lib/libc/gen/clock.c

   1 /*      $NetBSD: clock.c,v 1.10 2009/01/11 02:46:27 christos Exp $      */
   2
   3 /*
   4  * Copyright (c) 1989, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 #if 0
  35 static char sccsid[] = "@(#)clock.c     8.1 (Berkeley) 6/4/93";
  36 #else
  37 __RCSID("$NetBSD: clock.c,v 1.10 2009/01/11 02:46:27 christos Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/param.h>
  42 #include <sys/time.h>
  43 #include <sys/resource.h>
  44
  45 #include <time.h>
  46
  47 /*
  48  * This code is all rather silly because the kernel counts actual
  49  * execution time (to usec accuracy) then splits it into user, system and
  50  * interrupt based on when clock ticks happen.  getrusage apportions the
  51  * time based on the number of ticks, and here we are trying to generate
  52  * a number which was, traditionally, the number of ticks!
  53  *
  54  * Due to the way the time is apportioned, this code (and indeed getrusage
  55  * itself) are not guaranteed monotonic.
  56  */
  57
  58 clock_t
  59 clock(void)
  60 {
  61         struct rusage ru;
  62         clock_t hz = CLOCKS_PER_SEC;
  63
  64         if (getrusage(RUSAGE_SELF, &ru))
  65                 return ((clock_t) -1);
  66         return (clock_t)((ru.ru_utime.tv_sec + ru.ru_stime.tv_sec) * hz +
  67             (ru.ru_utime.tv_usec + ru.ru_stime.tv_usec + 50)
  68             / 100 * hz / 10000);
  69 }