55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
/* Subtract two struct timespec values.
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Copyright (C) 2011-2024 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(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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/* Written by Paul Eggert. */
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/* Return the difference between two timespec values A and B. On
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overflow, return an extremal value. This assumes 0 <= tv_nsec <
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TIMESPEC_HZ. */
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#include <config.h>
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#include "timespec.h"
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#include <stdckdint.h>
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#include "intprops.h"
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struct timespec
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timespec_sub (struct timespec a, struct timespec b)
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{
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int nsdiff = a.tv_nsec - b.tv_nsec;
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int borrow = nsdiff < 0;
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time_t rs;
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int rns;
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bool v = ckd_sub (&rs, a.tv_sec, b.tv_sec);
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if (v == ckd_sub (&rs, rs, borrow))
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rns = nsdiff + TIMESPEC_HZ * borrow;
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else
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{
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if ((TYPE_MINIMUM (time_t) + TYPE_MAXIMUM (time_t)) / 2 < rs)
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{
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rs = TYPE_MINIMUM (time_t);
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rns = 0;
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}
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else
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{
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rs = TYPE_MAXIMUM (time_t);
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rns = TIMESPEC_HZ - 1;
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}
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}
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return make_timespec (rs, rns);
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}
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