Avoid integer overflow in MonotonicClock{S,MS,US}

This is Darwin specific: the previous implementation was causing an integer overflow when base.numer is very large. On PPC Darwin, the timebase info is 1000000000/33330116 and this is too large for integer arithmetic.

Avoid integer overflow in MonotonicClock{S,MS,US}
39abd3ec · PHO · Max Kellermann · 7bf638b0 · 39abd3ec · 39abd3ec
Commit 39abd3ec authored Jan 26, 2015 by PHO Committed by Max Kellermann Jan 29, 2015
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NEWS NEWS +1 -0

Clock.cxx src/system/Clock.cxx +6 -6

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--- a/NEWS
+++ b/NEWS
 ver 0.19.9 (not yet released)
 * decoder
  - dsdiff, dsf: raise ID3 tag limit to 1 MB
+* fix clock integer overflow on OS X
 * fix build failure with uClibc
 * fix build failure on non-POSIX operating systems

--- a/src/system/Clock.cxx
+++ b/src/system/Clock.cxx
@@ -40,8 +40,8 @@ MonotonicClockS(void)
 	if (base.denom == 0)
 		(void)mach_timebase_info(&base);
-	return (unsigned)((mach_absolute_time() * base.numer / 1000)
+	return (unsigned)(((double)mach_absolute_time() * base.numer / 1000)
-			  / (1000000 * base.denom));
+			  / base.denom / 1000000);
 #elif defined(CLOCK_MONOTONIC)
 	struct timespec ts;
 	clock_gettime(CLOCK_MONOTONIC, &ts);
@@ -62,8 +62,8 @@ MonotonicClockMS(void)
 	if (base.denom == 0)
 		(void)mach_timebase_info(&base);
-	return (unsigned)((mach_absolute_time() * base.numer)
+	return (unsigned)(((double)mach_absolute_time() * base.numer)
-			  / (1000000 * base.denom));
+			  / base.denom / 1000000);
 #elif defined(CLOCK_MONOTONIC)
 	struct timespec ts;
 	clock_gettime(CLOCK_MONOTONIC, &ts);
@@ -104,8 +104,8 @@ MonotonicClockUS(void)
 	if (base.denom == 0)
 		(void)mach_timebase_info(&base);
-	return ((uint64_t)mach_absolute_time() * (uint64_t)base.numer)
+	return (uint64_t)(((double)mach_absolute_time() * base.numer)
-		/ (1000 * (uint64_t)base.denom);
+		/ base.denom / 1000);
 #elif defined(CLOCK_MONOTONIC)
 	struct timespec ts;
 	clock_gettime(CLOCK_MONOTONIC, &ts);