content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.network.protocol.databuffer;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  
  /**
   * This interface is a simple wrapper for the optional data that an RPCMessage may have. This allows
   * subclasses to support different representations of the data.
   */
  public interface DataBuffer {
    /**
     * Returns an object for writing to a netty channel.
     *
     * @return the object to output to Netty. Must be ByteBuf or FileRegion
     */
    Object getNettyOutput();
  
    /**
     * Returns the length of the data.
     *
     * @return the length of the data in bytes
     */
    long getLength();
  
    /**
     * Returns a {@link ByteBuffer} for read-only access to the data.
     *
     * @return a read-only ByteBuffer representing the data
     */
    ByteBuffer getReadOnlyByteBuffer();
  
    /**
     * Transfers this buffer's data to the specified destination starting at
     * the current {@code readerIndex} and increases the {@code readerIndex}
     * by the number of the transferred bytes (= {@code length}).
     *
     * @param dst the destination
     * @param dstIndex the first index of the destination
     * @param length the number of bytes to transfer
     */
    void readBytes(byte[] dst, int dstIndex, int length);
  
    /**
     * Transfers this buffer's data to the given stream.
     *
     * @param outputStream the stream to transfer data to
     * @param length length of the data to be transferred
     */
    void readBytes(OutputStream outputStream, int length) throws IOException;
  
    /**
     * Transfers this buffer's data to the given {@link ByteBuffer}.
     *
     * @param outputBuf the buffer to transfer data to
     */
    void readBytes(ByteBuffer outputBuf);
  
    /**
     * @return the number of readable bytes remaining
     */
    int readableBytes();
  
    /**
     * Releases the underlying buffer of this DataBuffer if no longer needed.
     */
    void release();
  }
  