/*
* 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.MessageToByteEncoder;
import java.util.zip.Adler32;
import java.util.zip.Checksum;
import static io.netty.handler.codec.compression.FastLz.*;
/**
* Compresses a {@link ByteBuf} using the FastLZ algorithm.
*
* See <a href="https://github.com/netty/netty/issues/2750">FastLZ format</a>.
*/
public class FastLzFrameEncoder extends MessageToByteEncoder<ByteBuf> {
/**
* Compression level.
*/
private final int level;
/**
* Underlying checksum calculator in use.
*/
private final Checksum checksum;
/**
* Creates a FastLZ encoder without checksum calculator and with auto detection of compression level.
*/
public FastLzFrameEncoder() {
this(LEVEL_AUTO, null);
}
/**
* Creates a FastLZ encoder with specified compression level and without checksum calculator.
*
* @param level supports only these values:
* 0 - Encoder will choose level automatically depending on the length of the input buffer.
* 1 - Level 1 is the fastest compression and generally useful for short data.
* 2 - Level 2 is slightly slower but it gives better compression ratio.
*/
public FastLzFrameEncoder(int level) {
this(level, null);
}
/**
* Creates a FastLZ encoder with auto detection of compression
* level and calculation of checksums as specified.
*
* @param validateChecksums
* If true, the checksum of each block will be calculated and this value
* will be added to the header of block.
* By default {@link FastLzFrameEncoder} uses {@link java.util.zip.Adler32}
* for checksum calculation.
*/
public FastLzFrameEncoder(boolean validateChecksums) {
this(LEVEL_AUTO, validateChecksums ? new Adler32() : null);
}
/**
* Creates a FastLZ encoder with specified compression level and checksum calculator.
*
* @param level supports only these values:
* 0 - Encoder will choose level automatically depending on the length of the input buffer.
* 1 - Level 1 is the fastest compression and generally useful for short data.
* 2 - Level 2 is slightly slower but it gives better compression ratio.
* @param checksum
* the {@link Checksum} instance to use to check data for integrity.
* You may set {@code null} if you don't want to validate checksum of each block.
*/
public FastLzFrameEncoder(int level, Checksum checksum) {
super(false);
if (level != LEVEL_AUTO && level != LEVEL_1 && level != LEVEL_2) {
throw new IllegalArgumentException(String.format(
"level: %d (expected: %d or %d or %d)", level, LEVEL_AUTO, LEVEL_1, LEVEL_2));
}
this.level = level;
this.checksum = checksum;
}
@Override
protected void encode(ChannelHandlerContext ctx, ByteBuf in, ByteBuf out) throws Exception {
final Checksum checksum = this.checksum;
for (;;) {
if (!in.isReadable()) {
return;
}
final int idx = in.readerIndex();
final int length = Math.min(in.readableBytes(), MAX_CHUNK_LENGTH);
final int outputIdx = out.writerIndex();
out.setMedium(outputIdx, MAGIC_NUMBER);
int outputOffset = outputIdx + CHECKSUM_OFFSET + (checksum != null ? 4 : 0);
final byte blockType;
final int chunkLength;
if (length < MIN_LENGTH_TO_COMPRESSION) {
blockType = BLOCK_TYPE_NON_COMPRESSED;
out.ensureWritable(outputOffset + 2 + length);
final byte[] output = out.array();
final int outputPtr = out.arrayOffset() + outputOffset + 2;
if (checksum != null) {
final byte[] input;
final int inputPtr;
if (in.hasArray()) {
input = in.array();
inputPtr = in.arrayOffset() + idx;
} else {
input = new byte[length];
in.getBytes(idx, input);
inputPtr = 0;
}
checksum.reset();
checksum.update(input, inputPtr, length);
out.setInt(outputIdx + CHECKSUM_OFFSET, (int) checksum.getValue());
System.arraycopy(input, inputPtr, output, outputPtr, length);
} else {
in.getBytes(idx, output, outputPtr, length);
}
chunkLength = length;
} else {
// try to compress
final byte[] input;
final int inputPtr;
if (in.hasArray()) {
input = in.array();
inputPtr = in.arrayOffset() + idx;
} else {
input = new byte[length];
in.getBytes(idx, input);
inputPtr = 0;
}
if (checksum != null) {
checksum.reset();
checksum.update(input, inputPtr, length);
out.setInt(outputIdx + CHECKSUM_OFFSET, (int) checksum.getValue());
}
final int maxOutputLength = calculateOutputBufferLength(length);
out.ensureWritable(outputOffset + 4 + maxOutputLength);
final byte[] output = out.array();
final int outputPtr = out.arrayOffset() + outputOffset + 4;
final int compressedLength = compress(input, inputPtr, length, output, outputPtr, level);
if (compressedLength < length) {
blockType = BLOCK_TYPE_COMPRESSED;
chunkLength = compressedLength;
out.setShort(outputOffset, chunkLength);
outputOffset += 2;
} else {
blockType = BLOCK_TYPE_NON_COMPRESSED;
System.arraycopy(input, inputPtr, output, outputPtr - 2, length);
chunkLength = length;
}
}
out.setShort(outputOffset, length);
out.setByte(outputIdx + OPTIONS_OFFSET,
blockType | (checksum != null ? BLOCK_WITH_CHECKSUM : BLOCK_WITHOUT_CHECKSUM));
out.writerIndex(outputOffset + 2 + chunkLength);
in.skipBytes(length);
}
}
}