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The Netty project is an effort to provide an asynchronous event-driven
network application framework and tools for rapid development of
maintainable high performance and high scalability protocol servers and
clients. In other words, Netty is a NIO client server framework which
enables quick and easy development of network applications such as protocol
servers and clients. It greatly simplifies and streamlines network
programming such as TCP and UDP socket server.
/*
* Copyright 2012 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 org.jboss.netty.handler.codec.compression;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
import org.jboss.netty.util.internal.jzlib.JZlib;
import org.jboss.netty.util.internal.jzlib.ZStream;
/**
* Decompresses a {@link ChannelBuffer} using the deflate algorithm.
* @apiviz.landmark
* @apiviz.has org.jboss.netty.handler.codec.compression.ZlibWrapper
*/
public class ZlibDecoder extends OneToOneDecoder {
private final ZStream z = new ZStream();
private byte[] dictionary;
private volatile boolean finished;
/**
* Creates a new instance with the default wrapper ({@link ZlibWrapper#ZLIB}).
*
* @throws CompressionException if failed to initialize zlib
*/
public ZlibDecoder() {
this(ZlibWrapper.ZLIB);
}
/**
* Creates a new instance with the specified wrapper.
*
* @throws CompressionException if failed to initialize zlib
*/
public ZlibDecoder(ZlibWrapper wrapper) {
if (wrapper == null) {
throw new NullPointerException("wrapper");
}
synchronized (z) {
int resultCode = z.inflateInit(ZlibUtil.convertWrapperType(wrapper));
if (resultCode != JZlib.Z_OK) {
ZlibUtil.fail(z, "initialization failure", resultCode);
}
}
}
/**
* 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.
*
* @throws CompressionException if failed to initialize zlib
*/
public ZlibDecoder(byte[] dictionary) {
if (dictionary == null) {
throw new NullPointerException("dictionary");
}
this.dictionary = dictionary;
synchronized (z) {
int resultCode;
resultCode = z.inflateInit(JZlib.W_ZLIB);
if (resultCode != JZlib.Z_OK) {
ZlibUtil.fail(z, "initialization failure", resultCode);
}
}
}
/**
* Returns {@code true} if and only if the end of the compressed stream
* has been reached.
*/
public boolean isClosed() {
return finished;
}
@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
if (!(msg instanceof ChannelBuffer) || finished) {
return msg;
}
synchronized (z) {
try {
// Configure input.
ChannelBuffer compressed = (ChannelBuffer) msg;
byte[] in = new byte[compressed.readableBytes()];
compressed.readBytes(in);
z.next_in = in;
z.next_in_index = 0;
z.avail_in = in.length;
// Configure output.
byte[] out = new byte[in.length << 1];
ChannelBuffer decompressed = ChannelBuffers.dynamicBuffer(
compressed.order(), out.length,
ctx.getChannel().getConfig().getBufferFactory());
z.next_out = out;
z.next_out_index = 0;
z.avail_out = out.length;
loop: for (;;) {
// Decompress 'in' into 'out'
int resultCode = z.inflate(JZlib.Z_SYNC_FLUSH);
if (z.next_out_index > 0) {
decompressed.writeBytes(out, 0, z.next_out_index);
z.avail_out = out.length;
}
z.next_out_index = 0;
switch (resultCode) {
case JZlib.Z_NEED_DICT:
if (dictionary == null) {
ZlibUtil.fail(z, "decompression failure", resultCode);
} else {
resultCode = z.inflateSetDictionary(dictionary, dictionary.length);
if (resultCode != JZlib.Z_OK) {
ZlibUtil.fail(z, "failed to set the dictionary", resultCode);
}
}
break;
case JZlib.Z_STREAM_END:
finished = true; // Do not decode anymore.
z.inflateEnd();
break loop;
case JZlib.Z_OK:
break;
case JZlib.Z_BUF_ERROR:
if (z.avail_in <= 0) {
break loop;
}
break;
default:
ZlibUtil.fail(z, "decompression failure", resultCode);
}
}
if (decompressed.writerIndex() != 0) { // readerIndex is always 0
return decompressed;
} else {
return null;
}
} finally {
// Deference the external references explicitly to tell the VM that
// the allocated byte arrays are temporary so that the call stack
// can be utilized.
// I'm not sure if the modern VMs do this optimization though.
z.next_in = null;
z.next_out = null;
}
}
}
}