murmurhash3.c

Go to the documentation of this file.

/*
 * MurmurHash3 Implementation - Direct copy from HPC_Embeddings
 *
 * High-performance 32-bit hash function.
 */
 
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
 
uint32_t ck_murmurhash3(const char* key, uint32_t len, uint32_t seed) {
    const uint32_t c1 = 0xcc9e2d51;
    const uint32_t c2 = 0x1b873593;
    const uint32_t r1 = 15;
    const uint32_t r2 = 13;
    const uint32_t m = 5;
    const uint32_t n = 0xe6546b64;
 
    uint32_t hash = seed;
 
    const int nblocks = len / 4;
    const uint32_t *blocks = (const uint32_t *)(key);
    int i;
    for (i = 0; i < nblocks; i++) {
        uint32_t k = blocks[i];
 
        k *= c1;
        k = (k << r1) | (k >> (32 - r1));
        k *= c2;
 
        hash ^= k;
        hash = (hash << r2) | (hash >> (32 - r2));
        hash = hash * m + n;
    }
 
    const uint8_t *tail = (const uint8_t *)(key + nblocks * 4);
    uint32_t k1 = 0;
 
    switch (len & 3) {
        case 3:
            k1 ^= tail[2] << 16;
        case 2:
            k1 ^= tail[1] << 8;
        case 1:
            k1 ^= tail[0];
            k1 *= c1;
            k1 = (k1 << r1) | (k1 >> (32 - r1));
            k1 *= c2;
            hash ^= k1;
    }
 
    hash ^= len;
    hash ^= hash >> 16;
    hash *= 0x85ebca6b;
    hash ^= hash >> 13;
    hash *= 0xc2b2ae35;
    hash ^= hash >> 16;
 
    return hash;
}
 
/* Convenience wrapper for null-terminated strings */
static inline uint32_t ck_murmurhash3_str(const char *key, uint32_t seed) {
    return ck_murmurhash3(key, (uint32_t)strlen(key), seed);
}
 
/* Alias for ck_murmurhash3_32 compatibility */
uint32_t ck_murmurhash3_32(const void *key, size_t len, uint32_t seed) {
    return ck_murmurhash3((const char *)key, (uint32_t)len, seed);
}