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hash_64.c
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hash_64.c
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/*
* hash_64 - 64 bit Fowler/Noll/Vo-0 hash code
*
* @(#) $Revision: 5.1 $
* @(#) $Id: hash_64.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64.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 64 bit FNV-0 historic hash, pass FNV0_64_INIT as the
* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_str().
*
* To use the recommended 64 bit FNV-1 hash, pass FNV1_64_INIT as the
* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_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"
/*
* FNV-0 defines the initial basis to be zero
*/
#if !defined(HAVE_64BIT_LONG_LONG)
const Fnv64_t fnv0_64_init = { 0UL, 0UL };
#endif /* ! HAVE_64BIT_LONG_LONG */
/*
* FNV-1 defines the initial basis to be non-zero
*/
#if !defined(HAVE_64BIT_LONG_LONG)
const Fnv64_t fnv1_64_init = { 0x84222325UL, 0xcbf29ce4UL };
#endif /* ! HAVE_64BIT_LONG_LONG */
/*
* 64 bit magic FNV-0 and FNV-1 prime
*/
#if defined(HAVE_64BIT_LONG_LONG)
#define FNV_64_PRIME ((Fnv64_t)0x100000001b3ULL)
#else /* HAVE_64BIT_LONG_LONG */
#define FNV_64_PRIME_LOW ((unsigned long)0x1b3) /* lower bits of FNV prime */
#define FNV_64_PRIME_SHIFT (8) /* top FNV prime shift above 2^32 */
#endif /* HAVE_64BIT_LONG_LONG */
/*
* fnv_64_buf - perform a 64 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:
* 64 bit hash as a static hash type
*
* NOTE: To use the 64 bit FNV-0 historic hash, use FNV0_64_INIT as the hval
* argument on the first call to either fnv_64_buf() or fnv_64_str().
*
* NOTE: To use the recommended 64 bit FNV-1 hash, use FNV1_64_INIT as the hval
* argument on the first call to either fnv_64_buf() or fnv_64_str().
*/
Fnv64_t
fnv_64_buf(void *buf, size_t len, Fnv64_t hval)
{
unsigned char *bp = (unsigned char *)buf; /* start of buffer */
unsigned char *be = bp + len; /* beyond end of buffer */
#if defined(HAVE_64BIT_LONG_LONG)
/*
* FNV-1 hash each octet of the buffer
*/
while (bp < be) {
/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_64_PRIME;
#else /* NO_FNV_GCC_OPTIMIZATION */
hval += (hval << 1) + (hval << 4) + (hval << 5) +
(hval << 7) + (hval << 8) + (hval << 40);
#endif /* NO_FNV_GCC_OPTIMIZATION */
/* xor the bottom with the current octet */
hval ^= (Fnv64_t)*bp++;
}
#else /* HAVE_64BIT_LONG_LONG */
unsigned long val[4]; /* hash value in base 2^16 */
unsigned long tmp[4]; /* tmp 64 bit value */
/*
* Convert Fnv64_t hval into a base 2^16 array
*/
val[0] = hval.w32[0];
val[1] = (val[0] >> 16);
val[0] &= 0xffff;
val[2] = hval.w32[1];
val[3] = (val[2] >> 16);
val[2] &= 0xffff;
/*
* FNV-1 hash each octet of the buffer
*/
while (bp < be) {
/*
* multiply by the 64 bit FNV magic prime mod 2^64
*
* Using 0x100000001b3 we have the following digits base 2^16:
*
* 0x0 0x100 0x0 0x1b3
*
* which is the same as:
*
* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
*/
/* multiply by the lowest order digit base 2^16 */
tmp[0] = val[0] * FNV_64_PRIME_LOW;
tmp[1] = val[1] * FNV_64_PRIME_LOW;
tmp[2] = val[2] * FNV_64_PRIME_LOW;
tmp[3] = val[3] * FNV_64_PRIME_LOW;
/* multiply by the other non-zero digit */
tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
/* propagate carries */
tmp[1] += (tmp[0] >> 16);
val[0] = tmp[0] & 0xffff;
tmp[2] += (tmp[1] >> 16);
val[1] = tmp[1] & 0xffff;
val[3] = tmp[3] + (tmp[2] >> 16);
val[2] = tmp[2] & 0xffff;
/*
* Doing a val[3] &= 0xffff; is not really needed since it simply
* removes multiples of 2^64. We can discard these excess bits
* outside of the loop when we convert to Fnv64_t.
*/
/* xor the bottom with the current octet */
val[0] ^= (unsigned long)*bp++;
}
/*
* Convert base 2^16 array back into an Fnv64_t
*/
hval.w32[1] = ((val[3]<<16) | val[2]);
hval.w32[0] = ((val[1]<<16) | val[0]);
#endif /* HAVE_64BIT_LONG_LONG */
/* return our new hash value */
return hval;
}
/*
* fnv_64_str - perform a 64 bit Fowler/Noll/Vo hash on a buffer
*
* input:
* buf - start of buffer to hash
* hval - previous hash value or 0 if first call
*
* returns:
* 64 bit hash as a static hash type
*
* NOTE: To use the 64 bit FNV-0 historic hash, use FNV0_64_INIT as the hval
* argument on the first call to either fnv_64_buf() or fnv_64_str().
*
* NOTE: To use the recommended 64 bit FNV-1 hash, use FNV1_64_INIT as the hval
* argument on the first call to either fnv_64_buf() or fnv_64_str().
*/
Fnv64_t
fnv_64_str(char *str, Fnv64_t hval)
{
unsigned char *s = (unsigned char *)str; /* unsigned string */
#if defined(HAVE_64BIT_LONG_LONG)
/*
* FNV-1 hash each octet of the string
*/
while (*s) {
/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_64_PRIME;
#else /* NO_FNV_GCC_OPTIMIZATION */
hval += (hval << 1) + (hval << 4) + (hval << 5) +
(hval << 7) + (hval << 8) + (hval << 40);
#endif /* NO_FNV_GCC_OPTIMIZATION */
/* xor the bottom with the current octet */
hval ^= (Fnv64_t)*s++;
}
#else /* !HAVE_64BIT_LONG_LONG */
unsigned long val[4]; /* hash value in base 2^16 */
unsigned long tmp[4]; /* tmp 64 bit value */
/*
* Convert Fnv64_t hval into a base 2^16 array
*/
val[0] = hval.w32[0];
val[1] = (val[0] >> 16);
val[0] &= 0xffff;
val[2] = hval.w32[1];
val[3] = (val[2] >> 16);
val[2] &= 0xffff;
/*
* FNV-1 hash each octet of the string
*/
while (*s) {
/*
* multiply by the 64 bit FNV magic prime mod 2^64
*
* Using 1099511628211, we have the following digits base 2^16:
*
* 0x0 0x100 0x0 0x1b3
*
* which is the same as:
*
* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
*/
/* multiply by the lowest order digit base 2^16 */
tmp[0] = val[0] * FNV_64_PRIME_LOW;
tmp[1] = val[1] * FNV_64_PRIME_LOW;
tmp[2] = val[2] * FNV_64_PRIME_LOW;
tmp[3] = val[3] * FNV_64_PRIME_LOW;
/* multiply by the other non-zero digit */
tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
/* propagate carries */
tmp[1] += (tmp[0] >> 16);
val[0] = tmp[0] & 0xffff;
tmp[2] += (tmp[1] >> 16);
val[1] = tmp[1] & 0xffff;
val[3] = tmp[3] + (tmp[2] >> 16);
val[2] = tmp[2] & 0xffff;
/*
* Doing a val[3] &= 0xffff; is not really needed since it simply
* removes multiples of 2^64. We can discard these excess bits
* outside of the loop when we convert to Fnv64_t.
*/
/* xor the bottom with the current octet */
val[0] ^= (unsigned long)(*s++);
}
/*
* Convert base 2^16 array back into an Fnv64_t
*/
hval.w32[1] = ((val[3]<<16) | val[2]);
hval.w32[0] = ((val[1]<<16) | val[0]);
#endif /* !HAVE_64BIT_LONG_LONG */
/* return our new hash value */
return hval;
}