New kbhit and cgetc functions from Karri

git-svn-id: svn://svn.cc65.org/cc65/trunk@3295 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/lynx/cgetc.s

@@ -0,0 +1,41 @@
+;
+; Karri Kaksonen, 2004-11-01
+;
+; char cgetc (void);
+;
+
+       	.export		_cgetc
+       	.import		_kbhit
+       	.import		KBBUF
+
+; --------------------------------------------------------------------------
+; The Atari Lynx has a very small keyboard - only 3 keys
+; Opt1, Opt2 and Pause.
+; But the designers have decided that pressing Pause and Opt1 at the
+; same time means Restart and pressing Pause and Opt2 means Flip screen.
+
+; For "easter egg" use I have also included all three keys pressed '?'
+; and Opt1 + Opt2 pressed '3'.
+; So the keyboard returns '1', '2', '3', 'P', 'R', 'F' or '?'.
+
+_cgetc:
+    	jsr    	_kbhit	       	; Check for char available
+        tax                     ; Test result
+	beq	_cgetc
+
+	ldx	#5		; Wait for some time... 0.2 seconds or so.
+@L1:	ldy	#255
+@L2:	lda	#255
+@L3:	dec
+	bne	@L3
+	dey
+	bne	@L2
+	dex
+	bne	@L1
+
+    	jsr    	_kbhit	       	; Check for double pressed buttons
+	lda	KBBUF
+	stz	KBBUF
+       	ldx	#0
+       	rts
+