[Scummvm-cvs-logs] CVS: scummvm/backends/midi emumidi.h,1.2,1.3

[Torbjörn Andersson]

Update of /cvsroot/scummvm/scummvm/backends/midi
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv28357

Modified Files:
	emumidi.h 
Log Message:
Made the calculation of _samples_per_tick a bit less prone to arithmetic
overflow. It failed if the output rate was 44100 Hz. (It didn't use to, but
somewhere along the line an unsigned value was changed to a signed. This
seemed like a better fix, though.)


Index: emumidi.h
===================================================================
RCS file: /cvsroot/scummvm/scummvm/backends/midi/emumidi.h,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -d -r1.2 -r1.3
--- emumidi.h	17 Oct 2004 19:34:43 -0000	1.2
+++ emumidi.h	19 Oct 2004 08:47:10 -0000	1.3
@@ -54,7 +54,14 @@
 
 	int open() {
 		_isOpen = true;
-		_samples_per_tick = (getRate() << FIXP_SHIFT) / BASE_FREQ;
+
+		int d = getRate() / BASE_FREQ;
+		int r = getRate() % BASE_FREQ;
+
+		// This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
+		// but less prone to arithmetic overflow.
+
+		_samples_per_tick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / BASE_FREQ;
 		return 0;
 	}
 
@@ -71,11 +78,12 @@
 		const int stereoFactor = isStereo() ? 2 : 1;
 		int len = numSamples / stereoFactor;
 		int step;
-	
+
 		do {
 			step = len;
 			if (step > (_next_tick >> FIXP_SHIFT))
 				step = (_next_tick >> FIXP_SHIFT);
+
 			generate_samples(data, step);
 	
 			_next_tick -= step << FIXP_SHIFT;