1 | /* Subtract 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 difference between two timespec values A and B. On |
21 | overflow, return an extremal value. This assumes 0 <= tv_nsec < |
22 | TIMESPEC_HZ. */ |
23 | |
24 | #include <config.h> |
25 | #include "timespec.h" |
26 | |
27 | #include "intprops.h" |
28 | |
29 | struct timespec |
30 | timespec_sub (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 rns = ns; |
36 | time_t tmin = TYPE_MINIMUM (time_t); |
37 | time_t tmax = TYPE_MAXIMUM (time_t); |
38 | |
39 | if (ns < 0) |
40 | { |
41 | rns = ns + TIMESPEC_HZ; |
42 | if (bs < tmax) |
43 | bs++; |
44 | else if (- TYPE_SIGNED (time_t) < rs) |
45 | rs--; |
46 | else |
47 | goto low_overflow; |
48 | } |
49 | |
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) |
54 | rs -= bs; |
55 | else |
56 | { |
57 | if (rs < 0) |
58 | { |
59 | low_overflow: |
60 | rs = tmin; |
61 | rns = 0; |
62 | } |
63 | else |
64 | { |
65 | rs = tmax; |
66 | rns = TIMESPEC_HZ - 1; |
67 | } |
68 | } |
69 | |
70 | return make_timespec (rs, rns); |
71 | } |
72 | |