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|
;
; int printf (const char* Format, ...);
;
; Ullrich von Bassewitz, 1.12.2000
;
.export _printf
.import _stdout, pushax, addysp, _vfprintf
.importzp sp, ptr1
.macpack generic
; ----------------------------------------------------------------------------
; Data
.bss
ParamSize: .res 1 ; Number of parameter bytes
; ----------------------------------------------------------------------------
; Code
.code
_printf:
sty ParamSize ; Number of param bytes passed in Y
; We are using a (hopefully) clever trick here to reduce code size. On entry,
; the stack pointer points to the last pushed parameter of the variable
; parameter list. Adding the number of parameter bytes, would result in a
; pointer that points *after* the Format parameter.
; Since we have to push stdout anyway, we will do that here, so
;
; * we will save the subtraction of 2 (__fixargs__) later
; * we will have the address of the Format parameter which needs to
; be pushed next.
;
lda _stdout
ldx _stdout+1
jsr pushax
; Now calculate the va_list pointer, which does points to Format
lda sp
ldx sp+1
add ParamSize
bcc @L1
inx
@L1: sta ptr1
stx ptr1+1
; Push Format
ldy #1
lda (ptr1),y
tax
dey
lda (ptr1),y
jsr pushax
; Load va_list (last and __fastcall__ parameter to vfprintf)
lda ptr1
ldx ptr1+1
; Call vfprintf
jsr _vfprintf
; Cleanup the stack. We will return what we got from vfprintf
ldy ParamSize
jmp addysp
|
