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/*
* hash_32 - 32 bit Fowler/Noll/Vo FNV-1a hash code
*
* @(#) $Revision: 5.1 $
* @(#) $Id: hash_32a.c,v 5.1 2009/06/30 09:13:32 chongo Exp $
* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_32a.c,v $
*
***
*
* Fowler/Noll/Vo hash
*
* The basis of this hash algorithm was taken from an idea sent
* as reviewer comments to the IEEE POSIX P1003.2 committee by:
*
* Phong Vo (http://www.research.att.com/info/kpv/)
* Glenn Fowler (http://www.research.att.com/~gsf/)
*
* In a subsequent ballot round:
*
* Landon Curt Noll (http://www.isthe.com/chongo/)
*
* improved on their algorithm. Some people tried this hash
* and found that it worked rather well. In an EMail message
* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
*
* FNV hashes are designed to be fast while maintaining a low
* collision rate. The FNV speed allows one to quickly hash lots
* of data while maintaining a reasonable collision rate. See:
*
* http://www.isthe.com/chongo/tech/comp/fnv/index.html
*
* for more details as well as other forms of the FNV hash.
***
*
* To use the recommended 32 bit FNV-1a hash, pass FNV1_32A_INIT as the
* Fnv32_t hashval argument to fnv_32a_buf() or fnv_32a_str().
*
***
*
* Please do not copyright this code. This code is in the public domain.
*
* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*
* By:
* chongo <Landon Curt Noll> /\oo/\
* http://www.isthe.com/chongo/
*
* Share and Enjoy! :-)
*/
#include <stdlib.h>
#include "fnv.h"
/*
* 32 bit magic FNV-1a prime
*/
#define FNV_32_PRIME ((Fnv32_t)0x01000193)
/*
* fnv_32a_buf - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a buffer
*
* input:
* buf - start of buffer to hash
* len - length of buffer in octets
* hval - previous hash value or 0 if first call
*
* returns:
* 32 bit hash as a static hash type
*
* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
*/
Fnv32_t
fnv_32a_buf(void *buf, size_t len, Fnv32_t hval)
{
unsigned char *bp = (unsigned char *)buf; /* start of buffer */
unsigned char *be = bp + len; /* beyond end of buffer */
/*
* FNV-1a hash each octet in the buffer
*/
while (bp < be) {
/* xor the bottom with the current octet */
hval ^= (Fnv32_t)*bp++;
/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_32_PRIME;
#else
hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif
}
/* return our new hash value */
return hval;
}
/*
* fnv_32a_str - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a string
*
* input:
* str - string to hash
* hval - previous hash value or 0 if first call
*
* returns:
* 32 bit hash as a static hash type
*
* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
*/
Fnv32_t
fnv_32a_str(char *str, Fnv32_t hval)
{
unsigned char *s = (unsigned char *)str; /* unsigned string */
/*
* FNV-1a hash each octet in the buffer
*/
while (*s) {
/* xor the bottom with the current octet */
hval ^= (Fnv32_t)*s++;
/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_32_PRIME;
#else
hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif
}
/* return our new hash value */
return hval;
}
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