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54 lines
2.0 KiB
Plaintext
54 lines
2.0 KiB
Plaintext
; 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 SRCLO and SRCHI
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; and external constants DELKEY, ESCKEY, and RTNKEY
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;char getc()
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GETC EQU GETKEY ;Alias to external GETKEY routine
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;void putc(c)
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PUTC EQU PRCHR ;Alias to external PRCHR Routine
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;char gets(&s)
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GETS: JSR SETSRC ;Initialize Source String
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GETSL: JSR GETC ;Get Keypress
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CMP #DELKEY ;If Delete
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BNE GETSE ;Then
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TYA ; If Offset is Zero
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BEQ GETSL ; 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 GETSL ; and Get Next Character
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GETSE: CMP #ESCKEY ;Else If Escape
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BNE GETSC ;Then
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LDY #$FF ; Return -1
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BNE GETSY
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GETSC: CMP #RTNKEY ;Else If Not Carriage Return
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BEQ GETSX
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JSR PUTC ; Echo Character
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STA (SRCLO),Y ; Store Character at offset
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INY ; increment offset and
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BPL GETSL ; loop if less than 128
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GETSX: JSR NEWLIN ;Else Advance Cursor to Next Line
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LDA #$00 ; Terminate String
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STA (SRCLO),Y ; and
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GETSY: TYA ; Return String Length
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RTS
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;char puts(n, &s)
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PUTS: LDA #$00 ;Set Start Position to 0
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;and fall into putsub
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;char putsub(n, &s)
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PUTSUB: JSR SETSRC ;Initialize Source String
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TAY ;Initialize character offset
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PUTSUL: LDA (SRCLO),Y ;Read next character in string
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BEQ PUTSUX ;If Not 0
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JSR PUTC ; Print character at offset,
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INY ; increment offset, and
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BPL PUTSUL ; loop if less than 128
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PUTSUX: TAY ;Return number of
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RTS ; characters printed
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;char putln(&s)
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PUTLN: JSR PUTS ;Write string to screen
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JMP NEWLIN ;Call external NEWLINe routine and return
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