Lz4XXHash32 Class — netty Architecture

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/Lz4XXHash32.java lines 49–107

public final class Lz4XXHash32 extends ByteBufChecksum {

    private static final XXHash32 XXHASH32 = XXHashFactory.fastestInstance().hash32();

    private final int seed;
    private boolean used;
    private int value;

    @SuppressWarnings("WeakerAccess")
    public Lz4XXHash32(int seed) {
        this.seed = seed;
    }

    @Override
    public void update(int b) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void update(byte[] b, int off, int len) {
        if (used) {
            throw new IllegalStateException();
        }
        value = XXHASH32.hash(b, off, len, seed);
        used = true;
    }

    @Override
    public void update(ByteBuf b, int off, int len) {
        if (used) {
            throw new IllegalStateException();
        }
        if (b.hasArray()) {
            value = XXHASH32.hash(b.array(), b.arrayOffset() + off, len, seed);
        } else {
            value = XXHASH32.hash(CompressionUtil.safeNioBuffer(b, off, len), seed);
        }
        used = true;
    }

    @Override
    public long getValue() {
        if (!used) {
            throw new IllegalStateException();
        }
        /*
         * If you look carefully, you'll notice that the most significant nibble
         * is being discarded; we believe this to be a bug, but this is what
         * StreamingXXHash32#asChecksum() implementation of getValue() does,
         * so we have to retain this behaviour for compatibility reasons.
         */
        return value & 0xFFFFFFFL;
    }

    @Override
    public void reset() {
        used = false;
    }
}