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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.example.proxy;
  
  import org.jboss.netty.bootstrap.ClientBootstrap;
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelStateEvent;
  import org.jboss.netty.channel.ExceptionEvent;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
  import org.jboss.netty.channel.socket.ClientSocketChannelFactory;
  
  import java.net.InetSocketAddress;
  
  public class HexDumpProxyInboundHandler extends SimpleChannelUpstreamHandler {
  
      private final ClientSocketChannelFactory cf;
  
      // This lock guards against the race condition that overrides the
      // OP_READ flag incorrectly.
      // See the related discussion: http://markmail.org/message/x7jc6mqx6ripynqf
      final Object trafficLock = new Object();
  
      private volatile Channel outboundChannel;
  
      public HexDumpProxyInboundHandler(ClientSocketChannelFactory cf) {
          this.cf = cf;
      }
  
      @Override
      public void channelOpen(ChannelHandlerContext ctx, ChannelStateEvent e) {
          // Suspend incoming traffic until connected to the remote host.
          final Channel inboundChannel = e.getChannel();
          inboundChannel.setReadable(false);
  
          // Start the connection attempt.
          ClientBootstrap cb = new ClientBootstrap(cf);
          cb.getPipeline().addLast("handler", new OutboundHandler(e.getChannel()));
          ChannelFuture f = cb.connect(new InetSocketAddress(HexDumpProxy.REMOTE_HOST, HexDumpProxy.REMOTE_PORT));
  
          outboundChannel = f.getChannel();
          f.addListener(new ChannelFutureListener() {
              public void operationComplete(ChannelFuture future) {
                  if (future.isSuccess()) {
                      // Connection attempt succeeded:
                      // Begin to accept incoming traffic.
                      inboundChannel.setReadable(true);
                  } else {
                      // Close the connection if the connection attempt has failed.
                      inboundChannel.close();
                  }
              }
          });
      }
  
      @Override
      public void messageReceived(ChannelHandlerContext ctx, final MessageEvent e) {
          ChannelBuffer msg = (ChannelBuffer) e.getMessage();
          //System.err.println(">>> " + ChannelBuffers.hexDump(msg));
          synchronized (trafficLock) {
              outboundChannel.write(msg);
              // If outboundChannel is saturated, do not read until notified in
              // OutboundHandler.channelInterestChanged().
              if (!outboundChannel.isWritable()) {
                  e.getChannel().setReadable(false);
              }
          }
      }
  
      @Override
      public void channelInterestChanged(ChannelHandlerContext ctx, ChannelStateEvent e) {
          // If inboundChannel is not saturated anymore, continue accepting
          // the incoming traffic from the outboundChannel.
          synchronized (trafficLock) {
              if (e.getChannel().isWritable()) {
                  if (outboundChannel != null) {
                      outboundChannel.setReadable(true);
                  }
              }
          }
      }
 
     @Override
     public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) {
         if (outboundChannel != null) {
             closeOnFlush(outboundChannel);
         }
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
         e.getCause().printStackTrace();
         closeOnFlush(e.getChannel());
     }
 
     private class OutboundHandler extends SimpleChannelUpstreamHandler {
 
         private final Channel inboundChannel;
 
         OutboundHandler(Channel inboundChannel) {
             this.inboundChannel = inboundChannel;
         }
 
         @Override
         public void messageReceived(ChannelHandlerContext ctx, final MessageEvent e) {
             ChannelBuffer msg = (ChannelBuffer) e.getMessage();
             //System.err.println("<<< " + ChannelBuffers.hexDump(msg));
             synchronized (trafficLock) {
                 inboundChannel.write(msg);
                 // If inboundChannel is saturated, do not read until notified in
                 // HexDumpProxyInboundHandler.channelInterestChanged().
                 if (!inboundChannel.isWritable()) {
                     e.getChannel().setReadable(false);
                 }
             }
         }
 
         @Override
         public void channelInterestChanged(ChannelHandlerContext ctx, ChannelStateEvent e) {
             // If outboundChannel is not saturated anymore, continue accepting
             // the incoming traffic from the inboundChannel.
             synchronized (trafficLock) {
                 if (e.getChannel().isWritable()) {
                     inboundChannel.setReadable(true);
                 }
             }
         }
 
         @Override
         public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) {
             closeOnFlush(inboundChannel);
         }
 
         @Override
         public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
             e.getCause().printStackTrace();
             closeOnFlush(e.getChannel());
         }
     }
 
     /**
      * Closes the specified channel after all queued write requests are flushed.
      */
     static void closeOnFlush(Channel ch) {
         if (ch.isConnected()) {
             ch.write(ChannelBuffers.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
         }
     }
 }