content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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 org.apache.spark.network.buffer;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.ByteBuffer;
  
  /**
   * This interface provides an immutable view for data in the form of bytes. The implementation
   * should specify how the data is provided:
   *
   * - {@link FileSegmentManagedBuffer}: data backed by part of a file
   * - {@link NioManagedBuffer}: data backed by a NIO ByteBuffer
   * - {@link NettyManagedBuffer}: data backed by a Netty ByteBuf
   *
   * The concrete buffer implementation might be managed outside the JVM garbage collector.
   * For example, in the case of {@link NettyManagedBuffer}, the buffers are reference counted.
   * In that case, if the buffer is going to be passed around to a different thread, retain/release
   * should be called.
   */
  public abstract class ManagedBuffer {
  
    /** Number of bytes of the data. */
    public abstract long size();
  
    /**
     * Exposes this buffer's data as an NIO ByteBuffer. Changing the position and limit of the
     * returned ByteBuffer should not affect the content of this buffer.
     */
    // TODO: Deprecate this, usage may require expensive memory mapping or allocation.
    public abstract ByteBuffer nioByteBuffer() throws IOException;
  
    /**
     * Exposes this buffer's data as an InputStream. The underlying implementation does not
     * necessarily check for the length of bytes read, so the caller is responsible for making sure
     * it does not go over the limit.
     */
    public abstract InputStream createInputStream() throws IOException;
  
    /**
     * Increment the reference count by one if applicable.
     */
    public abstract ManagedBuffer retain();
  
    /**
     * If applicable, decrement the reference count by one and deallocates the buffer if the
     * reference count reaches zero.
     */
    public abstract ManagedBuffer release();
  
    /**
     * Convert the buffer into an Netty object, used to write the data out. The return value is either
     * a {@link io.netty.buffer.ByteBuf} or a {@link io.netty.channel.FileRegion}.
     *
     * If this method returns a ByteBuf, then that buffer's reference count will be incremented and
     * the caller will be responsible for releasing this new reference.
     */
    public abstract Object convertToNetty() throws IOException;
  }
  