Added VIC20 port changes from Steve Schmidtke

git-svn-id: svn://svn.cc65.org/cc65/trunk@1376 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/vic20/cgetc.s

@@ -0,0 +1,61 @@
+;
+; Ullrich von Bassewitz, 06.08.1998
+;
+; char cgetc (void);
+;
+
+	.export		_cgetc
+	.import		cursor
+
+	.include	"vic20.inc"
+
+_cgetc:	lda	KEY_COUNT	; Get number of characters
+       	bne    	L3		; Jump if there are already chars waiting
+
+; Switch on the cursor if needed
+
+  	lda	CURS_FLAG
+  	pha
+  	lda	cursor
+  	jsr	setcursor
+L1:	lda	KEY_COUNT
+  	beq	L1
+  	ldx	#0
+    	pla
+	bne	L2
+       	inx
+L2:    	txa
+       	jsr	setcursor
+
+L3:    	jsr	KBDREAD		; Read char and return in A
+	ldx	#0
+	rts
+
+
+; Switch the cursor on or off
+
+.proc	setcursor
+
+       	tax			; On or off?
+    	bne    	seton		; Go set it on
+    	lda	CURS_FLAG	; Is the cursor currently off?
+    	bne    	crs9		; Jump if yes
+    	lda	#1
+    	sta	CURS_FLAG	; Mark it as off
+    	lda	CURS_STATE	; Cursor currently displayed?
+    	beq    	crs8   	       	; Jump if no
+    	ldy	CURS_X		; Get the character column
+       	lda    	(SCREEN_PTR),y	; Get character
+	eor	#$80
+    	sta	(SCREEN_PTR),y	; Store character back
+    	lda    	CURS_COLOR
+    	sta	(CRAM_PTR),y	; Store color back
+crs8:	lda	#0
+	sta	CURS_STATE	; Cursor not displayed
+crs9: 	rts
+
+seton: 	lda	#0
+	sta	CURS_FLAG
+	rts
+
+.endproc