inputmethod/latin/BinaryDictionary.java

/*
 * Copyright (C) 2008 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.content.Context;
import android.text.TextUtils;

import com.android.inputmethod.keyboard.ProximityInfo;
import com.android.inputmethod.latin.SuggestedWords.SuggestedWordInfo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Locale;

/**
 * Implements a static, compacted, binary dictionary of standard words.
 */
public class BinaryDictionary extends Dictionary {

    public static final String DICTIONARY_PACK_AUTHORITY =
            "com.android.inputmethod.latin.dictionarypack";

    /**
     * There is a difference between what java and native code can handle.
     * This value should only be used in BinaryDictionary.java
     * It is necessary to keep it at this value because some languages e.g. German have
     * really long words.
     */
    public static final int MAX_WORD_LENGTH = 48;
    public static final int MAX_WORDS = 18;
    public static final int MAX_SPACES = 16;

    private static final String TAG = "BinaryDictionary";
    private static final int MAX_PREDICTIONS = 60;
    private static final int MAX_RESULTS = Math.max(MAX_PREDICTIONS, MAX_WORDS);

    private static final int TYPED_LETTER_MULTIPLIER = 2;

    private long mNativeDict;
    private final int[] mInputCodes = new int[MAX_WORD_LENGTH];
    private final char[] mOutputChars = new char[MAX_WORD_LENGTH * MAX_RESULTS];
    private final int[] mSpaceIndices = new int[MAX_SPACES];
    private final int[] mOutputScores = new int[MAX_RESULTS];

    private final boolean mUseFullEditDistance;

    /**
     * Constructor for the binary dictionary. This is supposed to be called from the
     * dictionary factory.
     * All implementations should pass null into flagArray, except for testing purposes.
     * @param context the context to access the environment from.
     * @param filename the name of the file to read through native code.
     * @param offset the offset of the dictionary data within the file.
     * @param length the length of the binary data.
     * @param useFullEditDistance whether to use the full edit distance in suggestions
     * @param dictType the dictionary type, as a human-readable string
     */
    public BinaryDictionary(final Context context,
            final String filename, final long offset, final long length,
            final boolean useFullEditDistance, final Locale locale, final String dictType) {
        super(dictType);
        mUseFullEditDistance = useFullEditDistance;
        loadDictionary(filename, offset, length);
    }

    static {
        JniUtils.loadNativeLibrary();
    }

    private native long openNative(String sourceDir, long dictOffset, long dictSize,
            int typedLetterMultiplier, int fullWordMultiplier, int maxWordLength, int maxWords,
            int maxPredictions);
    private native void closeNative(long dict);
    private native int getFrequencyNative(long dict, int[] word, int wordLength);
    private native boolean isValidBigramNative(long dict, int[] word1, int[] word2);
    private native int getSuggestionsNative(long dict, long proximityInfo, int[] xCoordinates,
            int[] yCoordinates, int[] times, int[] pointerIds, int[] inputCodes, int codesSize,
            int commitPoint, boolean isGesture,
            int[] prevWordCodePointArray, boolean useFullEditDistance, char[] outputChars,
            int[] scores, int[] outputIndices);
    private native int getBigramsNative(long dict, int[] prevWord, int prevWordLength,
            int[] inputCodes, int inputCodesLength, char[] outputChars, int[] scores);
    private static native float calcNormalizedScoreNative(
            char[] before, int beforeLength, char[] after, int afterLength, int score);
    private static native int editDistanceNative(
            char[] before, int beforeLength, char[] after, int afterLength);

    private final void loadDictionary(String path, long startOffset, long length) {
        mNativeDict = openNative(path, startOffset, length, TYPED_LETTER_MULTIPLIER,
                FULL_WORD_SCORE_MULTIPLIER, MAX_WORD_LENGTH, MAX_WORDS, MAX_PREDICTIONS);
    }

    @Override
    public ArrayList<SuggestedWordInfo> getSuggestions(final WordComposer composer,
            final CharSequence prevWord, final ProximityInfo proximityInfo) {
        if (!isValidDictionary()) return null;
        Arrays.fill(mInputCodes, WordComposer.NOT_A_CODE);
        Arrays.fill(mOutputChars, (char) 0);
        Arrays.fill(mOutputScores, 0);
        // TODO: toLowerCase in the native code
        final int[] prevWordCodePointArray = (null == prevWord)
                ? null : StringUtils.toCodePointArray(prevWord.toString());
        final int composerSize = composer.size();

        final boolean isGesture = composer.isBatchMode();
        if (composerSize <= 1 || !isGesture) {
            if (composerSize > MAX_WORD_LENGTH - 1) return null;
            for (int i = 0; i < composerSize; i++) {
                mInputCodes[i] = composer.getCodeAt(i);
            }
        }

        final int count;
        if (!isGesture && composerSize <= 1) {
            if (TextUtils.isEmpty(prevWord)) return null;
            int tmpCount = getBigramsNative(mNativeDict, prevWordCodePointArray,
                    prevWordCodePointArray.length, mInputCodes, composerSize,
                    mOutputChars, mOutputScores);
            count = Math.min(tmpCount, MAX_PREDICTIONS);
        } else {
            final InputPointers ips = composer.getInputPointers();
            final int codesSize = isGesture ? ips.getPointerSize() : composerSize;
            // proximityInfo and/or prevWordForBigrams may not be null.
            count = getSuggestionsNative(mNativeDict, proximityInfo.getNativeProximityInfo(),
                ips.getXCoordinates(), ips.getYCoordinates(), ips.getTimes(), ips.getPointerIds(),
                mInputCodes, codesSize, 0 /* unused */, isGesture, prevWordCodePointArray,
                mUseFullEditDistance, mOutputChars, mOutputScores, mSpaceIndices);
        }

        final ArrayList<SuggestedWordInfo> suggestions = new ArrayList<SuggestedWordInfo>();
        for (int j = 0; j < count; ++j) {
            if (composerSize > 0 && mOutputScores[j] < 1) break;
            final int start = j * MAX_WORD_LENGTH;
            int len = 0;
            while (len <  MAX_WORD_LENGTH && mOutputChars[start + len] != 0) {
                ++len;
            }
            if (len > 0) {
                suggestions.add(new SuggestedWordInfo(
                        new String(mOutputChars, start, len),
                        mOutputScores[j], SuggestedWordInfo.KIND_CORRECTION, mDictType));
            }
        }
        return suggestions;
    }

    /* package for test */ boolean isValidDictionary() {
        return mNativeDict != 0;
    }

    public static float calcNormalizedScore(String before, String after, int score) {
        return calcNormalizedScoreNative(before.toCharArray(), before.length(),
                after.toCharArray(), after.length(), score);
    }

    public static int editDistance(String before, String after) {
        return editDistanceNative(
                before.toCharArray(), before.length(), after.toCharArray(), after.length());
    }

    @Override
    public boolean isValidWord(CharSequence word) {
        return getFrequency(word) >= 0;
    }

    @Override
    public int getFrequency(CharSequence word) {
        if (word == null) return -1;
        int[] chars = StringUtils.toCodePointArray(word.toString());
        return getFrequencyNative(mNativeDict, chars, chars.length);
    }

    // TODO: Add a batch process version (isValidBigramMultiple?) to avoid excessive numbers of jni
    // calls when checking for changes in an entire dictionary.
    public boolean isValidBigram(CharSequence word1, CharSequence word2) {
        if (TextUtils.isEmpty(word1) || TextUtils.isEmpty(word2)) return false;
        int[] chars1 = StringUtils.toCodePointArray(word1.toString());
        int[] chars2 = StringUtils.toCodePointArray(word2.toString());
        return isValidBigramNative(mNativeDict, chars1, chars2);
    }

    @Override
    public synchronized void close() {
        closeInternal();
    }

    private void closeInternal() {
        if (mNativeDict != 0) {
            closeNative(mNativeDict);
            mNativeDict = 0;
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            closeInternal();
        } finally {
            super.finalize();
        }
    }
}