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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.net.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 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);
}
}