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 
17 package android.app.backup;
18 
19 import android.content.Context;
20 import android.os.ParcelFileDescriptor;
21 import android.util.Log;
22 
23 import java.io.File;
24 
25 /**
26  * A helper class that 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. When backup first occurs,
30  * every file in the list provided to {@link #FileBackupHelper} will be backed up.
31  * <p>
32  * During restore, if the helper encounters data for a file that was not
33  * specified when the FileBackupHelper object was constructed, that data
34  * will be ignored.
35  * <p class="note"><strong>Note:</strong> This should be
36  * used only with small configuration files, not large binary files.
37  */
38 public class FileBackupHelper extends FileBackupHelperBase implements BackupHelper {
39     private static final String TAG = "FileBackupHelper";
40     private static final boolean DEBUG = false;
41 
42     Context mContext;
43     File mFilesDir;
44     String[] mFiles;
45 
46     /**
47      * Construct a helper to manage backup/restore of entire files within the
48      * application's data directory hierarchy.
49      *
50      * @param context The backup agent's Context object
51      * @param files A list of the files to be backed up or restored.
52      */
FileBackupHelper(Context context, String... files)53     public FileBackupHelper(Context context, String... files) {
54         super(context);
55 
56         mContext = context;
57         mFilesDir = context.getFilesDir();
58         mFiles = files;
59     }
60 
61     /**
62      * Based on <code>oldState</code>, determine which of the files from the
63      * application's data directory need to be backed up, write them to the data
64      * stream, and fill in <code>newState</code> with the state as it exists
65      * now. When <code>oldState</code> is <code>null</code>, all the files will
66      * be backed up.
67      * <p>
68      * This should only be called directly from within the {@link BackupAgentHelper}
69      * implementation. See
70      * {@link android.app.backup.BackupAgent#onBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor)}
71      * for a description of parameter meanings.
72      */
performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState)73     public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
74             ParcelFileDescriptor newState) {
75         // file names
76         String[] files = mFiles;
77         File base = mContext.getFilesDir();
78         final int N = files.length;
79         String[] fullPaths = new String[N];
80         for (int i=0; i<N; i++) {
81             fullPaths[i] = (new File(base, files[i])).getAbsolutePath();
82         }
83 
84         // go
85         performBackup_checked(oldState, data, newState, fullPaths, files);
86     }
87 
88     /**
89      * Restore one record [representing a single file] from the restore dataset.
90      * <p>
91      * This should only be called directly from within the {@link BackupAgentHelper}
92      * implementation.
93      */
restoreEntity(BackupDataInputStream data)94     public void restoreEntity(BackupDataInputStream data) {
95         if (DEBUG) Log.d(TAG, "got entity '" + data.getKey() + "' size=" + data.size());
96         String key = data.getKey();
97         if (isKeyInList(key, mFiles)) {
98             File f = new File(mFilesDir, key);
99             writeFile(f, data);
100         }
101     }
102 }
103 
104