lib/dtotimespec.c

   1 /* Convert double to timespec.
   2
   3    Copyright (C) 2011-2013 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 <http://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   double min_representable = TYPE_MINIMUM (time_t);
  33   double max_representable =
  34     ((TYPE_MAXIMUM (time_t) * (double) TIMESPEC_RESOLUTION
  35       + (TIMESPEC_RESOLUTION - 1))
  36      / TIMESPEC_RESOLUTION);
  37
  38   if (! (min_representable < sec))
  39     return make_timespec (TYPE_MINIMUM (time_t), 0);
  40   else if (! (sec < max_representable))
  41     return make_timespec (TYPE_MAXIMUM (time_t), TIMESPEC_RESOLUTION - 1);
  42   else
  43     {
  44       time_t s = sec;
  45       double frac = TIMESPEC_RESOLUTION * (sec - s);
  46       long ns = frac;
  47       ns += ns < frac;
  48       s += ns / TIMESPEC_RESOLUTION;
  49       ns %= TIMESPEC_RESOLUTION;
  50
  51       if (ns < 0)
  52         {
  53           s--;
  54           ns += TIMESPEC_RESOLUTION;
  55         }
  56
  57       return make_timespec (s, ns);
  58     }
  59 }