diff options
Diffstat (limited to 'lib/fnv/hash_64.c')
| -rw-r--r-- | lib/fnv/hash_64.c | 312 | 
1 files changed, 312 insertions, 0 deletions
| diff --git a/lib/fnv/hash_64.c b/lib/fnv/hash_64.c new file mode 100644 index 0000000000..4338605dca --- /dev/null +++ b/lib/fnv/hash_64.c @@ -0,0 +1,312 @@ +/* + * 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; +} | 
