Commit | Line | Data |
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c8fff863 PE |
1 | /* Subtract two struct timespec values. |
2 | ||
ab422c4d | 3 | Copyright (C) 2011-2013 Free Software Foundation, Inc. |
c8fff863 PE |
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 <http://www.gnu.org/licenses/>. */ | |
17 | ||
18 | /* Written by Paul Eggert. */ | |
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 | 999999999. */ | |
23 | ||
c8fff863 PE |
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 | struct timespec r; | |
33 | time_t rs = a.tv_sec; | |
34 | time_t bs = b.tv_sec; | |
35 | int ns = a.tv_nsec - b.tv_nsec; | |
36 | int rns = ns; | |
37 | ||
38 | if (ns < 0) | |
39 | { | |
40 | rns = ns + 1000000000; | |
41 | if (rs == TYPE_MINIMUM (time_t)) | |
42 | { | |
43 | if (bs <= 0) | |
44 | goto low_overflow; | |
45 | bs--; | |
46 | } | |
47 | else | |
48 | rs--; | |
49 | } | |
50 | ||
51 | if (INT_SUBTRACT_OVERFLOW (rs, bs)) | |
52 | { | |
53 | if (rs < 0) | |
54 | { | |
55 | low_overflow: | |
56 | rs = TYPE_MINIMUM (time_t); | |
57 | rns = 0; | |
58 | } | |
59 | else | |
60 | { | |
61 | rs = TYPE_MAXIMUM (time_t); | |
62 | rns = 999999999; | |
63 | } | |
64 | } | |
65 | else | |
66 | rs -= bs; | |
67 | ||
68 | r.tv_sec = rs; | |
69 | r.tv_nsec = rns; | |
70 | return r; | |
71 | } |