1 /* Subtract two struct timespec values.
3 Copyright (C) 2011-2017 Free Software Foundation, Inc.
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.
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.
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/>. */
18 /* Written by Paul Eggert. */
20 /* Return the difference between two timespec values A and B. On
21 overflow, return an extremal value. This assumes 0 <= tv_nsec <
22 TIMESPEC_RESOLUTION. */
30 timespec_sub (struct timespec a
, struct timespec b
)
34 int ns
= a
.tv_nsec
- b
.tv_nsec
;
36 time_t tmin
= TYPE_MINIMUM (time_t);
37 time_t tmax
= TYPE_MAXIMUM (time_t);
41 rns
= ns
+ TIMESPEC_RESOLUTION
;
44 else if (- TYPE_SIGNED (time_t) < rs
)
50 /* INT_SUBTRACT_WRAPV is not appropriate since time_t might be unsigned.
51 In theory time_t might be narrower than int, so plain
52 INT_SUBTRACT_OVERFLOW does not suffice. */
53 if (! INT_SUBTRACT_OVERFLOW (rs
, bs
) && tmin
<= rs
- bs
&& rs
- bs
<= tmax
)
66 rns
= TIMESPEC_RESOLUTION
- 1;
70 return make_timespec (rs
, rns
);