cc65/libsrc/common/sprintf.s

;
; int sprintf (char* buf, const char* Format, ...);
;
; Ullrich von Bassewitz, 1.12.2000
;

	.export	      	_sprintf
	.import		pushax, addysp, decsp4, _vsprintf
	.importzp	sp, ptr1

	.macpack	generic

; ----------------------------------------------------------------------------
; Data

.bss

ParamSize: 	.res  	1 		; Number of parameter bytes

; ----------------------------------------------------------------------------
; Code

.code


_sprintf:
  	sty	ParamSize 		; Number of param bytes passed in Y

; We have to push buf and format, both in the order they already have on stack.
; To make this somewhat more efficient, we will create space on the stack and
; the do a copy of the complete block instead of pushing each parameter
; separately. Since the size of the arguments passed is the same as the size
; of the fixed arguments, this will allow us to calculate the pointer to the
; fixed size arguments easier (they're just ParamSize bytes away).

	jsr	decsp4

; Calculate a pointer to the Format argument

	lda	ParamSize
	add	sp
	sta	ptr1
	ldx	sp+1
	bcc	@L1
	inx
@L1:	stx	ptr1+1

; Now copy both, buf and format

	ldy	#4-1
@L2:	lda	(ptr1),y
	sta	(sp),y
	dey
	bpl	@L2

; Load va_list (last and __fastcall__ parameter to vsprintf)

 	lda    	ptr1
 	ldx    	ptr1+1

; Call vsprintf

	jsr	_vsprintf

; Cleanup the stack. We will return what we got from vsprintf

	ldy	ParamSize
	jmp	addysp