cc65/libsrc/common/vfprintf.s

; vfprintf.s
;
; int fastcall vfprintf(FILE* f, const char* Format, va_list ap);
;
; 2005-02-08, Ullrich von Bassewitz
; 2005-02-11, Greg King

        .export	      	_vfprintf
        .import	       	push1, pushwysp, incsp6
        .import	       	_fwrite, __printf
        .importzp      	sp, ptr1

        .macpack      	generic


.data

; ----------------------------------------------------------------------------
; Static data for the _vfprintf routine
;
outdesc:                        ; Static outdesc structure
ccount: .res	2
        .word	out		; Output function pointer
ptr:    .res	2		; Points to output file
        .res	2		; (Not used by this function)

.code

; ----------------------------------------------------------------------------
; Callback routine used for the actual output.
;
; Since we know, that this routine is always called with "our" outdesc, we
; can ignore the passed pointer d, and access the data directly. While this
; is not very clean, it gives better and shorter code.
;
; static void out (struct outdesc* d, const char* buf, unsigned count)
; /* Routine used for writing */
; {
;     register size_t cnt;
;
;     /* Write to the file */
;     if ((cnt = fwrite(buf, 1, count, ptr)) == 0) {
;         ccount = -1;
;     } else {
;         ccount += cnt;
;     }
; }

; About to call
;
;       fwrite (buf, 1, count, ptr);
;
out:    ldy     #5
        jsr     pushwysp        ; Push buf
        jsr     push1           ; Push #1
        ldy     #7
        jsr     pushwysp        ; Push count
        lda     ptr
        ldx     ptr+1   
        jsr	_fwrite
        sta	ptr1 	       	; Save function result
        stx	ptr1+1

; Check the return value.

        ora     ptr1+1
        bne	@Ok

; We had an error. Store -1 into ccount

.ifp02
        lda	#<-1
.else
        dec	a
.endif
        sta     ccount
        bne     @Done           ; Branch always

; Result was ok, count bytes written

@Ok:    lda     ptr1
        add     ccount
        sta     ccount
        txa
        adc     ccount+1
@Done:  sta     ccount+1
        jmp     incsp6          ; Drop stackframe


; ----------------------------------------------------------------------------
; vfprintf - formatted output
;
; int fastcall vfprintf(FILE* f, const char* format, va_list ap)
; {
;     static struct outdesc d = {
;         0,
;         out
;     };
;
;     /* Setup descriptor */
;     d.ccount = 0;
;     d.ptr  = f;
;
;     /* Do formatting and output */
;     _printf (&d, format, ap);
;
;     /* Return bytes written */
;     return d.ccount;
; }
;
_vfprintf:
        pha			; Save low byte of ap

; Setup the outdesc structure

        lda	#0
        sta	ccount
        sta	ccount+1	; Clear character-count

; Reorder the stack. Replace f on the stack by &d, so the stack frame is
; exactly as _printf expects it. Parameters will get dropped by _printf.

        ldy	#2
        lda	(sp),y		; Low byte of f
        sta	ptr
        lda	#<outdesc
        sta	(sp),y
        iny
        lda	(sp),y	 	; High byte of f
        sta	ptr+1
        lda	#>outdesc
        sta	(sp),y

; Restore low byte of ap and call _printf

        pla
        jsr	__printf

; Return the number of bytes written

        lda	ccount
        ldx	ccount+1
        rts