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SCCS-file: difftime.c

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SCCS-SID: 7.13
This commit is contained in:
Arthur David Olson
2004-10-25 14:59:05 -04:00
committed by Paul Eggert
parent c554d2f7e5
commit 514fa06671
1 changed files with 14 additions and 17 deletions
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difftime.c
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@@ -1,6 +1,6 @@
/*
** This file is in the public domain, so clarified as of
** June 5, 1996 by Arthur David Olson (arthur_david_olson@nih.gov).
** 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
*/
#ifndef lint
@@ -40,22 +40,19 @@ const time_t time0;
} else {
/*
** time_t is integral and signed.
** If a double is much wider than a time_t,
** simply convert and subtract.
** 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 (sizeof (double) >= 2 * sizeof (time_t))
return (double) time1 - (double) time0;
else {
/*
** As elsewhere in the time zone package,
** use modular arithmetic to avoid overflow.
*/
register time_t lead;
register time_t trail;
lead = time1 / 2 - time0 / 2;
trail = time1 % 2 - time0 % 2;
return 2.0 * lead + trail;
}
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;
}
}