lib/dtotimespec.c

   1 /* Convert double to timespec.
   2
   3    Copyright (C) 2011-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* written by Paul Eggert */
  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 <config.h>
  24
  25 #include "timespec.h"
  26
  27 #include "intprops.h"
  28
  29 struct timespec
  30 dtotimespec (double sec)
  31 {
  32   if (! (TYPE_MINIMUM (time_t) < sec))
  33     return make_timespec (TYPE_MINIMUM (time_t), 0);
  34   else if (! (sec < 1.0 + TYPE_MAXIMUM (time_t)))
  35     return make_timespec (TYPE_MAXIMUM (time_t), TIMESPEC_HZ - 1);
  36   else
  37     {
  38       time_t s = sec;
  39       double frac = TIMESPEC_HZ * (sec - s);
  40       long ns = frac;
  41       ns += ns < frac;
  42       s += ns / TIMESPEC_HZ;
  43       ns %= TIMESPEC_HZ;
  44
  45       if (ns < 0)
  46         {
  47           s--;
  48           ns += TIMESPEC_HZ;
  49         }
  50
  51       return make_timespec (s, ns);
  52     }
  53 }