Bzip2BitWriter Class — netty Architecture

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/Bzip2BitWriter.java lines 25–120

final class Bzip2BitWriter {
    /**
     * A buffer of bits waiting to be written to the output stream.
     */
    private long bitBuffer;

    /**
     * The number of bits currently buffered in {@link #bitBuffer}.
     */
    private int bitCount;

    /**
     * Writes up to 32 bits to the output {@link ByteBuf}.
     * @param count The number of bits to write (maximum {@code 32} as a size of {@code int})
     * @param value The bits to write
     */
    void writeBits(ByteBuf out, final int count, final long value) {
        if (count < 0 || count > 32) {
            throw new IllegalArgumentException("count: " + count + " (expected: 0-32)");
        }
        int bitCount = this.bitCount;
        long bitBuffer = this.bitBuffer | value << 64 - count >>> bitCount;
        bitCount += count;

        if (bitCount >= 32) {
            out.writeInt((int) (bitBuffer >>> 32));
            bitBuffer <<= 32;
            bitCount -= 32;
        }
        this.bitBuffer = bitBuffer;
        this.bitCount = bitCount;
    }

    /**
     * Writes a single bit to the output {@link ByteBuf}.
     * @param value The bit to write
     */
    void writeBoolean(ByteBuf out, final boolean value) {
        int bitCount = this.bitCount + 1;
        long bitBuffer = this.bitBuffer | (value ? 1L << 64 - bitCount : 0L);

        if (bitCount == 32) {
            out.writeInt((int) (bitBuffer >>> 32));
            bitBuffer = 0;
            bitCount = 0;
        }
        this.bitBuffer = bitBuffer;
        this.bitCount = bitCount;
    }

    /**
     * Writes a zero-terminated unary number to the output {@link ByteBuf}.
     * Example of the output for value = 6: {@code 1111110}
     * @param value The number of {@code 1} to write
     */
    void writeUnary(ByteBuf out, int value) {
        if (value < 0) {
            throw new IllegalArgumentException("value: " + value + " (expected 0 or more)");
        }
        while (value-- > 0) {
            writeBoolean(out, true);
        }
        writeBoolean(out, false);
    }

    /**
     * Writes an integer as 32 bits to the output {@link ByteBuf}.
     * @param value The integer to write
     */
    void writeInt(ByteBuf out, final int value) {
        writeBits(out, 32, value);
    }

    /**
     * Writes any remaining bits to the output {@link ByteBuf},
     * zero padding to a whole byte as required.
     */
    void flush(ByteBuf out) {
        final int bitCount = this.bitCount;

        if (bitCount > 0) {