murmurhash.cpp

#include "murmurhash.h"

uint64_t murmurhash64(const void *key, size_t len, uint64_t seed) {
    const uint64_t m = 0xc6a4a7935bd1e995ULL;
    const int r = 47;

    uint64_t h = seed ^ (len * m);

    const uint64_t *data = (const uint64_t *)key;
    const uint64_t *end = data + (len / 8);

    while (data != end) {
        uint64_t k = *data++;

        k *= m;
        k ^= k >> r;
        k *= m;

        h ^= k;
        h *= m;
    }

    const unsigned char *data2 = (const unsigned char *)data;

    switch (len & 7) {
        case 7: h ^= (uint64_t)data2[6] << 48;
        case 6: h ^= (uint64_t)data2[5] << 40;
        case 5: h ^= (uint64_t)data2[4] << 32;
        case 4: h ^= (uint64_t)data2[3] << 24;
        case 3: h ^= (uint64_t)data2[2] << 16;
        case 2: h ^= (uint64_t)data2[1] << 8;
        case 1: h ^= (uint64_t)data2[0];
                h *= m;
    }

    h ^= h >> r;
    h *= m;
    h ^= h >> r;

    return h;
}