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 com.datastax.oss.driver.internal.core.protocol;
  
  import com.datastax.oss.driver.api.core.connection.CrcMismatchException;
  import com.datastax.oss.protocol.internal.Segment;
  import com.datastax.oss.protocol.internal.SegmentCodec;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
  import java.nio.ByteOrder;
  import net.jcip.annotations.NotThreadSafe;
  
  /**
   * Decodes {@link Segment}s from a stream of bytes.
   *
   * <p>This works like a regular length-field-based decoder, but we override {@link
   * #getUnadjustedFrameLength} to handle two peculiarities: the length is encoded on 17 bits, and we
   * also want to check the header CRC before we use it. So we parse the whole segment header ahead of
   * time, and store it until we're ready to build the segment.
   */
  @NotThreadSafe
  public class BytesToSegmentDecoder extends LengthFieldBasedFrameDecoder {
  
    private final SegmentCodec<ByteBuf> segmentCodec;
    private SegmentCodec.Header header;
  
    public BytesToSegmentDecoder(@NonNull SegmentCodec<ByteBuf> segmentCodec) {
      super(
          // max length (Netty wants this to be the overall length including everything):
          segmentCodec.headerLength()
              + SegmentCodec.CRC24_LENGTH
              + Segment.MAX_PAYLOAD_LENGTH
              + SegmentCodec.CRC32_LENGTH,
          // offset and size of the "length" field: that's the whole header
          0,
          segmentCodec.headerLength() + SegmentCodec.CRC24_LENGTH,
          // length adjustment: add the trailing CRC to the declared length
          SegmentCodec.CRC32_LENGTH,
          // bytes to skip: the header (we've already parsed it while reading the length)
          segmentCodec.headerLength() + SegmentCodec.CRC24_LENGTH);
      this.segmentCodec = segmentCodec;
    }
  
    @Override
    protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
      try {
        ByteBuf payloadAndCrc = (ByteBuf) super.decode(ctx, in);
        if (payloadAndCrc == null) {
          return null;
        } else {
          assert header != null;
          try {
            Segment<ByteBuf> segment = segmentCodec.decode(header, payloadAndCrc);
            header = null;
            return segment;
          } catch (com.datastax.oss.protocol.internal.CrcMismatchException e) {
            throw new CrcMismatchException(e.getMessage());
          }
        }
      } catch (Exception e) {
        // Don't hold on to a stale header if we failed to decode the rest of the segment
        header = null;
        throw e;
      }
    }
  
    @Override
    protected long getUnadjustedFrameLength(ByteBuf buffer, int offset, int length, ByteOrder order) {
      // The parent class calls this repeatedly for the same "frame" if there weren't enough
      // accumulated bytes the first time. Only decode the header the first time:
      if (header == null) {
        try {
          header = segmentCodec.decodeHeader(buffer.slice(offset, length));
        } catch (com.datastax.oss.protocol.internal.CrcMismatchException e) {
          throw new CrcMismatchException(e.getMessage());
        }
      }
      return header.payloadLength;
    }
  }
  