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emacs/lib/dtotimespec.c
2013-01-01 09:11:05 +00:00

70 lines
1.7 KiB
C

/* Convert double to timespec.
Copyright (C) 2011-2013 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 3 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, see <http://www.gnu.org/licenses/>. */
/* written by Paul Eggert */
/* Convert the double value SEC to a struct timespec. Round toward
positive infinity. On overflow, return an extremal value. */
#include <config.h>
#include "timespec.h"
#include "intprops.h"
struct timespec
dtotimespec (double sec)
{
enum { BILLION = 1000 * 1000 * 1000 };
double min_representable = TYPE_MINIMUM (time_t);
double max_representable =
((TYPE_MAXIMUM (time_t) * (double) BILLION + (BILLION - 1))
/ BILLION);
struct timespec r;
if (! (min_representable < sec))
{
r.tv_sec = TYPE_MINIMUM (time_t);
r.tv_nsec = 0;
}
else if (! (sec < max_representable))
{
r.tv_sec = TYPE_MAXIMUM (time_t);
r.tv_nsec = BILLION - 1;
}
else
{
time_t s = sec;
double frac = BILLION * (sec - s);
long ns = frac;
ns += ns < frac;
s += ns / BILLION;
ns %= BILLION;
if (ns < 0)
{
s--;
ns += BILLION;
}
r.tv_sec = s;
r.tv_nsec = ns;
}
return r;
}