vcprintf.s

;
; int vcprintf (const char* Format, va_list ap);
;
; Ullrich von Bassewitz, 2.12.2000
;

   	.export	      	_vcprintf
	.import	      	pushax, popax
	.import	      	__printf, _cputc
	.importzp     	sp, ptr1, ptr2, ptr3, tmp1

	.macpack      	generic


.data

; ----------------------------------------------------------------------------
;
; Static data for the _vsprintf routine
;

outdesc:	    	 	; Static outdesc structure
	.word	0   	 	; ccount
	.word	out 	 	; Output function pointer
	.word	0   	 	; ptr
       	.word  	0   		; uns

.code

; ----------------------------------------------------------------------------
; Callback routine used for the actual output.
;
; static void out (struct outdesc* d, const char* buf, unsigned count)
; /* Routine used for writing */
; {
;     /* Fast screen output */
;     d->ccount += count;
;     while (count) {
;  	  cputc (*buf);
;  	  ++buf;
;  	  --count;
;     }
; }
;
; We're using ptr1 and tmp1, since we know that the cputc routine will not use
; them (they're also used in cputs, so they must be safe).

out:	jsr	popax 		; count
  	sta    	ptr2
	eor	#$FF
	sta	outdesc+6
	txa
	sta	ptr2+1
	eor	#$FF
       	sta	outdesc+7

  	jsr	popax 		; buf
       	sta    	ptr1
  	stx	ptr1+1

  	jsr	popax 		; d
  	sta	ptr3
  	stx	ptr3+1

; Sum up the total count of characters

  	ldy	#0  		; ccount in struct outdesc
	sty	tmp1		; Initialize tmp1 while we have zero available
  	lda	(ptr3),y
  	add	ptr2
  	sta	(ptr3),y
  	iny
  	lda	(ptr3),y
  	adc	ptr2+1
  	sta	(ptr3),y

; Loop outputting characters

@L1:	inc	outdesc+6
   	beq	@L4
@L2:	ldy	tmp1
    	lda	(ptr1),y
    	iny
    	bne	@L3
       	inc    	ptr1+1
@L3:	sty	tmp1
    	jsr	_cputc
    	jmp	@L1

@L4:	inc	outdesc+7
    	bne	@L2
   	rts

; ----------------------------------------------------------------------------
; vcprintf - formatted console i/o
;
; int vcprintf (const char* format, va_list ap)
; {
;     struct outdesc d;
;
;     /* Setup descriptor */
;     d.fout = out;
;
;     /* Do formatting and output */
;     _printf (&d, format, ap);
;
;     /* Return bytes written */
;     return d.ccount;
; }
;
; It is intentional that this function does not have __fastcall__ calling
; conventions - we need the space on the stack anyway, so there's nothing
; gained by using __fastcall__.

_vcprintf:
  	sta	ptr1  		; Save ap
  	stx	ptr1+1

; Setup the outdesc structure

   	lda	#0
   	sta	outdesc
   	sta	outdesc+1	; Clear ccount

; Get the format parameter and push it again

	ldy	#1
	lda	(sp),y
	tax
	dey
	lda	(sp),y
	jsr	pushax

; Replace the passed format parameter on the stack by &d - this creates
; exactly the stack frame _printf expects. Parameters will get dropped
; by _printf.

	ldy	#2    		; Low byte of d
	lda	#<outdesc
	sta	(sp),y
	iny
	lda	#>outdesc
	sta	(sp),y

; Restore ap and call _printf

	lda	ptr1
	ldx	ptr1+1
	jsr	__printf

; Return the number of bytes written.

    	lda	outdesc		; ccount
    	ldx	outdesc+1
	rts

		      

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