siphash.c

#include "siphash.h"
#include "siphash_impl.h"


static uint64_t INLINE
U8TO64_LE(const unsigned char *p) {
        return *(const uint64_t *)p;
}

/*
static void INLINE
U64TO8_LE(unsigned char *p, const uint64_t v) {
        *(uint64_t *)p = v;
}
*/

uint64_t
siphash(const unsigned char key[16], const unsigned char *m, size_t len) {
        uint64_t v0, v1, v2, v3;
        uint64_t mi, k0, k1;
        uint64_t last7;
        size_t i, blocks;

        k0 = U8TO64_LE(key + 0);
        k1 = U8TO64_LE(key + 8);
        v0 = k0 ^ 0x736f6d6570736575ull;
        v1 = k1 ^ 0x646f72616e646f6dull;
        v2 = k0 ^ 0x6c7967656e657261ull;
        v3 = k1 ^ 0x7465646279746573ull;

        last7 = (uint64_t)(len & 0xff) << 56;

#define sipcompress() \
        v0 += v1; v2 += v3; \
        v1 = ROTL64(v1,13);     v3 = ROTL64(v3,16); \
        v1 ^= v0; v3 ^= v2; \
        v0 = ROTL64(v0,32); \
        v2 += v1; v0 += v3; \
        v1 = ROTL64(v1,17); v3 = ROTL64(v3,21); \
        v1 ^= v2; v3 ^= v0; \
        v2 = ROTL64(v2,32);

        for (i = 0, blocks = (len & ~7); i < blocks; i += 8) {
                mi = U8TO64_LE(m + i);
                v3 ^= mi;
                sipcompress()
                v0 ^= mi;
        }

        switch (len - blocks) {
                case 7: last7 |= (uint64_t)m[i + 6] << 48;
                case 6: last7 |= (uint64_t)m[i + 5] << 40;
                case 5: last7 |= (uint64_t)m[i + 4] << 32;
                case 4: last7 |= (uint64_t)m[i + 3] << 24;
                case 3: last7 |= (uint64_t)m[i + 2] << 16;
                case 2: last7 |= (uint64_t)m[i + 1] <<  8;
                case 1: last7 |= (uint64_t)m[i + 0]      ;
                case 0:
                default:;
        };
        v3 ^= last7;
        sipcompress()
        v0 ^= last7;
        v2 ^= 0xff;
        sipcompress()
        sipcompress()
        sipcompress()
        return v0 ^ v1 ^ v2 ^ v3;
}