Merge from emacs-24; up to 2012-05-04T19:17:01Z!monnier@iro.umontreal.ca
[emacs.git] / lib / timespec-sub.c
blob7c4c781b7f633799bf80ed35fe42388c2e683331
1 /* Subtract two struct timespec values.
3 Copyright (C) 2011-2012 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 999999999. */
24 #include <config.h>
25 #include "timespec.h"
27 #include "intprops.h"
29 struct timespec
30 timespec_sub (struct timespec a, struct timespec b)
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;
38 if (ns < 0)
40 rns = ns + 1000000000;
41 if (rs == TYPE_MINIMUM (time_t))
43 if (bs <= 0)
44 goto low_overflow;
45 bs--;
47 else
48 rs--;
51 if (INT_SUBTRACT_OVERFLOW (rs, bs))
53 if (rs < 0)
55 low_overflow:
56 rs = TYPE_MINIMUM (time_t);
57 rns = 0;
59 else
61 rs = TYPE_MAXIMUM (time_t);
62 rns = 999999999;
65 else
66 rs -= bs;
68 r.tv_sec = rs;
69 r.tv_nsec = rns;
70 return r;