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94 lines
2.2 KiB
ArmAsm
94 lines
2.2 KiB
ArmAsm
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; 2017-07-05, 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 popax
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.importzp ptr1, ptr2, ptr3, tmp1, tmp2
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.macpack generic
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; Get a system-specific file.
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; Note: The cbm610, and c128 targets need special
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; versions that handle RAM banking and the 80-column VDC.
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.if .def(__C16__)
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.include "plus4.inc" ; both C16 and Plus4
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.elseif .def(__C64__)
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.include "c64.inc"
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.elseif .def(__CBM510__)
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.import CURS_X: zp, SCREEN_PTR: zp
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.include "cbm510.inc"
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.elseif .def(__PET__)
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.include "pet.inc"
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.elseif .def(__VIC20__)
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.include "vic20.inc"
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.endif
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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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lda SCREEN_PTR
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ldx SCREEN_PTR+1
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sta ptr2
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stx ptr2+1
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ldy CURS_X
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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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; Convert the screen code into a PetSCII code.
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; $00 - $1F: +$40
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; $20 - $3F
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; $40 - $5f: +$20
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; $60 - $7F: +$40
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cmp #$20
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blt @sk1 ;(bcc)
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cmp #$40
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blt L5
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cmp #$60
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blt @sk2 ;(bcc)
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clc
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@sk1: adc #$20
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@sk2: ;clc ; both above cmp and adc clear carry flag
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adc #$20
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L5: 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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