/*
* Copyright 2014 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:
*
* 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 io.netty.handler.codec.compression;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.util.internal.EmptyArrays;
import java.util.List;
import java.util.zip.Adler32;
import java.util.zip.Checksum;
import static io.netty.handler.codec.compression.FastLz.*;
/**
* Uncompresses a {@link ByteBuf} encoded by {@link FastLzFrameEncoder} using the FastLZ algorithm.
*
* See <a href="https://github.com/netty/netty/issues/2750">FastLZ format</a>.
*/
public class FastLzFrameDecoder extends ByteToMessageDecoder {
/**
* Current state of decompression.
*/
private enum State {
INIT_BLOCK,
INIT_BLOCK_PARAMS,
DECOMPRESS_DATA,
CORRUPTED
}
private State currentState = State.INIT_BLOCK;
/**
* Underlying checksum calculator in use.
*/
private final Checksum checksum;
/**
* Length of current received chunk of data.
*/
private int chunkLength;
/**
* Original of current received chunk of data.
* It is equal to {@link #chunkLength} for non compressed chunks.
*/
private int originalLength;
/**
* Indicates is this chunk compressed or not.
*/
private boolean isCompressed;
/**
* Indicates is this chunk has checksum or not.
*/
private boolean hasChecksum;
/**
* Checksum value of current received chunk of data which has checksum.
*/
private int currentChecksum;
/**
* Creates the fastest FastLZ decoder without checksum calculation.
*/
public FastLzFrameDecoder() {
this(false);
}
/**
* Creates a FastLZ decoder with calculation of checksums as specified.
*
* @param validateChecksums
* If true, the checksum field will be validated against the actual
* uncompressed data, and if the checksums do not match, a suitable
* {@link DecompressionException} will be thrown.
* Note, that in this case decoder will use {@link java.util.zip.Adler32}
* as a default checksum calculator.
*/
public FastLzFrameDecoder(boolean validateChecksums) {
this(validateChecksums ? new Adler32() : null);
}
/**
* Creates a FastLZ decoder with specified checksum calculator.
*
* @param checksum
* the {@link Checksum} instance to use to check data for integrity.
* You may set {@code null} if you do not want to validate checksum of each block.
*/
public FastLzFrameDecoder(Checksum checksum) {
this.checksum = checksum;
}
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
try {
switch (currentState) {
case INIT_BLOCK:
if (in.readableBytes() < 4) {
break;
}
final int magic = in.readUnsignedMedium();
if (magic != MAGIC_NUMBER) {
throw new DecompressionException("unexpected block identifier");
}
final byte options = in.readByte();
isCompressed = (options & 0x01) == BLOCK_TYPE_COMPRESSED;
hasChecksum = (options & 0x10) == BLOCK_WITH_CHECKSUM;
currentState = State.INIT_BLOCK_PARAMS;
case INIT_BLOCK_PARAMS:
if (in.readableBytes() < 2 + (isCompressed ? 2 : 0) + (hasChecksum ? 4 : 0)) {
break;
}
currentChecksum = hasChecksum ? in.readInt() : 0;
chunkLength = in.readUnsignedShort();
originalLength = isCompressed ? in.readUnsignedShort() : chunkLength;
currentState = State.DECOMPRESS_DATA;
case DECOMPRESS_DATA:
final int chunkLength = this.chunkLength;
if (in.readableBytes() < chunkLength) {
break;
}
final int idx = in.readerIndex();
final int originalLength = this.originalLength;
final ByteBuf uncompressed;
final byte[] output;
final int outputPtr;
if (originalLength != 0) {
uncompressed = ctx.alloc().heapBuffer(originalLength, originalLength);
output = uncompressed.array();
outputPtr = uncompressed.arrayOffset() + uncompressed.writerIndex();
} else {
uncompressed = null;
output = EmptyArrays.EMPTY_BYTES;
outputPtr = 0;
}
boolean success = false;
try {
if (isCompressed) {
final byte[] input;
final int inputPtr;
if (in.hasArray()) {
input = in.array();
inputPtr = in.arrayOffset() + idx;
} else {
input = new byte[chunkLength];
in.getBytes(idx, input);
inputPtr = 0;
}
final int decompressedBytes = decompress(input, inputPtr, chunkLength,
output, outputPtr, originalLength);
if (originalLength != decompressedBytes) {
throw new DecompressionException(String.format(
"stream corrupted: originalLength(%d) and actual length(%d) mismatch",
originalLength, decompressedBytes));
}
} else {
in.getBytes(idx, output, outputPtr, chunkLength);
}
final Checksum checksum = this.checksum;
if (hasChecksum && checksum != null) {
checksum.reset();
checksum.update(output, outputPtr, originalLength);
final int checksumResult = (int) checksum.getValue();
if (checksumResult != currentChecksum) {
throw new DecompressionException(String.format(
"stream corrupted: mismatching checksum: %d (expected: %d)",
checksumResult, currentChecksum));
}
}
if (uncompressed != null) {
uncompressed.writerIndex(uncompressed.writerIndex() + originalLength);
out.add(uncompressed);
}
in.skipBytes(chunkLength);
currentState = State.INIT_BLOCK;
success = true;
} finally {
if (!success) {
uncompressed.release();
}
}
break;
case CORRUPTED:
in.skipBytes(in.readableBytes());
break;
default:
throw new IllegalStateException();
}
} catch (Exception e) {
currentState = State.CORRUPTED;
throw e;
}
}
}