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312 lines
8.6 KiB
312 lines
8.6 KiB
/*
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* hash_64 - 64 bit Fowler/Noll/Vo-0 hash code
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*
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* @(#) $Revision: 5.1 $
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* @(#) $Id: hash_64.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
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* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64.c,v $
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*
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***
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*
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* Fowler/Noll/Vo hash
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*
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* The basis of this hash algorithm was taken from an idea sent
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* as reviewer comments to the IEEE POSIX P1003.2 committee by:
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*
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* Phong Vo (http://www.research.att.com/info/kpv/)
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* Glenn Fowler (http://www.research.att.com/~gsf/)
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*
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* In a subsequent ballot round:
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*
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* Landon Curt Noll (http://www.isthe.com/chongo/)
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*
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* improved on their algorithm. Some people tried this hash
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* and found that it worked rather well. In an EMail message
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* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
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*
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* FNV hashes are designed to be fast while maintaining a low
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* collision rate. The FNV speed allows one to quickly hash lots
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* of data while maintaining a reasonable collision rate. See:
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*
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* http://www.isthe.com/chongo/tech/comp/fnv/index.html
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*
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* for more details as well as other forms of the FNV hash.
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*
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***
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*
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* NOTE: The FNV-0 historic hash is not recommended. One should use
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* the FNV-1 hash instead.
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*
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* To use the 64 bit FNV-0 historic hash, pass FNV0_64_INIT as the
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* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_str().
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*
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* To use the recommended 64 bit FNV-1 hash, pass FNV1_64_INIT as the
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* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_str().
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*
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***
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*
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* Please do not copyright this code. This code is in the public domain.
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*
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* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
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* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
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* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*
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* By:
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* chongo <Landon Curt Noll> /\oo/\
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* http://www.isthe.com/chongo/
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*
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* Share and Enjoy! :-)
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*/
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#include <stdlib.h>
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#include "fnv.h"
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/*
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* FNV-0 defines the initial basis to be zero
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*/
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#if !defined(HAVE_64BIT_LONG_LONG)
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const Fnv64_t fnv0_64_init = { 0UL, 0UL };
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#endif /* ! HAVE_64BIT_LONG_LONG */
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/*
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* FNV-1 defines the initial basis to be non-zero
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*/
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#if !defined(HAVE_64BIT_LONG_LONG)
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const Fnv64_t fnv1_64_init = { 0x84222325UL, 0xcbf29ce4UL };
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#endif /* ! HAVE_64BIT_LONG_LONG */
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/*
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* 64 bit magic FNV-0 and FNV-1 prime
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*/
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#if defined(HAVE_64BIT_LONG_LONG)
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#define FNV_64_PRIME ((Fnv64_t)0x100000001b3ULL)
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#else /* HAVE_64BIT_LONG_LONG */
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#define FNV_64_PRIME_LOW ((unsigned long)0x1b3) /* lower bits of FNV prime */
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#define FNV_64_PRIME_SHIFT (8) /* top FNV prime shift above 2^32 */
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#endif /* HAVE_64BIT_LONG_LONG */
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/*
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* fnv_64_buf - perform a 64 bit Fowler/Noll/Vo hash on a buffer
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*
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* input:
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* buf - start of buffer to hash
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* len - length of buffer in octets
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* hval - previous hash value or 0 if first call
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*
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* returns:
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* 64 bit hash as a static hash type
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*
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* NOTE: To use the 64 bit FNV-0 historic hash, use FNV0_64_INIT as the hval
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* argument on the first call to either fnv_64_buf() or fnv_64_str().
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*
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* NOTE: To use the recommended 64 bit FNV-1 hash, use FNV1_64_INIT as the hval
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* argument on the first call to either fnv_64_buf() or fnv_64_str().
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*/
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Fnv64_t
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fnv_64_buf(void *buf, size_t len, Fnv64_t hval)
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{
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unsigned char *bp = (unsigned char *)buf; /* start of buffer */
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unsigned char *be = bp + len; /* beyond end of buffer */
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#if defined(HAVE_64BIT_LONG_LONG)
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/*
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* FNV-1 hash each octet of the buffer
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*/
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while (bp < be) {
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/* multiply by the 64 bit FNV magic prime mod 2^64 */
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#if defined(NO_FNV_GCC_OPTIMIZATION)
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hval *= FNV_64_PRIME;
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#else /* NO_FNV_GCC_OPTIMIZATION */
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hval += (hval << 1) + (hval << 4) + (hval << 5) +
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(hval << 7) + (hval << 8) + (hval << 40);
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#endif /* NO_FNV_GCC_OPTIMIZATION */
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/* xor the bottom with the current octet */
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hval ^= (Fnv64_t)*bp++;
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}
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#else /* HAVE_64BIT_LONG_LONG */
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unsigned long val[4]; /* hash value in base 2^16 */
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unsigned long tmp[4]; /* tmp 64 bit value */
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/*
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* Convert Fnv64_t hval into a base 2^16 array
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*/
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val[0] = hval.w32[0];
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val[1] = (val[0] >> 16);
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val[0] &= 0xffff;
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val[2] = hval.w32[1];
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val[3] = (val[2] >> 16);
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val[2] &= 0xffff;
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/*
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* FNV-1 hash each octet of the buffer
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*/
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while (bp < be) {
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/*
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* multiply by the 64 bit FNV magic prime mod 2^64
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*
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* Using 0x100000001b3 we have the following digits base 2^16:
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*
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* 0x0 0x100 0x0 0x1b3
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*
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* which is the same as:
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*
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* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
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*/
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/* multiply by the lowest order digit base 2^16 */
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tmp[0] = val[0] * FNV_64_PRIME_LOW;
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tmp[1] = val[1] * FNV_64_PRIME_LOW;
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tmp[2] = val[2] * FNV_64_PRIME_LOW;
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tmp[3] = val[3] * FNV_64_PRIME_LOW;
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/* multiply by the other non-zero digit */
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tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
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tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
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/* propagate carries */
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tmp[1] += (tmp[0] >> 16);
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val[0] = tmp[0] & 0xffff;
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tmp[2] += (tmp[1] >> 16);
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val[1] = tmp[1] & 0xffff;
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val[3] = tmp[3] + (tmp[2] >> 16);
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val[2] = tmp[2] & 0xffff;
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/*
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* Doing a val[3] &= 0xffff; is not really needed since it simply
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* removes multiples of 2^64. We can discard these excess bits
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* outside of the loop when we convert to Fnv64_t.
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*/
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/* xor the bottom with the current octet */
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val[0] ^= (unsigned long)*bp++;
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}
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/*
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* Convert base 2^16 array back into an Fnv64_t
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*/
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hval.w32[1] = ((val[3]<<16) | val[2]);
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hval.w32[0] = ((val[1]<<16) | val[0]);
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#endif /* HAVE_64BIT_LONG_LONG */
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/* return our new hash value */
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return hval;
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}
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/*
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* fnv_64_str - perform a 64 bit Fowler/Noll/Vo hash on a buffer
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*
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* input:
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* buf - start of buffer to hash
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* hval - previous hash value or 0 if first call
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*
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* returns:
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* 64 bit hash as a static hash type
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*
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* NOTE: To use the 64 bit FNV-0 historic hash, use FNV0_64_INIT as the hval
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* argument on the first call to either fnv_64_buf() or fnv_64_str().
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*
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* NOTE: To use the recommended 64 bit FNV-1 hash, use FNV1_64_INIT as the hval
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* argument on the first call to either fnv_64_buf() or fnv_64_str().
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*/
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Fnv64_t
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fnv_64_str(char *str, Fnv64_t hval)
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{
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unsigned char *s = (unsigned char *)str; /* unsigned string */
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#if defined(HAVE_64BIT_LONG_LONG)
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/*
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* FNV-1 hash each octet of the string
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*/
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while (*s) {
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/* multiply by the 64 bit FNV magic prime mod 2^64 */
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#if defined(NO_FNV_GCC_OPTIMIZATION)
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hval *= FNV_64_PRIME;
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#else /* NO_FNV_GCC_OPTIMIZATION */
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hval += (hval << 1) + (hval << 4) + (hval << 5) +
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(hval << 7) + (hval << 8) + (hval << 40);
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#endif /* NO_FNV_GCC_OPTIMIZATION */
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/* xor the bottom with the current octet */
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hval ^= (Fnv64_t)*s++;
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}
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#else /* !HAVE_64BIT_LONG_LONG */
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unsigned long val[4]; /* hash value in base 2^16 */
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unsigned long tmp[4]; /* tmp 64 bit value */
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/*
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* Convert Fnv64_t hval into a base 2^16 array
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*/
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val[0] = hval.w32[0];
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val[1] = (val[0] >> 16);
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val[0] &= 0xffff;
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val[2] = hval.w32[1];
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val[3] = (val[2] >> 16);
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val[2] &= 0xffff;
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/*
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* FNV-1 hash each octet of the string
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*/
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while (*s) {
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/*
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* multiply by the 64 bit FNV magic prime mod 2^64
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*
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* Using 1099511628211, we have the following digits base 2^16:
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*
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* 0x0 0x100 0x0 0x1b3
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*
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* which is the same as:
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*
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* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
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*/
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/* multiply by the lowest order digit base 2^16 */
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tmp[0] = val[0] * FNV_64_PRIME_LOW;
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tmp[1] = val[1] * FNV_64_PRIME_LOW;
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tmp[2] = val[2] * FNV_64_PRIME_LOW;
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tmp[3] = val[3] * FNV_64_PRIME_LOW;
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/* multiply by the other non-zero digit */
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tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
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tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
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/* propagate carries */
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tmp[1] += (tmp[0] >> 16);
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val[0] = tmp[0] & 0xffff;
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tmp[2] += (tmp[1] >> 16);
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val[1] = tmp[1] & 0xffff;
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val[3] = tmp[3] + (tmp[2] >> 16);
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val[2] = tmp[2] & 0xffff;
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/*
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* Doing a val[3] &= 0xffff; is not really needed since it simply
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* removes multiples of 2^64. We can discard these excess bits
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* outside of the loop when we convert to Fnv64_t.
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*/
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/* xor the bottom with the current octet */
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val[0] ^= (unsigned long)(*s++);
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}
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/*
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* Convert base 2^16 array back into an Fnv64_t
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*/
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hval.w32[1] = ((val[3]<<16) | val[2]);
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hval.w32[0] = ((val[1]<<16) | val[0]);
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#endif /* !HAVE_64BIT_LONG_LONG */
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/* return our new hash value */
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return hval;
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}
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