greatly simplfy and correct difftime for large time_t. ok guenther

1 files changed, 5 insertions, 55 deletions

diff --git a/lib/libc/time/difftime.c b/lib/libc/time/difftime.c
index 8521a60110c..1cb246b34c7 100644
--- a/lib/libc/time/difftime.c
+++ b/lib/libc/time/difftime.c
@@ -1,60 +1,10 @@
-/*	$OpenBSD: difftime.c,v 1.9 2005/08/08 08:05:38 espie Exp $ */
-/*
-** This file is in the public domain, so clarified as of
-** 1996-06-05 by Arthur David Olson.
-*/
+/*	$OpenBSD: difftime.c,v 1.10 2015/02/09 08:36:53 tedu Exp $ */
+/* This file is placed in the public domain by Ted Unangst. */
 
-/*LINTLIBRARY*/
-
-#include "private.h"	/* for time_t, TYPE_INTEGRAL, and TYPE_SIGNED */
+#include "private.h"
 
 double
-difftime(time1, time0)
-const time_t	time1;
-const time_t	time0;
+difftime(time_t time1, time_t time0)
 {
-	/*
-	** If (sizeof (double) > sizeof (time_t)) simply convert and subtract
-	** (assuming that the larger type has more precision).
-	** This is the common real-world case circa 2004.
-	*/
-	if (sizeof (double) > sizeof (time_t))
-		return (double) time1 - (double) time0;
-	if (!TYPE_INTEGRAL(time_t)) {
-		/*
-		** time_t is floating.
-		*/
-		return time1 - time0;
-	}
-	if (!TYPE_SIGNED(time_t)) {
-		/*
-		** time_t is integral and unsigned.
-		** The difference of two unsigned values can't overflow
-		** if the minuend is greater than or equal to the subtrahend.
-		*/
-		if (time1 >= time0)
-			return time1 - time0;
-		else	return -((double) (time0 - time1));
-	}
-	/*
-	** 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))
-		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);
+	return time1 - time0;
 }