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// File: crn_hash.cpp
// See Paul Hsieh's page at: http://www.azillionmonkeys.com/qed/hash.html
// Also see http://www.concentric.net/~Ttwang/tech/inthash.htm,
// http://burtleburtle.net/bob/hash/integer.html
#include "crn_core.h"
#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) || defined(_MSC_VER) || defined(__BORLANDC__) || defined(__TURBOC__)
#define get16bits(d) (*((const uint16*)(d)))
#endif
#if !defined(get16bits)
#define get16bits(d) ((((uint32)(((const uint8*)(d))[1])) << 8) + (uint32)(((const uint8*)(d))[0]))
#endif
namespace crnlib {
uint32 fast_hash(const void* p, int len) {
const char* data = static_cast<const char*>(p);
uint32 hash = len, tmp;
int rem;
if (len <= 0 || data == NULL)
return 0;
rem = len & 3;
len >>= 2;
/* Main loop */
for (; len > 0; len--) {
hash += get16bits(data);
tmp = (get16bits(data + 2) << 11) ^ hash;
hash = (hash << 16) ^ tmp;
data += 2 * sizeof(uint16);
hash += hash >> 11;
}
/* Handle end cases */
switch (rem) {
case 3:
hash += get16bits(data);
hash ^= hash << 16;
hash ^= data[sizeof(uint16)] << 18;
hash += hash >> 11;
break;
case 2:
hash += get16bits(data);
hash ^= hash << 11;
hash += hash >> 17;
break;
case 1:
hash += *data;
hash ^= hash << 10;
hash += hash >> 1;
}
/* Force "avalanching" of final 127 bits */
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 4;
hash += hash >> 17;
hash ^= hash << 25;
hash += hash >> 6;
return hash;
}
} // namespace crnlib
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