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glibc/manual/examples/timeval_subtract.c
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/* struct timeval subtraction. | |
Copyright (C) 1991-2015 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, if not, see <http://www.gnu.org/licenses/>. | |
*/ | |
/* Subtract the `struct timeval' values X and Y, | |
storing the result in RESULT. | |
Return 1 if the difference is negative, otherwise 0. */ | |
int | |
timeval_subtract (struct timeval *result, struct timeval *x, struct timeval *y) | |
{ | |
/* Perform the carry for the later subtraction by updating @var{y}. */ | |
if (x->tv_usec < y->tv_usec) { | |
int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1; | |
y->tv_usec -= 1000000 * nsec; | |
y->tv_sec += nsec; | |
} | |
if (x->tv_usec - y->tv_usec > 1000000) { | |
int nsec = (x->tv_usec - y->tv_usec) / 1000000; | |
y->tv_usec += 1000000 * nsec; | |
y->tv_sec -= nsec; | |
} | |
/* Compute the time remaining to wait. | |
@code{tv_usec} is certainly positive. */ | |
result->tv_sec = x->tv_sec - y->tv_sec; | |
result->tv_usec = x->tv_usec - y->tv_usec; | |
/* Return 1 if result is negative. */ | |
return x->tv_sec < y->tv_sec; | |
} |