From: Andre Noll <maan@systemlinux.org>
Date: Tue, 13 Nov 2007 19:08:06 +0000 (+0100)
Subject: Fix tv_divide().
X-Git-Tag: v0.3.0~116
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=88648fbe815c12e36e48f7d244b274c45366cad1

Fix tv_divide().

The old code contained an integer overflow which caused the mp3 audio
format handler to compute the chunk of large mp3 files incorrectly.

Moreover, the code was more complicated than necessary. So replace it
by a simple calculation which just transforms the given struct timeval
into its number of microseconds, does the division and transforms
the quotient back to a struct timeval.

Thanks to Gerrit Renker for pointing out the problem.
---

diff --git a/time.c b/time.c
index b7713829..155e11d8 100644
--- a/time.c
+++ b/time.c
@@ -121,17 +121,10 @@ void tv_scale(const unsigned long mult, const struct timeval *tv,
 void tv_divide(const unsigned long divisor, const struct timeval *tv,
 	struct timeval *result)
 {
-	long unsigned q;
+	uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) / divisor;
 
-	q = tv->tv_usec / divisor;
-	result->tv_sec = tv->tv_sec / divisor;
-	result->tv_usec = (tv->tv_sec - result->tv_sec * divisor)
-		* 1000 * 1000 / divisor;
-	if (result->tv_usec + q >= 1000 * 1000) {
-		result->tv_sec++;
-		result->tv_usec = 1000 * 1000 - result->tv_usec - q;
-	} else
-		result->tv_usec += q;
+	result->tv_sec = x / 1000 / 1000;
+	result->tv_usec = x % (1000 * 1000);
 }
 
 /**