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   /*
    * Copyright 2013 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.handler.codec.http.websocketx;
  
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
  import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
  
  /**
   * Handler that aggregate fragmented WebSocketFrame's.
   *
   * Be aware if PING/PONG/CLOSE frames are send in the middle of a fragmented {@link WebSocketFrame} they will
   * just get forwarded to the next handler in the pipeline.
   */
  public class WebSocketFrameAggregator extends OneToOneDecoder {
      private final int maxFrameSize;
      private WebSocketFrame currentFrame;
      private boolean tooLongFrameFound;
  
      /**
       * Construct a new instance
       *
       * @param maxFrameSize      If the size of the aggregated frame exceeds this value,
       *                          a {@link TooLongFrameException} is thrown.
       */
      public WebSocketFrameAggregator(int maxFrameSize) {
          if (maxFrameSize < 1) {
              throw new IllegalArgumentException("maxFrameSize must be > 0");
          }
          this.maxFrameSize = maxFrameSize;
      }
  
      @Override
      protected Object decode(ChannelHandlerContext ctx, Channel channel, Object message) throws Exception {
          if (!(message instanceof WebSocketFrame)) {
              return message;
          }
          WebSocketFrame msg = (WebSocketFrame) message;
          if (currentFrame == null) {
              tooLongFrameFound = false;
              if (msg.isFinalFragment()) {
                  return msg;
              }
              ChannelBuffer buf = msg.getBinaryData();
  
              if (msg instanceof TextWebSocketFrame) {
                  currentFrame = new TextWebSocketFrame(true, msg.getRsv(), buf);
              } else if (msg instanceof BinaryWebSocketFrame) {
                  currentFrame = new BinaryWebSocketFrame(true, msg.getRsv(), buf);
              } else {
                  throw new IllegalStateException(
                          "WebSocket frame was not of type TextWebSocketFrame or BinaryWebSocketFrame");
              }
              return null;
          }
          if (msg instanceof ContinuationWebSocketFrame) {
              if (tooLongFrameFound) {
                  if (msg.isFinalFragment()) {
                      currentFrame = null;
                  }
                  return null;
              }
              ChannelBuffer content = currentFrame.getBinaryData();
              if (content.readableBytes() > maxFrameSize - msg.getBinaryData().readableBytes()) {
                  tooLongFrameFound = true;
                  throw new TooLongFrameException(
                          "WebSocketFrame length exceeded " + content +
                                  " bytes.");
              }
              currentFrame.setBinaryData(ChannelBuffers.wrappedBuffer(content, msg.getBinaryData()));
  
              if (msg.isFinalFragment()) {
                  WebSocketFrame currentFrame = this.currentFrame;
                  this.currentFrame = null;
                  return currentFrame;
              } else {
                  return null;
              }
          }
          // It is possible to receive CLOSE/PING/PONG frames during fragmented frames so just pass them to the next
          // handler in the chain
          return msg;
     }
 }