Alexander Suvorov
69 lines
1.6 KiB
C++
69 lines
1.6 KiB
C++
// 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
|