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/* Downloaded from http://sites.google.com/site/murmurhash/ which says "All
* code is released to the public domain. For business purposes, Murmurhash is
* under the MIT license."
* This is modified from the original:
* ULL tag on 0xc6a4a7935bd1e995 so this will compile on 32-bit.
* length changed to unsigned int.
* placed in namespace util
* add MurmurHashNative
* default option = 0 for seed
*/
#include "util/murmur_hash.hh"
namespace util {
//-----------------------------------------------------------------------------
// MurmurHash2, 64-bit versions, by Austin Appleby
// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment
// and endian-ness issues if used across multiple platforms.
// 64-bit hash for 64-bit platforms
uint64_t MurmurHash64A ( const void * key, std::size_t len, unsigned int seed )
{
const uint64_t m = 0xc6a4a7935bd1e995ULL;
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);
while(data != end)
{
uint64_t k = *data++;
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
}
const unsigned char * 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;
}
// 64-bit hash for 32-bit platforms
uint64_t MurmurHash64B ( const void * key, std::size_t len, unsigned int seed )
{
const unsigned int m = 0x5bd1e995;
const int r = 24;
unsigned int h1 = seed ^ len;
unsigned int h2 = 0;
const unsigned int * data = (const unsigned int *)key;
while(len >= 8)
{
unsigned int k1 = *data++;
k1 *= m; k1 ^= k1 >> r; k1 *= m;
h1 *= m; h1 ^= k1;
len -= 4;
unsigned int k2 = *data++;
k2 *= m; k2 ^= k2 >> r; k2 *= m;
h2 *= m; h2 ^= k2;
len -= 4;
}
if(len >= 4)
{
unsigned int k1 = *data++;
k1 *= m; k1 ^= k1 >> r; k1 *= m;
h1 *= m; h1 ^= k1;
len -= 4;
}
switch(len)
{
case 3: h2 ^= ((unsigned char*)data)[2] << 16;
case 2: h2 ^= ((unsigned char*)data)[1] << 8;
case 1: h2 ^= ((unsigned char*)data)[0];
h2 *= m;
};
h1 ^= h2 >> 18; h1 *= m;
h2 ^= h1 >> 22; h2 *= m;
h1 ^= h2 >> 17; h1 *= m;
h2 ^= h1 >> 19; h2 *= m;
uint64_t h = h1;
h = (h << 32) | h2;
return h;
}
uint64_t MurmurHashNative(const void * key, std::size_t len, unsigned int seed) {
if (sizeof(int) == 4) {
return MurmurHash64B(key, len, seed);
} else {
return MurmurHash64A(key, len, seed);
}
}
} // namespace util
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