/* struct timeval subtraction.

   Copyright (C) 1991-2018 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;

}