cc65/libsrc/atari/getdefdev.s

;
; Freddy Offenga & Christian Groessler, December 2004
;
; function to get default device: char *_getdefdev(void);
;
; SpartaDOS:
; the ZCRNAME routine is only used to get the default drive because
; ZCRNAME has two disadvantages:
; 1. It will convert D: into D1: instead of Dn: (n = default drive)
; 2. It will give a 'no arguments' status if it detects something
;    like Dn: (without filename).
;
; OS/A+ DOS:
; ZCRNAME is slightly different from SpartaDOS. It will convert D:
; into Dn: where n is the default drive.

        .include        "atari.inc"
        .import         __dos_type
        .export         __getdefdev             ; get default device
        .export         __defdev                ; this is the default device string (e.g. "D1:")
.ifdef  DYNAMIC_DD
        .constructor    __getdefdev,24
.endif

; Get default device (LBUF will be destroyed!!)

__getdefdev:

        lda     __dos_type      ; which DOS?
        cmp     #ATARIDOS
        beq     finish
        cmp     #MYDOS
        beq     finish

        ldy     #BUFOFF
        lda     #0
        sta     (DOSVEC),y      ; reset buffer offset

; Store dummy argument

        ldy     #LBUF
        lda     #'X'
        sta     (DOSVEC),y
        iny
        lda     #ATEOL
        sta     (DOSVEC),y

; One extra store to avoid the buggy sequence from OS/A+ DOS:
; <D><RETURN><:> => drive number = <RETURN>

        iny
        sta     (DOSVEC),y

; Create crunch vector

        ldy     #ZCRNAME+1
        lda     (DOSVEC),y
        sta     crvec+1
        iny
        lda     (DOSVEC),y
        sta     crvec+2

crvec:  jsr     $FFFF           ; will be set to crunch vector

; Get default device

        ldy     #COMFNAM        ;  COMFNAM is always "Dn:"
        lda     (DOSVEC),y
        sta     __defdev
        iny
        lda     (DOSVEC),y
        sta     __defdev+1

; Return pointer to default device

finish: lda     #<__defdev
        ldx     #>__defdev
        rts

        .data

; Default device

__defdev:
.ifdef  DEFAULT_DEVICE
        .byte   'D', '0'+DEFAULT_DEVICE, ':', 0
.else
        .byte   "D1:", 0
.endif