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7c1ec1b7d0
This saves a few instructions. BORROW cannot be -1, since NSEC_DIFF is at most 999999999. Idea taken from Gnulib, here: https://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=fe33f943054b93af8b965ce6564b8713b0979a21
37 lines
1.3 KiB
C
37 lines
1.3 KiB
C
/* struct timespec subtraction.
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Copyright (C) 1991-2024 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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#include <stdckdint.h>
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#include <time.h>
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/* Put into *R the difference between X and Y.
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Return true if overflow occurs, false otherwise. */
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bool
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timespec_subtract (struct timespec *r,
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struct timespec x, struct timespec y)
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{
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/* Compute nanoseconds, setting @var{borrow} to 1 or 0
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for propagation into seconds. */
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long int nsec_diff = x.tv_nsec - y.tv_nsec;
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bool borrow = nsec_diff < 0;
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r->tv_nsec = nsec_diff + 1000000000 * borrow;
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/* Compute seconds, returning true if this overflows. */
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bool v = ckd_sub (&r->tv_sec, x.tv_sec, y.tv_sec);
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return v ^ ckd_sub (&r->tv_sec, r->tv_sec, borrow);
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}
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