hash.c

#include "hash.h"

static uint64_t
murmur3_hash64(const void *key, size_t len, uint64_t seed)
{
	const uint64_t m = UINT64_C(0xc6a4a7935bd1e995);
	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);
	const unsigned char * data2;

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

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

	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;
}

uint64_t
db_hash(const void *key, size_t len)
{
	return murmur3_hash64(key, len, 0);
}