kc3-lang/gnulib/lib/timespec-add.c

• Show log

  Commit

• Hash : fe33f943
  Author :
  Date : 2024-06-14T23:11:05
  

  timespec-add,timespec-sub: tune
  
  * lib/timespec-add.c (timespec_add):
  * lib/timespec-sub.c (timespec_sub):
  Simplify by detecting overflow when the two overflow bits of the
  underlying operation differ.  This avoids some gotos and labels
  and conditional branches; GCC 14 x86-64 now generates just one
  conditional branch for the resulting code.  Idea stolen from
  my recent changes to the glibc manual’s time chapter.
  * modules/timespec-add (Depends-on):
  * modules/timespec-sub (Depends-on): Add stdbool.
  

Download

• lib/timespec-add.c

• /* Add two struct timespec values.
  
     Copyright (C) 2011-2024 Free Software Foundation, Inc.
  
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 3 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  
  /* Written by Paul Eggert.  */
  
  /* Return the sum of two timespec values A and B.  On overflow, return
     an extremal value.  This assumes 0 <= tv_nsec < TIMESPEC_HZ.  */
  
  #include <config.h>
  #include "timespec.h"
  
  #include <stdckdint.h>
  #include "intprops.h"
  
  struct timespec
  timespec_add (struct timespec a, struct timespec b)
  {
    int nssum = a.tv_nsec + b.tv_nsec;
    int carry = TIMESPEC_HZ <= nssum;
    time_t rs;
    int rns;
    bool v = ckd_add (&rs, a.tv_sec, b.tv_sec);
    if (v == ckd_add (&rs, rs, carry))
      rns = nssum - TIMESPEC_HZ * carry;
    else
      {
        if ((TYPE_MINIMUM (time_t) + TYPE_MAXIMUM (time_t)) / 2 < rs)
          {
            rs = TYPE_MINIMUM (time_t);
            rns = 0;
          }
        else
          {
            rs = TYPE_MAXIMUM (time_t);
            rns = TIMESPEC_HZ - 1;
          }
      }
  
    return make_timespec (rs, rns);
  }
  

Download