content: /*
   * Copyright (C) 2009 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 android.app.backup;
  
  import android.annotation.UnsupportedAppUsage;
  import java.io.InputStream;
  import java.io.IOException;
  
  /**
   * Provides an {@link java.io.InputStream}-like interface for accessing an
   * entity's data during a restore operation. Used by {@link BackupHelper} classes within the {@link
   * BackupAgentHelper} mechanism.
   * <p>
   * When {@link BackupHelper#restoreEntity(BackupDataInputStream) BackupHelper.restoreEntity()}
   * is called, the current entity's header has already been read from the underlying
   * {@link BackupDataInput}.  The entity's key string and total data size are available
   * through this class's {@link #getKey()} and {@link #size()} methods, respectively.
   * <p class="note">
   * <strong>Note:</strong> The caller should take care not to seek or close the underlying data
   * source, nor read more than {@link #size()} bytes from the stream.</p>
   *
   * @see BackupAgentHelper
   * @see BackupHelper
   */
  public class BackupDataInputStream extends InputStream {
  
      @UnsupportedAppUsage
      String key;
      @UnsupportedAppUsage
      int dataSize;
  
      BackupDataInput mData;
      byte[] mOneByte;
  
      /** @hide */
      BackupDataInputStream(BackupDataInput data) {
          mData = data;
      }
  
      /**
       * Read one byte of entity data from the stream, returning it as
       * an integer value.  If more than {@link #size()} bytes of data
       * are read from the stream, the output of this method is undefined.
       *
       * @return The byte read, or undefined if the end of the stream has been reached.
       */
      public int read() throws IOException {
          byte[] one = mOneByte;
          if (mOneByte == null) {
              one = mOneByte = new byte[1];
          }
          mData.readEntityData(one, 0, 1);
          return one[0];
      }
  
      /**
       * Read up to {@code size} bytes of data into a byte array, beginning at position
       * {@code offset} within the array.
       *
       * @param b Byte array into which the data will be read
       * @param offset The data will be stored in {@code b} beginning at this index
       *   within the array.
       * @param size The number of bytes to read in this operation.  If insufficient
       *   data exists within the entity to fulfill this request, only as much data
       *   will be read as is available.
       * @return The number of bytes of data read, or zero if all of the entity's
       *   data has already been read.
       */
      public int read(byte[] b, int offset, int size) throws IOException {
          return mData.readEntityData(b, offset, size);
      }
  
      /**
       * Read enough entity data into a byte array to fill the array.
       *
       * @param b Byte array to fill with data from the stream.  If the stream does not
       *   have sufficient data to fill the array, then the contents of the remainder of
       *   the array will be undefined.
       * @return The number of bytes of data read, or zero if all of the entity's
       *   data has already been read.
       */
      public int read(byte[] b) throws IOException {
          return mData.readEntityData(b, 0, b.length);
      }
  
      /**
       * Report the key string associated with this entity within the backup data set.
       *
       * @return The key string for this entity, equivalent to calling
       *   {@link BackupDataInput#getKey()} on the underlying {@link BackupDataInput}.
       */
      public String getKey() {
          return this.key;
      }
  
      /**
       * Report the total number of bytes of data available for the current entity.
       *
       * @return The number of data bytes available, equivalent to calling
       *   {@link BackupDataInput#getDataSize()} on the underlying {@link BackupDataInput}.
       */
      public int size() {
          return this.dataSize;
      }
  }
  
  
  