You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
142 lines
3.9 KiB
142 lines
3.9 KiB
/* |
|
* 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 <stdint.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(const 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(const 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; |
|
}
|
|
|