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/* timespec -- System time interface
Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2011 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/>. */
#if ! defined TIMESPEC_H
# define TIMESPEC_H
# include <time.h>
/* Return negative, zero, positive if A < B, A == B, A > B, respectively.
For each time stamp T, this code assumes that either:
* T.tv_nsec is in the range 0..999999999; or
* T.tv_sec corresponds to a valid leap second on a host that supports
leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or
* T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or
T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000.
This allows for special struct timespec values that are less or
greater than all possible valid time stamps.
In all these cases, it is safe to subtract two tv_nsec values and
convert the result to integer without worrying about overflow on
any platform of interest to the GNU project, since all such
platforms have 32-bit int or wider.
Replacing "(int) (a.tv_nsec - b.tv_nsec)" with something like
"a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause
this function to work in some cases where the above assumption is
violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2,
b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the
extra instructions. Using a subtraction has the advantage of
detecting some invalid cases on platforms that detect integer
overflow.
The (int) cast avoids a gcc -Wconversion warning. */
static inline int
timespec_cmp (struct timespec a, struct timespec b)
{
return (a.tv_sec < b.tv_sec ? -1
: a.tv_sec > b.tv_sec ? 1
: (int) (a.tv_nsec - b.tv_nsec));
}
void gettime (struct timespec *);
int settime (struct timespec const *);
#endif
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