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55 lines
1.2 KiB
ArmAsm
55 lines
1.2 KiB
ArmAsm
;
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; 2017-06-20, Greg King
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;
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; void cpeeks (char* s, unsigned length);
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;
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.export _cpeeks
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.import setscrptr, popax
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.importzp ptr1, ptr2, ptr3, tmp1, tmp2
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.macpack generic
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_cpeeks:
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eor #<$FFFF ; counting a word upward is faster
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sta ptr3 ; so, we use -(length + 1)
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txa
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eor #>$FFFF
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sta ptr3+1
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jsr setscrptr ; Set ptr2 and .Y to the cursor's address
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sty tmp2
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jsr popax
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sta tmp1 ; (will be a .Y index)
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stx ptr1+1
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ldx #<$0000
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stx ptr1
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bze L3 ; branch always
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L4: ldy tmp2
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lda (ptr2),y ; Get char
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iny
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bnz L2
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inc ptr2+1
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L2: sty tmp2
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and #<~$80 ; Remove reverse bit
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ldy tmp1
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sta (ptr1),y
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iny
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bnz L1
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inc ptr1+1
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L1: sty tmp1
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L3: inc ptr3 ; count length
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bnz L4
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inc ptr3+1
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bnz L4
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txa ; terminate the string
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ldy tmp1
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sta (ptr1),y
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rts
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