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SCCS-file: difftime.c

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SCCS-SID: 7.14
This commit is contained in:
Arthur David Olson
2004-10-26 12:24:05 -04:00
committed by Paul Eggert
parent cb1b5e292d
commit 21f5496c8a
1 changed files with 23 additions and 18 deletions
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41
difftime.c
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@@ -28,7 +28,8 @@ const time_t time0;
if (sizeof (time_t) >= sizeof (double))
return time1 - time0;
else return (double) time1 - (double) time0;
} else if (!TYPE_SIGNED(time_t)) {
}
if (!TYPE_SIGNED(time_t)) {
/*
** time_t is integral and unsigned.
** The difference of two unsigned values can't overflow
@@ -37,22 +38,26 @@ const time_t time0;
if (time1 >= time0)
return time1 - time0;
else return -((double) (time0 - time1));
} else {
/*
** time_t is integral and signed.
** Handle cases where both time1 and time0 have the same sign
** (meaning that their difference cannot overflow).
** Handle the more common case (both non-negative) first.
*/
if (time1 >= 0 && time0 >= 0)
return time1 - time0;
if (time1 < 0 && time0 < 0)
return time1 - time0;
/*
** Punt everything else.
** Note that we can't use the % operator on time_t values;
** doing so is invalid on systems where time_t isn't integral.
*/
return (double) time1 - (double) time0;
}
/*
** time_t is integral and signed.
** Handle cases where both time1 and time0 have the same sign
** (meaning that their difference cannot overflow).
*/
if (time1 >= 0 && time0 >= 0 || time1 < 0 && time0 < 0)
return time1 - time0;
/*
** time1 and time0 have opposite signs.
** Punt if unsigned long is too narrow.
*/
if (sizeof (unsigned long) < sizeof (time_t))
return (double) time1 - (double) time0;
/*
** Stay calm...decent optimizers will eliminate the complexity below.
*/
if (time1 >= 0 /* && time0 < 0 */)
return (unsigned long) time1 +
(unsigned long) (-(time0 + 1)) + 1;
return -(double) ((unsigned long) time0 +
(unsigned long) (-(time1 + 1)) + 1);
}