text: /*
   * hash_64 - 64 bit Fowler/Noll/Vo-0 hash code
   *
   * @(#) $Revision: 1.8 $
   * @(#) $Id: hash_64.c,v 1.8 2003/10/03 20:37:04 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 = { 0, 0 };
  #endif
  
  
  /*
   * FNV-1 defines the initial basis to be non-zero
   */
  #if !defined(HAVE_64BIT_LONG_LONG)
  const Fnv64_t fnv1_64_init = { 0x84222325, 0xcbf29ce4 };
  #endif
  
  
  /*
   * 64 bit magic FNV-0 and FNV-1 prime
   */
  #if defined(HAVE_64BIT_LONG_LONG)
  #define FNV_64_PRIME ((Fnv64_t)0x100000001b3ULL)
  #else
  #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
  
  
  /*
   * 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)
  {
  #if defined(HAVE_64BIT_LONG_LONG)
  
      unsigned char *bp = (unsigned char *)buf;	/* start of buffer */
      unsigned char *be = bp + len;		/* beyond end of buffer */
  
      /*
       * 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
  	hval += (hval << 1) + (hval << 4) + (hval << 5) +
  		(hval << 7) + (hval << 8) + (hval << 40);
  #endif
  
  	/* 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
  	hval += (hval << 1) + (hval << 4) + (hval << 5) +
  		(hval << 7) + (hval << 8) + (hval << 40);
  #endif
  
  	/* 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;
  }
  