lib/libc/uuid/uuid_hash.c

   1 /*-
   2  * Copyright (c) 2002,2005 Marcel Moolenaar
   3  * Copyright (c) 2002 Hiten Mahesh Pandya
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  *
  27  * $FreeBSD: src/lib/libc/uuid/uuid_hash.c,v 1.3 2005/01/03 02:56:15 marcel Exp $
  28  * $DragonFly: src/lib/libc/uuid/uuid_hash.c,v 1.1 2007/06/16 19:57:14 dillon Exp $
  29  */
  30
  31 #include <uuid.h>
  32
  33 /*
  34  * uuid_hash() - generate a hash value.
  35  * See also:
  36  *      http://www.opengroup.org/onlinepubs/009629399/uuid_hash.htm
  37  */
  38 uint16_t
  39 uuid_hash(const uuid_t *u, uint32_t *status)
  40 {
  41
  42         if (status)
  43                 *status = uuid_s_ok;
  44
  45         /*
  46          * Use the most frequently changing bits in the UUID as the hash
  47          * value. This should yield a good enough distribution...
  48          */
  49         return ((u) ? u->time_low & 0xffff : 0);
  50 }