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      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      */
     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      */
     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      */
     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