1 /*
2  * Copyright (C) 2018 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 com.android.server.backup;
18 
19 import static com.android.server.backup.BackupManagerService.DEBUG;
20 import static com.android.server.backup.BackupManagerService.TAG;
21 
22 import android.util.Slog;
23 
24 import java.io.File;
25 import java.io.FileInputStream;
26 import java.io.FileOutputStream;
27 import java.io.IOException;
28 
29 /** User settings which are persisted across reboots. */
30 final class UserBackupManagerFilePersistedSettings {
31     // File containing backup-enabled state. Contains a single byte to denote enabled status.
32     // Nonzero is enabled; file missing or a zero byte is disabled.
33     private static final String BACKUP_ENABLE_FILE = "backup_enabled";
34 
readBackupEnableState(int userId)35     static boolean readBackupEnableState(int userId) {
36         return readBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId));
37     }
38 
writeBackupEnableState(int userId, boolean enable)39     static void writeBackupEnableState(int userId, boolean enable) {
40         writeBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId), enable);
41     }
42 
readBackupEnableState(File baseDir)43     private static boolean readBackupEnableState(File baseDir) {
44         File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
45         if (enableFile.exists()) {
46             try (FileInputStream fin = new FileInputStream(enableFile)) {
47                 int state = fin.read();
48                 return state != 0;
49             } catch (IOException e) {
50                 // can't read the file; fall through to assume disabled
51                 Slog.e(TAG, "Cannot read enable state; assuming disabled");
52             }
53         } else {
54             if (DEBUG) {
55                 Slog.i(TAG, "isBackupEnabled() => false due to absent settings file");
56             }
57         }
58         return false;
59     }
60 
writeBackupEnableState(File baseDir, boolean enable)61     private static void writeBackupEnableState(File baseDir, boolean enable) {
62         File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
63         File stage = new File(baseDir, BACKUP_ENABLE_FILE + "-stage");
64         try (FileOutputStream fout = new FileOutputStream(stage)) {
65             fout.write(enable ? 1 : 0);
66             fout.close();
67             stage.renameTo(enableFile);
68             // will be synced immediately by the try-with-resources call to close()
69         } catch (IOException | RuntimeException e) {
70             Slog.e(
71                     TAG,
72                     "Unable to record backup enable state; reverting to disabled: "
73                             + e.getMessage());
74             enableFile.delete();
75             stage.delete();
76         }
77     }
78 }
79