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#ifndef _MURMUR_HASH_H_
#define _MURMUR_HASH_H_
//NOTE: quite fast, nice collision properties, but endian dependent hash values
#include "have_64_bits.h"
typedef uintptr_t MurmurInt;
// MurmurHash2, by Austin Appleby
static const uint32_t DEFAULT_SEED=2654435769U;
#if HAVE_64_BITS
//MurmurInt MurmurHash(void const *key, int len, uint32_t seed=DEFAULT_SEED);
inline uint64_t MurmurHash64( const void * key, int len, unsigned int seed=DEFAULT_SEED )
{
const uint64_t m = 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);
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;
}
inline uint32_t MurmurHash32(void const *key, int len, uint32_t seed=DEFAULT_SEED)
{
return (uint32_t) MurmurHash64(key,len,seed);
}
inline MurmurInt MurmurHash(void const *key, int len, uint32_t seed=DEFAULT_SEED)
{
return MurmurHash64(key,len,seed);
}
#else
// 32-bit
// Note - This code makes a few assumptions about how your machine behaves -
// 1. We can read a 4-byte value from any address without crashing
// 2. sizeof(int) == 4
inline uint32_t MurmurHash32 ( const void * key, int len, uint32_t seed=DEFAULT_SEED)
{
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
const uint32_t m = 0x5bd1e995;
const int r = 24;
// 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;
}
inline MurmurInt MurmurHash ( const void * key, int len, uint32_t seed=DEFAULT_SEED) {
return MurmurHash32(key,len,seed);
}
// 64-bit hash for 32-bit platforms
inline uint64_t MurmurHash64 ( const void * key, int len, uint32_t seed=DEFAULT_SEED)
{
const uint32_t m = 0x5bd1e995;
const int r = 24;
uint32_t h1 = seed ^ len;
uint32_t h2 = 0;
const uint32_t * data = (const uint32_t *)key;
while(len >= 8)
{
uint32_t k1 = *data++;
k1 *= m; k1 ^= k1 >> r; k1 *= m;
h1 *= m; h1 ^= k1;
len -= 4;
uint32_t k2 = *data++;
k2 *= m; k2 ^= k2 >> r; k2 *= m;
h2 *= m; h2 ^= k2;
len -= 4;
}
if(len >= 4)
{
uint32_t 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;
}
#endif
//32bit
#endif
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