clock.c 1.8 KB

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  1. /* Copyright (C) 1991, 1992, 1996, 1999 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. The GNU C Library is free software; you can redistribute it and/or
  4. modify it under the terms of the GNU Library General Public License as
  5. published by the Free Software Foundation; either version 2 of the
  6. License, or (at your option) any later version.
  7. The GNU C Library is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10. Library General Public License for more details.
  11. You should have received a copy of the GNU Library General Public
  12. License along with the GNU C Library; see the file COPYING.LIB. If not,
  13. write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  14. Boston, MA 02111-1307, USA. */
  15. #include <time.h>
  16. #include <unistd.h>
  17. #include <sys/times.h>
  18. /* Return the time used by the program so far (user time + system time). */
  19. clock_t
  20. clock (void)
  21. {
  22. struct tms buf;
  23. long clk_tck = CLK_TCK;
  24. /* We don't check for errors here. The only error the kernel
  25. returns is EFAULT if the value cannot be written to the struct we
  26. pass a pointer to. Otherwise the kernel returns an `unsigned
  27. long' value which is the number of jiffies since system start.
  28. But this number can be negative (when read as `long') when the
  29. system is up for some time. Ignoring errors should therefore
  30. have no negative impacts but solve the problem. */
  31. times (&buf);
  32. return
  33. (clk_tck <= CLOCKS_PER_SEC) ?
  34. ((unsigned long) buf.tms_utime + buf.tms_stime) * (CLOCKS_PER_SEC / clk_tck) :
  35. ((unsigned long) buf.tms_utime + buf.tms_stime) / (clk_tck / CLOCKS_PER_SEC);
  36. }