| 1 | /* Subtract two struct timespec values. |
| 2 | |
| 3 | Copyright (C) 2011-2014 Free Software Foundation, Inc. |
| 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 | TIMESPEC_RESOLUTION. */ |
| 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 | |
| 37 | if (ns < 0) |
| 38 | { |
| 39 | rns = ns + TIMESPEC_RESOLUTION; |
| 40 | if (rs == TYPE_MINIMUM (time_t)) |
| 41 | { |
| 42 | if (bs <= 0) |
| 43 | goto low_overflow; |
| 44 | bs--; |
| 45 | } |
| 46 | else |
| 47 | rs--; |
| 48 | } |
| 49 | |
| 50 | if (INT_SUBTRACT_OVERFLOW (rs, bs)) |
| 51 | { |
| 52 | if (rs < 0) |
| 53 | { |
| 54 | low_overflow: |
| 55 | rs = TYPE_MINIMUM (time_t); |
| 56 | rns = 0; |
| 57 | } |
| 58 | else |
| 59 | { |
| 60 | rs = TYPE_MAXIMUM (time_t); |
| 61 | rns = TIMESPEC_RESOLUTION - 1; |
| 62 | } |
| 63 | } |
| 64 | else |
| 65 | rs -= bs; |
| 66 | |
| 67 | return make_timespec (rs, rns); |
| 68 | } |