io.netty.handler.codec.compression.FastLzFrameDecoder Maven / Gradle / Ivy

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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.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;

import java.util.List;
import java.util.zip.Adler32;
import java.util.zip.Checksum;

import static io.netty.handler.codec.compression.FastLz.BLOCK_TYPE_COMPRESSED;
import static io.netty.handler.codec.compression.FastLz.BLOCK_WITH_CHECKSUM;
import static io.netty.handler.codec.compression.FastLz.MAGIC_NUMBER;
import static io.netty.handler.codec.compression.FastLz.decompress;

/**
 * Uncompresses a {@link ByteBuf} encoded by {@link FastLzFrameEncoder} using the FastLZ algorithm.
 *
 * See FastLZ format.
 */
public class FastLzFrameDecoder extends ByteToMessageDecoder {
    /**
     * Current state of decompression.
     */
    private enum State {
        INIT_BLOCK,
        INIT_BLOCK_PARAMS,
        DECOMPRESS_DATA,
        CORRUPTED
    }

    private State currentState = State.INIT_BLOCK;

    /**
     * Underlying checksum calculator in use.
     */
    private final ByteBufChecksum checksum;

    /**
     * Length of current received chunk of data.
     */
    private int chunkLength;

    /**
     * Original of current received chunk of data.
     * It is equal to {@link #chunkLength} for non compressed chunks.
     */
    private int originalLength;

    /**
     * Indicates is this chunk compressed or not.
     */
    private boolean isCompressed;

    /**
     * Indicates is this chunk has checksum or not.
     */
    private boolean hasChecksum;

    /**
     * Checksum value of current received chunk of data which has checksum.
     */
    private int currentChecksum;

    /**
     * Creates the fastest FastLZ decoder without checksum calculation.
     */
    public FastLzFrameDecoder() {
        this(false);
    }

    /**
     * Creates a FastLZ decoder with calculation of checksums as specified.
     *
     * @param validateChecksums
     *        If true, the checksum field will be validated against the actual
     *        uncompressed data, and if the checksums do not match, a suitable
     *        {@link DecompressionException} will be thrown.
     *        Note, that in this case decoder will use {@link java.util.zip.Adler32}
     *        as a default checksum calculator.
     */
    public FastLzFrameDecoder(boolean validateChecksums) {
        this(validateChecksums ? new Adler32() : null);
    }

    /**
     * Creates a FastLZ decoder with specified checksum calculator.
     *
     * @param checksum
     *        the {@link Checksum} instance to use to check data for integrity.
     *        You may set {@code null} if you do not want to validate checksum of each block.
     */
    public FastLzFrameDecoder(Checksum checksum) {
        this.checksum = checksum == null ? null : ByteBufChecksum.wrapChecksum(checksum);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List