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/* $Id$
Part of SWI-Prolog
Author: Austin Appleby
License: Public domain
See: http://murmurhash.googlepages.com/
*/
#ifdef NO_SWIPL
#define uintptr_t long
#define DEBUG(l,g) (void)0
#else
#include <pl-incl.h>
#endif
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
The first one is actually MurmurHashNeutral2(). It produces the same
hash as MurmurHashAligned2() on little endian machines, but is
significantly slower. MurmurHashAligned2() however is broken on
big-endian machines, as it produces different hashes, depending on the
alignment.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#if WORDS_BIGENDIAN
unsigned int
MurmurHashAligned2(const void * key, size_t len, unsigned int seed)
{ const unsigned int m = 0x5bd1e995;
const int r = 24;
unsigned int h = seed ^ len;
const unsigned char * data = (const unsigned char *)key;
while( len >= 4 )
{ unsigned int k;
k = data[0];
k |= data[1] << 8;
k |= data[2] << 16;
k |= data[3] << 24;
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
switch( len )
{ case 3: h ^= data[2] << 16;
case 2: h ^= data[1] << 8;
case 1: h ^= data[0];
h *= m;
};
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
#else /*WORDS_BIGENDIAN*/
#define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
unsigned int
MurmurHashAligned2(const void *key, size_t len, unsigned int seed)
{ const unsigned int m = 0x5bd1e995;
const int r = 24;
const unsigned char * data = (const unsigned char *)key;
unsigned int h = seed ^ (unsigned int)len;
size_t align = (size_t)(uintptr_t)data & 3;
DEBUG(0, assert(sizeof(int) == 4));
if ( align && (len >= 4) )
{ unsigned int t = 0, d = 0;
int sl, sr;
switch( align )
{ case 1: t |= data[2] << 16;
case 2: t |= data[1] << 8;
case 3: t |= data[0];
}
t <<= (8 * align);
data += 4-align;
len -= 4-align;
sl = 8 * (4-(int)align);
sr = 8 * (int)align;
while ( len >= 4 )
{ unsigned int k;
d = *(unsigned int *)data;
t = (t >> sr) | (d << sl);
k = t;
MIX(h,k,m);
t = d;
data += 4;
len -= 4;
}
d = 0;
if ( len >= align )
{ unsigned int k;
switch( align )
{ case 3: d |= data[2] << 16;
case 2: d |= data[1] << 8;
case 1: d |= data[0];
}
k = (t >> sr) | (d << sl);
MIX(h,k,m);
data += align;
len -= align;
switch(len)
{ case 3: h ^= data[2] << 16;
case 2: h ^= data[1] << 8;
case 1: h ^= data[0];
h *= m;
};
} else
{ switch(len)
{ case 3: d |= data[2] << 16;
case 2: d |= data[1] << 8;
case 1: d |= data[0];
case 0: h ^= (t >> sr) | (d << sl);
h *= m;
}
}
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
} else
{ while( len >= 4 )
{ unsigned int k = *(unsigned int *)data;
MIX(h,k,m);
data += 4;
len -= 4;
}
switch(len)
{ case 3: h ^= data[2] << 16;
case 2: h ^= data[1] << 8;
case 1: h ^= data[0];
h *= m;
};
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
}
#endif /*WORDS_BIGENDIAN*/
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