sysdeps/unix/clock_nanosleep.c

   1 /* High-resolution sleep with the specified clock.
   2    Copyright (C) 2000, 2001 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <time.h>
  23
  24
  25 #ifndef CLOCK_P
  26 # define CLOCK_P(clock) 0
  27 #endif
  28
  29
  30 /* This implementation assumes that these is only a `nanosleep' system
  31    call.  So we have to remap all other activities.  */
  32 int
  33 clock_nanosleep (clockid_t clock_id, int flags, const struct timespec *req,
  34                  struct timespec *rem)
  35 {
  36   struct timespec now;
  37
  38   if (__builtin_expect (req->tv_nsec, 0) < 0
  39       || __builtin_expect (req->tv_nsec, 0) >= 1000000000)
  40     return EINVAL;
  41
  42   /* If we got an absolute time, remap it.  */
  43   if (flags == TIMER_ABSTIME)
  44     {
  45       long int nsec;
  46       long int sec;
  47
  48       /* Make sure we use safe data types.  */
  49       assert (sizeof (sec) >= sizeof (now.tv_sec));
  50
  51       /* Get the current time for this clock.  */
  52       if (__builtin_expect (clock_gettime (clock_id, &now), 0) != 0)
  53         return errno;
  54
  55       /* Compute the difference.  */
  56       nsec = req->tv_nsec - now.tv_nsec;
  57       sec = req->tv_sec - now.tv_sec - (nsec < 0);
  58       if (sec < 0)
  59         /* The time has already elapsed.  */
  60         return 0;
  61
  62       now.tv_sec = sec;
  63       now.tv_nsec = nsec + (nsec < 0 ? 1000000000 : 0);
  64
  65       /* From now on this is our time.  */
  66       req = &now;
  67
  68       /* Make sure we are not modifying the struct pointed to by REM.  */
  69       rem = NULL;
  70     }
  71   else if (__builtin_expect (flags, 0) != 0)
  72     return EINVAL;
  73   else if (clock_id != CLOCK_REALTIME)
  74     {
  75       /* Make sure the clock ID is correct.  */
  76       if (__builtin_expect (! CLOCK_P (clock_id), 0))
  77         return EINVAL;
  78     }
  79
  80   return __builtin_expect (nanosleep (req, rem), 0) ? errno : 0;
  81 }