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.acme.netty.custom.correlation.impl;
  
  import java.nio.charset.Charset;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.DecoderException;
  import io.netty.handler.codec.DelimiterBasedFrameDecoder;
  
  /**
   * Netty decoder that assembles a complete messages from the frames received by Netty.
   * The decoder uses delimter based on start and end byte markers, to know when all
   * data for a complete message has been received.
   */
  public class MyCodecDecoder extends DelimiterBasedFrameDecoder {
  
      private static final int MAX_FRAME_LENGTH = 4096;
  
      private static char startByte = 0x0b; // 11 decimal
      private static char endByte1 = 0x1c; // 28 decimal
      private static char endByte2 = 0x0d; // 13 decimal
  
      public MyCodecDecoder() {
          super(MAX_FRAME_LENGTH, true, Unpooled.copiedBuffer(
                  new char[] { endByte1, endByte2 }, Charset.defaultCharset()));
      }
  
      @Override
      protected Object decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception {
          ByteBuf buf = (ByteBuf) super.decode(ctx, buffer);
          if (buf != null) {
              try {
                  int pos = buf.bytesBefore((byte) startByte);
                  if (pos >= 0) {
                      ByteBuf msg = buf.readerIndex(pos + 1).slice();
                      return asString(msg);
                  } else {
                      throw new DecoderException("Did not find start byte " + (int) startByte);
                  }
              } finally {
                  // We need to release the buf here to avoid the memory leak
                  buf.release();
              }
          }
          // Message not complete yet - return null to be called again
          return null;
      }
  
      private String asString(ByteBuf msg) {
          // convert the message to a String which Camel will then use
          String text = msg.toString(Charset.defaultCharset());
          return text;
      }
  
  }
  