-UserBigram

-UnitTest for UserBigram
-Changes for number of bigrams to load

Change-Id: I2c6fbe6194d34112ccc52c7e199461d2350e8516

java/src/com/android/inputmethod/latin/AutoDictionary.java

@@ -83,14 +83,14 @@ public class AutoDictionary extends ExpandableDictionary {
         sDictProjectionMap.put(COLUMN_LOCALE, COLUMN_LOCALE);
     }
 
-    private static DatabaseHelper mOpenHelper = null;
+    private static DatabaseHelper sOpenHelper = null;
 
     public AutoDictionary(Context context, LatinIME ime, String locale, int dicTypeId) {
         super(context, dicTypeId);
         mIme = ime;
         mLocale = locale;
-        if (mOpenHelper == null) {
+        if (sOpenHelper == null) {
-            mOpenHelper = new DatabaseHelper(getContext());
+            sOpenHelper = new DatabaseHelper(getContext());
         }
         if (mLocale != null && mLocale.length() > 1) {
             loadDictionary();
@@ -169,7 +169,7 @@ public class AutoDictionary extends ExpandableDictionary {
             // Nothing pending? Return
             if (mPendingWrites.isEmpty()) return;
             // Create a background thread to write the pending entries
-            new UpdateDbTask(getContext(), mOpenHelper, mPendingWrites, mLocale).execute();
+            new UpdateDbTask(getContext(), sOpenHelper, mPendingWrites, mLocale).execute();
             // Create a new map for writing new entries into while the old one is written to db
             mPendingWrites = new HashMap<String, Integer>();
         }
@@ -209,7 +209,7 @@ public class AutoDictionary extends ExpandableDictionary {
         qb.setProjectionMap(sDictProjectionMap);
 
         // Get the database and run the query
-        SQLiteDatabase db = mOpenHelper.getReadableDatabase();
+        SQLiteDatabase db = sOpenHelper.getReadableDatabase();
         Cursor c = qb.query(db, null, selection, selectionArgs, null, null,
                 DEFAULT_SORT_ORDER);
         return c;

java/src/com/android/inputmethod/latin/BinaryDictionary.java

@@ -42,8 +42,8 @@ public class BinaryDictionary extends Dictionary {
 
     private static final String TAG = "BinaryDictionary";
     private static final int MAX_ALTERNATIVES = 16;
-    private static final int MAX_WORDS = 16;
+    private static final int MAX_WORDS = 18;
-    private static final int MAX_BIGRAMS = 255; // TODO Probably don't need all 255
+    private static final int MAX_BIGRAMS = 60;
 
     private static final int TYPED_LETTER_MULTIPLIER = 2;
     private static final boolean ENABLE_MISSED_CHARACTERS = true;
@@ -140,8 +140,10 @@ public class BinaryDictionary extends Dictionary {
             Log.w(TAG, "No available memory for binary dictionary");
         } finally {
             try {
-                for (int i = 0;i < is.length; i++) {
+                if (is != null) {
-                    is[i].close();
+                    for (int i = 0; i < is.length; i++) {
+                        is[i].close();
+                    }
                 }
             } catch (IOException e) {
                 Log.w(TAG, "Failed to close input stream");

java/src/com/android/inputmethod/latin/ContactsDictionary.java

@@ -125,8 +125,8 @@ public class ContactsDictionary extends ExpandableDictionary {
                                 super.addWord(word, FREQUENCY_FOR_CONTACTS);
                                 if (!TextUtils.isEmpty(prevWord)) {
                                     // TODO Do not add email address
-                                    super.addBigrams(prevWord, word,
+                                    // Not so critical
-                                            FREQUENCY_FOR_CONTACTS_BIGRAM);
+                                    super.setBigram(prevWord, word, FREQUENCY_FOR_CONTACTS_BIGRAM);
                                 }
                                 prevWord = word;
                             }

java/src/com/android/inputmethod/latin/ExpandableDictionary.java

@@ -20,8 +20,6 @@ import java.util.LinkedList;
 
 import android.content.Context;
 import android.os.AsyncTask;
-import android.os.SystemClock;
-import android.util.Log;
 
 /**
  * Base class for an in-memory dictionary that can grow dynamically and can
@@ -325,12 +323,21 @@ public class ExpandableDictionary extends Dictionary {
         }
     }
 
+    protected int setBigram(String word1, String word2, int frequency) {
+        return addOrSetBigram(word1, word2, frequency, false);
+    }
+
+    protected int addBigram(String word1, String word2, int frequency) {
+        return addOrSetBigram(word1, word2, frequency, true);
+    }
+
     /**
      * Adds bigrams to the in-memory trie structure that is being used to retrieve any word
-     * @param addFrequency adding frequency of the pair
+     * @param frequency frequency for this bigrams
+     * @param addFrequency if true, it adds to current frequency
      * @return returns the final frequency
      */
-    protected int addBigrams(String word1, String word2, int addFrequency) {
+    private int addOrSetBigram(String word1, String word2, int frequency, boolean addFrequency) {
         Node firstWord = searchWord(mRoots, word1, 0, null);
         Node secondWord = searchWord(mRoots, word2, 0, null);
         LinkedList<NextWord> bigram = firstWord.ngrams;
@@ -340,14 +347,18 @@ public class ExpandableDictionary extends Dictionary {
         } else {
             for (NextWord nw : bigram) {
                 if (nw.word == secondWord) {
-                    nw.frequency += addFrequency;
+                    if (addFrequency) {
+                        nw.frequency += frequency;
+                    } else {
+                        nw.frequency = frequency;
+                    }
                     return nw.frequency;
                 }
             }
         }
-        NextWord nw = new NextWord(secondWord, addFrequency);
+        NextWord nw = new NextWord(secondWord, frequency);
         firstWord.ngrams.add(nw);
-        return addFrequency;
+        return frequency;
     }
 
     /**
@@ -385,22 +396,44 @@ public class ExpandableDictionary extends Dictionary {
         return searchWord(childNode.children, word, depth + 1, childNode);
     }
 
-    @Override
+    // @VisibleForTesting
-    public void getBigrams(final WordComposer codes, final CharSequence previousWord,
+    boolean reloadDictionaryIfRequired() {
-            final WordCallback callback, int[] nextLettersFrequencies) {
         synchronized (mUpdatingLock) {
             // If we need to update, start off a background task
             if (mRequiresReload) startDictionaryLoadingTaskLocked();
             // Currently updating contacts, don't return any results.
-            if (mUpdatingDictionary) return;
+            return mUpdatingDictionary;
         }
+    }
 
+    private void runReverseLookUp(final CharSequence previousWord, final WordCallback callback) {
         Node prevWord = searchNode(mRoots, previousWord, 0, previousWord.length());
         if (prevWord != null && prevWord.ngrams != null) {
             reverseLookUp(prevWord.ngrams, callback);
         }
     }
 
+    @Override
+    public void getBigrams(final WordComposer codes, final CharSequence previousWord,
+            final WordCallback callback, int[] nextLettersFrequencies) {
+        if (!reloadDictionaryIfRequired()) {
+            runReverseLookUp(previousWord, callback);
+        }
+    }
+
+    /**
+     * Used only for testing purposes
+     * This function will wait for loading from database to be done
+     */
+    void waitForDictionaryLoading() {
+        while (mUpdatingDictionary) {
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+            }
+        }
+    }
+
     /**
      * reverseLookUp retrieves the full word given a list of terminal nodes and adds those words
      * through callback.
@@ -413,15 +446,18 @@ public class ExpandableDictionary extends Dictionary {
         for (NextWord nextWord : terminalNodes) {
             node = nextWord.word;
             freq = nextWord.frequency;
-            sb.setLength(0);
+            // TODO Not the best way to limit suggestion threshold
-            do {
+            if (freq >= UserBigramDictionary.SUGGEST_THRESHOLD) {
-                sb.insert(0, node.code);
+                sb.setLength(0);
-                node = node.parent;
+                do {
-            } while(node != null);
+                    sb.insert(0, node.code);
+                    node = node.parent;
+                } while(node != null);
 
-            // TODO better way to feed char array?
+                // TODO better way to feed char array?
-            callback.addWord(sb.toString().toCharArray(), 0, sb.length(), freq, mDicTypeId,
+                callback.addWord(sb.toString().toCharArray(), 0, sb.length(), freq, mDicTypeId,
-                    DataType.BIGRAM);
+                        DataType.BIGRAM);
+            }
         }
     }
 
@@ -460,18 +496,11 @@ public class ExpandableDictionary extends Dictionary {
         @Override
         protected Void doInBackground(Void... v) {
             loadDictionaryAsync();
-            return null;
-        }
-
-        @Override
-        protected void onPostExecute(Void result) {
-            // TODO Auto-generated method stub
             synchronized (mUpdatingLock) {
                 mUpdatingDictionary = false;
             }
-            super.onPostExecute(result);
+            return null;
         }
-        
     }
 
     static char toLowerCase(char c) {

java/src/com/android/inputmethod/latin/LatinIME.java

@@ -163,8 +163,7 @@ public class LatinIME extends InputMethodService
     KeyboardSwitcher mKeyboardSwitcher;
 
     private UserDictionary mUserDictionary;
-    // User Bigram is disabled for now
+    private UserBigramDictionary mUserBigramDictionary;
-    //private UserBigramDictionary mUserBigramDictionary;
     private ContactsDictionary mContactsDictionary;
     private AutoDictionary mAutoDictionary;
 
@@ -454,15 +453,12 @@ public class LatinIME extends InputMethodService
             mAutoDictionary.close();
         }
         mAutoDictionary = new AutoDictionary(this, this, mInputLocale, Suggest.DIC_AUTO);
-        // User Bigram is disabled for now
-        /*
         if (mUserBigramDictionary != null) {
             mUserBigramDictionary.close();
         }
         mUserBigramDictionary = new UserBigramDictionary(this, this, mInputLocale,
-                Suggest.DIC_USERBIGRAM);
+                Suggest.DIC_USER);
         mSuggest.setUserBigramDictionary(mUserBigramDictionary);
-        */
         mSuggest.setUserDictionary(mUserDictionary);
         mSuggest.setContactsDictionary(mContactsDictionary);
         mSuggest.setAutoDictionary(mAutoDictionary);
@@ -698,8 +694,7 @@ public class LatinIME extends InputMethodService
             mKeyboardSwitcher.getInputView().closing();
         }
         if (mAutoDictionary != null) mAutoDictionary.flushPendingWrites();
-        // User Bigram is disabled for now
+        if (mUserBigramDictionary != null) mUserBigramDictionary.flushPendingWrites();
-        //if (mUserBigramDictionary != null) mUserBigramDictionary.flushPendingWrites();
     }
 
     @Override
@@ -2007,15 +2002,14 @@ public class LatinIME extends InputMethodService
                     && !mSuggest.isValidWord(suggestion.toString().toLowerCase()))) {
                 mAutoDictionary.addWord(suggestion.toString(), frequencyDelta);
             }
-            // User Bigram is disabled for now
+
-            /*
             if (mUserBigramDictionary != null) {
-                CharSequence prevWord = EditingUtil.getPreviousWord(getCurrentInputConnection());
+                CharSequence prevWord = EditingUtil.getPreviousWord(getCurrentInputConnection(),
+                        mSentenceSeparators);
                 if (!TextUtils.isEmpty(prevWord)) {
-                    mUserBigramDictionary.addBigrams(prevWord.toString(), suggestion.toString(), 1);
+                    mUserBigramDictionary.addBigrams(prevWord.toString(), suggestion.toString());
                 }
             }
-            */
         }
     }
 

java/src/com/android/inputmethod/latin/Suggest.java

@@ -78,12 +78,13 @@ public class Suggest implements Dictionary.WordCallback {
     private Dictionary mUserBigramDictionary;
 
     private int mPrefMaxSuggestions = 12;
-    private int mPrefMaxBigrams = 255;
+
+    private static final int PREF_MAX_BIGRAMS = 60;
 
     private boolean mAutoTextEnabled;
 
     private int[] mPriorities = new int[mPrefMaxSuggestions];
-    private int[] mBigramPriorities = new int[mPrefMaxBigrams];
+    private int[] mBigramPriorities = new int[PREF_MAX_BIGRAMS];
 
     // Handle predictive correction for only the first 1280 characters for performance reasons
     // If we support scripts that need latin characters beyond that, we should probably use some
@@ -92,7 +93,7 @@ public class Suggest implements Dictionary.WordCallback {
     // latin characters.
     private int[] mNextLettersFrequencies = new int[1280];
     private ArrayList<CharSequence> mSuggestions = new ArrayList<CharSequence>();
-    private ArrayList<CharSequence> mBigramSuggestions  = new ArrayList<CharSequence>();
+    ArrayList<CharSequence> mBigramSuggestions  = new ArrayList<CharSequence>();
     private ArrayList<CharSequence> mStringPool = new ArrayList<CharSequence>();
     private boolean mHaveCorrection;
     private CharSequence mOriginalWord;
@@ -173,7 +174,7 @@ public class Suggest implements Dictionary.WordCallback {
         }
         mPrefMaxSuggestions = maxSuggestions;
         mPriorities = new int[mPrefMaxSuggestions];
-        mBigramPriorities = new int[mPrefMaxBigrams];
+        mBigramPriorities = new int[PREF_MAX_BIGRAMS];
         collectGarbage(mSuggestions, mPrefMaxSuggestions);
         while (mStringPool.size() < mPrefMaxSuggestions) {
             StringBuilder sb = new StringBuilder(getApproxMaxWordLength());
@@ -242,7 +243,7 @@ public class Suggest implements Dictionary.WordCallback {
                 || mCorrectionMode == CORRECTION_BASIC)) {
             // At first character typed, search only the bigrams
             Arrays.fill(mBigramPriorities, 0);
-            collectGarbage(mBigramSuggestions, mPrefMaxBigrams);
+            collectGarbage(mBigramSuggestions, PREF_MAX_BIGRAMS);
 
             if (!TextUtils.isEmpty(prevWordForBigram)) {
                 CharSequence lowerPrevWord = prevWordForBigram.toString().toLowerCase();
@@ -401,7 +402,7 @@ public class Suggest implements Dictionary.WordCallback {
         if(dataType == Dictionary.DataType.BIGRAM) {
             suggestions = mBigramSuggestions;
             priorities = mBigramPriorities;
-            prefMaxSuggestions = mPrefMaxBigrams;
+            prefMaxSuggestions = PREF_MAX_BIGRAMS;
         } else {
             suggestions = mSuggestions;
             priorities = mPriorities;
@@ -443,7 +444,6 @@ public class Suggest implements Dictionary.WordCallback {
                 pos++;
             }
         }
-
         if (pos >= prefMaxSuggestions) {
             return true;
         }

java/src/com/android/inputmethod/latin/UserBigramDictionary.java

@@ -0,0 +1,402 @@
+/*
+ * Copyright (C) 2010 Google Inc.
+ *
+ * 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;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.Cursor;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.database.sqlite.SQLiteQueryBuilder;
+import android.os.AsyncTask;
+import android.provider.BaseColumns;
+import android.util.Log;
+
+/**
+ * Stores all the pairs user types in databases. Prune the database if the size
+ * gets too big. Unlike AutoDictionary, it even stores the pairs that are already
+ * in the dictionary.
+ */
+public class UserBigramDictionary extends ExpandableDictionary {
+    private static final String TAG = "UserBigramDictionary";
+
+    /** Any pair being typed or picked */
+    private static final int FREQUENCY_FOR_TYPED = 2;
+
+    /** Maximum frequency for all pairs */
+    private static final int FREQUENCY_MAX = 127;
+
+    /**
+     * If this pair is typed 6 times, it would be suggested.
+     * Should be smaller than ContactsDictionary.FREQUENCY_FOR_CONTACTS_BIGRAM
+     */
+    protected static final int SUGGEST_THRESHOLD = 6 * FREQUENCY_FOR_TYPED;
+
+    /** Maximum number of pairs. Pruning will start when databases goes above this number. */
+    private static int sMaxUserBigrams = 10000;
+
+    /**
+     * When it hits maximum bigram pair, it will delete until you are left with
+     * only (sMaxUserBigrams - sDeleteUserBigrams) pairs.
+     * Do not keep this number small to avoid deleting too often.
+     */
+    private static int sDeleteUserBigrams = 1000;
+
+    /**
+     * Database version should increase if the database structure changes
+     */
+    private static final int DATABASE_VERSION = 1;
+
+    private static final String DATABASE_NAME = "userbigram_dict.db";
+
+    /** Name of the words table in the database */
+    private static final String MAIN_TABLE_NAME = "main";
+    // TODO: Consume less space by using a unique id for locale instead of the whole
+    // 2-5 character string. (Same TODO from AutoDictionary)
+    private static final String MAIN_COLUMN_ID = BaseColumns._ID;
+    private static final String MAIN_COLUMN_WORD1 = "word1";
+    private static final String MAIN_COLUMN_WORD2 = "word2";
+    private static final String MAIN_COLUMN_LOCALE = "locale";
+
+    /** Name of the frequency table in the database */
+    private static final String FREQ_TABLE_NAME = "frequency";
+    private static final String FREQ_COLUMN_ID = BaseColumns._ID;
+    private static final String FREQ_COLUMN_PAIR_ID = "pair_id";
+    private static final String FREQ_COLUMN_FREQUENCY = "freq";
+
+    private final LatinIME mIme;
+
+    /** Locale for which this auto dictionary is storing words */
+    private String mLocale;
+
+    private HashSet<Bigram> mPendingWrites = new HashSet<Bigram>();
+    private final Object mPendingWritesLock = new Object();
+    private static volatile boolean sUpdatingDB = false;
+
+    private final static HashMap<String, String> sDictProjectionMap;
+
+    static {
+        sDictProjectionMap = new HashMap<String, String>();
+        sDictProjectionMap.put(MAIN_COLUMN_ID, MAIN_COLUMN_ID);
+        sDictProjectionMap.put(MAIN_COLUMN_WORD1, MAIN_COLUMN_WORD1);
+        sDictProjectionMap.put(MAIN_COLUMN_WORD2, MAIN_COLUMN_WORD2);
+        sDictProjectionMap.put(MAIN_COLUMN_LOCALE, MAIN_COLUMN_LOCALE);
+
+        sDictProjectionMap.put(FREQ_COLUMN_ID, FREQ_COLUMN_ID);
+        sDictProjectionMap.put(FREQ_COLUMN_PAIR_ID, FREQ_COLUMN_PAIR_ID);
+        sDictProjectionMap.put(FREQ_COLUMN_FREQUENCY, FREQ_COLUMN_FREQUENCY);
+    }
+
+    private static DatabaseHelper sOpenHelper = null;
+
+    private static class Bigram {
+        String word1;
+        String word2;
+        int frequency;
+
+        Bigram(String word1, String word2, int frequency) {
+            this.word1 = word1;
+            this.word2 = word2;
+            this.frequency = frequency;
+        }
+
+        @Override
+        public boolean equals(Object bigram) {
+            Bigram bigram2 = (Bigram) bigram;
+            return (word1.equals(bigram2.word1) && word2.equals(bigram2.word2));
+        }
+
+        @Override
+        public int hashCode() {
+            return (word1 + " " + word2).hashCode();
+        }
+    }
+
+    public void setDatabaseMax(int maxUserBigram) {
+        sMaxUserBigrams = maxUserBigram;
+    }
+
+    public void setDatabaseDelete(int deleteUserBigram) {
+        sDeleteUserBigrams = deleteUserBigram;
+    }
+
+    public UserBigramDictionary(Context context, LatinIME ime, String locale, int dicTypeId) {
+        super(context, dicTypeId);
+        mIme = ime;
+        mLocale = locale;
+        if (sOpenHelper == null) {
+            sOpenHelper = new DatabaseHelper(getContext());
+        }
+        if (mLocale != null && mLocale.length() > 1) {
+            loadDictionary();
+        }
+    }
+
+    @Override
+    public void close() {
+        flushPendingWrites();
+        // Don't close the database as locale changes will require it to be reopened anyway
+        // Also, the database is written to somewhat frequently, so it needs to be kept alive
+        // throughout the life of the process.
+        // mOpenHelper.close();
+        super.close();
+    }
+
+    /**
+     * Pair will be added to the userbigram database.
+     */
+    public int addBigrams(String word1, String word2) {
+        // remove caps
+        if (mIme != null && mIme.getCurrentWord().isAutoCapitalized()) {
+            word2 = Character.toLowerCase(word2.charAt(0)) + word2.substring(1);
+        }
+
+        int freq = super.addBigram(word1, word2, FREQUENCY_FOR_TYPED);
+        if (freq > FREQUENCY_MAX) freq = FREQUENCY_MAX;
+        synchronized (mPendingWritesLock) {
+            if (freq == FREQUENCY_FOR_TYPED || mPendingWrites.isEmpty()) {
+                mPendingWrites.add(new Bigram(word1, word2, freq));
+            } else {
+                Bigram bi = new Bigram(word1, word2, freq);
+                mPendingWrites.remove(bi);
+                mPendingWrites.add(bi);
+            }
+        }
+
+        return freq;
+    }
+
+    /**
+     * Schedules a background thread to write any pending words to the database.
+     */
+    public void flushPendingWrites() {
+        synchronized (mPendingWritesLock) {
+            // Nothing pending? Return
+            if (mPendingWrites.isEmpty()) return;
+            // Create a background thread to write the pending entries
+            new UpdateDbTask(getContext(), sOpenHelper, mPendingWrites, mLocale).execute();
+            // Create a new map for writing new entries into while the old one is written to db
+            mPendingWrites = new HashSet<Bigram>();
+        }
+    }
+
+    /** Used for testing purpose **/
+    void waitUntilUpdateDBDone() {
+        synchronized (mPendingWritesLock) {
+            while (sUpdatingDB) {
+                try {
+                    Thread.sleep(100);
+                } catch (InterruptedException e) {
+                }
+            }
+            return;
+        }
+    }
+
+    @Override
+    public void loadDictionaryAsync() {
+        // Load the words that correspond to the current input locale
+        Cursor cursor = query(MAIN_COLUMN_LOCALE + "=?", new String[] { mLocale });
+        try {
+            if (cursor.moveToFirst()) {
+                int word1Index = cursor.getColumnIndex(MAIN_COLUMN_WORD1);
+                int word2Index = cursor.getColumnIndex(MAIN_COLUMN_WORD2);
+                int frequencyIndex = cursor.getColumnIndex(FREQ_COLUMN_FREQUENCY);
+                while (!cursor.isAfterLast()) {
+                    String word1 = cursor.getString(word1Index);
+                    String word2 = cursor.getString(word2Index);
+                    int frequency = cursor.getInt(frequencyIndex);
+                    // Safeguard against adding really long words. Stack may overflow due
+                    // to recursive lookup
+                    if (word1.length() < MAX_WORD_LENGTH && word2.length() < MAX_WORD_LENGTH) {
+                        super.setBigram(word1, word2, frequency);
+                    }
+                    cursor.moveToNext();
+                }
+            }
+        } finally {
+            cursor.close();
+        }
+    }
+
+    /**
+     * Query the database
+     */
+    private Cursor query(String selection, String[] selectionArgs) {
+        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
+
+        // main INNER JOIN frequency ON (main._id=freq.pair_id)
+        qb.setTables(MAIN_TABLE_NAME + " INNER JOIN " + FREQ_TABLE_NAME + " ON ("
+                + MAIN_TABLE_NAME + "." + MAIN_COLUMN_ID + "=" + FREQ_TABLE_NAME + "."
+                + FREQ_COLUMN_PAIR_ID +")");
+
+        qb.setProjectionMap(sDictProjectionMap);
+
+        // Get the database and run the query
+        SQLiteDatabase db = sOpenHelper.getReadableDatabase();
+        Cursor c = qb.query(db,
+                new String[] { MAIN_COLUMN_WORD1, MAIN_COLUMN_WORD2, FREQ_COLUMN_FREQUENCY },
+                selection, selectionArgs, null, null, null);
+        return c;
+    }
+
+    /**
+     * This class helps open, create, and upgrade the database file.
+     */
+    private static class DatabaseHelper extends SQLiteOpenHelper {
+
+        DatabaseHelper(Context context) {
+            super(context, DATABASE_NAME, null, DATABASE_VERSION);
+        }
+
+        @Override
+        public void onCreate(SQLiteDatabase db) {
+            db.execSQL("PRAGMA foreign_keys = ON;");
+            db.execSQL("CREATE TABLE " + MAIN_TABLE_NAME + " ("
+                    + MAIN_COLUMN_ID + " INTEGER PRIMARY KEY,"
+                    + MAIN_COLUMN_WORD1 + " TEXT,"
+                    + MAIN_COLUMN_WORD2 + " TEXT,"
+                    + MAIN_COLUMN_LOCALE + " TEXT"
+                    + ");");
+            db.execSQL("CREATE TABLE " + FREQ_TABLE_NAME + " ("
+                    + FREQ_COLUMN_ID + " INTEGER PRIMARY KEY,"
+                    + FREQ_COLUMN_PAIR_ID + " INTEGER,"
+                    + FREQ_COLUMN_FREQUENCY + " INTEGER,"
+                    + "FOREIGN KEY(" + FREQ_COLUMN_PAIR_ID + ") REFERENCES " + MAIN_TABLE_NAME
+                    + "(" + MAIN_COLUMN_ID + ")" + " ON DELETE CASCADE"
+                    + ");");
+        }
+
+        @Override
+        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+                    + newVersion + ", which will destroy all old data");
+            db.execSQL("DROP TABLE IF EXISTS " + MAIN_TABLE_NAME);
+            db.execSQL("DROP TABLE IF EXISTS " + FREQ_TABLE_NAME);
+            onCreate(db);
+        }
+    }
+
+    /**
+     * Async task to write pending words to the database so that it stays in sync with
+     * the in-memory trie.
+     */
+    private static class UpdateDbTask extends AsyncTask<Void, Void, Void> {
+        private final HashSet<Bigram> mMap;
+        private final DatabaseHelper mDbHelper;
+        private final String mLocale;
+
+        public UpdateDbTask(Context context, DatabaseHelper openHelper,
+                HashSet<Bigram> pendingWrites, String locale) {
+            mMap = pendingWrites;
+            mLocale = locale;
+            mDbHelper = openHelper;
+        }
+
+        /** Prune any old data if the database is getting too big. */
+        private void checkPruneData(SQLiteDatabase db) {
+            db.execSQL("PRAGMA foreign_keys = ON;");
+            Cursor c = db.query(FREQ_TABLE_NAME, new String[] { FREQ_COLUMN_PAIR_ID },
+                    null, null, null, null, null);
+            try {
+                int totalRowCount = c.getCount();
+                // prune out old data if we have too much data
+                if (totalRowCount > sMaxUserBigrams) {
+                    int numDeleteRows = (totalRowCount - sMaxUserBigrams) + sDeleteUserBigrams;
+                    int pairIdColumnId = c.getColumnIndex(FREQ_COLUMN_PAIR_ID);
+                    c.moveToFirst();
+                    int count = 0;
+                    while (count < numDeleteRows && !c.isAfterLast()) {
+                        String pairId = c.getString(pairIdColumnId);
+                        // Deleting from MAIN table will delete the frequencies
+                        // due to FOREIGN KEY .. ON DELETE CASCADE
+                        db.delete(MAIN_TABLE_NAME, MAIN_COLUMN_ID + "=?",
+                            new String[] { pairId });
+                        c.moveToNext();
+                        count++;
+                    }
+                }
+            } finally {
+                c.close();
+            }
+        }
+
+        @Override
+        protected void onPreExecute() {
+            sUpdatingDB = true;
+        }
+
+        @Override
+        protected Void doInBackground(Void... v) {
+            SQLiteDatabase db = mDbHelper.getWritableDatabase();
+            db.execSQL("PRAGMA foreign_keys = ON;");
+            // Write all the entries to the db
+            Iterator<Bigram> iterator = mMap.iterator();
+            while (iterator.hasNext()) {
+                Bigram bi = iterator.next();
+
+                // find pair id
+                Cursor c = db.query(MAIN_TABLE_NAME, new String[] { MAIN_COLUMN_ID },
+                        MAIN_COLUMN_WORD1 + "=? AND " + MAIN_COLUMN_WORD2 + "=? AND "
+                        + MAIN_COLUMN_LOCALE + "=?",
+                        new String[] { bi.word1, bi.word2, mLocale }, null, null, null);
+
+                int pairId;
+                if (c.moveToFirst()) {
+                    // existing pair
+                    pairId = c.getInt(c.getColumnIndex(MAIN_COLUMN_ID));
+                    db.delete(FREQ_TABLE_NAME, FREQ_COLUMN_PAIR_ID + "=?",
+                            new String[] { Integer.toString(pairId) });
+                } else {
+                    // new pair
+                    Long pairIdLong = db.insert(MAIN_TABLE_NAME, null,
+                            getContentValues(bi.word1, bi.word2, mLocale));
+                    pairId = pairIdLong.intValue();
+                }
+                c.close();
+
+                // insert new frequency
+                long s = db.insert(FREQ_TABLE_NAME, null,
+                        getFrequencyContentValues(pairId, bi.frequency));
+            }
+            checkPruneData(db);
+            sUpdatingDB = false;
+
+            return null;
+        }
+
+        private ContentValues getContentValues(String word1, String word2, String locale) {
+            ContentValues values = new ContentValues(3);
+            values.put(MAIN_COLUMN_WORD1, word1);
+            values.put(MAIN_COLUMN_WORD2, word2);
+            values.put(MAIN_COLUMN_LOCALE, locale);
+            return values;
+        }
+
+        private ContentValues getFrequencyContentValues(int pairId, int frequency) {
+           ContentValues values = new ContentValues(2);
+           values.put(FREQ_COLUMN_PAIR_ID, pairId);
+           values.put(FREQ_COLUMN_FREQUENCY, frequency);
+           return values;
+        }
+    }
+
+}

tests/src/com/android/inputmethod/latin/SuggestHelper.java

@@ -14,13 +14,13 @@
  * the License.
  */
 
-package com.android.inputmethod.latin.tests;
+package com.android.inputmethod.latin;
 
 import android.content.Context;
-import android.test.AndroidTestCase;
 import android.text.TextUtils;
 import android.util.Log;
 import com.android.inputmethod.latin.Suggest;
+import com.android.inputmethod.latin.UserBigramDictionary;
 import com.android.inputmethod.latin.WordComposer;
 
 import java.io.IOException;
@@ -29,28 +29,32 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.channels.Channels;
 import java.util.List;
+import java.util.Locale;
+import java.util.StringTokenizer;
 
 public class SuggestHelper {
     private Suggest mSuggest;
+    private UserBigramDictionary mUserBigram;
     private final String TAG;
 
+    /** Uses main dictionary only **/
     public SuggestHelper(String tag, Context context, int[] resId) {
         TAG = tag;
-        InputStream[] res = null;
+        InputStream[] is = null;
         try {
             // merging separated dictionary into one if dictionary is separated
             int total = 0;
-            res = new InputStream[resId.length];
+            is = new InputStream[resId.length];
             for (int i = 0; i < resId.length; i++) {
-                res[i] = context.getResources().openRawResource(resId[i]);
+                is[i] = context.getResources().openRawResource(resId[i]);
-                total += res[i].available();
+                total += is[i].available();
             }
 
             ByteBuffer byteBuffer =
                 ByteBuffer.allocateDirect(total).order(ByteOrder.nativeOrder());
             int got = 0;
             for (int i = 0; i < resId.length; i++) {
-                 got += Channels.newChannel(res[i]).read(byteBuffer);
+                 got += Channels.newChannel(is[i]).read(byteBuffer);
             }
             if (got != total) {
                 Log.w(TAG, "Read " + got + " bytes, expected " + total);
@@ -62,8 +66,10 @@ public class SuggestHelper {
             Log.w(TAG, "No available memory for binary dictionary");
         } finally {
             try {
-                for (int i = 0;i < res.length; i++) {
+                if (is != null) {
-                    res[i].close();
+                    for (int i = 0; i < is.length; i++) {
+                        is[i].close();
+                    }
                 }
             } catch (IOException e) {
                 Log.w(TAG, "Failed to close input stream");
@@ -73,6 +79,27 @@ public class SuggestHelper {
         mSuggest.setCorrectionMode(Suggest.CORRECTION_FULL_BIGRAM);
     }
 
+    /** Uses both main dictionary and user-bigram dictionary **/
+    public SuggestHelper(String tag, Context context, int[] resId, int userBigramMax,
+            int userBigramDelete) {
+        this(tag, context, resId);
+        mUserBigram = new UserBigramDictionary(context, null, Locale.US.toString(),
+                Suggest.DIC_USER);
+        mUserBigram.setDatabaseMax(userBigramMax);
+        mUserBigram.setDatabaseDelete(userBigramDelete);
+        mSuggest.setUserBigramDictionary(mUserBigram);
+    }
+
+    void changeUserBigramLocale(Context context, Locale locale) {
+        if (mUserBigram != null) {
+            flushUserBigrams();
+            mUserBigram.close();
+            mUserBigram = new UserBigramDictionary(context, null, locale.toString(),
+                    Suggest.DIC_USER);
+            mSuggest.setUserBigramDictionary(mUserBigram);
+        }
+    }
+
     private WordComposer createWordComposer(CharSequence s) {
         WordComposer word = new WordComposer();
         for (int i = 0; i < s.length(); i++) {
@@ -125,8 +152,8 @@ public class SuggestHelper {
     }
 
     private void getBigramSuggestions(CharSequence previous, CharSequence typed) {
-        if(!TextUtils.isEmpty(previous) && (typed.length() > 1)) {
+        if (!TextUtils.isEmpty(previous) && (typed.length() > 1)) {
-            WordComposer firstChar = createWordComposer(typed.charAt(0) + "");
+            WordComposer firstChar = createWordComposer(Character.toString(typed.charAt(0)));
             mSuggest.getSuggestions(null, firstChar, false, previous);
         }
     }
@@ -162,6 +189,54 @@ public class SuggestHelper {
         return mSuggest.isValidWord(typed);
     }
 
+    boolean isUserBigramSuggestion(CharSequence previous, char typed,
+           CharSequence expected) {
+        WordComposer word = createWordComposer(Character.toString(typed));
+
+        if (mUserBigram == null) return false;
+
+        flushUserBigrams();
+        if (!TextUtils.isEmpty(previous) && !TextUtils.isEmpty(Character.toString(typed))) {
+            WordComposer firstChar = createWordComposer(Character.toString(typed));
+            mSuggest.getSuggestions(null, firstChar, false, previous);
+            boolean reloading = mUserBigram.reloadDictionaryIfRequired();
+            if (reloading) mUserBigram.waitForDictionaryLoading();
+            mUserBigram.getBigrams(firstChar, previous, mSuggest, null);
+        }
+
+        List<CharSequence> suggestions = mSuggest.mBigramSuggestions;
+        for (int i = 0; i < suggestions.size(); i++) {
+            if (TextUtils.equals(suggestions.get(i), expected)) return true;
+        }
+
+        return false;
+    }
+
+    void addToUserBigram(String sentence) {
+        StringTokenizer st = new StringTokenizer(sentence);
+        String previous = null;
+        while (st.hasMoreTokens()) {
+            String current = st.nextToken();
+            if (previous != null) {
+                addToUserBigram(new String[] {previous, current});
+            }
+            previous = current;
+        }
+    }
+
+    void addToUserBigram(String[] pair) {
+        if (mUserBigram != null && pair.length == 2) {
+            mUserBigram.addBigrams(pair[0], pair[1]);
+        }
+    }
+
+    void flushUserBigrams() {
+        if (mUserBigram != null) {
+            mUserBigram.flushPendingWrites();
+            mUserBigram.waitUntilUpdateDBDone();
+        }
+    }
+
     final int[][] adjacents = {
                                {'a','s','w','q',-1},
                                {'b','h','v','n','g','j',-1},

tests/src/com/android/inputmethod/latin/SuggestPerformanceTests.java

@@ -14,16 +14,15 @@
  * the License.
  */
 
-package com.android.inputmethod.latin.tests;
+package com.android.inputmethod.latin;
 
 import android.test.AndroidTestCase;
 import android.util.Log;
-
+import com.android.inputmethod.latin.tests.R;
 import java.io.InputStreamReader;
 import java.io.InputStream;
 import java.io.BufferedReader;
 import java.util.StringTokenizer;
-import java.util.regex.Pattern;
 
 public class SuggestPerformanceTests extends AndroidTestCase {
     private static final String TAG = "SuggestPerformanceTests";
@@ -122,6 +121,6 @@ public class SuggestPerformanceTests extends AndroidTestCase {
      * Check the log for detail
      */
     public void testSuggestPerformance() {
-        assertTrue(runText(false) < runText(true));
+        assertTrue(runText(false) <= runText(true));
     }
 }

tests/src/com/android/inputmethod/latin/SuggestTests.java

@@ -14,10 +14,10 @@
  * the License.
  */
 
-package com.android.inputmethod.latin.tests;
+package com.android.inputmethod.latin;
 
 import android.test.AndroidTestCase;
-import android.util.Log;
+import com.android.inputmethod.latin.tests.R;
 
 public class SuggestTests extends AndroidTestCase {
     private static final String TAG = "SuggestTests";

tests/src/com/android/inputmethod/latin/UserBigramTests.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2010 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;
+
+import android.test.AndroidTestCase;
+import com.android.inputmethod.latin.tests.R;
+import java.util.Locale;
+
+public class UserBigramTests extends AndroidTestCase {
+    private static final String TAG = "UserBigramTests";
+
+    private static final int SUGGESTION_STARTS = 6;
+    private static final int MAX_DATA = 20;
+    private static final int DELETE_DATA = 10;
+
+    private SuggestHelper sh;
+
+    @Override
+    protected void setUp() {
+        int[] resId = new int[] { R.raw.test };
+        sh = new SuggestHelper(TAG, getTestContext(), resId, MAX_DATA, DELETE_DATA);
+    }
+
+    /************************** Tests ************************/
+
+    /**
+     * Test suggestion started at right time
+     */
+    public void testUserBigram() {
+        for (int i = 0; i < SUGGESTION_STARTS; i++) sh.addToUserBigram(pair1);
+        for (int i = 0; i < (SUGGESTION_STARTS - 1); i++) sh.addToUserBigram(pair2);
+
+        assertTrue(sh.isUserBigramSuggestion("user", 'b', "bigram"));
+        assertFalse(sh.isUserBigramSuggestion("android", 'p', "platform"));
+    }
+
+    /**
+     * Test loading correct (locale) bigrams
+     */
+    public void testOpenAndClose() {
+        for (int i = 0; i < SUGGESTION_STARTS; i++) sh.addToUserBigram(pair1);
+        assertTrue(sh.isUserBigramSuggestion("user", 'b', "bigram"));
+
+        // change to fr_FR
+        sh.changeUserBigramLocale(getTestContext(), Locale.FRANCE);
+        for (int i = 0; i < SUGGESTION_STARTS; i++) sh.addToUserBigram(pair3);
+        assertTrue(sh.isUserBigramSuggestion("locale", 'f', "france"));
+        assertFalse(sh.isUserBigramSuggestion("user", 'b', "bigram"));
+
+        // change back to en_US
+        sh.changeUserBigramLocale(getTestContext(), Locale.US);
+        assertFalse(sh.isUserBigramSuggestion("locale", 'f', "france"));
+        assertTrue(sh.isUserBigramSuggestion("user", 'b', "bigram"));
+    }
+
+    /**
+     * Test data gets pruned when it is over maximum
+     */
+    public void testPruningData() {
+        for (int i = 0; i < SUGGESTION_STARTS; i++) sh.addToUserBigram(sentence0);
+        sh.flushUserBigrams();
+        assertTrue(sh.isUserBigramSuggestion("Hello", 'w', "world"));
+
+        sh.addToUserBigram(sentence1);
+        sh.addToUserBigram(sentence2);
+        assertTrue(sh.isUserBigramSuggestion("Hello", 'w', "world"));
+
+        // pruning should happen
+        sh.addToUserBigram(sentence3);
+        sh.addToUserBigram(sentence4);
+
+        // trying to reopen database to check pruning happened in database
+        sh.changeUserBigramLocale(getTestContext(), Locale.US);
+        assertFalse(sh.isUserBigramSuggestion("Hello", 'w', "world"));
+    }
+
+    final String[] pair1 = new String[] {"user", "bigram"};
+    final String[] pair2 = new String[] {"android","platform"};
+    final String[] pair3 = new String[] {"locale", "france"};
+    final String sentence0 = "Hello world";
+    final String sentence1 = "This is a test for user input based bigram";
+    final String sentence2 = "It learns phrases that contain both dictionary and nondictionary "
+            + "words";
+    final String sentence3 = "This should give better suggestions than the previous version";
+    final String sentence4 = "Android stock keyboard is improving";
+}