Added fixpoint sine and cosine functions.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4399 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/cc65_cos.s

@@ -0,0 +1,48 @@
+;
+; Fixed point cosine function.
+;
+; Returns the cosine for the given argument as angular degree.
+; Valid argument range is 0..360
+;
+;
+; Ullrich von Bassewitz, 2009-10-29
+;
+
+        .export         _cc65_cos
+
+        .import         _cc65_sin
+
+
+
+; ---------------------------------------------------------------------------
+;
+
+.code
+
+.proc   _cc65_cos         
+
+; cos(x) = sin(x+90)
+
+        clc
+        adc     #90
+        bcc     L1
+        inx
+
+; If x is now larger than 360, we need to subtract 360.
+
+L1:     cpx     #>360
+        bne     L2
+        cmp     #<360
+L2:     bcc     L4
+
+        sbc     #<360
+        bcs     L3
+        dex
+L3:     dex
+
+L4:     jmp     _cc65_sin
+
+
+.endproc
+
+