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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:
    *
    * https://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 io.netty.handler.codec.sctp;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandler;
  import io.netty.channel.sctp.SctpMessage;
  import io.netty.handler.codec.MessageToMessageDecoder;
  import io.netty.util.collection.IntObjectHashMap;
  import io.netty.util.collection.IntObjectMap;
  
  import java.util.List;
  
  /**
   * {@link MessageToMessageDecoder} which will take care of handle fragmented {@link SctpMessage}s, so
   * only <strong>complete</strong> {@link SctpMessage}s will be forwarded to the next
   * {@link ChannelInboundHandler}.
   */
  public class SctpMessageCompletionHandler extends MessageToMessageDecoder<SctpMessage> {
      private final IntObjectMap<ByteBuf> fragments = new IntObjectHashMap<ByteBuf>();
  
      @Override
      protected void decode(ChannelHandlerContext ctx, SctpMessage msg, List<Object> out) throws Exception {
          final ByteBuf byteBuf = msg.content();
          final int protocolIdentifier = msg.protocolIdentifier();
          final int streamIdentifier = msg.streamIdentifier();
          final boolean isComplete = msg.isComplete();
          final boolean isUnordered = msg.isUnordered();
  
          ByteBuf frag = fragments.remove(streamIdentifier);
          if (frag == null) {
              frag = Unpooled.EMPTY_BUFFER;
          }
  
          if (isComplete && !frag.isReadable()) {
              //data chunk is not fragmented
              out.add(msg);
          } else if (!isComplete && frag.isReadable()) {
              //more message to complete
              fragments.put(streamIdentifier, Unpooled.wrappedBuffer(frag, byteBuf));
          } else if (isComplete && frag.isReadable()) {
              //last message to complete
              SctpMessage assembledMsg = new SctpMessage(
                      protocolIdentifier,
                      streamIdentifier,
                      isUnordered,
                      Unpooled.wrappedBuffer(frag, byteBuf));
              out.add(assembledMsg);
          } else {
              //first incomplete message
              fragments.put(streamIdentifier, byteBuf);
          }
          byteBuf.retain();
      }
  
      @Override
      public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
          for (ByteBuf buffer: fragments.values()) {
              buffer.release();
          }
          fragments.clear();
          super.handlerRemoved(ctx);
      }
  }