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59 lines
2.1 KiB
NASM
59 lines
2.1 KiB
NASM
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; C02 library stdio.h02 assembly language subroutines
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; Requires external routines getkey, prchr, delchr, and newlin
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; external zero page locations strlo and strhi
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; and external constants DELKEY, ESCKEY, and RTNKEY
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;char getchr()
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getchr: JMP getkey ;Call external getkey routine
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;void putchr(c)
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putchr: JMP prchr ;Call external print character
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;char getstr(&s)
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getstr: STX strlo ;Save Pointer in Store Index
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STY strhi
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LDY #$00 ;Initialize character offset
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getstl: JSR getchr ;Get Keypress
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getstd: CMP #DELKEY ;If Delete
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BNE getste ;Then
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TYA ; If Offset is Zero
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BEQ getstl ; Get Next Character
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DEY ; Else Decrement Offset
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JSR delchr ; Delete Previous Character
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JMP getstl ; and Get Next Character
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getste: CMP #ESCKEY ;Else If Escape
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BNE getstc ;Then
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LDY #$FF ; Return -1
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BNE getsty
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getstc: CMP #RTNKEY ;Else If Not Carriage Return
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BEQ getstx
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JSR putchr ; Echo Character
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STA (strlo),Y ; Store Character at offset
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INY ; increment offset and
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BPL getstl ; loop if less than 128
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getstx: JSR newlin ;Else Advance Cursor to Next Line
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LDA #$00 ; Terminate String
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STA (strlo),Y ; and
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getsty: TYA ; Return String Length
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RTS
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;char outstr(n, &s)
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outstr: LDA #$00 ;Set Start Position to 0
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;and fall into outsub
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;char outsub(n, &s)
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outsub: STX strlo ;Save pointer in Store Index
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STY strhi
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TAY ;Initialize character offset
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outsul: LDA (strlo),Y ;Read next character in string
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BEQ outsux ;If Not 0
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JSR putchr ; Print character at offset,
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INY ; increment offset, and
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BPL outsul ; loop if less than 128
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outsux: TAY ;Return number of
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RTS ; characters printed
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;char putstr(*s)
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putstr: JSR outstr ;Write string to screen
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JMP newlin ;Call external newline routine and return
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