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/*
* 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:
*
* https://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.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.ChannelPromise;
import io.netty.handler.codec.MessageToByteEncoder;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.PromiseNotifier;
import static io.netty.handler.codec.compression.Bzip2Constants.BASE_BLOCK_SIZE;
import static io.netty.handler.codec.compression.Bzip2Constants.END_OF_STREAM_MAGIC_1;
import static io.netty.handler.codec.compression.Bzip2Constants.END_OF_STREAM_MAGIC_2;
import static io.netty.handler.codec.compression.Bzip2Constants.MAGIC_NUMBER;
import static io.netty.handler.codec.compression.Bzip2Constants.MAX_BLOCK_SIZE;
import static io.netty.handler.codec.compression.Bzip2Constants.MIN_BLOCK_SIZE;
/**
* Compresses a {@link ByteBuf} using the Bzip2 algorithm.
*
* See Bzip2.
*/
public class Bzip2Encoder extends MessageToByteEncoder {
/**
* Current state of stream.
*/
private enum State {
INIT,
INIT_BLOCK,
WRITE_DATA,
CLOSE_BLOCK
}
private State currentState = State.INIT;
/**
* A writer that provides bit-level writes.
*/
private final Bzip2BitWriter writer = new Bzip2BitWriter();
/**
* The declared maximum block size of the stream (before final run-length decoding).
*/
private final int streamBlockSize;
/**
* The merged CRC of all blocks compressed so far.
*/
private int streamCRC;
/**
* The compressor for the current block.
*/
private Bzip2BlockCompressor blockCompressor;
/**
* (@code true} if the compressed stream has been finished, otherwise {@code false}.
*/
private volatile boolean finished;
/**
* Used to interact with its {@link ChannelPipeline} and other handlers.
*/
private volatile ChannelHandlerContext ctx;
/**
* Creates a new bzip2 encoder with the maximum (900,000 byte) block size.
*/
public Bzip2Encoder() {
this(MAX_BLOCK_SIZE);
}
/**
* Creates a new bzip2 encoder with the specified {@code blockSizeMultiplier}.
* @param blockSizeMultiplier
* The Bzip2 block size as a multiple of 100,000 bytes (minimum {@code 1}, maximum {@code 9}).
* Larger block sizes require more memory for both compression and decompression,
* but give better compression ratios. {@code 9} will usually be the best value to use.
*/
public Bzip2Encoder(final int blockSizeMultiplier) {
if (blockSizeMultiplier < MIN_BLOCK_SIZE || blockSizeMultiplier > MAX_BLOCK_SIZE) {
throw new IllegalArgumentException(
"blockSizeMultiplier: " + blockSizeMultiplier + " (expected: 1-9)");
}
streamBlockSize = blockSizeMultiplier * BASE_BLOCK_SIZE;
}
@Override
protected void encode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
if (finished) {
out.writeBytes(in);
return;
}
for (;;) {
switch (currentState) {
case INIT:
out.ensureWritable(4);
out.writeMedium(MAGIC_NUMBER);
out.writeByte('0' + streamBlockSize / BASE_BLOCK_SIZE);
currentState = State.INIT_BLOCK;
// fall through
case INIT_BLOCK:
blockCompressor = new Bzip2BlockCompressor(writer, streamBlockSize);
currentState = State.WRITE_DATA;
// fall through
case WRITE_DATA:
if (!in.isReadable()) {
return;
}
Bzip2BlockCompressor blockCompressor = this.blockCompressor;
final int length = Math.min(in.readableBytes(), blockCompressor.availableSize());
final int bytesWritten = blockCompressor.write(in, in.readerIndex(), length);
in.skipBytes(bytesWritten);
if (!blockCompressor.isFull()) {
if (in.isReadable()) {
break;
} else {
return;
}
}
currentState = State.CLOSE_BLOCK;
// fall through
case CLOSE_BLOCK:
closeBlock(out);
currentState = State.INIT_BLOCK;
break;
default:
throw new IllegalStateException();
}
}
}
/**
* Close current block and update {@link #streamCRC}.
*/
private void closeBlock(ByteBuf out) {
final Bzip2BlockCompressor blockCompressor = this.blockCompressor;
if (!blockCompressor.isEmpty()) {
blockCompressor.close(out);
final int blockCRC = blockCompressor.crc();
streamCRC = (streamCRC << 1 | streamCRC >>> 31) ^ blockCRC;
}
}
/**
* Returns {@code true} if and only if the end of the compressed stream has been reached.
*/
public boolean isClosed() {
return finished;
}
/**
* Close this {@link Bzip2Encoder} and so finish the encoding.
*
* The returned {@link ChannelFuture} will be notified once the operation completes.
*/
public ChannelFuture close() {
return close(ctx().newPromise());
}
/**
* Close this {@link Bzip2Encoder} and so finish the encoding.
* The given {@link ChannelFuture} will be notified once the operation
* completes and will also be returned.
*/
public ChannelFuture close(final ChannelPromise promise) {
ChannelHandlerContext ctx = ctx();
EventExecutor executor = ctx.executor();
if (executor.inEventLoop()) {
return finishEncode(ctx, promise);
} else {
executor.execute(new Runnable() {
@Override
public void run() {
ChannelFuture f = finishEncode(ctx(), promise);
PromiseNotifier.cascade(f, promise);
}
});
return promise;
}
}
@Override
public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
ChannelFuture f = finishEncode(ctx, ctx.newPromise());
EncoderUtil.closeAfterFinishEncode(ctx, f, promise);
}
private ChannelFuture finishEncode(final ChannelHandlerContext ctx, ChannelPromise promise) {
if (finished) {
promise.setSuccess();
return promise;
}
finished = true;
final ByteBuf footer = ctx.alloc().buffer();
closeBlock(footer);
final int streamCRC = this.streamCRC;
final Bzip2BitWriter writer = this.writer;
try {
writer.writeBits(footer, 24, END_OF_STREAM_MAGIC_1);
writer.writeBits(footer, 24, END_OF_STREAM_MAGIC_2);
writer.writeInt(footer, streamCRC);
writer.flush(footer);
} finally {
blockCompressor = null;
}
return ctx.writeAndFlush(footer, promise);
}
private ChannelHandlerContext ctx() {
ChannelHandlerContext ctx = this.ctx;
if (ctx == null) {
throw new IllegalStateException("not added to a pipeline");
}
return ctx;
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
this.ctx = ctx;
}
}
