Bzip2Decoder Class — netty Architecture

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java lines 44–344

public class Bzip2Decoder extends ByteToMessageDecoder {
    /**
     * Current state of stream.
     */
    private enum State {
        INIT,
        INIT_BLOCK,
        INIT_BLOCK_PARAMS,
        RECEIVE_HUFFMAN_USED_MAP,
        RECEIVE_HUFFMAN_USED_BITMAPS,
        RECEIVE_SELECTORS_NUMBER,
        RECEIVE_SELECTORS,
        RECEIVE_HUFFMAN_LENGTH,
        DECODE_HUFFMAN_DATA,
        EOF
    }
    private State currentState = State.INIT;

    /**
     * A reader that provides bit-level reads.
     */
    private final Bzip2BitReader reader = new Bzip2BitReader();

    /**
     * The decompressor for the current block.
     */
    private Bzip2BlockDecompressor blockDecompressor;

    /**
     * Bzip2 Huffman coding stage.
     */
    private Bzip2HuffmanStageDecoder huffmanStageDecoder;

    /**
     * Always: in the range 0 .. 9. The current block size is 100000 * this number.
     */
    private int blockSize;

    /**
     * The CRC of the current block as read from the block header.
     */
    private int blockCRC;

    /**
     * The merged CRC of all blocks decompressed so far.
     */
    private int streamCRC;

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        if (!in.isReadable()) {
            return;
        }

        final Bzip2BitReader reader = this.reader;
        reader.setByteBuf(in);

        for (;;) {
            switch (currentState) {
            case INIT:
                if (in.readableBytes() < 4) {
                    return;
                }
                int magicNumber = in.readUnsignedMedium();
                if (magicNumber != MAGIC_NUMBER) {
                    throw new DecompressionException("Unexpected stream identifier contents. Mismatched bzip2 " +
                            "protocol version?");
                }
                int blockSize = in.readByte() - '0';
                if (blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE) {
                    throw new DecompressionException("block size is invalid");
                }
                this.blockSize = blockSize * BASE_BLOCK_SIZE;

                streamCRC = 0;
                currentState = State.INIT_BLOCK;
                 // fall through
            case INIT_BLOCK:
                if (!reader.hasReadableBytes(10)) {
                    return;
                }