; C02 library stdio.h02 assembly language subroutines
; Requires external routines GETKEY, PRCHR, DELCHR, NEWLIN, and SETSRC
; external zero page locations SRCLO and SRCHI
; and external constants DELKEY, ESCKEY, and RTNKEY
;char getc()
GETC    EQU GETKEY     ;Alias to external GETKEY routine

;void putc(c)
PUTC    EQU PRCHR      ;Alias to external PRCHR Routine

;char gets(&s)
GETS:   JSR SETSRC     ;Initialize Source String
GETSL:  JSR GETC       ;Get Keypress
        CMP #DELKEY    ;If Delete
        BNE GETSE     ;Then  
        TYA            ;  If Offset is Zero
        BEQ GETSL     ;    Get Next Character
        DEY            ;  Else Decrement Offset
        JSR DELCHR     ;    Delete Previous Character
        JMP GETSL     ;    and Get Next Character
GETSE:  CMP #ESCKEY    ;Else If Escape
        BNE GETSC     ;Then  
        LDY #$FF       ;  Return -1
        BNE GETSY     
GETSC:  CMP #RTNKEY    ;Else If Not Carriage Return 
        BEQ GETSX
        JSR PUTC       ;  Echo Character
        STA (SRCLO),Y  ;  Store Character at offset
        INY            ;  increment offset and
        BPL GETSL     ;  loop if less than 128
GETSX:  JSR NEWLIN     ;Else Advance Cursor to Next Line
        LDA #$00       ;  Terminate String        
        STA (SRCLO),Y  ;  and 
GETSY:  TYA            ;  Return String Length
        RTS

;char puts(&s)
PUTS:   LDA #$00       ;Set Start Position to 0
                       ;and fall into putsub
;char putsub(n, &s)
PUTSUB: JSR SETSRC     ;Initialize Source String
        TAY            ;Initialize character offset
PUTSUL: LDA (SRCLO),Y  ;Read next character in string
        BEQ PUTSUX     ;If Not 0
        JSR PUTC       ;  Print character at offset,
        INY            ;  increment offset, and
        BPL PUTSUL     ;  loop if less than 128
PUTSUX: TYA            ;Return number of
        RTS            ;  characters printed

;char putln(&s)
PUTLN:  JSR PUTS       ;Write string to screen
        JMP NEWLIN     ;Execute external NEWLINe routine and return