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.cassandra.net;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.util.Collection;
  import java.util.zip.CRC32;
  
  import io.netty.channel.ChannelPipeline;
  import net.jpountz.lz4.LZ4Factory;
  import net.jpountz.lz4.LZ4SafeDecompressor;
  
  import static org.apache.cassandra.utils.Crc.*;
  
  /**
   * Framing format that compresses payloads with LZ4, and protects integrity of data in movement with CRCs
   * (of both header and payload).
   *
   * Every on-wire frame contains:
   * 1. Compressed length            (17 bits)
   * 2. Uncompressed length          (17 bits)
   * 3. {@code isSelfContained} flag (1 bit)
   * 4. Header padding               (5 bits)
   * 5. CRC24 of Header contents     (24 bits)
   * 6. Compressed Payload           (up to 2 ^ 17 - 1 bits)
   * 7. CRC32 of Compressed Payload  (32 bits)
   *
   *  0                   1                   2                   3
   *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |        Compressed Length        |     Uncompressed Length
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   *     |C|         |                 CRC24 of Header               |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                                                               |
   * +                                                               +
   * |                      Compressed Payload                       |
   * +                                                               +
   * |                                                               |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                  CRC32 of Compressed Payload                  |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   */
  public final class FrameDecoderLZ4 extends FrameDecoderWith8bHeader
  {
      public static FrameDecoderLZ4 fast(BufferPoolAllocator allocator)
      {
          return new FrameDecoderLZ4(allocator, LZ4Factory.fastestInstance().safeDecompressor());
      }
  
      private static final int HEADER_LENGTH = 8;
      private static final int TRAILER_LENGTH = 4;
      private static final int HEADER_AND_TRAILER_LENGTH = 12;
  
      private static int compressedLength(long header8b)
      {
          return ((int) header8b) & 0x1FFFF;
      }
      private static int uncompressedLength(long header8b)
      {
          return ((int) (header8b >>> 17)) & 0x1FFFF;
      }
      private static boolean isSelfContained(long header8b)
      {
          return 0 != (header8b & (1L << 34));
      }
      private static int headerCrc(long header8b)
      {
          return ((int) (header8b >>> 40)) & 0xFFFFFF;
      }
  
      private final LZ4SafeDecompressor decompressor;
  
      private FrameDecoderLZ4(BufferPoolAllocator allocator, LZ4SafeDecompressor decompressor)
      {
          super(allocator);
          this.decompressor = decompressor;
      }
  
      final long readHeader(ByteBuffer frame, int begin)
      {
          long header8b = frame.getLong(begin);
          if (frame.order() == ByteOrder.BIG_ENDIAN)
              header8b = Long.reverseBytes(header8b);
          return header8b;
      }
  
      final CorruptFrame verifyHeader(long header8b)
      {
          int computeLengthCrc = crc24(header8b, 5);
          int readLengthCrc = headerCrc(header8b);
  
          return readLengthCrc == computeLengthCrc ? null : CorruptFrame.unrecoverable(readLengthCrc, computeLengthCrc);
      }
  
      final int frameLength(long header8b)
      {
          return compressedLength(header8b) + HEADER_AND_TRAILER_LENGTH;
      }
  
      final Frame unpackFrame(ShareableBytes bytes, int begin, int end, long header8b)
      {
          ByteBuffer input = bytes.get();
  
          boolean isSelfContained = isSelfContained(header8b);
          int uncompressedLength = uncompressedLength(header8b);
  
          CRC32 crc = crc32();
          int readFullCrc = input.getInt(end - TRAILER_LENGTH);
          if (input.order() == ByteOrder.BIG_ENDIAN)
              readFullCrc = Integer.reverseBytes(readFullCrc);
  
          updateCrc32(crc, input, begin + HEADER_LENGTH, end - TRAILER_LENGTH);
          int computeFullCrc = (int) crc.getValue();
  
          if (readFullCrc != computeFullCrc)
              return CorruptFrame.recoverable(isSelfContained, uncompressedLength, readFullCrc, computeFullCrc);
  
          if (uncompressedLength == 0)
          {
              return new IntactFrame(isSelfContained, bytes.slice(begin + HEADER_LENGTH, end - TRAILER_LENGTH));
          }
          else
          {
              ByteBuffer out = allocator.get(uncompressedLength);
              try
              {
                  int sourceLength = end - (begin + HEADER_LENGTH + TRAILER_LENGTH);
                  decompressor.decompress(input, begin + HEADER_LENGTH, sourceLength, out, 0, uncompressedLength);
                  return new IntactFrame(isSelfContained, ShareableBytes.wrap(out));
              }
              catch (Throwable t)
              {
                  allocator.put(out);
                  throw t;
              }
          }
      }
  
      void decode(Collection<Frame> into, ShareableBytes bytes)
      {
          // TODO: confirm in assembly output that we inline the relevant nested method calls
          decode(into, bytes, HEADER_LENGTH);
      }
  
      void addLastTo(ChannelPipeline pipeline)
      {
          pipeline.addLast("frameDecoderLZ4", this);
      }
  }
  