mirror of https://github.com/cc65/cc65.git
75 lines
1.8 KiB
ArmAsm
75 lines
1.8 KiB
ArmAsm
;
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; int scanf(const char* Format, ...);
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;
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; 2000-12-01, Ullrich von Bassewitz
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; 2004-12-31, Greg King
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;
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.export _scanf
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.import _stdin, pushax, addysp, _vfscanf
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.import sp:zp, ptr1:zp
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.macpack generic
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; ----------------------------------------------------------------------------
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; Code
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;
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_scanf:
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sty ArgSize ; Number of argument bytes passed in .Y
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; We are using a (hopefully) clever trick here to reduce code size. On entry,
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; the stack pointer points to the last pushed argument of the variable
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; argument list. Adding the number of argument bytes, would result in a
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; pointer that points _above_ the Format argument.
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; Because we have to push stdin anyway, we will do that here, so:
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;
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; * we will save the subtraction of 2 (__fixargs__) later;
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; * we will have the address of the Format argument which needs to
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; be pushed next.
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lda _stdin
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ldx _stdin+1
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jsr pushax
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; Now, calculate the va_list pointer, which does point to Format.
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lda sp
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ldx sp+1
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add ArgSize
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bcc @L1
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inx
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@L1: sta ptr1
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stx ptr1+1
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; Push a copy of Format.
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ldy #1
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lda (ptr1),y
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tax
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dey
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lda (ptr1),y
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jsr pushax
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; Load va_list [last and __fastcall__ argument to vfscanf()].
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lda ptr1
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ldx ptr1+1
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; Call vfscanf().
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jsr _vfscanf
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; Clean up the stack. We will return what we got from vfscanf().
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ldy ArgSize
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jmp addysp
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; ----------------------------------------------------------------------------
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; Data
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;
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.bss
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ArgSize:
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.res 1 ; Number of argument bytes
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