raze-gles/source/common/utility/superfasthash.cpp

#include <stdint.h>
#include <ctype.h>
#include <string.h>

/* ======================================================================== */

/* By Paul Hsieh (C) 2004, 2005.  Covered under the Paul Hsieh derivative 
   license. See: 
   http://www.azillionmonkeys.com/qed/weblicense.html for license details.

   http://www.azillionmonkeys.com/qed/hash.html */

#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif

#if !defined (get16bits)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
                       +(uint32_t)(((const uint8_t *)(d))[0]) )
#endif

uint32_t SuperFastHash (const char *data, size_t len)
{
	uint32_t hash = 0, tmp;
	size_t 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_t);
		hash  += hash >> 11;
	}

	/* Handle end cases */
	switch (rem)
	{
		case 3:	hash += get16bits (data);
				hash ^= hash << 16;
				hash ^= data[sizeof (uint16_t)] << 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;
}

/* A modified version to do a case-insensitive hash */

#undef get16bits
#define get16bits(d) ((((uint32_t)tolower(((const uint8_t *)(d))[1])) << 8)\
                       +(uint32_t)tolower(((const uint8_t *)(d))[0]) )

uint32_t SuperFastHashI (const char *data, size_t len)
{
	uint32_t hash = 0, tmp;
	size_t 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_t);
		hash  += hash >> 11;
	}

	/* Handle end cases */
	switch (rem)
	{
		case 3:	hash += get16bits (data);
				hash ^= hash << 16;
				hash ^= tolower(data[sizeof (uint16_t)]) << 18;
				hash += hash >> 11;
				break;
		case 2:	hash += get16bits (data);
				hash ^= hash << 11;
				hash += hash >> 17;
				break;
		case 1: hash += tolower(*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;
}

/* ======================================================================== */

unsigned int MakeKey (const char *s)
{
	if (s == NULL)
	{
		return 0;
	}
	return SuperFastHashI (s, strlen (s));
}

unsigned int MakeKey (const char *s, size_t len)
{
	return SuperFastHashI (s, len);
}