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64 lines
1.5 KiB
ArmAsm
64 lines
1.5 KiB
ArmAsm
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; 2020-07-14, Groepaz
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; void cpeeks (char* s, unsigned length);
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;
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; get string from current position, do NOT advance cursor
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.export _cpeeks
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.import popax
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.importzp ptr1, ptr2, tmp1, tmp2
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.macpack generic
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.include "pce.inc"
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.include "extzp.inc"
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_cpeeks:
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eor #<$FFFF ; counting a word upward is faster
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sta ptr2 ; so, we use -(length + 1)
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txa
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eor #>$FFFF
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sta ptr2+1
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st0 #VDC_MARR ; Memory-Address Read
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ldy SCREEN_PTR
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ldx SCREEN_PTR+1
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sty VDC_DATA_LO
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stx VDC_DATA_HI
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st0 #VDC_VRR ; VRAM Read Register
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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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beq L2 ; branch always
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L3: ldy tmp2
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lda VDC_DATA_LO ; get character
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bit VDC_DATA_HI ; we need to "read" the highbyte to advance the address
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iny
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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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bne L1
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inc ptr1+1
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L1: sty tmp1
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L2: inc ptr2 ; count length
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bne L3
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inc ptr2+1
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bne L3
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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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