(buffer);
+
+        int wordPos = 0, address = buffer.position(), nodeOriginAddress = buffer.position();
+        final int[] codePoints = FusionDictionary.getCodePoints(word);
+        final int wordLen = codePoints.length;
+
+        for (int depth = 0; depth < Constants.Dictionary.MAX_WORD_LENGTH; ++depth) {
+            if (wordPos >= wordLen) break;
+            nodeOriginAddress = buffer.position();
+            int nodeParentAddress = -1;
             final int charGroupCount = BinaryDictInputOutput.readCharGroupCount(buffer);
-            groupOffset += BinaryDictInputOutput.getGroupCountSize(charGroupCount);
+            boolean foundNextGroup = false;
 
             for (int i = 0; i < charGroupCount; ++i) {
-                final int charGroupPos = buffer.position();
+                address = buffer.position();
                 final CharGroupInfo currentInfo = BinaryDictInputOutput.readCharGroup(buffer,
                         buffer.position(), header.mFormatOptions);
-                boolean same = true;
-                for (int p = 0, j = word.offsetByCodePoints(0, wordPos);
-                        p < currentInfo.mCharacters.length;
-                        ++p, j = word.offsetByCodePoints(j, 1)) {
-                    if (wordPos + p >= wordLen
-                            || word.codePointAt(j) != currentInfo.mCharacters[p]) {
-                        same = false;
+                final boolean isMovedGroup = BinaryDictInputOutput.isMovedGroup(currentInfo.mFlags,
+                        header.mFormatOptions);
+                if (isMovedGroup) continue;
+                nodeParentAddress = (currentInfo.mParentAddress == FormatSpec.NO_PARENT_ADDRESS)
+                        ? FormatSpec.NO_PARENT_ADDRESS : currentInfo.mParentAddress + address;
+                boolean matched = true;
+                for (int p = 0; p < currentInfo.mCharacters.length; ++p) {
+                    if (wordPos + p >= wordLen) {
+                        /*
+                         * splitting
+                         * before
+                         *  abcd - ef
+                         *
+                         * insert "abc"
+                         *
+                         * after
+                         *  abc - d - ef
+                         */
+                        final int newNodeAddress = buffer.limit();
+                        final int flags = BinaryDictInputOutput.makeCharGroupFlags(p > 1,
+                                isTerminal, 0, hasShortcuts, hasBigrams, false /* isNotAWord */,
+                                false /* isBlackListEntry */, header.mFormatOptions);
+                        int written = moveGroup(newNodeAddress, currentInfo.mCharacters, p, flags,
+                                frequency, nodeParentAddress, shortcuts, bigrams, destination,
+                                buffer, nodeOriginAddress, address, header.mFormatOptions);
+
+                        final int[] characters2 = Arrays.copyOfRange(currentInfo.mCharacters, p,
+                                currentInfo.mCharacters.length);
+                        if (currentInfo.mChildrenAddress != FormatSpec.NO_CHILDREN_ADDRESS) {
+                            updateParentAddresses(buffer, currentInfo.mChildrenAddress,
+                                    newNodeAddress + written + 1, header.mFormatOptions);
+                        }
+                        final CharGroupInfo newInfo2 = new CharGroupInfo(
+                                newNodeAddress + written + 1, -1 /* endAddress */,
+                                currentInfo.mFlags, characters2, currentInfo.mFrequency,
+                                newNodeAddress + 1, currentInfo.mChildrenAddress,
+                                currentInfo.mShortcutTargets, currentInfo.mBigrams);
+                        writeNode(destination, new CharGroupInfo[] { newInfo2 });
+                        return;
+                    } else if (codePoints[wordPos + p] != currentInfo.mCharacters[p]) {
+                        if (p > 0) {
+                            /*
+                             * splitting
+                             * before
+                             *   ab - cd
+                             *
+                             * insert "ac"
+                             *
+                             * after
+                             *   a - b - cd
+                             *     |
+                             *     - c
+                             */
+
+                            final int newNodeAddress = buffer.limit();
+                            final int childrenAddress = currentInfo.mChildrenAddress;
+
+                            // move prefix
+                            final int prefixFlags = BinaryDictInputOutput.makeCharGroupFlags(p > 1,
+                                    false /* isTerminal */, 0 /* childrenAddressSize*/,
+                                    false /* hasShortcut */, false /* hasBigrams */,
+                                    false /* isNotAWord */, false /* isBlackListEntry */,
+                                    header.mFormatOptions);
+                            int written = moveGroup(newNodeAddress, currentInfo.mCharacters, p,
+                                    prefixFlags, -1 /* frequency */, nodeParentAddress, null, null,
+                                    destination, buffer, nodeOriginAddress, address,
+                                    header.mFormatOptions);
+
+                            final int[] suffixCharacters = Arrays.copyOfRange(
+                                    currentInfo.mCharacters, p, currentInfo.mCharacters.length);
+                            if (currentInfo.mChildrenAddress != FormatSpec.NO_CHILDREN_ADDRESS) {
+                                updateParentAddresses(buffer, currentInfo.mChildrenAddress,
+                                        newNodeAddress + written + 1, header.mFormatOptions);
+                            }
+                            final int suffixFlags = BinaryDictInputOutput.makeCharGroupFlags(
+                                    suffixCharacters.length > 1,
+                                    (currentInfo.mFlags & FormatSpec.FLAG_IS_TERMINAL) != 0,
+                                    0 /* childrenAddressSize */,
+                                    (currentInfo.mFlags & FormatSpec.FLAG_HAS_SHORTCUT_TARGETS)
+                                            != 0,
+                                    (currentInfo.mFlags & FormatSpec.FLAG_HAS_BIGRAMS) != 0,
+                                    isNotAWord, isBlackListEntry, header.mFormatOptions);
+                            final CharGroupInfo suffixInfo = new CharGroupInfo(
+                                    newNodeAddress + written + 1, -1 /* endAddress */, suffixFlags,
+                                    suffixCharacters, currentInfo.mFrequency, newNodeAddress + 1,
+                                    currentInfo.mChildrenAddress, currentInfo.mShortcutTargets,
+                                    currentInfo.mBigrams);
+                            written += computeGroupSize(suffixInfo, header.mFormatOptions) + 1;
+
+                            final int[] newCharacters = Arrays.copyOfRange(codePoints, wordPos + p,
+                                    codePoints.length);
+                            final int flags = BinaryDictInputOutput.makeCharGroupFlags(
+                                    newCharacters.length > 1, isTerminal,
+                                    0 /* childrenAddressSize */, hasShortcuts, hasBigrams,
+                                    isNotAWord, isBlackListEntry, header.mFormatOptions);
+                            final CharGroupInfo newInfo = new CharGroupInfo(
+                                    newNodeAddress + written, -1 /* endAddress */, flags,
+                                    newCharacters, frequency, newNodeAddress + 1,
+                                    FormatSpec.NO_CHILDREN_ADDRESS, shortcuts, bigrams);
+                            writeNode(destination, new CharGroupInfo[] { suffixInfo, newInfo });
+                            return;
+                        }
+                        matched = false;
                         break;
                     }
                 }
 
-                if (same) {
+                if (matched) {
                     if (wordPos + currentInfo.mCharacters.length == wordLen) {
-                        if (currentInfo.mFrequency == CharGroup.NOT_A_TERMINAL) {
-                            return FormatSpec.NOT_VALID_WORD;
-                        } else {
-                            return charGroupPos;
-                        }
+                        // the word exists in the dictionary.
+                        // only update group.
+                        final int newNodeAddress = buffer.limit();
+                        final boolean hasMultipleChars = currentInfo.mCharacters.length > 1;
+                        final int flags = BinaryDictInputOutput.makeCharGroupFlags(hasMultipleChars,
+                                isTerminal, 0 /* childrenAddressSize */, hasShortcuts, hasBigrams,
+                                isNotAWord, isBlackListEntry, header.mFormatOptions);
+                        final CharGroupInfo newInfo = new CharGroupInfo(newNodeAddress + 1,
+                                -1 /* endAddress */, flags, currentInfo.mCharacters, frequency,
+                                nodeParentAddress, currentInfo.mChildrenAddress, shortcuts,
+                                bigrams);
+                        moveCharGroup(destination, buffer, newInfo, nodeOriginAddress, address,
+                                header.mFormatOptions);
+                        return;
                     }
                     wordPos += currentInfo.mCharacters.length;
                     if (currentInfo.mChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS) {
-                        return FormatSpec.NOT_VALID_WORD;
+                        /*
+                         * found the prefix of the word.
+                         * make new node and link to the node from this group.
+                         *
+                         * before
+                         * ab - cd
+                         *
+                         * insert "abcde"
+                         *
+                         * after
+                         * ab - cd - e
+                         */
+                        final int newNodeAddress = buffer.limit();
+                        updateChildrenAddress(buffer, address, newNodeAddress,
+                                header.mFormatOptions);
+                        final int newGroupAddress = newNodeAddress + 1;
+                        final boolean hasMultipleChars = (wordLen - wordPos) > 1;
+                        final int flags = BinaryDictInputOutput.makeCharGroupFlags(hasMultipleChars,
+                                isTerminal, 0 /* childrenAddressSize */, hasShortcuts, hasBigrams,
+                                isNotAWord, isBlackListEntry, header.mFormatOptions);
+                        final int[] characters = Arrays.copyOfRange(codePoints, wordPos, wordLen);
+                        final CharGroupInfo newInfo = new CharGroupInfo(newGroupAddress, -1, flags,
+                                characters, frequency, address, FormatSpec.NO_CHILDREN_ADDRESS,
+                                shortcuts, bigrams);
+                        writeNode(destination, new CharGroupInfo[] { newInfo });
+                        return;
                     }
                     buffer.position(currentInfo.mChildrenAddress);
+                    foundNextGroup = true;
                     break;
                 }
-                groupOffset = currentInfo.mEndAddress;
+            }
 
-                // not found
-                if (i >= charGroupCount - 1) {
-                    return FormatSpec.NOT_VALID_WORD;
-                }
+            if (foundNextGroup) continue;
+
+            // reached the end of the array.
+            final int linkAddressPosition = buffer.position();
+            int nextLink = buffer.readUnsignedInt24();
+            if ((nextLink & MSB24) != 0) {
+                nextLink = -(nextLink & SINT24_MAX);
+            }
+            if (nextLink == FormatSpec.NO_FORWARD_LINK_ADDRESS) {
+                /*
+                 * expand this node.
+                 *
+                 * before
+                 * ab - cd
+                 *
+                 * insert "abef"
+                 *
+                 * after
+                 * ab - cd
+                 *    |
+                 *    - ef
+                 */
+
+                // change the forward link address.
+                final int newNodeAddress = buffer.limit();
+                buffer.position(linkAddressPosition);
+                writeSInt24ToBuffer(buffer, newNodeAddress);
+
+                final int[] characters = Arrays.copyOfRange(codePoints, wordPos, wordLen);
+                final int flags = BinaryDictInputOutput.makeCharGroupFlags(characters.length > 1,
+                        isTerminal, 0 /* childrenAddressSize */, hasShortcuts, hasBigrams,
+                        isNotAWord, isBlackListEntry, header.mFormatOptions);
+                final CharGroupInfo newInfo = new CharGroupInfo(newNodeAddress + 1,
+                        -1 /* endAddress */, flags, characters, frequency, nodeParentAddress,
+                        FormatSpec.NO_CHILDREN_ADDRESS, shortcuts, bigrams);
+                writeNode(destination, new CharGroupInfo[]{ newInfo });
+                return;
+            } else {
+                depth--;
+                buffer.position(nextLink);
             }
         }
-        return FormatSpec.NOT_VALID_WORD;
+    }
+
+    /**
+     * Find a word from the buffer.
+     *
+     * @param buffer the buffer representing the body of the dictionary file.
+     * @param word the word searched
+     * @return the found group
+     * @throws IOException
+     * @throws UnsupportedFormatException
+     */
+    @UsedForTesting
+    public static CharGroupInfo findWordFromBuffer(final FusionDictionaryBufferInterface buffer,
+            final String word) throws IOException, UnsupportedFormatException {
+        int position = getTerminalPosition(buffer, word);
+        if (position != FormatSpec.NOT_VALID_WORD) {
+            buffer.position(0);
+            final FileHeader header = BinaryDictInputOutput.readHeader(buffer);
+            buffer.position(position);
+            return BinaryDictInputOutput.readCharGroup(buffer, position, header.mFormatOptions);
+        }
+        return null;
     }
 }