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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.discard;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelEvent;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelState;
  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.WriteCompletionEvent;
  
  /**
   * Handles a client-side channel.
   */
  public class DiscardClientHandler extends SimpleChannelUpstreamHandler {
  
      private long transferredBytes;
      private final byte[] content;
  
      public DiscardClientHandler() {
          content = new byte[DiscardClient.SIZE];
      }
  
      public long getTransferredBytes() {
          return transferredBytes;
      }
  
      @Override
      public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
          if (e instanceof ChannelStateEvent) {
              if (((ChannelStateEvent) e).getState() != ChannelState.INTEREST_OPS) {
                  System.err.println(e);
              }
          }
  
          // Let SimpleChannelHandler call actual event handler methods below.
          super.handleUpstream(ctx, e);
      }
  
      @Override
      public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) {
          // Send the initial messages.
          generateTraffic(e);
      }
  
      @Override
      public void channelInterestChanged(ChannelHandlerContext ctx, ChannelStateEvent e) {
          // Keep sending messages whenever the current socket buffer has room.
          generateTraffic(e);
      }
  
      @Override
      public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
          // Server is supposed to send nothing.  Therefore, do nothing.
      }
  
      @Override
      public void writeComplete(ChannelHandlerContext ctx, WriteCompletionEvent e) {
          transferredBytes += e.getWrittenAmount();
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
          // Close the connection when an exception is raised.
          e.getCause().printStackTrace();
          e.getChannel().close();
      }
  
      private void generateTraffic(ChannelStateEvent e) {
          // Keep generating traffic until the channel is unwritable.
          // A channel becomes unwritable when its internal buffer is full.
          // If you keep writing messages ignoring this property,
          // you will end up with an OutOfMemoryError.
          Channel channel = e.getChannel();
          while (channel.isWritable()) {
              ChannelBuffer m = nextMessage();
              if (m == null) {
                  break;
              }
              channel.write(m);
          }
     }
 
     private ChannelBuffer nextMessage() {
         return ChannelBuffers.wrappedBuffer(content);
     }
 }