/*
* Copyright 2013 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 java.util.List;
import java.util.zip.CRC32;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;
/**
* Decompress a {@link ByteBuf} using the inflate algorithm.
*/
public class JdkZlibDecoder extends ZlibDecoder {
private static final int FHCRC = 0x02;
private static final int FEXTRA = 0x04;
private static final int FNAME = 0x08;
private static final int FCOMMENT = 0x10;
private static final int FRESERVED = 0xE0;
private Inflater inflater;
private final byte[] dictionary;
// GZIP related
private final CRC32 crc;
private enum GzipState {
HEADER_START,
HEADER_END,
FLG_READ,
XLEN_READ,
SKIP_FNAME,
SKIP_COMMENT,
PROCESS_FHCRC,
FOOTER_START,
}
private GzipState gzipState = GzipState.HEADER_START;
private int flags = -1;
private int xlen = -1;
private volatile boolean finished;
private boolean decideZlibOrNone;
/**
* Creates a new instance with the default wrapper ({@link ZlibWrapper#ZLIB}).
*/
public JdkZlibDecoder() {
this(ZlibWrapper.ZLIB, null);
}
/**
* Creates a new instance with the specified preset dictionary. The wrapper
* is always {@link ZlibWrapper#ZLIB} because it is the only format that
* supports the preset dictionary.
*/
public JdkZlibDecoder(byte[] dictionary) {
this(ZlibWrapper.ZLIB, dictionary);
}
/**
* Creates a new instance with the specified wrapper.
* Be aware that only {@link ZlibWrapper#GZIP}, {@link ZlibWrapper#ZLIB} and {@link ZlibWrapper#NONE} are
* supported atm.
*/
public JdkZlibDecoder(ZlibWrapper wrapper) {
this(wrapper, null);
}
private JdkZlibDecoder(ZlibWrapper wrapper, byte[] dictionary) {
if (wrapper == null) {
throw new NullPointerException("wrapper");
}
switch (wrapper) {
case GZIP:
inflater = new Inflater(true);
crc = new CRC32();
break;
case NONE:
inflater = new Inflater(true);
crc = null;
break;
case ZLIB:
inflater = new Inflater();
crc = null;
break;
case ZLIB_OR_NONE:
// Postpone the decision until decode(...) is called.
decideZlibOrNone = true;
crc = null;
break;
default:
throw new IllegalArgumentException("Only GZIP or ZLIB is supported, but you used " + wrapper);
}
this.dictionary = dictionary;
}
@Override
public boolean isClosed() {
return finished;
}
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
if (finished) {
// Skip data received after finished.
in.skipBytes(in.readableBytes());
return;
}
int readableBytes = in.readableBytes();
if (readableBytes == 0) {
return;
}
if (decideZlibOrNone) {
// First two bytes are needed to decide if it's a ZLIB stream.
if (readableBytes < 2) {
return;
}
boolean nowrap = !looksLikeZlib(in.getShort(in.readerIndex()));
inflater = new Inflater(nowrap);
decideZlibOrNone = false;
}
if (crc != null) {
switch (gzipState) {
case FOOTER_START:
if (readGZIPFooter(in)) {
finished = true;
}
return;
default:
if (gzipState != GzipState.HEADER_END) {
if (!readGZIPHeader(in)) {
return;
}
}
}
// Some bytes may have been consumed, and so we must re-set the number of readable bytes.
readableBytes = in.readableBytes();
}
if (in.hasArray()) {
inflater.setInput(in.array(), in.arrayOffset() + in.readerIndex(), readableBytes);
} else {
byte[] array = new byte[readableBytes];
in.getBytes(in.readerIndex(), array);
inflater.setInput(array);
}
int maxOutputLength = inflater.getRemaining() << 1;
ByteBuf decompressed = ctx.alloc().heapBuffer(maxOutputLength);
try {
boolean readFooter = false;
byte[] outArray = decompressed.array();
while (!inflater.needsInput()) {
int writerIndex = decompressed.writerIndex();
int outIndex = decompressed.arrayOffset() + writerIndex;
int length = decompressed.writableBytes();
if (length == 0) {
// completely filled the buffer allocate a new one and start to fill it
out.add(decompressed);
decompressed = ctx.alloc().heapBuffer(maxOutputLength);
outArray = decompressed.array();
continue;
}
int outputLength = inflater.inflate(outArray, outIndex, length);
if (outputLength > 0) {
decompressed.writerIndex(writerIndex + outputLength);
if (crc != null) {
crc.update(outArray, outIndex, outputLength);
}
} else {
if (inflater.needsDictionary()) {
if (dictionary == null) {
throw new DecompressionException(
"decompression failure, unable to set dictionary as non was specified");
}
inflater.setDictionary(dictionary);
}
}
if (inflater.finished()) {
if (crc == null) {
finished = true; // Do not decode anymore.
} else {
readFooter = true;
}
break;
}
}
in.skipBytes(readableBytes - inflater.getRemaining());
if (readFooter) {
gzipState = GzipState.FOOTER_START;
if (readGZIPFooter(in)) {
finished = true;
}
}
} catch (DataFormatException e) {
throw new DecompressionException("decompression failure", e);
} finally {
if (decompressed.isReadable()) {
out.add(decompressed);
} else {
decompressed.release();
}
}
}
@Override
protected void handlerRemoved0(ChannelHandlerContext ctx) throws Exception {
super.handlerRemoved0(ctx);
if (inflater != null) {
inflater.end();
}
}
private boolean readGZIPHeader(ByteBuf in) {
switch (gzipState) {
case HEADER_START:
if (in.readableBytes() < 10) {
return false;
}
// read magic numbers
int magic0 = in.readByte();
int magic1 = in.readByte();
if (magic0 != 31) {
throw new DecompressionException("Input is not in the GZIP format");
}
crc.update(magic0);
crc.update(magic1);
int method = in.readUnsignedByte();
if (method != Deflater.DEFLATED) {
throw new DecompressionException("Unsupported compression method "
+ method + " in the GZIP header");
}
crc.update(method);
flags = in.readUnsignedByte();
crc.update(flags);
if ((flags & FRESERVED) != 0) {
throw new DecompressionException(
"Reserved flags are set in the GZIP header");
}
// mtime (int)
crc.update(in.readByte());
crc.update(in.readByte());
crc.update(in.readByte());
crc.update(in.readByte());
crc.update(in.readUnsignedByte()); // extra flags
crc.update(in.readUnsignedByte()); // operating system
gzipState = GzipState.FLG_READ;
case FLG_READ:
if ((flags & FEXTRA) != 0) {
if (in.readableBytes() < 2) {
return false;
}
int xlen1 = in.readUnsignedByte();
int xlen2 = in.readUnsignedByte();
crc.update(xlen1);
crc.update(xlen2);
xlen |= xlen1 << 8 | xlen2;
}
gzipState = GzipState.XLEN_READ;
case XLEN_READ:
if (xlen != -1) {
if (in.readableBytes() < xlen) {
return false;
}
byte[] xtra = new byte[xlen];
in.readBytes(xtra);
crc.update(xtra);
}
gzipState = GzipState.SKIP_FNAME;
case SKIP_FNAME:
if ((flags & FNAME) != 0) {
if (!in.isReadable()) {
return false;
}
do {
int b = in.readUnsignedByte();
crc.update(b);
if (b == 0x00) {
break;
}
} while (in.isReadable());
}
gzipState = GzipState.SKIP_COMMENT;
case SKIP_COMMENT:
if ((flags & FCOMMENT) != 0) {
if (!in.isReadable()) {
return false;
}
do {
int b = in.readUnsignedByte();
crc.update(b);
if (b == 0x00) {
break;
}
} while (in.isReadable());
}
gzipState = GzipState.PROCESS_FHCRC;
case PROCESS_FHCRC:
if ((flags & FHCRC) != 0) {
if (in.readableBytes() < 4) {
return false;
}
verifyCrc(in);
}
crc.reset();
gzipState = GzipState.HEADER_END;
case HEADER_END:
return true;
default:
throw new IllegalStateException();
}
}
private boolean readGZIPFooter(ByteBuf buf) {
if (buf.readableBytes() < 8) {
return false;
}
verifyCrc(buf);
// read ISIZE and verify
int dataLength = 0;
for (int i = 0; i < 4; ++i) {
dataLength |= buf.readUnsignedByte() << i * 8;
}
int readLength = inflater.getTotalOut();
if (dataLength != readLength) {
throw new DecompressionException(
"Number of bytes mismatch. Expected: " + dataLength + ", Got: " + readLength);
}
return true;
}
private void verifyCrc(ByteBuf in) {
long crcValue = 0;
for (int i = 0; i < 4; ++i) {
crcValue |= (long) in.readUnsignedByte() << i * 8;
}
long readCrc = crc.getValue();
if (crcValue != readCrc) {
throw new DecompressionException(
"CRC value missmatch. Expected: " + crcValue + ", Got: " + readCrc);
}
}
/*
* Returns true if the cmf_flg parameter (think: first two bytes of a zlib stream)
* indicates that this is a zlib stream.
* <p>
* You can lookup the details in the ZLIB RFC:
* <a href="http://tools.ietf.org/html/rfc1950#section-2.2">RFC 1950</a>.
*/
private static boolean looksLikeZlib(short cmf_flg) {
return (cmf_flg & 0x7800) == 0x7800 &&
cmf_flg % 31 == 0;
}
}