murmur3.c

#include "murmur3.h"

#include <string.h>

static inline uint32_t murmur_32_scramble(uint32_t k)
{
    k *= 0xcc9e2d51;
    k = (k << 15) | (k >> 17);
    k *= 0x1b873593;
    return k;
}

uint32_t murmur3_32(const uint8_t *key, size_t len, uint32_t seed)
{
    uint32_t h = seed;
    uint32_t k;
    /* Read in groups of 4. */
    for (size_t i = len >> 2; i; i--) {
        memcpy(&k, key, sizeof(uint32_t));
        key += sizeof(uint32_t);
        h ^= murmur_32_scramble(k);
        h = (h << 13) | (h >> 19);
        h = h * 5 + 0xe6546b64;
    }
    /* Read the rest. */
    k = 0;
    for (size_t i = len & 3; i; i--) {
        k <<= 8;
        k |= key[i - 1];
    }
    h ^= murmur_32_scramble(k);
    /* Finalize. */
    h ^= len;
    h ^= h >> 16;
    h *= 0x85ebca6b;
    h ^= h >> 13;
    h *= 0xc2b2ae35;
    h ^= h >> 16;
    return h;
}