SCCS-file: difftime.c

SCCS-SID: 7.14

difftime.c

@@ -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);
 }