/*
* 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 java.util.List;
import static io.netty.handler.codec.compression.Bzip2Constants.*;
/**
* Uncompresses a {@link ByteBuf} encoded with the Bzip2 format.
*
* See <a href="http://en.wikipedia.org/wiki/Bzip2">Bzip2</a>.
*/
public class Bzip2Decoder extends ByteToMessageDecoder {
/**
* Current state of stream.
*/
private enum State {
INIT,
INIT_BLOCK,
INIT_BLOCK_PARAMS,
RECEIVE_HUFFMAN_USED_MAP,
RECEIVE_HUFFMAN_USED_BITMAPS,
RECEIVE_SELECTORS_NUMBER,
RECEIVE_SELECTORS,
RECEIVE_HUFFMAN_LENGTH,
DECODE_HUFFMAN_DATA,
EOF
}
private State currentState = State.INIT;
/**
* A reader that provides bit-level reads.
*/
private final Bzip2BitReader reader = new Bzip2BitReader();
/**
* The decompressor for the current block.
*/
private Bzip2BlockDecompressor blockDecompressor;
/**
* Bzip2 Huffman coding stage.
*/
private Bzip2HuffmanStageDecoder huffmanStageDecoder;
/**
* Always: in the range 0 .. 9. The current block size is 100000 * this number.
*/
private int blockSize;
/**
* The CRC of the current block as read from the block header.
*/
private int blockCRC;
/**
* The merged CRC of all blocks decompressed so far.
*/
private int streamCRC;
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
if (!in.isReadable()) {
return;
}
final Bzip2BitReader reader = this.reader;
reader.setByteBuf(in);
for (;;) {
switch (currentState) {
case INIT:
if (in.readableBytes() < 4) {
return;
}
int magicNumber = in.readUnsignedMedium();
if (magicNumber != MAGIC_NUMBER) {
throw new DecompressionException("Unexpected stream identifier contents. Mismatched bzip2 " +
"protocol version?");
}
int blockSize = in.readByte() - '0';
if (blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE) {
throw new DecompressionException("block size is invalid");
}
this.blockSize = blockSize * BASE_BLOCK_SIZE;
streamCRC = 0;
currentState = State.INIT_BLOCK;
case INIT_BLOCK:
if (!reader.hasReadableBytes(10)) {
return;
}
// Get the block magic bytes.
final int magic1 = reader.readBits(24);
final int magic2 = reader.readBits(24);
if (magic1 == END_OF_STREAM_MAGIC_1 && magic2 == END_OF_STREAM_MAGIC_2) {
// End of stream was reached. Check the combined CRC.
final int storedCombinedCRC = reader.readInt();
if (storedCombinedCRC != streamCRC) {
throw new DecompressionException("stream CRC error");
}
currentState = State.EOF;
break;
}
if (magic1 != BLOCK_HEADER_MAGIC_1 || magic2 != BLOCK_HEADER_MAGIC_2) {
throw new DecompressionException("bad block header");
}
blockCRC = reader.readInt();
currentState = State.INIT_BLOCK_PARAMS;
case INIT_BLOCK_PARAMS:
if (!reader.hasReadableBits(25)) {
return;
}
final boolean blockRandomised = reader.readBoolean();
final int bwtStartPointer = reader.readBits(24);
blockDecompressor = new Bzip2BlockDecompressor(this.blockSize, blockCRC,
blockRandomised, bwtStartPointer, reader);
currentState = State.RECEIVE_HUFFMAN_USED_MAP;
case RECEIVE_HUFFMAN_USED_MAP:
if (!reader.hasReadableBits(16)) {
return;
}
blockDecompressor.huffmanInUse16 = reader.readBits(16);
currentState = State.RECEIVE_HUFFMAN_USED_BITMAPS;
case RECEIVE_HUFFMAN_USED_BITMAPS:
Bzip2BlockDecompressor blockDecompressor = this.blockDecompressor;
final int inUse16 = blockDecompressor.huffmanInUse16;
final int bitNumber = Integer.bitCount(inUse16);
final byte[] huffmanSymbolMap = blockDecompressor.huffmanSymbolMap;
if (!reader.hasReadableBits(bitNumber * HUFFMAN_SYMBOL_RANGE_SIZE + 3)) {
return;
}
int huffmanSymbolCount = 0;
if (bitNumber > 0) {
for (int i = 0; i < 16; i++) {
if ((inUse16 & 1 << 15 >>> i) != 0) {
for (int j = 0, k = i << 4; j < HUFFMAN_SYMBOL_RANGE_SIZE; j++, k++) {
if (reader.readBoolean()) {
huffmanSymbolMap[huffmanSymbolCount++] = (byte) k;
}
}
}
}
}
blockDecompressor.huffmanEndOfBlockSymbol = huffmanSymbolCount + 1;
int totalTables = reader.readBits(3);
if (totalTables < HUFFMAN_MINIMUM_TABLES || totalTables > HUFFMAN_MAXIMUM_TABLES) {
throw new DecompressionException("incorrect huffman groups number");
}
int alphaSize = huffmanSymbolCount + 2;
if (alphaSize > HUFFMAN_MAX_ALPHABET_SIZE) {
throw new DecompressionException("incorrect alphabet size");
}
huffmanStageDecoder = new Bzip2HuffmanStageDecoder(reader, totalTables, alphaSize);
currentState = State.RECEIVE_SELECTORS_NUMBER;
case RECEIVE_SELECTORS_NUMBER:
if (!reader.hasReadableBits(15)) {
return;
}
int totalSelectors = reader.readBits(15);
if (totalSelectors < 1 || totalSelectors > MAX_SELECTORS) {
throw new DecompressionException("incorrect selectors number");
}
huffmanStageDecoder.selectors = new byte[totalSelectors];
currentState = State.RECEIVE_SELECTORS;
case RECEIVE_SELECTORS:
Bzip2HuffmanStageDecoder huffmanStageDecoder = this.huffmanStageDecoder;
byte[] selectors = huffmanStageDecoder.selectors;
totalSelectors = selectors.length;
final Bzip2MoveToFrontTable tableMtf = huffmanStageDecoder.tableMTF;
int currSelector;
// Get zero-terminated bit runs (0..62) of MTF'ed Huffman table. length = 1..6
for (currSelector = huffmanStageDecoder.currentSelector;
currSelector < totalSelectors; currSelector++) {
if (!reader.hasReadableBits(HUFFMAN_SELECTOR_LIST_MAX_LENGTH)) {
// Save state if end of current ByteBuf was reached
huffmanStageDecoder.currentSelector = currSelector;
return;
}
int index = 0;
while (reader.readBoolean()) {
index++;
}
selectors[currSelector] = tableMtf.indexToFront(index);
}
currentState = State.RECEIVE_HUFFMAN_LENGTH;
case RECEIVE_HUFFMAN_LENGTH:
huffmanStageDecoder = this.huffmanStageDecoder;
totalTables = huffmanStageDecoder.totalTables;
final byte[][] codeLength = huffmanStageDecoder.tableCodeLengths;
alphaSize = huffmanStageDecoder.alphabetSize;
/* Now the coding tables */
int currGroup;
int currLength = huffmanStageDecoder.currentLength;
int currAlpha = 0;
boolean modifyLength = huffmanStageDecoder.modifyLength;
boolean saveStateAndReturn = false;
loop: for (currGroup = huffmanStageDecoder.currentGroup; currGroup < totalTables; currGroup++) {
// start_huffman_length
if (!reader.hasReadableBits(5)) {
saveStateAndReturn = true;
break;
}
if (currLength < 0) {
currLength = reader.readBits(5);
}
for (currAlpha = huffmanStageDecoder.currentAlpha; currAlpha < alphaSize; currAlpha++) {
// delta_bit_length: 1..40
if (!reader.isReadable()) {
saveStateAndReturn = true;
break loop;
}
while (modifyLength || reader.readBoolean()) { // 0=>next symbol; 1=>alter length
if (!reader.isReadable()) {
modifyLength = true;
saveStateAndReturn = true;
break loop;
}
// 1=>decrement length; 0=>increment length
currLength += reader.readBoolean() ? -1 : 1;
modifyLength = false;
if (!reader.isReadable()) {
saveStateAndReturn = true;
break loop;
}
}
codeLength[currGroup][currAlpha] = (byte) currLength;
}
currLength = -1;
currAlpha = huffmanStageDecoder.currentAlpha = 0;
modifyLength = false;
}
if (saveStateAndReturn) {
// Save state if end of current ByteBuf was reached
huffmanStageDecoder.currentGroup = currGroup;
huffmanStageDecoder.currentLength = currLength;
huffmanStageDecoder.currentAlpha = currAlpha;
huffmanStageDecoder.modifyLength = modifyLength;
return;
}
// Finally create the Huffman tables
huffmanStageDecoder.createHuffmanDecodingTables();
currentState = State.DECODE_HUFFMAN_DATA;
case DECODE_HUFFMAN_DATA:
blockDecompressor = this.blockDecompressor;
final int oldReaderIndex = in.readerIndex();
final boolean decoded = blockDecompressor.decodeHuffmanData(this.huffmanStageDecoder);
if (!decoded) {
return;
}
// It used to avoid "Bzip2Decoder.decode() did not read anything but decoded a message" exception.
// Because previous operation may read only a few bits from Bzip2BitReader.bitBuffer and
// don't read incoming ByteBuf.
if (in.readerIndex() == oldReaderIndex && in.isReadable()) {
reader.refill();
}
final int blockLength = blockDecompressor.blockLength();
final ByteBuf uncompressed = ctx.alloc().buffer(blockLength);
boolean success = false;
try {
int uncByte;
while ((uncByte = blockDecompressor.read()) >= 0) {
uncompressed.writeByte(uncByte);
}
int currentBlockCRC = blockDecompressor.checkCRC();
streamCRC = (streamCRC << 1 | streamCRC >>> 31) ^ currentBlockCRC;
out.add(uncompressed);
success = true;
} finally {
if (!success) {
uncompressed.release();
}
}
currentState = State.INIT_BLOCK;
break;
case EOF:
in.skipBytes(in.readableBytes());
return;
default:
throw new IllegalStateException();
}
}
}
/**
* Returns {@code true} if and only if the end of the compressed stream
* has been reached.
*/
public boolean isClosed() {
return currentState == State.EOF;
}
}