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200 lines
4.2 KiB
ArmAsm
200 lines
4.2 KiB
ArmAsm
;
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; int vsnprintf (char* Buf, size_t size, const char* Format, va_list ap);
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;
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; Ullrich von Bassewitz, 2009-09-26
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;
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.export _vsnprintf, vsnprintf
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.import ldaxysp, popax, incsp2, incsp6
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.import _memcpy, __printf
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.importzp sp, ptr1
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.macpack generic
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.data
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; ----------------------------------------------------------------------------
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;
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; Static data for the _vsnprintf routine
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;
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outdesc: ; Static outdesc structure
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ccount: .word 0 ; ccount
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func: .word out ; Output function pointer
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bufptr: .word 0 ; ptr
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bufsize:.word 0 ; Buffer size
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.code
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; ----------------------------------------------------------------------------
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; vsprintf - formatted output into a buffer
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;
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; int __fastcall__ vsnprintf (char* buf, size_t size, const char* format, va_list ap);
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;
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_vsnprintf:
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pha ; Save ap
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txa
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pha
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; Setup the outdesc structure. This is also an additional entry point for
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; vsprintf with ap on stack
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vsnprintf:
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lda #0
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sta ccount+0
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sta ccount+1 ; Clear ccount
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; Get the size parameter and replace it by a pointer to outdesc. This is to
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; build a stack frame for the call to _printf.
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; If size is zero, there's nothing to do.
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ldy #2
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lda (sp),y
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sta ptr1
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lda #<outdesc
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sta (sp),y
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iny
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lda (sp),y
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sta ptr1+1
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ora ptr1
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beq L9
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lda #>outdesc
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sta (sp),y
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; Write size-1 to outdesc.uns
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ldy ptr1+1
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ldx ptr1
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bne L1
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dey
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L1: dex
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stx bufsize+0
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sty bufsize+1
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; Copy buf to the outdesc.ptr
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ldy #5
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jsr ldaxysp
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sta bufptr+0
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stx bufptr+1
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; Restore ap and call _printf
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pla
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tax
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pla
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jsr __printf
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; Terminate the string. The last char is either at bufptr+ccount or
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; bufptr+bufsize, whichever is smaller.
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lda ccount+0
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ldx ccount+1
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cpx bufsize+1
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bne L2
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cmp bufsize+0
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L2: bcc L3
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lda bufsize+0
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ldx bufsize+1
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clc
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L3: adc bufptr+0
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sta ptr1
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txa
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adc bufptr+1
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sta ptr1+1
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lda #0
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tay
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sta (ptr1),y
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; Return the number of bytes written and drop buf
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lda ccount+0
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ldx ccount+1
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jmp incsp2
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; Bail out if size is zero.
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L9: pla
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pla ; Discard ap
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lda #0
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tax
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jmp incsp6 ; Drop parameters
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; ----------------------------------------------------------------------------
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; Callback routine used for the actual output.
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;
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; static void out (struct outdesc* d, const char* buf, unsigned count)
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; /* Routine used for writing */
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;
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; Since we know, we're called with a pointer to our static outdesc structure,
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; we don't need the pointer passed on the stack.
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out:
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; Calculate the space left in the buffer. If no space is left, don't copy
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; any characters
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lda bufsize+0 ; Low byte of buffer size
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sec
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sbc ccount+0 ; Low byte of bytes already written
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sta ptr1
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lda bufsize+1
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sbc ccount+1
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sta ptr1+1
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bcs @L0 ; Branch if space left
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lda #$00
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sta ptr1
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sta ptr1+1 ; No space left
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; Replace the pointer to d by a pointer to the write position in the buffer
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; for the call to memcpy that follows.
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@L0: lda bufptr+0
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clc
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adc ccount+0
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ldy #4
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sta (sp),y
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lda bufptr+1
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adc ccount+1
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iny
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sta (sp),y
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; Get Count from stack
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jsr popax
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; outdesc.ccount += Count;
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pha
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clc
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adc ccount+0
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sta ccount+0
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txa
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adc ccount+1
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sta ccount+1
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pla
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; if (Count > Left) Count = Left;
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cpx ptr1+1
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bne @L1
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cmp ptr1
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@L1: bcc @L2
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lda ptr1
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ldx ptr1+1
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; Jump to memcpy, which will cleanup the stack and return to the caller
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@L2: jmp _memcpy
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