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.apache.bifromq.basecluster.transport;
  
  import static io.netty.handler.codec.ByteToMessageDecoder.MERGE_CUMULATOR;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.handler.codec.ByteToMessageDecoder;
  import io.netty.handler.codec.compression.FastLzFrameDecoder;
  
  public class ProbeHandler extends ChannelInboundHandlerAdapter {
      static final int MAGIC_NUMBER_FAST_LZ = 'F' << 16 | 'L' << 8 | 'Z';
      static final int MAGIC_NUMBER_BYTES = 4;
  
      private ByteBuf cumulation;
      private final ByteToMessageDecoder.Cumulator cumulator = MERGE_CUMULATOR;
  
      @Override
      public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
          if (msg instanceof ByteBuf) {
              ByteBuf in = (ByteBuf) msg;
              boolean first = cumulation == null;
              cumulation = cumulator.cumulate(ctx.alloc(),
                  first ? Unpooled.EMPTY_BUFFER : cumulation, (ByteBuf) msg);
              if (cumulation.readableBytes() < MAGIC_NUMBER_BYTES) {
                  return;
              }
  
              int magic = in.getUnsignedMedium(0);
              if (magic == MAGIC_NUMBER_FAST_LZ) {
                  ctx.pipeline().addAfter("probe", "decompressor", new FastLzFrameDecoder());
              }
              ctx.pipeline().remove("probe");
              super.channelRead(ctx, cumulation);
          } else {
              super.channelRead(ctx, msg);
          }
      }
  }
  