cc65/libsrc/c64/cgetc.s

;
; Ullrich von Bassewitz, 06.08.1998
;
; char cgetc (void);
;

        .export         _cgetc
        .import         cursor

        .include        "cbm_kernal.inc"
        .include        "c64.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