Nils O. Selåsdal
56 lines
1007 B
C
56 lines
1007 B
C
#include "ucore_hash.h"
|
|
|
|
// 'm' and 'r' are mixing constants generated offline.
|
|
// They're not really 'magic', they just happen to work well.
|
|
#define m 0x5bd1e995
|
|
#define r 24
|
|
|
|
uint32_t
|
|
uc_murmurmash2(const void *key, int len, uint32_t seed )
|
|
{
|
|
|
|
|
|
// Initialize the hash to a 'random' value
|
|
|
|
uint32_t h = seed ^ len;
|
|
|
|
// Mix 4 bytes at a time into the hash
|
|
|
|
const unsigned char * data = (const unsigned char *)key;
|
|
|
|
while(len >= 4)
|
|
{
|
|
uint32_t k = *(uint32_t *)data;
|
|
|
|
k *= m;
|
|
k ^= k >> r;
|
|
k *= m;
|
|
|
|
h *= m;
|
|
h ^= k;
|
|
|
|
data += 4;
|
|
len -= 4;
|
|
}
|
|
|
|
// Handle the last few bytes of the input array
|
|
|
|
switch(len)
|
|
{
|
|
case 3: h ^= data[2] << 16;
|
|
case 2: h ^= data[1] << 8;
|
|
case 1: h ^= data[0];
|
|
h *= m;
|
|
};
|
|
|
|
// Do a few final mixes of the hash to ensure the last few
|
|
// bytes are well-incorporated.
|
|
|
|
h ^= h >> 13;
|
|
h *= m;
|
|
h ^= h >> 15;
|
|
|
|
return h;
|
|
}
|
|
|