inputmethod/latin/DictionaryFactory.java

/*
 * Copyright (C) 2011 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.content.res.AssetFileDescriptor;
import android.content.res.Resources;
import android.util.Log;

import java.io.File;
import java.util.Locale;

/**
 * Factory for dictionary instances.
 */
public class DictionaryFactory {

    private static String TAG = DictionaryFactory.class.getSimpleName();

    /**
     * Initializes a dictionary from a dictionary pack.
     *
     * This searches for a content provider providing a dictionary pack for the specified
     * locale. If none is found, it falls back to using the resource passed as fallBackResId
     * as a dictionary.
     * @param context application context for reading resources
     * @param locale the locale for which to create the dictionary
     * @param fallbackResId the id of the resource to use as a fallback if no pack is found
     * @return an initialized instance of Dictionary
     */
    public static Dictionary createDictionaryFromManager(Context context, Locale locale,
            int fallbackResId) {
        if (null == locale) {
            Log.e(TAG, "No locale defined for dictionary");
            return new DictionaryCollection(createBinaryDictionary(context, fallbackResId));
        }

        final AssetFileAddress dictFile = BinaryDictionaryGetter.getDictionaryFile(locale,
                context, fallbackResId);
        if (null == dictFile) return null;
        return new DictionaryCollection(new BinaryDictionary(context,
                dictFile.mFilename, dictFile.mOffset, dictFile.mLength, null));
    }

    /**
     * Initializes a dictionary from a raw resource file
     * @param context application context for reading resources
     * @param resId the resource containing the raw binary dictionary
     * @return an initialized instance of BinaryDictionary
     */
    protected static BinaryDictionary createBinaryDictionary(Context context, int resId) {
        AssetFileDescriptor afd = null;
        try {
            // TODO: IMPORTANT: Do not create a dictionary from a placeholder.
            afd = context.getResources().openRawResourceFd(resId);
            if (afd == null) {
                Log.e(TAG, "Found the resource but it is compressed. resId=" + resId);
                return null;
            }
            if (!isFullDictionary(afd)) return null;
            final String sourceDir = context.getApplicationInfo().sourceDir;
            final File packagePath = new File(sourceDir);
            // TODO: Come up with a way to handle a directory.
            if (!packagePath.isFile()) {
                Log.e(TAG, "sourceDir is not a file: " + sourceDir);
                return null;
            }
            return new BinaryDictionary(context,
                    sourceDir, afd.getStartOffset(), afd.getLength(), null);
        } catch (android.content.res.Resources.NotFoundException e) {
            Log.e(TAG, "Could not find the resource. resId=" + resId);
            return null;
        } finally {
            if (null != afd) {
                try {
                    afd.close();
                } catch (java.io.IOException e) {
                    /* IOException on close ? What am I supposed to do ? */
                }
            }
        }
    }

    /**
     * Create a dictionary from passed data. This is intended for unit tests only.
     * @param context the test context to create this data from.
     * @param dictionary the file to read
     * @param startOffset the offset in the file where the data starts
     * @param length the length of the data
     * @param flagArray the flags to use with this data for testing
     * @return the created dictionary, or null.
     */
    public static Dictionary createDictionaryForTest(Context context, File dictionary,
            long startOffset, long length, Flag[] flagArray) {
        if (dictionary.isFile()) {
            return new BinaryDictionary(context, dictionary.getAbsolutePath(), startOffset, length,
                    flagArray);
        } else {
            Log.e(TAG, "Could not find the file. path=" + dictionary.getAbsolutePath());
            return null;
        }
    }

    /**
     * Find out whether a dictionary is available for this locale.
     * @param context the context on which to check resources.
     * @param locale the locale to check for.
     * @return whether a (non-placeholder) dictionary is available or not.
     */
    public static boolean isDictionaryAvailable(Context context, Locale locale) {
        final Resources res = context.getResources();
        final Locale saveLocale = Utils.setSystemLocale(res, locale);

        final int resourceId = Utils.getMainDictionaryResourceId(res);
        final AssetFileDescriptor afd = res.openRawResourceFd(resourceId);
        final boolean hasDictionary = isFullDictionary(afd);
        try {
            if (null != afd) afd.close();
        } catch (java.io.IOException e) {
            /* Um, what can we do here exactly? */
        }

        Utils.setSystemLocale(res, saveLocale);
        return hasDictionary;
    }

    // TODO: Find the Right Way to find out whether the resource is a placeholder or not.
    // Suggestion : strip the locale, open the placeholder file and store its offset.
    // Upon opening the file, if it's the same offset, then it's the placeholder.
    private static final long PLACEHOLDER_LENGTH = 34;
    /**
     * Finds out whether the data pointed out by an AssetFileDescriptor is a full
     * dictionary (as opposed to null, or to a place holder).
     * @param afd the file descriptor to test, or null
     * @return true if the dictionary is a real full dictionary, false if it's null or a placeholder
     */
    protected static boolean isFullDictionary(final AssetFileDescriptor afd) {
        return (afd != null && afd.getLength() > PLACEHOLDER_LENGTH);
    }
}