lib/timespec-add.c

   1 /* Add two struct timespec values.
   2
   3    Copyright (C) 2011-2015 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 /* Return the sum of two timespec values A and B.  On overflow, return
  21    an extremal value.  This assumes 0 <= tv_nsec < TIMESPEC_RESOLUTION.  */
  22
  23 #include <config.h>
  24 #include "timespec.h"
  25
  26 #include "intprops.h"
  27
  28 struct timespec
  29 timespec_add (struct timespec a, struct timespec b)
  30 {
  31   time_t rs = a.tv_sec;
  32   time_t bs = b.tv_sec;
  33   int ns = a.tv_nsec + b.tv_nsec;
  34   int nsd = ns - TIMESPEC_RESOLUTION;
  35   int rns = ns;
  36
  37   if (0 <= nsd)
  38     {
  39       rns = nsd;
  40       if (rs == TYPE_MAXIMUM (time_t))
  41         {
  42           if (0 <= bs)
  43             goto high_overflow;
  44           bs++;
  45         }
  46       else
  47         rs++;
  48     }
  49
  50   if (INT_ADD_OVERFLOW (rs, bs))
  51     {
  52       if (rs < 0)
  53         {
  54           rs = TYPE_MINIMUM (time_t);
  55           rns = 0;
  56         }
  57       else
  58         {
  59         high_overflow:
  60           rs = TYPE_MAXIMUM (time_t);
  61           rns = TIMESPEC_RESOLUTION - 1;
  62         }
  63     }
  64   else
  65     rs += bs;
  66
  67   return make_timespec (rs, rns);
  68 }