/* * hash_32 - 32 bit Fowler/Noll/Vo hash code * * @(#) $Revision: 5.1 $ * @(#) $Id: hash_32.c,v 5.1 2009/06/30 09:13:32 chongo Exp $ * @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_32.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. *** * * NOTE: The FNV-0 historic hash is not recommended. One should use * the FNV-1 hash instead. * * To use the 32 bit FNV-0 historic hash, pass FNV0_32_INIT as the * Fnv32_t hashval argument to fnv_32_buf() or fnv_32_str(). * * To use the recommended 32 bit FNV-1 hash, pass FNV1_32_INIT as the * Fnv32_t hashval argument to fnv_32_buf() or fnv_32_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-0 and FNV-1 prime */ #define FNV_32_PRIME ((Fnv32_t)0x01000193) /* * fnv_32_buf - perform a 32 bit Fowler/Noll/Vo 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 32 bit FNV-0 historic hash, use FNV0_32_INIT as the hval * argument on the first call to either fnv_32_buf() or fnv_32_str(). * * NOTE: To use the recommended 32 bit FNV-1 hash, use FNV1_32_INIT as the hval * argument on the first call to either fnv_32_buf() or fnv_32_str(). */ Fnv32_t fnv_32_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-1 hash each octet in the buffer */ while (bp < be) { /* 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 /* xor the bottom with the current octet */ hval ^= (Fnv32_t)*bp++; } /* return our new hash value */ return hval; } /* * fnv_32_str - perform a 32 bit Fowler/Noll/Vo 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 32 bit FNV-0 historic hash, use FNV0_32_INIT as the hval * argument on the first call to either fnv_32_buf() or fnv_32_str(). * * NOTE: To use the recommended 32 bit FNV-1 hash, use FNV1_32_INIT as the hval * argument on the first call to either fnv_32_buf() or fnv_32_str(). */ Fnv32_t fnv_32_str(char *str, Fnv32_t hval) { unsigned char *s = (unsigned char *)str; /* unsigned string */ /* * FNV-1 hash each octet in the buffer */ while (*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 /* xor the bottom with the current octet */ hval ^= (Fnv32_t)*s++; } /* return our new hash value */ return hval; }