content: /*
   * Copyright (C) 2018 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.android.server.backup;
  
  import static com.android.server.backup.BackupManagerService.DEBUG;
  import static com.android.server.backup.BackupManagerService.TAG;
  
  import android.util.Slog;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  
  /** User settings which are persisted across reboots. */
  final class UserBackupManagerFilePersistedSettings {
      // File containing backup-enabled state. Contains a single byte to denote enabled status.
      // Nonzero is enabled; file missing or a zero byte is disabled.
      private static final String BACKUP_ENABLE_FILE = "backup_enabled";
  
      static boolean readBackupEnableState(int userId) {
          return readBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId));
      }
  
      static void writeBackupEnableState(int userId, boolean enable) {
          writeBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId), enable);
      }
  
      private static boolean readBackupEnableState(File baseDir) {
          File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
          if (enableFile.exists()) {
              try (FileInputStream fin = new FileInputStream(enableFile)) {
                  int state = fin.read();
                  return state != 0;
              } catch (IOException e) {
                  // can't read the file; fall through to assume disabled
                  Slog.e(TAG, "Cannot read enable state; assuming disabled");
              }
          } else {
              if (DEBUG) {
                  Slog.i(TAG, "isBackupEnabled() => false due to absent settings file");
              }
          }
          return false;
      }
  
      private static void writeBackupEnableState(File baseDir, boolean enable) {
          File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
          File stage = new File(baseDir, BACKUP_ENABLE_FILE + "-stage");
          try (FileOutputStream fout = new FileOutputStream(stage)) {
              fout.write(enable ? 1 : 0);
              fout.close();
              stage.renameTo(enableFile);
              // will be synced immediately by the try-with-resources call to close()
          } catch (IOException | RuntimeException e) {
              Slog.e(
                      TAG,
                      "Unable to record backup enable state; reverting to disabled: "
                              + e.getMessage());
              enableFile.delete();
              stage.delete();
          }
      }
  }
  