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.file;
  
  import io.netty.buffer.ByteBuf;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.RandomAccessFile;
  import java.nio.ByteBuffer;
  import java.nio.channels.Channels;
  import java.nio.channels.FileChannel;
  import java.nio.channels.ReadableByteChannel;
  import java.nio.channels.WritableByteChannel;
  
  /**
   * Netty Buf backed target buffer for zero-copy read from page store.
   */
  public class NettyBufTargetBuffer implements ReadTargetBuffer {
    private final ByteBuf mTarget;
  
    /**
     * @param target target buffer
     */
    public NettyBufTargetBuffer(ByteBuf target) {
      mTarget = target;
    }
  
    @Override
    public byte[] byteArray() {
      return mTarget.array();
    }
  
    @Override
    public ByteBuffer byteBuffer() {
      throw new UnsupportedOperationException();
    }
  
    @Override
    public int offset() {
      return mTarget.writerIndex();
    }
  
    @Override
    public void offset(int newOffset) {
      mTarget.writerIndex(newOffset);
    }
  
    @Override
    public WritableByteChannel byteChannel() {
      return new WritableByteChannel() {
        @Override
        public int write(ByteBuffer src) throws IOException {
          int readableBytes = src.remaining();
          mTarget.writeBytes(src);
          return readableBytes - src.remaining();
        }
  
        @Override
        public boolean isOpen() {
          return true;
        }
  
        @Override
        public void close() throws IOException {
        }
      };
    }
  
    @Override
    public long remaining() {
      return mTarget.writableBytes();
    }
  
    @Override
    public void writeBytes(byte[] srcArray, int srcOffset, int length) {
      mTarget.writeBytes(srcArray, srcOffset, length);
    }
  
    @Override
    public void writeBytes(ByteBuf buf) {
      mTarget.writeBytes(buf);
    }
  
    @Override
    public int readFromFile(RandomAccessFile file, int length) throws IOException {
      try (FileChannel channel = file.getChannel()) {
        return mTarget.writeBytes(channel, length);
      }
    }
  
    @Override
    public int readFromInputStream(InputStream is, int length) throws IOException {
      int bytesToRead = Math.min(length, mTarget.writableBytes());
      ReadableByteChannel source = Channels.newChannel(is);
      ByteBuffer slice = mTarget.nioBuffer(mTarget.writerIndex(), bytesToRead);
      int bytesRead = source.read(slice);
      if (bytesRead > 0) {
        mTarget.writerIndex(mTarget.writerIndex() + bytesRead);
      }
      return bytesRead;
    }
  
    /**
     * Get the internal Bytebuf object.
     * @return the internal Bytebuf object
     */
    public ByteBuf getTargetBuffer() {
      return mTarget;
    }
  }
  