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cc65/libsrc/common/_swap.s
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63 lines
717 B
ArmAsm

;
; Ullrich von Bassewitz, 09.12.1998
;
; void __fastcall__ _swap (void* p, void* q, size_t size);
;
.export __swap
.import popax
.importzp ptr1, ptr2, ptr3
__swap: sta ptr3 ; Save size
stx ptr3+1
jsr popax ; Get q
sta ptr2
stx ptr2+1
jsr popax ; Get p
sta ptr1
stx ptr1+1
; Prepare for swap
ldy #$00
; Swap 256 byte blocks
ldx ptr3+1
beq @L2
@L1: lda (ptr1),y
tax
lda (ptr2),y
sta (ptr1),y
txa
sta (ptr2),y
iny
bne @L1
dec ptr3+1
bne @L1
; Swap remaining bytes (Y is zero)
@L2: ldx ptr3
beq @L9
@L3: lda (ptr1),y
tax
lda (ptr2),y
sta (ptr1),y
txa
sta (ptr2),y
iny
dec ptr3
bne @L3
; Done
@L9: rts