1/* Add two struct timespec values.
2 Copyright (C) 2011-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library and is also part of gnulib.
4 Patches to this file should be submitted to both projects.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
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
28struct timespec
29timespec_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 time_t tmin = TYPE_MINIMUM (time_t);
37 time_t tmax = TYPE_MAXIMUM (time_t);
38
39 if (0 <= nsd)
40 {
41 rns = nsd;
42 if (bs < tmax)
43 bs++;
44 else if (rs < 0)
45 rs++;
46 else
47 goto high_overflow;
48 }
49
50 /* INT_ADD_WRAPV is not appropriate since time_t might be unsigned.
51 In theory time_t might be narrower than int, so plain
52 INT_ADD_OVERFLOW does not suffice. */
53 if (! INT_ADD_OVERFLOW (rs, bs) && tmin <= rs + bs && rs + bs <= tmax)
54 rs += bs;
55 else
56 {
57 if (rs < 0)
58 {
59 rs = tmin;
60 rns = 0;
61 }
62 else
63 {
64 high_overflow:
65 rs = tmax;
66 rns = TIMESPEC_HZ - 1;
67 }
68 }
69
70 return make_timespec (rs, rns);
71}
72