sysdeps/unix/sysv/linux/clock.c

   1 /* Return the time used by the program so far (user time + system time).
   2    Copyright (C) 1991-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/times.h>
  20 #include <time.h>
  21 #include <unistd.h>
  22
  23 #if CLOCKS_PER_SEC != 1000000l
  24 # error "CLOCKS_PER_SEC should be 1000000"
  25 #endif
  26
  27 clock_t
  28 clock (void)
  29 {
  30   struct timespec ts;
  31
  32   /* clock_gettime shouldn't fail here since CLOCK_PROCESS_CPUTIME_ID is
  33      supported since 2.6.12.  Check the return value anyway in case the kernel
  34      barfs on us for some reason.  */
  35   if (__glibc_unlikely (__clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &ts) != 0))
  36     return (clock_t) -1;
  37
  38   return (ts.tv_sec * CLOCKS_PER_SEC
  39           + ts.tv_nsec / (1000000000 / CLOCKS_PER_SEC));
  40 }