siphash 64 java

Main.java

package com.example;

public class Main {

    private static final int cROUNDS = 2;
    private static final int dROUNDS = 4;

    public static long ROTL(long value, int n) {
        return (value << n) | (value >>> (64 - n));
    }

    // Translated from https://github.com/veorq/SipHash/blob/master/siphash.c
    public static long siphash(byte[] buffer, long k0, long k1) {
        long v0 = 0x736f6d6570736575L;
        long v1 = 0x646f72616e646f6dL;
        long v2 = 0x6c7967656e657261L;
        long v3 = 0x7465646279746573L;

        final int end = buffer.length - buffer.length % 8;
        final int left = buffer.length & 7;
        long b = ((long) buffer.length) << 56;
        v3 ^= k1;
        v2 ^= k0;
        v1 ^= k1;
        v0 ^= k0;

        int pos = 0;
        for (; pos < end; pos += 8) {
            long m = ((long) (buffer[pos] & 0xff))
                    | (((long) (buffer[pos + 1] & 0xff)) << 8)
                    | (((long) (buffer[pos + 2] & 0xff)) << 16)
                    | (((long) (buffer[pos + 3] & 0xff)) << 24)
                    | (((long) (buffer[pos + 4] & 0xff)) << 32)
                    | (((long) (buffer[pos + 5] & 0xff)) << 40)
                    | (((long) (buffer[pos + 6] & 0xff)) << 48)
                    | (((long) (buffer[pos + 7] & 0xff)) << 56);
            v3 ^= m;

            for (int i = 0; i < cROUNDS; ++i) {
                v0 += v1;
                v1 = ROTL(v1, 13);
                v1 ^= v0;
                v0 = ROTL(v0, 32);
                v2 += v3;
                v3 = ROTL(v3, 16);
                v3 ^= v2;
                v0 += v3;
                v3 = ROTL(v3, 21);
                v3 ^= v0;
                v2 += v1;
                v1 = ROTL(v1, 17);
                v1 ^= v2;
                v2 = ROTL(v2, 32);
            }

            v0 ^= m;
        }

        switch (left) {
            case 7:
                b |= ((long) (buffer[pos + 6] & 0xff)) << 48;
            case 6:
                b |= ((long) (buffer[pos + 5] & 0xff)) << 40;
            case 5:
                b |= ((long) (buffer[pos + 4] & 0xff)) << 32;
            case 4:
                b |= ((long) (buffer[pos + 3] & 0xff)) << 24;
            case 3:
                b |= ((long) (buffer[pos + 2] & 0xff)) << 16;
            case 2:
                b |= ((long) (buffer[pos + 1] & 0xff)) << 8;
            case 1:
                b |= ((long) (buffer[pos + 0] & 0xff));
                break;
            case 0:
                break;
        }

        v3 ^= b;

        for (int i = 0; i < cROUNDS; ++i) {
            v0 += v1;
            v1 = ROTL(v1, 13);
            v1 ^= v0;
            v0 = ROTL(v0, 32);
            v2 += v3;
            v3 = ROTL(v3, 16);
            v3 ^= v2;
            v0 += v3;
            v3 = ROTL(v3, 21);
            v3 ^= v0;
            v2 += v1;
            v1 = ROTL(v1, 17);
            v1 ^= v2;
            v2 = ROTL(v2, 32);
        }

        v0 ^= b;

        v2 ^= 0xff;

        for (int i = 0; i < dROUNDS; ++i) {
            v0 += v1;
            v1 = ROTL(v1, 13);
            v1 ^= v0;
            v0 = ROTL(v0, 32);
            v2 += v3;
            v3 = ROTL(v3, 16);
            v3 ^= v2;
            v0 += v3;
            v3 = ROTL(v3, 21);
            v3 ^= v0;
            v2 += v1;
            v1 = ROTL(v1, 17);
            v1 ^= v2;
            v2 = ROTL(v2, 32);
        }

        b = v0 ^ v1 ^ v2 ^ v3;

        return b;
    }

    public static void main(String[] args) {
        System.out.println(siphash("a".getBytes(), 0, 0));
    }
}