support/dtotimespec.c

   1 /* Convert double to timespec.
   2    Copyright (C) 2011-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library and is also part of gnulib.
   4    Patches to this file should be submitted to both projects.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 /* Convert the double value SEC to a struct timespec.  Round toward
  21    positive infinity.  On overflow, return an extremal value.  */
  22
  23 #include <support/timespec.h>
  24 #include <intprops.h>
  25
  26 struct timespec
  27 dtotimespec (double sec)
  28 {
  29   if (sec <= TYPE_MINIMUM (time_t))
  30     return make_timespec (TYPE_MINIMUM (time_t), 0);
  31   else if (sec >= 1.0 + TYPE_MAXIMUM (time_t))
  32     return make_timespec (TYPE_MAXIMUM (time_t), TIMESPEC_HZ - 1);
  33   else
  34     {
  35       time_t s = sec;
  36       double frac = TIMESPEC_HZ * (sec - s);
  37       long ns = frac;
  38       ns += ns < frac;
  39       s += ns / TIMESPEC_HZ;
  40       ns %= TIMESPEC_HZ;
  41
  42       if (ns < 0)
  43         {
  44           s--;
  45           ns += TIMESPEC_HZ;
  46         }
  47
  48       return make_timespec (s, ns);
  49     }
  50 }