Moved fixed point multiplication and rounding into an asm module.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4447 b7a2c559-68d2-44c3-8de9-860c34a00d81

asminc/tgi-kernel.inc

@@ -170,6 +170,7 @@ TGI_TEXT_VERTICAL       = 1
         .global _tgi_getxres
         .global _tgi_getyres
         .global _tgi_gotoxy
+        .global _tgi_imulround
         .global _tgi_init
         .global _tgi_install
         .global _tgi_ioctl

include/tgi.h

@@ -218,6 +218,14 @@ void __fastcall__ tgi_ellipse (int x, int y, unsigned char rx, unsigned char ry)
  * drawing color.
  */
 
+void __fastcall__ tgi_arc (int x, int y, unsigned char rx, unsigned char ry,
+                           unsigned sa, unsigned ea);
+/* Draw an ellipse arc with center at x/y and radii rx/ry using the current
+ * drawing color. The arc covers the angle between sa and ea (startangle and
+ * endangle), which must be in the range 0..360 (otherwise the function may
+ * bevave unextectedly).
+ */
+
 void __fastcall__ tgi_bar (int x1, int y1, int x2, int y2);
 /* Draw a bar (a filled rectangle) using the current color. */
 

include/tgi/tgi-kernel.h

@@ -44,7 +44,7 @@
 
 
 
-/* TGI kernel variables */              
+/* TGI kernel variables */
 extern void*   	        tgi_drv;       	/* Pointer to driver */
 extern unsigned char  	tgi_error;     	/* Last error code */
 extern unsigned char    tgi_gmode;      /* Flag: Graphics mode active */
@@ -68,6 +68,11 @@ extern unsigned         tgi_aspectratio;/* Aspect ratio as fixed point 8.8 */
 const char* __fastcall__ tgi_map_mode (unsigned char mode);
 /* Map a tgi mode to a driver name. Returns NULL if no driver available. */
 
+int __fastcall__ tgi_imulround (int rhs, int lhs);
+/* Helper function for functions using sine/cosine: Multiply two values, one
+ * being an 8.8 fixed point one, and return the rounded and scaled result.
+ */
+
 
 
 /* End of tgi-kernel.h */

libsrc/tgi/Makefile

@@ -58,6 +58,7 @@ S_OBJS =       	tgi-kernel.o   	        \
                 tgi_getxres.o           \
                 tgi_getyres.o           \
                 tgi_gotoxy.o            \
+                tgi_imulround.o         \
                 tgi_init.o              \
                 tgi_ioctl.o             \
                 tgi_line.o              \

libsrc/tgi/tgi_arc.c

@@ -34,6 +34,7 @@
 
 
 #include <tgi.h>
+#include <tgi/tgi-kernel.h>
 #include <cc65.h>
 
 
@@ -44,18 +45,6 @@
 
 
 
-static int RoundMul (int rhs, int lhs)
-{
-    long res = cc65_imul16x16r32 (rhs, lhs);
-    if ((unsigned char)res & 0x80) {
-        return (int)(res >> 8) + 1;
-    } else {
-        return (int)(res >> 8);
-    }
-}
-
-
-
 void __fastcall__ tgi_arc (int x, int y, unsigned char rx, unsigned char ry,
                            unsigned sa, unsigned ea)
 /* Draw an ellipse arc with center at x/y and radii rx/ry using the current
@@ -81,16 +70,16 @@ void __fastcall__ tgi_arc (int x, int y, unsigned char rx, unsigned char ry,
     }
 
     /* Calculate the start coords */
-    x1 = x + RoundMul (rx, cc65_cos (sa));
-    y1 = y + RoundMul (ry, cc65_sin (sa));
+    x1 = x + tgi_imulround (rx, cc65_cos (sa));
+    y1 = y + tgi_imulround (ry, cc65_sin (sa));
     do {
         sa += inc;
         if (sa >= ea) {
             sa = ea;
             done = 1;
         }
-        x2 = x + RoundMul (rx, cc65_cos (sa));
-        y2 = y - RoundMul (ry, cc65_sin (sa));
+        x2 = x + tgi_imulround (rx, cc65_cos (sa));
+        y2 = y - tgi_imulround (ry, cc65_sin (sa));
         tgi_line (x1, y1, x2, y2);
         x1 = x2;
         y1 = y2;

libsrc/tgi/tgi_imulround.s

@@ -0,0 +1,54 @@
+;
+; Ullrich von Bassewitz, 2009-11-05
+;
+; Helper function for functions using sine/cosine: Multiply two values, one
+; being an 8.8 fixed point one, and return the rounded and scaled result.
+;
+
+
+        .export         _tgi_imulround
+        .import         popax, imul16x16r32
+
+        .include        "zeropage.inc"
+
+
+;----------------------------------------------------------------------------
+;
+
+.code
+.proc   _tgi_imulround
+
+; Get arguments
+
+        sta     ptr1
+        stx     ptr1+1                  ; Save lhs
+        jsr     popax                   ; Get rhs
+
+; Multiplicate
+
+        jsr     imul16x16r32
+
+; Round the result
+
+        cmp     #$80                    ; Frac(x) >= 0.5?
+        txa
+        ldy     sreg+1                  ; Check sign
+        bmi     @L1
+
+        adc     #$00
+        tay
+        lda     sreg
+        adc     #$00
+        tax
+        tya
+        rts
+
+@L1:    sbc     #$00
+        tay
+        lda     sreg
+        sbc     #$00
+        tax
+        tya
+        rts
+
+.endproc