1 files changed, 66 insertions, 0 deletions
diff --git a/src/mathline.h b/src/mathline.h
new file mode 100644
index 0000000..b1620a5
--- /dev/null
+++ b/src/mathline.h
@@ -0,0 +1,66 @@
+#ifndef MATHLINE_H
+#define MATHLINE_H
+
+#include <math.h>
+
+#define f2i(a, b) a = lrintf(b)
+
+/*
+
+ Fixed Point Multiply.
+
+
+ 16.16 * 16.16 -> 16.16
+ or
+ 16.16 * 0.32 -> 0.32
+
+ A proper version of this function ought to read
+ 16.16 * 16.16 -> 32.16
+ but this would require a __int64 result
+
+ Algorithm:
+
+ Take the mid 32 bits of the 64 bit result
+
+*/
+
+/*
+	These functions have been checked for suitability for 
+	a Pentium and look as if they would work adequately.
+	Might be worth a more detailed look at optimising
+	them though.
+*/
+
+static inline int MUL_FIXED(int a, int b)
+{
+/*
+	int retval;
+	_asm
+	{
+		mov eax,a
+		imul b
+		shrd eax,edx,16
+		mov retval,eax
+	}
+*/
+
+#if defined(ASM386)
+	int retval;
+__asm__("imull	%2			\n\t"
+	"shrdl	$16, %%edx, %%eax	\n\t"
+	: "=a" (retval)
+	: "0" (a), "m" (b)
+	: "%edx", "cc"
+	);
+	return retval;
+#else
+	__int64 aa = (__int64) a;
+	__int64 bb = (__int64) b;
+	
+	__int64 cc = aa * bb;
+	
+	return (int) ((cc >> 16) & 0xffffffff);
+#endif
+}
+
+#endif