path: root/java/src/com/android/inputmethod/latin/LatinIMEUtil.java

/*
 * 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.view.inputmethod.InputMethodManager;

import android.content.Context;
import android.os.AsyncTask;
import android.text.format.DateUtils;
import android.util.Log;

public class LatinIMEUtil {

    /**
     * Cancel an {@link AsyncTask}.
     *
     * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
     *        task should be interrupted; otherwise, in-progress tasks are allowed
     *        to complete.
     */
    public static void cancelTask(AsyncTask<?, ?, ?> task, boolean mayInterruptIfRunning) {
        if (task != null && task.getStatus() != AsyncTask.Status.FINISHED) {
            task.cancel(mayInterruptIfRunning);
        }
    }

    public static class GCUtils {
        private static final String TAG = "GCUtils";
        public static final int GC_TRY_COUNT = 2;
        // GC_TRY_LOOP_MAX is used for the hard limit of GC wait,
        // GC_TRY_LOOP_MAX should be greater than GC_TRY_COUNT.
        public static final int GC_TRY_LOOP_MAX = 5;
        private static final long GC_INTERVAL = DateUtils.SECOND_IN_MILLIS;
        private static GCUtils sInstance = new GCUtils();
        private int mGCTryCount = 0;

        public static GCUtils getInstance() {
            return sInstance;
        }

        public void reset() {
            mGCTryCount = 0;
        }

        public boolean tryGCOrWait(String metaData, Throwable t) {
            if (mGCTryCount == 0) {
                System.gc();
            }
            if (++mGCTryCount > GC_TRY_COUNT) {
                LatinImeLogger.logOnException(metaData, t);
                return false;
            } else {
                try {
                    Thread.sleep(GC_INTERVAL);
                    return true;
                } catch (InterruptedException e) {
                    Log.e(TAG, "Sleep was interrupted.");
                    LatinImeLogger.logOnException(metaData, t);
                    return false;
                }
            }
        }
    }

    public static boolean hasMultipleEnabledIMEs(Context context) {
        return ((InputMethodManager) context.getSystemService(
                Context.INPUT_METHOD_SERVICE)).getEnabledInputMethodList().size() > 1;
    }

    /* package */ static class RingCharBuffer {
        private static RingCharBuffer sRingCharBuffer = new RingCharBuffer();
        private static final char PLACEHOLDER_DELIMITER_CHAR = '\uFFFC';
        private static final int INVALID_COORDINATE = -2;
        /* package */ static final int BUFSIZE = 20;
        private Context mContext;
        private boolean mEnabled = false;
        private int mEnd = 0;
        /* package */ int mLength = 0;
        private char[] mCharBuf = new char[BUFSIZE];
        private int[] mXBuf = new int[BUFSIZE];
        private int[] mYBuf = new int[BUFSIZE];

        private RingCharBuffer() {
        }
        public static RingCharBuffer getInstance() {
            return sRingCharBuffer;
        }
        public static RingCharBuffer init(Context context, boolean enabled) {
            sRingCharBuffer.mContext = context;
            sRingCharBuffer.mEnabled = enabled;
            return sRingCharBuffer;
        }
        private int normalize(int in) {
            int ret = in % BUFSIZE;
            return ret < 0 ? ret + BUFSIZE : ret;
        }
        public void push(char c, int x, int y) {
            if (!mEnabled) return;
            mCharBuf[mEnd] = c;
            mXBuf[mEnd] = x;
            mYBuf[mEnd] = y;
            mEnd = normalize(mEnd + 1);
            if (mLength < BUFSIZE) {
                ++mLength;
            }
        }
        public char pop() {
            if (mLength < 1) {
                return PLACEHOLDER_DELIMITER_CHAR;
            } else {
                mEnd = normalize(mEnd - 1);
                --mLength;
                return mCharBuf[mEnd];
            }
        }
        public char getLastChar() {
            if (mLength < 1) {
                return PLACEHOLDER_DELIMITER_CHAR;
            } else {
                return mCharBuf[normalize(mEnd - 1)];
            }
        }
        public int getPreviousX(char c, int back) {
            int index = normalize(mEnd - 2 - back);
            if (mLength <= back
                    || Character.toLowerCase(c) != Character.toLowerCase(mCharBuf[index])) {
                return INVALID_COORDINATE;
            } else {
                return mXBuf[index];
            }
        }
        public int getPreviousY(char c, int back) {
            int index = normalize(mEnd - 2 - back);
            if (mLength <= back
                    || Character.toLowerCase(c) != Character.toLowerCase(mCharBuf[index])) {
                return INVALID_COORDINATE;
            } else {
                return mYBuf[index];
            }
        }
        public String getLastString() {
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < mLength; ++i) {
                char c = mCharBuf[normalize(mEnd - 1 - i)];
                if (!((LatinIME)mContext).isWordSeparator(c)) {
                    sb.append(c);
                } else {
                    break;
                }
            }
            return sb.reverse().toString();
        }
        public void reset() {
            mLength = 0;
        }
    }

    public static int editDistance(CharSequence s, CharSequence t) {
        if (s == null || t == null) {
            throw new IllegalArgumentException("editDistance: Arguments should not be null.");
        }
        final int sl = s.length();
        final int tl = t.length();
        int[][] dp = new int [sl + 1][tl + 1];
        for (int i = 0; i <= sl; i++) {
            dp[i][0] = i;
        }
        for (int j = 0; j <= tl; j++) {
            dp[0][j] = j;
        }
        for (int i = 0; i < sl; ++i) {
            for (int j = 0; j < tl; ++j) {
                if (s.charAt(i) == t.charAt(j)) {
                    dp[i + 1][j + 1] = dp[i][j];
                } else {
                    dp[i + 1][j + 1] = 1 + Math.min(dp[i][j],
                            Math.min(dp[i + 1][j], dp[i][j + 1]));
                }
            }
        }
        return dp[sl][tl];
    }

    // In dictionary.cpp, getSuggestion() method,
    // suggestion scores are computed using the below formula.
    // original score (called 'frequency')
    //  := pow(mTypedLetterMultiplier (this is defined 2),
    //         (the number of matched characters between typed word and suggested word))
    //     * (individual word's score which defined in the unigram dictionary,
    //         and this score is defined in range [0, 255].)
    //     * (when before.length() == after.length(),
    //         mFullWordMultiplier (this is defined 2))
    // So, maximum original score is pow(2, before.length()) * 255 * 2
    // So, we can normalize original score by dividing this value.
    private static final int MAX_INITIAL_SCORE = 255;
    private static final int TYPED_LETTER_MULTIPLIER = 2;
    private static final int FULL_WORD_MULTIPLYER = 2;
    public static double calcNormalizedScore(CharSequence before, CharSequence after, int score) {
        final int beforeLength = before.length();
        final int afterLength = after.length();
        final int distance = editDistance(before, after);
        final double maximumScore = MAX_INITIAL_SCORE
                * Math.pow(TYPED_LETTER_MULTIPLIER, beforeLength)
                * FULL_WORD_MULTIPLYER;
        // add a weight based on edit distance.
        // distance <= max(afterLength, beforeLength) == afterLength,
        // so, 0 <= distance / afterLength <= 1
        final double weight = 1.0 - (double) distance / afterLength;
        return (score / maximumScore) * weight;
    }
}