1  /* Add two struct timespec values.
       2  
       3     Copyright (C) 2011-2022 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  /* Return the sum of two timespec values A and B.  On overflow, return
      21     an extremal value.  This assumes 0 <= tv_nsec < TIMESPEC_HZ.  */
      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_HZ;
      35    int rns = ns;
      36  
      37    if (0 <= nsd)
      38      {
      39        rns = nsd;
      40        time_t bs1;
      41        if (!INT_ADD_WRAPV (bs, 1, &bs1))
      42          bs = bs1;
      43        else if (rs < 0)
      44          rs++;
      45        else
      46          goto high_overflow;
      47      }
      48  
      49    if (INT_ADD_WRAPV (rs, bs, &rs))
      50      {
      51        if (bs < 0)
      52          {
      53            rs = TYPE_MINIMUM (time_t);
      54            rns = 0;
      55          }
      56        else
      57          {
      58          high_overflow:
      59            rs = TYPE_MAXIMUM (time_t);
      60            rns = TIMESPEC_HZ - 1;
      61          }
      62      }
      63  
      64    return make_timespec (rs, rns);
      65  }