content: /*
   * Copyright (C) 2016 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.os;
  
  import android.system.ErrnoException;
  import android.system.OsConstants;
  
  /**
   * Callback that handles file system requests from ProxyFileDescriptor.
   *
   * All callback methods except for onRelease should throw {@link android.system.ErrnoException}
   * with proper errno on errors. See
   * <a href="http://man7.org/linux/man-pages/man3/errno.3.html">errno(3)</a> and
   * {@link android.system.OsConstants}.
   *
   * Typical errnos are
   *
   * <ul>
   * <li>{@link android.system.OsConstants#EIO} for general I/O issues
   * <li>{@link android.system.OsConstants#ENOENT} when the file is not found
   * <li>{@link android.system.OsConstants#EBADF} if the file doesn't allow read/write operations
   *     based on how it was opened.  (For example, trying to write a file that was opened read-only.)
   * <li>{@link android.system.OsConstants#ENOSPC} if you cannot handle a write operation to
   *     space/quota limitations.
   * </ul>
   * @see android.os.storage.StorageManager#openProxyFileDescriptor(int, ProxyFileDescriptorCallback,
   *     Handler)
   */
  public abstract class ProxyFileDescriptorCallback {
      /**
       * Returns size of bytes provided by the file descriptor.
       * @return Size of bytes.
       * @throws ErrnoException ErrnoException containing E constants in OsConstants.
       */
      public long onGetSize() throws ErrnoException {
          throw new ErrnoException("onGetSize", OsConstants.EBADF);
      }
  
      /**
       * Provides bytes read from file descriptor.
       * It needs to return exact requested size of bytes unless it reaches file end.
       * @param offset Offset in bytes from the file head specifying where to read bytes. If a seek
       *     operation is conducted on the file descriptor, then a read operation is requested, the
       *     offset refrects the proper position of requested bytes.
       * @param size Size for read bytes.
       * @param data Byte array to store read bytes.
       * @return Size of bytes returned by the function.
       * @throws ErrnoException ErrnoException containing E constants in OsConstants.
       */
      public int onRead(long offset, int size, byte[] data) throws ErrnoException {
          throw new ErrnoException("onRead", OsConstants.EBADF);
      }
  
      /**
       * Handles bytes written to file descriptor.
       * @param offset Offset in bytes from the file head specifying where to write bytes. If a seek
       *     operation is conducted on the file descriptor, then a write operation is requested, the
       *     offset refrects the proper position of requested bytes.
       * @param size Size for write bytes.
       * @param data Byte array to be written to somewhere.
       * @return Size of bytes processed by the function.
       * @throws ErrnoException ErrnoException containing E constants in OsConstants.
       */
      public int onWrite(long offset, int size, byte[] data) throws ErrnoException {
          throw new ErrnoException("onWrite", OsConstants.EBADF);
      }
  
      /**
       * Ensures all the written data are stored in permanent storage device.
       * For example, if it has data stored in on memory cache, it needs to flush data to storage
       * device.
       * @throws ErrnoException ErrnoException containing E constants in OsConstants.
       */
      public void onFsync() throws ErrnoException {
          throw new ErrnoException("onFsync", OsConstants.EINVAL);
      }
  
      /**
       * Invoked after the file is closed.
       */
      abstract public void onRelease();
  }
  