; Requires external routines SETSRC and SETDST
; Requires the following RAM locations be defined
; external zero page byte pairs SRCLO,SRCHI and DSTLO,DSTHI
; and external bytes TEMP0, TEMP1, TEMP2, and TEMP3
; as well as constant FOMAX and a table of FOMAX+1 
; consecutive bytes named FTBL

;finit() - Initialize File System
FSINIT: LDA #$40        ;Control Messages Only
        JSR SETMSG      ;Kernal - Set System Messages
        JMP FSHUT       ;Close All Files

        LDA #15         ;OPEN 15,8,15,"I"
        LDX #8
        TAY 
        JMP SETLFS
        LDA 1
        LDY #>FSINII
        LDX #<FSINII
        JMP OPEN
FSINII: DC "I"        
        
;fshut() - Shut Down File System
FSHUT:  LDA #0          ;Clear File Table
        LDX #FOMAX
FSHUTL: STA FTBL,X
        DEX
        BPL FSHUTL        
        JMP CLALL       ;Kernal - Close All Files

;fsptr(fn) - Generate File Pointer
;Returns: A,X = An Unused File Pointer (Logical File Number)
;               0 if None Available
FSPTR:  LDX #FOMAX      ;Start at Top of Table
FSPTRL: LDA FTBL,X      ;Check File Table Entry
        BEQ FSPTRX      ;If Not 0
        DEX             ;  Decrement Index and
        BNE FSPTRL      ;  Loop if Greater Than 0
FSPTRX: TXA             ;Move Channel# to Accumulator
        RTS             ;and Return        
 
;fschk(fn) - Check File Pointer
;Args: A = File Pointer (Logical File Number)
;Sets: TEMP0 = Logical File Number
;Returns: A = 0 if File Pointer is Valid
;             255 if File Pointer is Invalid
;         X = Logical file number
FSCHK:  STA TEMP0       ;Save Logical File Number
        TAX             ;Transfer LFN to X register
        BEQ FERR        ;If LFN is 0, Return ERROR
        JSR FSTCK       ;Get File Table Entry
        BNE FZERO       ;If Populated, Return 0
        BEQ FERR        ;Else Return ERROR

;fstat(fn) - Get Status of Channel
;Args: A = File Pointer (Logical File Number)
;Returns: A = Result of Last READST if Argument is 0
;             Contents of File Table Entry
;             255 if File Pointer is Greater Than FOMAX
;         X = Logical file number
FSTAT:  TAX             ;Transfer Logical File Number to X Register
FSTCK:  CLC             ;If LFN
        SBC #FOMAX      ;    is Greater Than FOMAX
        BCS FERR        ;  Return ERROR
        LDA FTBL,X      ;Load File Table Entry
        RTS             ;And Return It
        
;fopen(dn, &s) - Open File with Specified Name
;Args: A = Device Number
;      Y,X = Pointer to File Name
;Sets: TEMP0 = Logical File Number
;      TEMP1 = Device Number 
;      TEMP4 = Length of File Name
;Returns: A = Logical file number
FOPEN:  STA TEMP1       ;Save Device Number
        JSR STRLEN      ;Get File Name Length
        STA TEMP3       ;and Save It
        JSR FSPTR       ;Find Unused Channel
        BEQ FRTS        ;If None Found - Return 0
        STA TEMP0       ;Save Logical File Number
        LDX TEMP1       ;Load Device Number
        LDY TEMP0       ;Set Secondary Address tp
        INY             ;  Logical File Number+1
        JSR SETLFS      ;Set Up Logical File
        LDA TEMP3       ;Load File Name Length
        JSR GETSRC      ;Kernal - Load File Name Pointer
        JSR SETNAM      ;Kernal - Set File Name
        JSR OPEN        ;Open File
        JSR READST      ;Kernal - Read Status Word
        STA FTBL        ;Save in File Table Entry 0
        BNE FZERO       ;If No Errors
        LDX TEMP0       ;  Load Logical File Number
        LDA TEMP1       ;  Load Device Number
        STA FTBL,X      ;  Store in Table Entry
        TXA             ;  Return Logical File Number
        RTS
FZERO:  LDA #0          ;Return 0
        RTS
        
;fclose(fn) - Close File
;Args: A = File Pointer (Logical File Number)
;Returns: A = 0,240 (see FSTAT)
FCLOSE: JSR FSCHK       ;Save and Check Logical File Number
        BNE FRTS        ;If Invalid, then Return
        JSR CLOSE       ;Execute Kernal Close and Return
        BCC FCLOSX      ;If Error On Close
        JSR FSERR       ;  If File System Error
        BNE FERR        ;    Return 255
FCLOSX: LDX TEMP0       ;Retrieve Logical File Number
        LDA #0          ;Ensure that Z Flag is Set
        STA FTBL,X      ;Clear File Table Entry
        RTS             ;and Return 0

;feof(fn) - Check for End of File
;Args: A = Logical file number
;Affects: A,X
FEOF:   TAX             ;Move Channel# to X
        LDA FTBL,X      ;Test File Table Entry
        BPL FZERO       ;If High Bit Clear, Return 0
FERR:   LDA #$FF        ;Set Generic Error Condition
FRTS:   RTS             ;Return from Subroutine

;ferror(fn) - Check for Error
;Args: A = Logical file number
;Affects: A,X
;Returns: A = Error Bit Mask  
;         Bit  Cassette Read  Serial Bus I/O     Tape Load/Verify
;         $01                  Write Timeout
;         $02                  Read Timeout
;         $04   Short Block                         Short Block
;         $08   Long Block                          Long Block
;         $10   Read Error                          Any Mismatch
;         $20   Checksum Err                        Checksum Err
;         $40   End of File    EOI Line
;         $80   End of Tape    Device Not Present   End of Tape
FERROR  LDA FTBL       ;File Table Entry 0 Contains Last Error
        RTS

;fgetc(fn) - Read character from file
;Args: A = Logical file number
;Stack:   9
;Affects: A,X
;Returns: A = 0,240 (see FERROR)
FGETC:  JSR FSCHK      ;Save and Validate Logical File Number 
        BNE FRTS       ;If Error, Return 255
        JSR CHKIN      ;Open channel for input
        JSR CHRIN      ;Get character from input channel
        PHA            ;Save read character
        JSR FSERR      ;Check for Error
        JSR CLRCHN     ;Clear I/O channels
        PLA            ;Retrieve read Character
        RTS

;fputc(fn) - Write character to file
;Args: A = Logical file number
;      Y = Character to Write
;Stack:   9
;Affects: A,X
;Returns: A = 0,240 (see FERROR)
FPUTC:  JSR FSCHK      ;Save and Validate Logical File Number 
        BNE FRTS       ;If Error, Return 255
        JSR CHKOUT     ;Open channel for input
        TYA            ;Move character to accumulator
FPUTCH: JSR CHROUT     ;Output a character
        JSR FSERR      ;Check for Error
        JMP CLRCHN     ;Clear I/O channels and return

;fgets(fn, &s) - Read string from file
;Requires: DSTLO, DSTHI - Pointer to destination string
;Args: A = Logical file number
;      Y,X = Pointer to String
;Stack: 9
;Affects: X,Y
;Returns: A = Number of bytes read
FGETS:  JSR SETSRC      ;Save string address and initialize pointer 
        JSR FSCHK       ;Save and Validate Logical File Number 
        BNE FRTS       ;If Error, Return 255
        JSR CHKIN       ;Open Channel for Input (X set in FSCHK)
FGETSL: JSR CHRIN       ;Get character from input channel
        STA TEMP3
        JSR FSERR       ;Check for Error
        BNE FGETSX      ;If Not 0, Exit
        LDA TEMP3       ;Retrieve read character
        STA (SRCLO),Y   ;Store character in string
        CMP #$0D         ;If Carriage Return
        BEQ FGETSX      ;  Then Exit
        INY             ;Increment pointer
        BPL FGETSL      ;and loop if less than 128
FGETSX: LDA #$00        ;Terminate String        
        STA (SRCLO),Y   ; 
FGETSY: JSR CLRCHN      ;Clear I/O channels
        TYA             ;Return string length
        RTS

;fputs(fn, &s) - Write String to File
;Requires: DSTLO, DSTHI - Pointer to source string
;Args: A = Logical file number
;      Y,X = Pointer to String
;Affects: X,Y
;Returns: A = Number of bytes written
FPUTS:  JSR SETSRC     ;Save string address & initialize pointer 
        BNE FRTS       ;If Error, Return 255
        JSR FSCHK      ;Save and Validate Logical File Number 
        JSR CHKOUT     ;Open channel for Output
FPUTSL: LDA (SRCLO),Y  ;Load next character
        CMP #$00       ;If Null Terminator
        BEQ FGETSY     ;  Then Exit
        JSR CHROUT     ;Write character to output channel
        JSR FSERR      ;Check for Error
        BNE FGETSY     ;If Not 0, Exit
        INY            ;Increment pointer
        BPL FPUTSL     ;If less than 128 then loop
        BMI FGETSY     ;Else exit
        
;fserr() - Check for File Read/Write Error
;Requires: TEMP0 - Logical File Number of Last Read/Write
;Sets: High Bit of File Table Entry to 1 if Error
;Returns: A = 0 if No Error, Otherwise LFN | $80
;         N = 1 if Error, 0 if None
;         X = Logical File Number
;Check for End of File and Set Flag
FSERR:  JSR READST      ;Read status word
        STA FTBL        ;and Save It
        BEQ FSERRX      ;If Not 0
        LDX TEMP0       ;  Get Channel#
        LDA FTBL,X      ;  Load Table Entry
        ORA #$80        ;  Set High Bit
        STA FTBL,X      ;  and Save
FSERRX: RTS

;fsdst(&s) - Set Destination String 
;            Called before fread()
;Args: X,Y = Pointer to destination string
;Sets: DSTLO,DSTHI = Pointer to destination string
;Affects: N,Z
FSDST  EQU SETDST      ;Aliased to System Header function

;fread(fn, n) - Read bytes from file
;Requires: DSTLO, DSTHI - Pointer to destination string
;Args: A = Logical file number
;      Y = Maximum number of bytes to read
;Affects: X,Y
;Returns: A = Number of bytes read
FREAD:  STY TEMP1       ;Save Number of Bytes to Read
        LDY #0          ;Initialize pointer 
        JSR FSCHK       ;Save and Validate Logical File Number 
        BNE FREADR      ;If Error, Return 255
        JSR CHKIN       ;Open Channel for Input (X set in FSCHK)
FREADL: JSR CHRIN       ;Get character from input channel
        STA TEMP3
        JSR FSERR       ;Check for Error
        BNE FREADX      ;If Not 0, Exit
        LDA TEMP3       ;Retrieve read character
        STA (DSTLO),Y   ;Store character in string
        INY             ;Increment pointer
        CPY TEMP1       ;If Less Than Maximum
        BNE FREADL      ;  Then Loop
FREADX: JSR CLRCHN      ;Clear I/O channels
        TYA             ;Return string length
FREADR: RTS

;fssrc(&s) - Set Destination String 
;            Called before fwrite()
;Args: X,Y = Pointer to destination string
;Sets: SRCLO,SRCHI = Pointer to destination string
;Affects: N,Z
FSSRC  EQU SETSRC      ;Aliased to System Header function

;fwrite(fn, n) - Write bytes from file
;Requires: SRCLO, SRCHI - Pointer to destination string
;Args: A = Logical file number
;      Y = Maximum number of bytes to read
;Affects: X,Y
;Returns: A = Number of bytes written
FWRITE: STY TEMP1       ;Save Number of Bytes to Writre
        LDY #0          ;Initialize pointer 
        JSR FSCHK       ;Save and Validate Logical File Number 
        BNE FWRITR      ;If Error, Return 255
        JSR CHKOUT      ;Open Channel for Input (X set in FSCHK)
FWRITL: LDA (SRCLO),Y   ;Get Byte to Write
        JSR CHROUT      ;Get character from input channel
        JSR FSERR       ;Check for Error
        BNE FWRITX      ;If Not 0, Exit
        INY             ;Increment pointer
        CPY TEMP1       ;If Less Than Maximum
        BNE FWRITL      ;  Then Loop
FWRITX: JSR CLRCHN      ;Clear I/O channels
        TYA             ;Return string length
FWRITR: RTS