1 /* Add two struct timespec values.
2
3 Copyright (C) 2011-2023 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 <stdckdint.h>
27 #include "intprops.h"
28
29 struct timespec
30 timespec_add (struct timespec a, struct timespec b)
31 {
32 time_t rs = a.tv_sec;
33 time_t bs = b.tv_sec;
34 int ns = a.tv_nsec + b.tv_nsec;
35 int nsd = ns - TIMESPEC_HZ;
36 int rns = ns;
37
38 if (0 <= nsd)
39 {
40 rns = nsd;
41 time_t bs1;
42 if (!ckd_add (&bs1, bs, 1))
43 bs = bs1;
44 else if (rs < 0)
45 rs++;
46 else
47 goto high_overflow;
48 }
49
50 if (ckd_add (&rs, rs, bs))
51 {
52 if (bs < 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_HZ - 1;
62 }
63 }
64
65 return make_timespec (rs, rns);
66 }