murmurhash.c

#include <stdlib.h>
#include <stdint.h>
#include <math.h>

/*Taken from https://en.wikipedia.org/wiki/MurmurHash*/

uint32_t murmur3_32(const char* key, size_t len, uint32_t seed) {
	uint32_t h = seed;
	if (len > 3) {
		const uint32_t* key_x4 = (const uint32_t*) key;
		size_t i = len >> 2;
		do {
			uint32_t k = *key_x4++;
			k *= 0xcc9e2d51;
			k = (k << 15) | (k >> 17);
			k *= 0x1b873593;
			h ^= k;
			h = (h << 13) | (h >> 19);
			h += (h << 2) + 0xe6546b64;
		} while (--i);
		key = (const uint8_t*) key_x4;
	}
	if (len & 3) {
		size_t i = len & 3;
		uint32_t k = 0;
		key = &key[i - 1];
		do {
			k <<= 8;
			k |= *key--;
		} while (--i);
		k *= 0xcc9e2d51;
		k = (k << 15) | (k >> 17);
		k *= 0x1b873593;
		h ^= k;
	}
	h ^= len;
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;
	return h;
}