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45 lines
1.6 KiB
C
45 lines
1.6 KiB
C
/* struct timeval subtraction.
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Copyright (C) 1991-2020 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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/* Subtract the `struct timeval' values X and Y,
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storing the result in RESULT.
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Return 1 if the difference is negative, otherwise 0. */
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int
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timeval_subtract (struct timeval *result, struct timeval *x, struct timeval *y)
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{
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/* Perform the carry for the later subtraction by updating @var{y}. */
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if (x->tv_usec < y->tv_usec) {
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int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
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y->tv_usec -= 1000000 * nsec;
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y->tv_sec += nsec;
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}
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if (x->tv_usec - y->tv_usec > 1000000) {
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int nsec = (x->tv_usec - y->tv_usec) / 1000000;
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y->tv_usec += 1000000 * nsec;
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y->tv_sec -= nsec;
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}
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/* Compute the time remaining to wait.
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@code{tv_usec} is certainly positive. */
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result->tv_sec = x->tv_sec - y->tv_sec;
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result->tv_usec = x->tv_usec - y->tv_usec;
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/* Return 1 if result is negative. */
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return x->tv_sec < y->tv_sec;
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}
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