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/* struct timespec subtraction.
Copyright (C) 1991-2024 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <stdckdint.h>
#include <time.h>
/* Put into *R the difference between X and Y.
Return true if overflow occurs, false otherwise. */
bool
timespec_subtract (struct timespec *r,
struct timespec x, struct timespec y)
{
/* Compute nanoseconds, setting @var{borrow} to 1, 0, or -1
for propagation into seconds. */
long int nsec_diff = x.tv_nsec - y.tv_nsec;
int borrow = (nsec_diff < 0) - ! (nsec_diff < 1000000000);
r->tv_nsec = nsec_diff + 1000000000 * borrow;
/* Compute seconds, returning true if this overflows. */
bool v = ckd_sub (&r->tv_sec, x.tv_sec, y.tv_sec);
return v ^ ckd_sub (&r->tv_sec, r->tv_sec, borrow);
}
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