FileBackupHelper.java revision 4e14a829129feee14ebe453f61a124784c870610 
1/*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of 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,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.app.backup;
18
19import android.content.Context;
20import android.os.ParcelFileDescriptor;
21import android.util.Log;
22
23import java.io.File;
24
25/**
26 * A helper class which can be used in conjunction with
27 * {@link android.app.backup.BackupAgentHelper} to manage the backup of a set of
28 * files. Whenever backup is performed, all files changed since the last backup
29 * will be saved in their entirety.  During the first time the backup happens,
30 * every file in the list will be backed up.  Note that this should only be
31 * used with small configuration files, not with large binary files.
32 * <p>
33 * During restore, if the helper encounters data for a file that was not
34 * specified when the FileBackupHelper object was constructed, that data
35 * will be ignored.
36 */
37public class FileBackupHelper extends FileBackupHelperBase implements BackupHelper {
38    private static final String TAG = "FileBackupHelper";
39    private static final boolean DEBUG = false;
40
41    Context mContext;
42    File mFilesDir;
43    String[] mFiles;
44
45    /**
46     * Construct a helper to manage backup/restore of entire files within the
47     * application's data directory hierarchy.
48     *
49     * @param context The backup agent's Context object
50     * @param files A list of the files to be backed up or restored.
51     */
52    public FileBackupHelper(Context context, String... files) {
53        super(context);
54
55        mContext = context;
56        mFilesDir = context.getFilesDir();
57        mFiles = files;
58    }
59
60    /**
61     * Based on <code>oldState</code>, determine which of the files from the
62     * application's data directory need to be backed up, write them to the data
63     * stream, and fill in <code>newState</code> with the state as it exists
64     * now. When <code>oldState</code> is <code>null</code>, all the files will
65     * be backed up.
66     * <p>
67     * This should only be called directly from within the {@link BackupAgentHelper}
68     * implementation. See
69     * {@link android.app.backup.BackupAgent#onBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor)}
70     * for a description of parameter meanings.
71     */
72    public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
73            ParcelFileDescriptor newState) {
74        // file names
75        String[] files = mFiles;
76        File base = mContext.getFilesDir();
77        final int N = files.length;
78        String[] fullPaths = new String[N];
79        for (int i=0; i<N; i++) {
80            fullPaths[i] = (new File(base, files[i])).getAbsolutePath();
81        }
82
83        // go
84        performBackup_checked(oldState, data, newState, fullPaths, files);
85    }
86
87    /**
88     * Restore one record [representing a single file] from the restore dataset.
89     * <p>
90     * This should only be called directly from within the {@link BackupAgentHelper}
91     * implementation.
92     */
93    public void restoreEntity(BackupDataInputStream data) {
94        if (DEBUG) Log.d(TAG, "got entity '" + data.getKey() + "' size=" + data.size());
95        String key = data.getKey();
96        if (isKeyInList(key, mFiles)) {
97            File f = new File(mFilesDir, key);
98            writeFile(f, data);
99        }
100    }
101}
102
103