MetadataHandler.java revision a91561aa58db1c43092c1caecc051a11fa5391c7 
1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5 * use this file except in compliance with the License. You may obtain a copy of
6 * the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations under
14 * the License.
15 */
16
17package com.android.inputmethod.dictionarypack;
18
19import android.content.Context;
20import android.database.Cursor;
21
22import java.io.IOException;
23import java.io.InputStreamReader;
24import java.util.Collections;
25import java.util.ArrayList;
26import java.util.List;
27
28/**
29 * Helper class to easy up manipulation of dictionary pack metadata.
30 */
31public class MetadataHandler {
32    @SuppressWarnings("unused")
33    private static final String TAG = "DictionaryProvider:" + MetadataHandler.class.getSimpleName();
34
35    // The canonical file name for metadata. This is not the name of a real file on the
36    // device, but a symbolic name used in the database and in metadata handling. It is never
37    // tested against, only used for human-readability as the file name for the metadata.
38    public final static String METADATA_FILENAME = "metadata.json";
39
40    /**
41     * Reads the data from the cursor and store it in metadata objects.
42     * @param results the cursor to read data from.
43     * @return the constructed list of wordlist metadata.
44     */
45    private static List<WordListMetadata> makeMetadataObject(final Cursor results) {
46        final ArrayList<WordListMetadata> buildingMetadata = new ArrayList<>();
47        if (null != results && results.moveToFirst()) {
48            final int localeColumn = results.getColumnIndex(MetadataDbHelper.LOCALE_COLUMN);
49            final int typeColumn = results.getColumnIndex(MetadataDbHelper.TYPE_COLUMN);
50            final int descriptionColumn =
51                    results.getColumnIndex(MetadataDbHelper.DESCRIPTION_COLUMN);
52            final int idIndex = results.getColumnIndex(MetadataDbHelper.WORDLISTID_COLUMN);
53            final int updateIndex = results.getColumnIndex(MetadataDbHelper.DATE_COLUMN);
54            final int fileSizeIndex = results.getColumnIndex(MetadataDbHelper.FILESIZE_COLUMN);
55            final int rawChecksumIndex =
56                    results.getColumnIndex(MetadataDbHelper.RAW_CHECKSUM_COLUMN);
57            final int checksumIndex = results.getColumnIndex(MetadataDbHelper.CHECKSUM_COLUMN);
58            final int localFilenameIndex =
59                    results.getColumnIndex(MetadataDbHelper.LOCAL_FILENAME_COLUMN);
60            final int remoteFilenameIndex =
61                    results.getColumnIndex(MetadataDbHelper.REMOTE_FILENAME_COLUMN);
62            final int versionIndex = results.getColumnIndex(MetadataDbHelper.VERSION_COLUMN);
63            final int formatVersionIndex =
64                    results.getColumnIndex(MetadataDbHelper.FORMATVERSION_COLUMN);
65            do {
66                buildingMetadata.add(new WordListMetadata(results.getString(idIndex),
67                        results.getInt(typeColumn),
68                        results.getString(descriptionColumn),
69                        results.getLong(updateIndex),
70                        results.getLong(fileSizeIndex),
71                        results.getString(rawChecksumIndex),
72                        results.getString(checksumIndex),
73                        results.getString(localFilenameIndex),
74                        results.getString(remoteFilenameIndex),
75                        results.getInt(versionIndex),
76                        results.getInt(formatVersionIndex),
77                        0, results.getString(localeColumn)));
78            } while (results.moveToNext());
79        }
80        return Collections.unmodifiableList(buildingMetadata);
81    }
82
83    /**
84     * Gets the whole metadata, for installed and not installed dictionaries.
85     * @param context The context to open files over.
86     * @param clientId the client id for retrieving the database. null for default (deprecated)
87     * @return The current metadata.
88     */
89    public static List<WordListMetadata> getCurrentMetadata(final Context context,
90            final String clientId) {
91        // If clientId is null, we get a cursor on the default database (see
92        // MetadataDbHelper#getInstance() for more on this)
93        final Cursor results = MetadataDbHelper.queryCurrentMetadata(context, clientId);
94        // If null, we should return makeMetadataObject(null), so we go through.
95        try {
96            return makeMetadataObject(results);
97        } finally {
98            if (null != results) {
99                results.close();
100            }
101        }
102    }
103
104    /**
105     * Read metadata from a stream.
106     * @param input The stream to read from.
107     * @return The read metadata.
108     * @throws IOException if the input stream cannot be read
109     * @throws BadFormatException if the stream is not in a known format
110     */
111    public static List<WordListMetadata> readMetadata(final InputStreamReader input)
112            throws IOException, BadFormatException {
113        return MetadataParser.parseMetadata(input);
114    }
115
116    /**
117     * Finds a single WordListMetadata inside a whole metadata chunk.
118     *
119     * Searches through the whole passed metadata for the first WordListMetadata associated
120     * with the passed ID. If several metadata chunks with the same id are found, it will
121     * always return the one with the bigger FormatVersion that is less or equal than the
122     * maximum supported format version (as listed in UpdateHandler).
123     * This will NEVER return the metadata with a FormatVersion bigger than what is supported,
124     * even if it is the only word list with this ID.
125     *
126     * @param metadata the metadata to search into.
127     * @param id the word list ID of the metadata to find.
128     * @return the associated metadata, or null if not found.
129     */
130    public static WordListMetadata findWordListById(final List<WordListMetadata> metadata,
131            final String id) {
132        WordListMetadata bestWordList = null;
133        int bestFormatVersion = Integer.MIN_VALUE; // To be sure we can't be inadvertently smaller
134        for (WordListMetadata wordList : metadata) {
135            if (id.equals(wordList.mId)
136                    && wordList.mFormatVersion <= UpdateHandler.MAXIMUM_SUPPORTED_FORMAT_VERSION
137                    && wordList.mFormatVersion > bestFormatVersion) {
138                bestWordList = wordList;
139                bestFormatVersion = wordList.mFormatVersion;
140            }
141        }
142        // If we didn't find any match we'll return null.
143        return bestWordList;
144    }
145}
146