Zapple-II/SOFTCARD80.ASM#040000

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; Z80 code running on Softcard
; Implements CP/M style BDOS interface
; Requires the companion SOFTCARD65 6502 code
; Assemble using Udo Munk's Z80asm.
; Tabstops every 4 chars.
; Bobbi 2019
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; References:
; 1) BDOS System Calls
;    https://www.seasip.info/Cpm/bdos.html
; 2) Programmer's CP/M Handbook - Johnson-Laird
; 3) ProDOS 8 Technical Reference Manual
;    http://www.easy68k.com/paulrsm/6502/PDOS8TRM.HTM
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;
; TODO: F_WRITE bug turns out to be bug in ProDOS 2.5.0a7 (SET_MARK)
;       Or maybe I was trashing memory. Need to retest.
; TODO: How does DIR / NSWEEP work out file sizes? Need to support this.
; TODO: Implement missing system calls:
;        - F_ATTRIB
;        - RS232 (A_READ, A_WRITE)
;        - Printer (LWRITE)
; TODO: F_ATTRIB needs to work with FCB with wildcards and leave the FCB at
;       DMAADDR
; TODO: IOBYTE doesn't do anything
; TODO: User number doesn't do anything
; TODO: Software R/O disk setting is not respected
; TODO: C_READSTR - Line editing functions
; TODO: C_WRITE - handle tabs
; Other Random TODO comments in the code
; 

BDOSADDR	EQU		08800H			; 
STCKTOP		EQU		097FFH			; Top of Z80 stack (below IOBUFs)

SOFTCARD	EQU		0E400H			; Softcard in slot 4 ($C400)

OFFSET		EQU		01000H			; Offset to add to Z80 addr to get 6502
									; address. Correct for Z80 addr <= 0AFFFH

; 6502 zero page, in Z80 address space
CMD			EQU		0F006H			; 6502 $06
AREG		EQU		0F007H			; 6502 $07
XREG		EQU		0F008H			; 6502 $08
YREG		EQU		0F009H			; 6502 $09
ADDR		EQU		0F0EBH			; 6502 $EB (LSB)
ADDRH		EQU		0F0ECH			; 6502 $EC (MSB)

; Addresses of 6502 routines, in 6502 address space
COUT		EQU		0FDEDH			; Print char in A
RDKEY		EQU		0FD0CH			; Read key, return in A
BELL		EQU		0FBE4H			; Sound the bell

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; Entry point when Z80 cold starts is 0000H
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			ORG		0000H
			JP		BDOSINIT		; Initialize BDOS

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; See obsolescence.wix.com/obsolescence/cpm-internals for info
; on low storage usage ...
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IOBYTE		DEFB	0				; Maps virtual to real devices

CURDRV		DEFB	0				; LS 4 bits; Current drive 0=A: etc
									; MS 4 bits: Current user number

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; BDOS entry point must be at address 0005H for CP/M compatibility
; Function to invoke is passed in C
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

BDOS		JP		BDOSIMP			; BDOS code is at top of memory

RVEC1		DEFW	0000H			; Restart vector 1
RVEC2		DEFW	0000H			; Restart vector 2
RVEC3		DEFW	0000H			; Restart vector 3
RVEC4		DEFW	0000H			; Restart vector 4
RVEC5		DEFW	0000H			; Restart vector 5
RVEC6		DEFW	0000H			; Restart vector 6
RVEC7		DEFW	0000H			; Restart vector 7

; Space for private BDOS data (implementation dependent) up to 005BH
DMAADDR		DEFW	0080H			; DMA address defaults to FILEBUF (0080H)
LOGVEC		DEFW	0000H			; Vector of logged in drives
ROVEC		DEFW	0000H			; Vector of read-only drives
TEMPWORD	DEFW	0000H			; Used by routines as a scratch space
TEMPBYTE	DEFB	0				; Used by routines as a scratch space
; End of private, implementation dependent space

			ORG		005CH			; Standard addr of 32 byte FCB1
FCB1								; File control block #1
FCB1DRV		DEFB	00H				; FCB Drive (0 current, 1 A:, 2 B: etc)
FCB1NAM		DEFM	'FILENAMEEXT'	; FCB filename and extension
FCB1EX		DEFB	00H				; FCB extent field
FCB1S1		DEFB	00H				; FCB S1 field
FCB1S2		DEFB	00H				; FCB S2 field
FCB1RC		DEFB	00H				; FCB RC field (# recs used this extent)
FCB1MAP								; Map of blocks in file (overlaps FCB2)

			ORG		006CH			; Standard addr of 32 byte FCB2
FCB2								; File control block #2
FCB2DRV		DEFB	00H				; FCB Drive (0 current, 1 A:, 2 B: etc)
FCB2NAM		DEFM	'FILENAMEEXT'	; FCB filename and extension
FCB2EX		DEFB	00H				; FCB extent field
FCB2S1		DEFB	00H				; FCB S1 field
FCB2S2		DEFB	00H				; FCB S2 field
FCB2RC		DEFB	00H				; FCB RC field (# recs used this extent)
FCB2MAP								; Map of blocks in file (overlaps buffer)

			ORG		0080H			; Standard addr of 128 byte File Buffer
FILEBUF		DEFS	128				; Command args go here too (Pascal string)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; The application program proper starts at 0100H
; in order to be compatible with CP/M .COM programs
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

			ORG		0100H

; Print signon message using C_WRITESTR
PROGSTRT	LD		DE,WELCOME		; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

; Print the alphabet using C_WRITE
			LD		B,'A'			; First character
L1			LD		E,B 			; Character to print
			LD		C,B_C_WRITE		;
			PUSH	BC				; Preserve B (and C)
			CALL	BDOS			;
			POP		BC				; Restore B (and C)
			INC		B				;
			LD		A,'Z'			; Last character
			CP		B				;
			JP		Z,S1			;
			JP		L1				;

; Loop until there is a keystroke waiting using C_STAT
S1			LD		C,B_C_STAT		;
			CALL	BDOS			;
			CP		0				; Anything?
			JR		Z,S1			; If not, loop

; Print a couple of asterisks
  			LD		E,'*'			;
			LD		C,B_C_WRITE		;
			CALL	BDOS			;
			LD		E,'*'			;
			LD		C,B_C_WRITE		;
			CALL	BDOS			;

			; Create FCB1 'A:TEST.TXT'
			LD		A,1				; A: drive
			LD		(FCB1DRV),A		;
			LD		A,'T'			; Filename
			LD		(FCB1NAM),A		;
			LD		A,'E'			; Filename
			LD		(FCB1NAM+1),A	;
			LD		A,'S'			; Filename
			LD		(FCB1NAM+2),A	;
			LD		A,'T'			; Filename
			LD		(FCB1NAM+3),A	;
			LD		A,' '			; Filename
			LD		(FCB1NAM+4),A	;
			LD		A,' '			; Filename
			LD		(FCB1NAM+5),A	;
			LD		A,' '			; Filename
			LD		(FCB1NAM+6),A	;
			LD		A,' '			; Filename
			LD		(FCB1NAM+7),A	;
			LD		A,'T'			; Extension
			LD		(FCB1NAM+8),A	;
			LD		A,'X'			; Extension
			LD		(FCB1NAM+9),A	;
			LD		A,'T'			; Extension
			LD		(FCB1NAM+10),A	;

			; Create FCB2 'A:????????.???'
			LD		A,1				; A: drive
			LD		(FCB2DRV),A		;
			LD		A,'?'			; Filename
			LD		(FCB2NAM),A		;
			LD		(FCB2NAM+1),A	;
			LD		(FCB2NAM+2),A	;
			LD		(FCB2NAM+3),A	;
			LD		(FCB2NAM+4),A	;
			LD		(FCB2NAM+5),A	;
			LD		(FCB2NAM+6),A	;
			LD		(FCB2NAM+7),A	;
			LD		(FCB2NAM+8),A	;
			LD		(FCB2NAM+9),A	;
			LD		(FCB2NAM+10),A	;

			; Create and open a file using ProDOS MLI
			; Creates 'A/TEST.TXT'
			; Directory 'A' needs to exist already

			LD		DE,CMSG			; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_MAKE		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Set the DMA buffer to point to our text
			LD		DE,TEXTBUF		;
			LD		C,B_F_DMAOFF	;
			CALL	BDOS			;
			
			; Write to the file

			LD		DE,WMSG			; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_WRITE		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Close the file

			LD		DE,CLMSG		; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_CLOSE		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Set the DMA buffer to point to FILEBUF (0080H)
			LD		DE,FILEBUF		;
			LD		C,B_F_DMAOFF	;
			CALL	BDOS			;
			
			; Search for the file in the directory

			LD		DE,SFMSG		; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_SFIRST	;
			CALL	BDOS			;

			CP		0				;
			JP		Z,FOUND			;
			LD		DE,SFMSGNF		;
			JP		PRFNF			;
FOUND		LD		DE,SFMSGF		;
PRFNF		LD		C,B_C_WRTSTR	;
			CALL	BDOS			;
			
			;CALL	CHECKOK

			; Search for all files in the directory using wildcards

			LD		DE,SFMSG2		; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB2			; Default FCB address 2
			LD		C,B_F_SFIRST	;
			CALL	BDOS			;

			CP		0				;
			JP		Z,FOUND2		;
			LD		DE,SFMSGNF		;
			JP		PRFNF2			;
FOUND2		LD		A,13			; HACK to terminate string
			LD		(FILEBUF+12),A	; 
			LD		A,'$'			;
			LD		(FILEBUF+13),A	; 
			LD		DE,FILEBUF+1	;
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;
			JP		DIRLOOP			; Jump forwards to DIR loop
PRFNF2		LD		C,B_C_WRTSTR	;
			CALL	BDOS			;
			
DIRLOOP		LD		DE,FCB2			; Default FCB address 2
			LD		C,B_F_SNEXT		;
			CALL	BDOS			;

			CP		0				;
			JP		Z,FOUND3		;
			LD		DE,SFMSGNF		;
			JP		PRFNF3			;
FOUND3		LD		A,13			; HACK to terminate string
			LD		(FILEBUF+12),A	; 
			LD		A,'$'			;
			LD		(FILEBUF+13),A	; 
			LD		DE,FILEBUF+1	;
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;
			JP		DIRLOOP			; Loop for all files in dir
PRFNF3		LD		C,B_C_WRTSTR	;
			CALL	BDOS			;
			
			;CALL	CHECKOK

			; Overwrite DMA buffer just to be sure it is read
			LD		A,'X'			;
			LD		HL,(DMAADDR)	;
			LD		(HL),A			;
			INC		HL
			LD		(HL),A			;
			INC		HL
			LD		(HL),A			;

			; Open the file

			LD		DE,OMSG			; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_OPEN		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Read from the file

			LD		DE,RMSG			; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_READ		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Print out what we just read
			LD		DE,(DMAADDR)	;
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

END

			; Close the file

			LD		DE,CLMSG		; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_CLOSE		;
			CALL	BDOS			;

			CALL	CHECKOK

			; Delete the file

			LD		DE,DMSG			; Address of string
			LD		C,B_C_WRTSTR	;
			CALL	BDOS			;

			LD		DE,FCB1			; Default FCB address
			LD		C,B_F_DELETE	;
			CALL	BDOS			;

			CALL	CHECKOK

; Read keyboard and echo to screen C_READ, C_WRITE
L2			LD		C,B_C_READ		;
			CALL	BDOS			;
			LD		E,A				; Prepare to echo keystroke
			LD		C,B_C_WRITE		;
			CALL	BDOS			;
			JP		L2				; Forever and ever

; Check an MLI call was successful and print out message accordingly
CHECKOK		LD		A,(AREG)		; Look at the return code
			CP		0				; Success?
			JP		Z,COKS1			;
			PUSH	AF				; Preserve A
			LD		DE,FAILMSG1		; Fail message
			CALL	C_WRITESTR		;
			POP		AF				; Restore A
			LD		L,A				; Copy to HL for NUM2HEX
			LD		H,0				; ...
			LD		DE,HEXBUF		; Generate hex string to HEXBUF
			CALL	NUM2HEX			; ...
			LD		A,0FFH			; 0FFH for error
			LD		L,A				; Return code in L also
			LD		DE,HEXBUF+2		; Write hex value to console
			CALL	C_WRITESTR		;
			LD		DE,FAILMSG2		; Fail message
			CALL	C_WRITESTR		;
			JP		COKS2			;
COKS1		LD		DE,SUCCMSG		; Success message
			CALL	C_WRITESTR		;
COKS2		LD		(TEMPWORD),SP	; Print out stack pointer
			LD		HL,(TEMPWORD)	;
			LD		DE,HEXBUF		; Generate hex string to HEXBUF
			CALL	NUM2HEX			;
			LD		DE,HEXBUF		;
			CALL	C_WRITESTR		;
			LD		DE,CRMSG		; Carriage return
			CALL	C_WRITESTR		;
			RET

WELCOME		DEFB	13
			DEFM	'Zapple-II Test Stub...'
			DEFB	13, '$'
			
CMSG		DEFB	13
			DEFM	'Creating & opening A/TEST.TXT'
			DEFB	13, '$'
			
WMSG		DEFB	13
			DEFM	'Writing record to A/TEST.TXT'
			DEFB	13, '$'
			
CLMSG		DEFB	13
			DEFM	'Closing A/TEST.TXT'
			DEFB	13, '$'
			
SFMSG		DEFB	13
			DEFM	'Searching directory for TEST.TXT'
			DEFB	13, '$'
			
SFMSGF		DEFB	'Found'
			DEFB	13, '$'
			
SFMSGNF		DEFB	'NOT found'
			DEFB	13, '$'
			
SFMSG2		DEFB	13
			DEFM	'Searching directory for ????????.???'
			DEFB	13, '$'
			
OMSG		DEFB	13
			DEFM	'Opening A/TEST.TXT'
			DEFB	13, '$'
			
RMSG		DEFB	13
			DEFM	'Reading record from A/TEST.TXT'
			DEFB	13, '$'
			
DMSG		DEFB	13
			DEFM	'Deleting A/TEST.TXT'
			DEFB	13, '$'
			
SUCCMSG		DEFM	'Success! SP=$'
			
FAILMSG1	DEFM	'FAIL (0x$'
			
FAILMSG2	DEFM	') SP=$'

CRMSG		DEFB	13, '$'

TEXTBUF		DEFM	'Mary had a little lamb. Its fleece was white as snow. '
			DEFM	'And everywhere that Mary went, that lamb was sure to go.$'

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Implementation of CP/M STYLE BDOS
; Function to invoke is passed in C, as follows:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
B_C_TERMCPM		EQU		00H			; System reset
B_C_READ		EQU		01H			; Console read
B_C_WRITE		EQU		02H			; Console write
B_C_RAWIO		EQU		06H			; Direct console I/O
B_GET_IOB		EQU		07H			; Get IOBYTE
B_SET_IOB		EQU		08H			; Set IOBYTE
B_C_WRTSTR		EQU		09H			; Console write string
B_C_RDSTR		EQU		0AH			; Read console string
B_C_STAT		EQU		0BH			; Console status
B_S_BDOSVER		EQU		0CH			; Return version number
B_DRV_ALLRST	EQU		0DH			; Reset disks
B_DRV_SET		EQU		0EH			; Select disk
B_F_OPEN		EQU		0FH			; Open file
B_F_CLOSE		EQU		10H			; Close file
B_F_SFIRST		EQU		11H			; Search for first match in directory
B_F_SNEXT		EQU		12H			; Search for next match in directory
B_F_DELETE		EQU		13H			; Delete file
B_F_READ		EQU		14H			; Read file sequentially
B_F_WRITE 		EQU		15H			; Write file sequentially
B_F_MAKE		EQU		16H			; Create and open file
B_F_RENAME		EQU		17H			; Rename file 
B_DRV_LOGVEC	EQU		18H			; Return bitmap of logged-in drives
B_DRV_GET		EQU		19H			; Return current drive
B_F_DMAOFF		EQU		1AH			; Set DMA address
B_DRV_AVEC		EQU		1BH			; Return address of allocation map
B_DRV_SRO		EQU		1CH			; Software write-protect current drive
B_DRV_ROVEC		EQU		1DH			; Return bitmap of read-only drives
B_DRV_DPB		EQU		1FH			; Get Drive Parameter Block address
B_F_USERNUM		EQU		20H			; Get/set user number
B_F_RDRAND		EQU		21H			; Random access read record
B_F_WRTRAND		EQU		22H			; Random access write record
B_F_SIZE		EQU		23H			; Compute file size
B_F_RANDREC		EQU		24H			; Update random access pointer
B_DRV_RESET		EQU		25H			; Selectively reset disk drives
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

			ORG		BDOSADDR

BDOSINIT	LD		SP,STCKTOP		; Initialize SP
			XOR		A				; A=0
			LD		(IOBYTE),A		; Initialize IOBYTE
			LD		(CURDRV),A		; Drive A:, User 0
			LD		(FILEBUF),A		; Zero chars in command tail
			LD		(FRN1),A		; Initialize FRNs to zero
			LD		(FRN2),A		; ...
			LD		(FRN3),A		; ...
			LD		(FRN4),A		; ...
			LD		HL,0080H		; Initialize DMAADDR to 0080H
			LD		(DMAADDR),HL	; ...
			LD		HL,0000H		; Initialize LOGVEC & ROVEC to 0000H
			LD		(LOGVEC),HL		; ...
			LD		(ROVEC),HL		; ...
			JP		PROGSTRT		; Run user program
BDOSIMP		LD		A,C				; Prepare to check C is in range
			CP		41				; Max syscall# for CP/M 2.2 is 40
			JP		NC,UNIMP		; If >41 then call UNIMP
			LD		HL,BDOSVEC		; Start of vector table
			SLA		C				; Multiply C by 2
			LD		B,0				; MSB of BC is zero
			ADD		HL,BC			; Address of vector in HL
			LD		C,(HL)			; Read LSB of address to jump to
			INC		HL				; Read MSB of address to jump to
			LD		H,(HL)			; ...
			LD		L,C				; Address needs to be in HL
			JP		(HL)			; Jump to it!

; Vector table
BDOSVEC		DEFW	C_TERMCPM		; C=00H
			DEFW	C_READ			; C=01H
			DEFW	C_WRITE			; C=02H
			DEFW	UNIMP			; C=03H  (A_READ)   AUX
			DEFW	UNIMP			; C=04H  (A_WRITE)  AUX
			DEFW	UNIMP			; C=05H  (L_WRITE)  PRN
			DEFW	C_RAWIO			; C=06H
			DEFW	GET_IOB			; C=07H
			DEFW	SET_IOB			; C=08H
			DEFW	C_WRITESTR		; C=09H
			DEFW	C_READSTR		; C=0AH
			DEFW	C_STAT			; C=0BH
			DEFW	S_BDOSVER		; C=0CH
			DEFW	DRV_ALLRST		; C=0DH
			DEFW	DRV_SET			; C=0EH
			DEFW	F_OPEN			; C=0FH
			DEFW	F_CLOSE			; C=10H
			DEFW	F_SFIRST		; C=11H
			DEFW	F_SNEXT			; C=12H
			DEFW	F_DELETE		; C=13H
			DEFW	F_READ			; C=14H
			DEFW	F_WRITE			; C=15H
			DEFW	F_MAKE			; C=16H
			DEFW	F_RENAME		; C=17H
			DEFW	DRV_LOGVEC		; C=18H
			DEFW	DRV_GET			; C=19H
			DEFW	F_DMAOFF		; C=1AH
			DEFW	DRV_AVEC		; C=1BH
			DEFW	DRV_SETRO		; C=1CH
			DEFW	DRV_ROVEC		; C=1DH
			DEFW	UNIMP			; C=1EH  (F_ATTRIB)
			DEFW	DRV_DPB			; C=1FH
			DEFW	F_USERNUM		; C=20H
			DEFW	F_READRAND		; C=21H
			DEFW	F_WRITERAND		; C=22H
			DEFW	F_SIZE			; C=23H
			DEFW	F_RANDREC		; C=24H
			DEFW	DRV_RESET		; C=25H
			DEFW	UNIMP			; C=26H  (*nothing* in CP/M 2.2)
			DEFW	UNIMP			; C=27H  (*nothing* in CP/M 2.2)
			DEFW	F_WRITERAND		; C=28H  (F_WRITEZF)

; Unimplemented BDOS call, just ring the bell
UNIMP		LD		HL,BELL			; We are going to call BELL
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD 		(SOFTCARD),A	; Do it!
			RET						; Return to calling program

; System reset.  Jump to $0000 - doesn't return
C_TERMCPM	RST		0				; Quick jump to zero

; Wait for a character from the console, return it in A and L
; Also echoes the char to the console
C_READ		LD		HL,RDKEY		; We are going to call RDKEY
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it!
			LD		A,(AREG)		; Grab the return value
			PUSH	AF				; Preserve A (and F)
			
			LD		HL,COUT			; Echo the character using COUT
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it!

			POP		AF				; Restore A (and F)
			AND		7FH				; Mask high bit
			LD		L,A				; Copy A to L
			RET						; Return to calling program

; Write character in E to the console
; TODO: Handle tabs
C_WRITE		LD		A,80H			; Set high bit
			OR		E				; ...
			CP		8AH				; Check for linefeed
			RET		Z				; If LF, don't print it
			LD		(AREG),A		; Pass char to COUT in 6502 A
			LD		HL,COUT			; We are going to call COUT
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it!
			RET						; Return to calling program

; If E if 0FFH then input a character from console and return it in A and L
; without echoing the input character. Otherwise output char in E to the
; console (no tabs, ^S or ^Q supported)
C_RAWIO		LD		A,E				; See if E if 0FFH
			CP		0FFH			; ...
			JP		Z,RIS1			; If so, then read

			; Write to console
			LD		A,80H			; Set high bit
			OR		E				; ...
			CP		8AH				; Check for linefeed
			RET		Z				; If LF, don't print it
			LD		(AREG),A		; Pass char to COUT in 6502 A
			LD		HL,COUT			; We are going to call COUT
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it!
			RET

			; If character is waiting, read from console & return in A
			; Otherwise, return 00H in A
RIS1		LD		A,3				; CMD=3 means peek at keyboard
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it
			LD		A,(AREG)		; Grab the return value
			CP		0				; If zero, no chars are waiting
			JP		Z,RIS2			; ...
			LD		HL,RDKEY		; We are going to call RDKEY
			LD		(ADDR),HL		; ...
			LD		A,1				; CMD=1 means call 6502 sub
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it!
			LD		A,(AREG)		; Grab the return value
			AND		7FH				; Mask high bit
			LD		L,A				; Copy A to L
			RET						; 
RIS2		XOR		A				; No chars waiting, A=0
			LD		L,A				; Return in L also
			RET

; Get the IOBYTE in A and L
GET_IOB		LD		A,(IOBYTE)		;
			LD		L,A				; Copy to L
			RET

; Set the IOBYTE
; E contains the IOBYTE value to set
SET_IOB		LD		A,E				;
			LD		(IOBYTE),A		;
			RET

; Write ASCII string to console. '$' is the terminator
; DE contains the address of the string
C_WRITESTR	LD		A,(DE)			; Fetch character from string
			CP		'$'				; Is it '$'?
			RET		Z				; If so, we are done
			PUSH	DE				; We are gonna need E
			LD		E,A				; For C_WRITE
			CALL	C_WRITE			; Sent char to console
			POP		DE				; Recover the pointer
			INC		DE				; Advance pointer
			JP		C_WRITESTR		; Handle the next char

; Read console string
; DE points to the string buffer. First byte of the buffer is the capacity
; of the buffer. This function writes the number of bytes written in second
; byte.  Entry finishes on CR or when the buffer is filled up.
; TODO: Line editing is supposed to be supported here
C_READSTR	LD		H,D				; HL will be the working pointer
			LD		L,E				; ...
			INC		HL				; Advance to first character ...
			INC		HL				; ... 3rd byte of the buffer
			PUSH	DE				; Put DE into IX
			POP		IX				; ...
			XOR		A				; Set number of chars read to zero
			LD		(IX+1),A		; ...
CRSL1		PUSH	HL				; Preserve HL
			CALL	C_READ			; Read a character into A
			POP		HL				; Restore HL
			CP		13				; Carriage return?
			RET		Z				; If so, we are done
			CP		10				; Line feed?
			RET		Z				; If so, we are done
			LD		B,A				; Stash character in B
			LD		A,(IX+0)		; Buffer capacity -> A
			SUB		(IX+1)			; Subtract characters read
			CP		0				; If no space left ...
			RET		Z				;  ... we are done
			LD		(HL),B			; Write character to buffer
			INC		HL				; Advance to next character
			INC		(IX+1)			; Increment character count
			JP		CRSL1			; Loop
			RET

; Returns 0 in A and L if no chars waiting, non zero otherwise
C_STAT		LD		A,3				; CMD=3 means peek at keyboard
			LD		(CMD),A			; ...
			LD		(SOFTCARD),A	; Do it
			LD		A,(AREG)		; Grab the return value
			LD		L,A				; Copy A to L
			RET

; Returns system type in B and H, BDOS version in A and L
S_BDOSVER	LD		B,0				; System is 8080 CP/M
			LD		H,B				; Also in H
			LD		A,22H			; Pretend to v2.2
			LD		L,A				; Also in A
			RET

; Reset disks
; Makes A: drive the default
DRV_ALLRST	LD		A,(CURDRV)		; Contains both user & current drive
			AND		0F0H			; Set drive to 0, meaning A:
			LD		(CURDRV),A		; Store in CURDRV
			LD		BC,FILEBUF		; FILEBUF is at 0080H
			LD		(DMAADDR),BC	; Reset DMA address
			LD		HL,FLMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI to flush all files
			RET

; Select disk
; Disk to select is passed in E (A: is 0, B: is 1 etc.)
; Return 00 for success, 0FFH for error in A and L
DRV_SET		LD		A,E				; Prepare to compare disk number
			CP		16				; Support 16 'drives' A: - P:
			JP		NC,DSERR		; If A>15 ... error
			LD		B,A				; Stash in B for now
			LD		A,(CURDRV)		; Has both user number & current drive
			AND		0F0H			; Mask out old drive number
			OR		B				; Replace with new drive number
			LD		(CURDRV),A		; Store the requested drive number
			XOR		A				; A=0: Return code meaning success
			JP		DSRET			; 
DSERR		LD		A,0FFH			; Return code for error
DSRET		LD		L,A				; Return code in L too
			RET

; Open file
; DE is the address of the FCB describing the file to open
; Returns error codes in A and L:
; Returns 0 for success.  The FCB for the file opened is left at DMAADDR (slot 0)
; Returns 0FFH if file not found
; TODO: F_OPEN should use the record count field of the FCB and (if non zero) seek
; to appropriate point in the file
F_OPEN		PUSH	DE				; Preserve pointer to FCB
			CALL	F_SFIRST		; Find first matching directory entry
			POP		DE				; Restore pointer to FCB

; Alternative entrypoint used for opening ProDOS directory file only
_F_OPEN		LD		IX,PATHBUF		; Destination buffer
			CALL	FCB2PATH		; Populate PATHLEN and PATH

			PUSH	DE				; Copy pointer to FCB ...
			POP		IY				; ... into IY

			; Work out which IOBUF to allocate for this file
			XOR		A				; Looking for FRN slot with value 0
			CALL	GETIOADDR		; Returns FRN slot in A, IOBUF in HL
			CP		0FFH			; Check for error
			JP		Z,FOERR			; If no slots available, error out

			LD		(TEMPBYTE),A	; Record the buffer index in local var
			LD		BC,OFFSET		; Add offset to convert to 6502 address
			ADD		HL,BC			; ...
			LD		(FOMLII),HL		; Store in parameter list

			LD		HL,FOMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FOERR		; Handle error

			; Store ProDOS FRN in S2 field of FCB
			LD		A,(FOMLIN)		; Get ProDOS file reference number
			LD		(IY+0EH),A		; Store file reference number in S2 field

			; ProDOS GET_EOF call
			; Assumes no files > 64K on ProDOS filesystem
			LD		(GEMLIN),A		; Store file ref num in param list
			LD      HL,GEMLI       ; Pass address of 6502 JSR instruction
			CALL    PRODOS          ; Invoke ProDOS MLI (GET_EOF)

			; Convert length in bytes to length in records
			LD		HL,(GEMLIE2)	; Load 16 bit length
			CALL	LEN2RECS		; Leaves number of records in A

			; Store records used
			LD		(IY+0FH),A		; Set records used field

			; Set sequential record number to zero
			XOR		A				; Zero the sequential record number
			LD		(IY+20H),A		; ...

			; Store ProDOS FRN in slot FRN1 - FRN4
			LD		A,(TEMPBYTE)	; Obtain IOBUF idx (1,2,3,4)
			LD		HL,FRN1-1		; Compute address of FRN slot to use
			LD		B,0				; ...
			LD		C,A				; ...
			ADD		HL,BC			; ...
			LD		A,(FOMLIN)		; Get ProDOS file reference number
			LD		(HL),A			; Store in FRN slot

			XOR		A				; Success
			LD		L,A				; Copy to L
			RET						; Done

FOERR		LD		A,0FFH			; Error return status
			LD		L,A				; Copy to L
			RET						; Done (error)

; Close file
; DE is the address of the FCB describing the file to close
; Returns error codes in A and L:
F_CLOSE		LD		H,D				; Pointer to FCB ...
			LD		L,E				; ... into HL
			LD		BC,0EH			; Offset to S2 field (reserved field)
			ADD		HL,BC			; Compute address
			LD		A,(HL)			; Obtain file reference num from FCB S2
			CP		0				; If file reference number is zero ...
			JP		Z,FCSUCC		; ... Nothing to do, just return
			LD		(FCMLIN),A		; Store in parameter list
			LD		HL,FCMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FCERR		; Handle error

			LD		A,(FCMLIN)		; Obtain file reference number again
			CALL	GETIOADDR		; Returns FRN slot in A, IOBUF in HL
			CP		0FFH			; Check for error
			JP		Z,FCERR			; If FRN not found, error out

			LD		HL,FRN1-1		; Compute addr of FRN slot to set to zero
			LD		B,0				; ...
			LD		C,A				; ...
			ADD		HL,BC			; ...
			XOR		A				; And zero it
			LD		(HL),A			; ...

			PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ... into IX
			XOR		A				; Zero out the S2 field
			LD		(IX+0EH),A		; ...

FCSUCC		XOR		A				; Return zero for error
			LD		L,A				; Return in L also
			RET

FCERR		LD		A,0FFH			; 0FFH for error
			LD		L,A				; Return code in L also
			RET

DIRHDSZ		EQU		2BH				; Size of ProDOS directory header
FILEENTSZ	EQU		27H				; Size of ProDOS file entry
ENTPERBLK	EQU		0DH				; Number of file entries per block

; Search for first match of filename in directory
; DE is the address of the FCB describing the file to look for
; Returns error codes in A and L: 0 for success, 0FFH for not found
; The matching FCB is always in slot 0, so success return code always 0
; TODO: Should handle '?' in extent field also
F_SFIRST 	LD		(TEMPWORD),DE	; Store pointer to search FCB
			LD		A,(DE)			; Obtain drive number
			LD		(DFCBDRV),A		; Copy to directory FCB
			LD		DE,DFCB			; Use this FCB to open the directory
			CALL	F_CLOSE			; Close the directory, if open
			LD		DE,DFCB			; Use this FCB to open the directory
			CALL	_F_OPEN			; Open the directory (avoiding recursion!)

FSFL1		CALL	RDDIRBLK		; Read first 512 byte block
			CP		0				; See if it was an error
			JP		NZ,FSFS2		; If error, assume EOF & just return

			LD		HL,DIRBUF		; Skip over directory header
			LD		BC,DIRHDSZ		; ...
			ADD		HL,BC			; ...
			LD		(CDBPTR),HL		; Start out at first file entry
			XOR		A				; Set file count to zero
			LD		(CDBCOUNT),A	; ...

			LD		DE,(TEMPWORD)	; Get ptr to search FCB back
			CALL	CHKDIRBLK		; Search directory block
			CP		0				; See if it was a match
			JP		Z,FSFS1			; If so, return
			JP		FSFL1			; Loop

FSFS1		XOR		A				; Match
			RET						;
FSFS2		LD		A,0FFH			; No match
			RET

; Search for next match of filename in directory
; DE is the address of the FCB describing the file to look for
; Returns error codes in A and L: 0 for success, 0FFH for not found
; The matching FCB is always in slot 0, so success return code always 0
; TODO: Should handle '?' in extent field also
F_SNEXT		LD		(TEMPWORD),DE	; Store pointer to search FCB
			LD		HL,(CDBPTR)		; Pointer into current block
			LD		A,(CDBCOUNT)	; File count for current block
FSNL1		CALL	CHKDIRBLK		; Search directory block
			CP		0				; See if it was a match
			JP		Z,FSNS1			; If so, return

			CALL	RDDIRBLK		; Read next 512 byte block
			CP		0				; See if it was an error
			JP		NZ,FSNS2		; If error, assume EOF & just return

			LD		HL,DIRBUF		; Skip over directory header
			LD		BC,DIRHDSZ		; ...
			ADD		HL,BC			; ...
			LD		(CDBPTR),HL		; Start out at first file entry
			XOR		A				; Set file count to zero
			LD		(CDBCOUNT),A	; ...

			JP		FSNL1			; Loop

FSNS1		XOR		A				; Match
			RET						;
FSNS2		LD		A,0FFH			; No match
			RET

; Delete file
; DE is the address of the FCB describing the file to delete
; Returns error codes in A and L:
F_DELETE	CALL	F_SFIRST		; Search for file, create FCB
			CP		0FFH			; If not found ...
			JP		Z,FDERR			; ... Return with error
			LD		IX,PATHBUF		; Destination buffer
			CALL	FCB2PATH		; Populate PATHLEN and PATH
			LD		HL,FDMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FDERR		; Handle error
			LD		L,A				; ... and L too
			RET
FDERR		LD		A,0FFH			; 0FFH for error
			LD		L,A				; Return code in L also
			RET

; Read next record
; DE is the address of the FCB describing the file from which to read
; Returns error codes in A and L:
; 0 OK, 1 EOF, 9 invalid FCB, 10 media changed, 0FFH h/w error
F_READ		PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ... into IX
			LD		A,(IX+0EH)		; Obtain file reference num from FCB S2
			LD		(SMMLIN),A		; Store in parameter list for SET_MARK
			LD		(FRMLIN),A		; Store in parameter list for READ

			LD		A,(IX+20H)		; Obtain sequential record number
			LD		B,(IX+0CH)		; Obtain extent from FCB
			CALL	EXRC2LEN		; Leaves the length in bytes in HL
			LD		(SMMLIP1),HL	; Write 16 bit length in FRMLIP1,FRMLIP2
			XOR		A				; Set FRMLIP3 to zero
			LD		(SMMLIP3),A		; ...
			LD		HL,SMMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - SET_MARK
			CP		4DH				; See if position was out of range
			JP		Z,FRBFCB		; If so, return invalid FCB code (9)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FRBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FRERR		; If so, return code 0FFH (h/w error)

			LD		HL,(DMAADDR)	; Read from DMA buffer address
			LD		BC,OFFSET		; Convert to 6502 address
			ADD		HL,BC			; ...
			LD		(FRMLIDB),HL	; Store I/O buffer address in parm list

			LD		HL,FRMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - READ
			CP		4CH				; See if it was EOF
			JP		Z,FREOF			; If so, return EOF code (1)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FRBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FRERR		; If so, return code 0FFH (h/w error)

			LD		A,(IX+20H)		; Get sequential rec num from FCB
			INC		(IX+20H)		; Increment sequential record number
			CP		129				; Is it 129? 128 is the max
			JP		NZ,FRS1			; If not, then nothing else to do
			XOR		A				; Set sequential rec num to zero
			LD		(IX+20H),A		; ...
			INC		(IX+0CH)		; Increment the extent

FRS1		XOR		A				; Zero for success
			LD		L,A				; Return code in L also
			RET						; Done
FREOF		LD		A,1				; EOF return code
			LD		L,A				; Return code in L also
			RET						; Done (EOF)
FRBFCB		LD		A,9				; Invalid FCB return code
			LD		L,A				; Return code in L also
			RET						; Done (Bad FCB)
FRERR		LD		A,0FFH			; All other errors are 0FFH
			LD		L,A				; Return code in L aslo
			RET						; Done (error)

; Write next record
; DE is the address of the FCB describing the file to which to write
; Returns error codes in A and L:
; 0 OK, 1 dir full, 2 disk full, 9 invalid FCB, 10 media changed, 0FFH h/w error
F_WRITE		PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ... into IX
			LD		A,(IX+0EH)		; Obtain file reference num from FCB S2
			LD		(SMMLIN),A		; Store in parameter list for SET_MARK
			LD		(FWMLIN),A		; Store in parameter list for WRITE

			LD		A,(IX+20H)		; Obtain sequential record number
			LD		B,(IX+0CH)		; Obtain extent from FCB
			CALL	EXRC2LEN		; Leaves the length in bytes in HL

;;			; DEBUG
;;			PUSH	HL
;;			LD		DE,HEXBUF		; Generate hex string to HEXBUF
;;			CALL	NUM2HEX			; ...
;;			LD		DE,HEXBUF		; Write hex value to console
;;			CALL	C_WRITESTR		;
;;			POP		HL
;;			; END DEBUG

			LD		(SMMLIP1),HL	; Write 16 bit length in SMMLIP1,SMMLIP2
			XOR		A				; Set SMMLIP3 to zero
			LD		(SMMLIP3),A		; ...
			LD		HL,SMMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - SET_MARK
			CP		4DH				; See if position was out of range
			JP		Z,FWBFCB		; If so, return invalid FCB code (9)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FWBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FWERR		; If so, return code 0FFH (h/w error)

			LD		HL,(DMAADDR)	; Write data at DMA address
			LD		BC,OFFSET		; Convert to 6502 address
			ADD		HL,BC			; ...
			LD		(FWMLIDB),HL	; Store I/O buffer address in parm list

			LD		HL,FWMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - WRITE
			CP		43H				; See if it is a bad reference number
			JP		Z,FWBFCB		; If so, return invalid FCB code (9)
			CP		48H				; See if it was an overrun error
			JP		Z,FWDF			; If so, return disk full code (2)
			CP		0				; See if there was some other error
			JP		NZ,FWERR		; If so, return code 0FFH (h/w error)

			LD		A,(IX+20H)		; Get sequential rec num from FCB
			INC		(IX+20H)		; Increment sequential record number
			CP		129				; Is it 129? 128 is the max
			JP		NZ,FWS1			; If not, then nothing else to do
			XOR		A				; Set sequential rec num to zero
			LD		(IX+20H),A		; ...
			INC		(IX+0CH)		; Increment the extent

FWS1		XOR		A				; Zero for success
			LD		L,A				; Return code in L also
			RET						; Done
FWBFCB		LD		A,9				; Invalid FCB return code
			LD		L,A				; Return code in L also
			RET						; Done (EOF)
FWDF		LD		A,2				; Disk full return code
			LD		L,A				; Return code in L also
			RET						; Done (Disk Full)
FWERR		LD		A,0FFH			; All other errors are 0FFH
			LD		L,A				; Return code in L aslo
			RET						; Done (error)

; Create (and open) file
; DE is the address of the FCB describing the file to create
; Returns error codes in A and L:
; 0 for success, 0FFH if file could not be created
F_MAKE		LD		IX,PATHBUF		; Destination buffer
			CALL	FCB2PATH		; Populate PATHLEN and PATH
			LD		HL,FMMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FMERR		; Handle error
			CALL	F_OPEN			; Open the file using same FCB (DE ptr)
			RET						; Return with status from F_OPEN
FMERR		LD		A,0FFH			; 0FFH for error
			LD		L,A				; Return code in L also
			RET

; Rename file
; DE is the address of the FCB describing the file to be renamed. The new name
; is stuffed into FCB+16 (where the allocation map usually goes)
; Returns error codes in A and L - 0 for success, 0FFH for file not found
F_RENAME	CALL	F_SFIRST		; Search for file, create FCB
			CP		0FFH			; If not found ...
			JP		Z,FRNERR		; ... Return with error
			LD		IX,PATHBUF		; Destination buffer 1
			CALL	FCB2PATH		; Populate PATHLEN and PATH for first file
			LD		IX,PATHBUF2		; Destination buffer 2
			LD		H,D				; DE -> HL for addition
			LD		L,E				; ...
			LD		BC,16			; Increment by 16 bytes to 2nd part of FCB
			ADD		HL,BC			; ...
			LD		D,H				; HL back to DE
			LD		E,L				; ...
			CALL	FCB2PATH		; Populate PATHLEN and PATH for second file
			LD		HL,FRNMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FRNERR		; Handle error
			XOR		A				; Success
			LD		L,A				; Return code in L also
			RET
FRNERR		LD		A,0FFH			; 0FFH for error
			LD		L,A				; Return code in L also
			RET

; Return bitmap of logged-in drives in HL
DRV_LOGVEC	LD		HL,(LOGVEC)		;
			RET

; Return current drive in A
DRV_GET		LD		A,(CURDRV)		; Contains user number & current drive
			AND		0FH				; Mask out user number
			RET

; Set DMA address
; DMA address is passed in DE
F_DMAOFF	LD		(DMAADDR),DE	;
			RET

; Return address of allocation map in HL
DRV_AVEC	LD		HL,ALLOCVEC		;
			RET

; Software write-protect current disk
DRV_SETRO	LD		B,80H			; Set MS-bit in B, will rotate this below
			LD		A,(CURDRV)		; Current drive (0 A:, 1 B: ...)
			AND		0FH				; Mask out user number
			INC		A				; It is easier if A: is 1, B is 2 etc.
			CP		9				; See if it in LS-byte or MS-byte of ROVEC
			JP		NC,DSRMSB		; If A>8 then drive bit in in MS-byte
DSRL1		RL		B				; 
			DEC		A				;
			JP		NZ,DSRL1		;
			LD		A,(ROVEC)		; Fetch the LS-byte of ROVEC
			OR		B				; Set the bit using OR
			LD		(ROVEC),A		; Store LS-byte back to ROVEC
			RET						; We're done
DSRMSB		LD		C,8				; Subtract 8 from the drive number
			SUB		C				; A = A-8
DSRL2		RL		B				;
			DEC		A				;
			JP		NZ,DSRL2		;
			LD		A,(ROVEC+1)		; Fetch the MS-byte of ROVEC
			OR		B				; Set the bit using OR
			LD		(ROVEC+1),A		; Store MS-byte back to ROVEC
			RET

; Return bitmap of read-only drives in HL
DRV_ROVEC	LD		HL,(ROVEC)		; Bit 0 of L is A:, bit 7 of H is P:
			RET

; Return pointer to Drive Parameter Block in HL
DRV_DPB		LD		HL,DPB			; Pointer to drive parameter block
			RET

; Get/set user number
; E contains the user number to set, or 0FFH to get current user number
; If E is 0FFH then user number is returned in A
F_USERNUM	LD		A,E				; See if it is get or set
			CP		0FFH			; 0FFH means 'get'
			JP		Z,FUNS1			; It is 'get'
			LD		B,A				; Stash the user number to set in B
			SLA		B				; Left shift four times
			SLA		B				; ...
			SLA		B				; ...
			SLA		B				; ...
			LD		A,(CURDRV)		; Contains user number & current drive
			AND		0FH				; Mask out current user number
			OR		B				; OR in the new user number
			LD		(CURDRV),A		; Store updated user number & curr drv
			RET						;
FUNS1		LD		A,(CURDRV)		; Contains user number & current drive
			AND		0F0H			; Mask out current drive
			SRA		A				; Right shift the user number 4 times
			SRA		A				; ...
			SRA		A				; ...
			SRA		A				; ...
			RET

; Random access read record
; DE contains address of FCB describing the file to read
; Return code in A and L:
; 0 success, 1 reading unwritten data, 4 reading unwritten extent,
; 6 rec number out of range, 9 invalid FCB, 10 media changed, 0FFH h/w err
F_READRAND	PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ...
			LD		A,(IX+0EH)		; Obtain file reference num from FCB S2
			LD		(SMMLIN),A		; Store in parameter list for SET_MARK
			LD		(FRMLIN),A		; Store in parameter list for READ

			LD		L,(IX+21H)		; Load LSB of random record number
			LD		H,(IX+22H)		; Load MSB of random record number
			CALL	RRN2LEN			; Leaves the length in bytes in HL
			LD		(SMMLIP1),HL	; Write 16 bit length in FRMLIP1,FRMLIP2
			XOR		A				; Set FRMLIP3 to zero
			LD		(SMMLIP3),A		; ...
			LD		HL,SMMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - SET_MARK
			CP		4DH				; See if position was out of range
			JP		Z,FRRBFCB		; If so, return invalid FCB code (9)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FRRBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FRRERR		; If so, return code 0FFH (h/w error)

			LD		HL,(DMAADDR)	; Read from DMA buffer address
			LD		BC,OFFSET		; Convert to 6502 address
			ADD		HL,BC			; ...
			LD		(FRMLIDB),HL	; Store I/O buffer address in parm list
			LD		HL,FRMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - READ
			CP		4CH				; See if it was EOF
			JP		Z,FRREOF		; If so, return EOF code (1)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FRBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FRRERR		; If so, return code 0FFH (h/w error)

			LD		L,(IX+21H)		; Load LSB of random record number
			LD		H,(IX+22H)		; Load MSB of random record number
			CALL	RECS2EXRC		; Puts extent in B, recs in A
			LD		A,(IX+20H),A	; Update sequential record number
			LD		B,(IX+0CH),B	; Update sequential extent number

			XOR		A				; Zero for success
			LD		L,A				; Return code in L also
			RET						; Done
FRREOF		LD		A,1				; EOF return code
			LD		L,A				; Return code in L also
			RET						; Done (EOF)
FRRBFCB		LD		A,9				; Invalid FCB return code
			LD		L,A				; Return code in L also
			RET						; Done (Bad FCB)
FRRERR		LD		A,0FFH			; All other errors are 0FFH
			LD		L,A				; Return code in L aslo
			RET						; Done (error)

; Random access write record
; DE contains address of FCB describing the file to write
; Return code in A and L:
; 0 success, 1 reading unwritten data, 4 reading unwritten extent,
; 6 rec number out of range, 9 invalid FCB, 10 media changed, 0FFH h/w err
F_WRITERAND	PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ...
			LD		A,(IX+0EH)		; Obtain file reference num from FCB S2
			LD		(GEMLIN),A		; Store in parameter list for GET_EOF
			LD		(SEMLIN),A		; Store in parameter list for SET_EOF
			LD		(SMMLIN),A		; Store in parameter list for SET_MARK
			LD		(FWMLIN),A		; Store in parameter list for WRITE

			LD		HL,GEMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - GET_EOF
		
			LD		L,(IX+21H)		; Load LSB of random record number
			LD		H,(IX+22H)		; Load MSB of random record number
			CALL	RRN2LEN			; Leaves the length in bytes in HL
			LD		(SMMLIP1),HL	; 16 bit len in SMMLIP1,2 for SET_MARK
			XOR		A				; Set SMMLIP3 to zero
			LD		(SMMLIP3),A		; ...

			LD		HL,(GEMLIE1)	; Load current EOF into HL
			LD		BC,(SMMLIP1)	; Load requested offset into BC
			AND		A				; Clear carry
			SBC		HL,BC			; Subtract requested byte offset from EOF
			JP		NC,FWRS1		; If >=0 no need to SET_EOF

			LD		(SEMLIE1),BC	; Requested offset for SET_EOF
			LD		HL,SEMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - SET_EOF

FWRS1		LD		HL,SMMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - SET_MARK
			CP		4DH				; See if position was out of range
			JP		Z,FWRBFCB		; If so, return invalid FCB code (9)
			CP		43H				; See if it was a bad file ref number
			JP		Z,FWRBFCB		; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FWRERR		; If so, return code 0FFH (h/w error)

			LD		HL,(DMAADDR)	; Get DMA buffer address
			LD		BC,OFFSET		; Convert to 6502 address
			ADD		HL,BC			; ...
			LD		(FWMLIDB),HL	; Store I/O buffer address in parm list
			LD		HL,FWMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI - WRITE
			CP		43H				; See if it was a bad file ref number
			JP		Z,FWRBFCB		; If so, return invalid FCB code (9)
			CP		48H				; See if it was a bad file ref number
			JP		Z,FWRDF			; If so, return invalid FCB code (9)
			CP		0				; See if there was some other error
			JP		NZ,FWRERR		; If so, return code 0FFH (h/w error)

			LD		L,(IX+21H)		; Load LSB of random record number
			LD		H,(IX+22H)		; Load MSB of random record number
			CALL	RECS2EXRC		; Puts extent in B, recs in A
			LD		A,(IX+20H),A	; Update sequential record number
			LD		B,(IX+0CH),B	; Update sequential extent number

			XOR		A				; Zero for success
			LD		L,A				; Return code in L also
			RET						; Done
FWRBFCB		LD		A,9				; Invalid FCB return code
			LD		L,A				; Return code in L also
			RET						; Done (Disk Full)
FWRDF		LD		A,2				; Disk fill return code
			LD		L,A				; Return code in L also
			RET						; Done (Bad FCB)
FWRERR		LD		A,0FFH			; All other errors are 0FFH
			LD		L,A				; Return code in L aslo
			RET						; Done (error)


; Compute file size
; DE contains address of FCB describing the file
; Error codes are returned in A and L (0 for success, 0FFH if file not found)
; Returns the number of 128 byte records in random record count field of FCB
F_SIZE		CALL	FCB2PATH		; Populate PATHLEN and PATH
			LD		HL,GFIMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,FSERR		; Handle error
			LD		HL,(GFIMLIBU)	; Obtain the blocks used field
			ADD		HL,HL			; Mult x 4 to get 128 byte records
			ADD		HL,HL			; ...

			; Store records used in R0,R1 fields of FCB
			PUSH	DE				; Copy DE ...
			POP		IX				; ... into IX
			LD		(IX+21H),L		; Store LSB of recs used in R0
			LD		(IX+22H),H		; Store LSB of recs used in R1
			XOR		A				; Store zero in R2
			LD		(IX+23H),A		; ...

			XOR		A				; Success
			LD		L,A				; Return in L also
			RET
FSERR		LD		A,0FFH			; File not found
			LD		L,A				; Return in L also
			RET

; Update random access pointer
; DE contains the pointer to the FCB to update
; Sets the random access record of the FCB to the value of the last record
; read or written sequentially
F_RANDREC	PUSH	DE				; Copy pointer to FCB ...
			POP		IX				; ... into IX
			LD		A,(IX+20H)		; Obtain sequential record number
			LD		B,(IX+0CH)		; Obtain extent from FCB
			CALL	EXRC2RECS		; Leaves the length in records in HL
			DEC		HL				; Because F_READ/F_WRITE advance this
			LD		(IX+21H),L		; Store in random access pointer ...
			LD		(IX+22H),H		; ... In little endian format
			RET

; Selectively reset disk drives
; DE contains bitmap of drives to reset (bit 0 of E if A:, bit 7 of D is P:)
; Returns A=00H if okay, A=FFH if error
; Resetting means removing the read-only status
DRV_RESET	LD		A,(ROVEC)		; Do the LSB ...
			XOR		E				; ... with E
			LD		(ROVEC),A		;
			LD		A,(ROVEC+1)		; Then the MSB ...
			XOR		D				; ... with D
			LD		(ROVEC+1),A		;
			RET

; Make a ProDOS MLI call
; Address of 6502 JSR instruction in front of ProDOS parameter list is
; passed in in register pair HL, in Z80 address space
; Return code is passed back in A
PRODOS		LD		BC,OFFSET		; Add offset to convert Z80->6502 address
			ADD		HL,BC			; ...
			LD		(ADDR),HL		; Store it for 6502
			LD		A,2				; CMD=2 means ProDOS MLI call
			LD		(CMD),A			; ...
			LD 		(SOFTCARD),A	; Do it!
			LD		A,(AREG)		; Get return code from the MLI call
			RET

; Populate the PATH buffer (and PATHLEN) by copying from FCB
; If the FCB contains A:TEST____.TXT then the PATH buffer will be A/TEST.TXT
; DE contains a pointer to the FCB
; IX contains pointer to the path buffer into which to write
FCB2PATH	PUSH	IX				; Copy IX->IY
			POP		IY				; So IY keeps track of size byte at start
			INC		IX				; Advance past the size byte before writing
			LD		A,(DE)			; Get drive number from FCB
			CP		0				; See if it is zero (default drive)
			JP		NZ,F2PS1		; If drive explicit
			LD		A,(CURDRV)		; If default drive use CURDRV
			AND		0FH				; Mask out user number
			INC		A				; CURDRV is zero based
F2PS1		ADD		A,'A'-1			; Convert to drive letter
			LD		(IX+0),A		; Store as first char of path
			INC		IX				; Advance IX to next char of path to write
			LD		A,'/'			; Second char of path is '/'
			LD		(IX+0),A		; Store as second char of path
			INC		IX				; Advance IX to next char of path to write
			LD		C,2				; Use C to count chars in filename
			LD		H,D				; Copy address of FCB from DE ...
			LD		L,E				; ... to HL
			INC		HL				; HL points to filename in FCB

			LD		A,(HL)			; First character of filename
			CP		' '				; Is it space? ie: no file specified
			JP		Z,F2PS6			; Don't handle filename or extension

F2PL1		; Handle the filename - up to 8 characters
			LD		A,(HL)			; Obtain filename character
			CP		' '				; See if it is a space
			JP		Z,F2PS3			; If so we are done with filename
			EX		AF,AF'			; We need to re-use A here
			LD		A,C				; Get character count
			CP		10				; Drive letter, slash and 8 char filename
			JP		Z,F2PS2			; If so we are done with filename
			EX		AF,AF'			; Swap back to original A reg
			LD		(IX+0),A		; Copy to PATH buffer
			INC		C				; Increment filename char count
			INC		HL				; Next byte of filename in FCB
			INC		IX				; Next byte of PATH buffer
			JP		F2PL1			; Loop till done

F2PS2		EX		AF,AF'			; Swap back to original A reg

F2PS3		; Eat any space characters at end of filename
F2PL2		LD		A,(HL)			; Read next character from FCB
			CP		' '				; Is it space?
			JP		NZ,F2PS4		; If not, we are done eating!
			INC		HL				; Otherwise advance to next char
			JP		F2PL2			; And loop

F2PS4		LD		A,'.'			; Separator is a period
			LD		(IX+0),A		; Write to buffer
			INC		C				; Count the character!
			INC		IX				; Advance to next character in buffer
			LD		B,0				; Use B to track num chars in extension

			; Handle the extension - up to 3 characters
F2PL3		LD		A,(HL)			; Obtain extension character
			CP		' '				; See if it is a space (? or NULL maybe?)
			JP		Z,F2PS6			; If so we are done with extension
			EX		AF,AF'			; We need to re-use A here
			LD		A,B				; Get character count
			CP		3				; Extension can be up to 3 chars
			JP		Z,F2PS5			; If so we are done with filename
			EX		AF,AF'			; Swap back to original A reg
			LD		(IX+0),A		; Copy to PATH buffer
			INC		C				; Count the chars (overall)
			INC		B				; Count the chars (in extension)
			INC		HL				; Next byte of filename in FCB
			INC		IX				; Next byte of PATH buffer
			JP		F2PL3			; Loop till done

F2PS5		EX		AF,AF'			; Swap back to original A reg

F2PS6		LD		A,C				; Store length of string
			LD		(IY+0),A		; We kept size byte in IY at start
			RET						;

; This operation is almost the inverse of FCB2PATH.  It takes a pointer to the
; beginning of the ProDOS dirent and converts it to FCB format (8.3 with
; spaces for any unused characters.)
; HL points to the file entry in the ProDOS directory
; B contains the drive number (1 for A:, 2 for B: etc)
; The FCB is written to the buffer pointed to by DMAADDR
; Trashes pretty much all registers (except IX, IY)
PATH2FCB	EX		DE,HL			; Stash HL in DE so we can use HL here

			LD		HL,(DMAADDR)	; Set all 32 bytes to FCB to zero
			LD		C,0				; ...
			XOR		A				; ...
P2FL1		LD		(HL),C			; ...
			INC		HL				; ...
			INC		A				; ...
			CP		32				; ...
			JP		NZ,P2FL1		; ...

			LD		HL,(DMAADDR)	; Set all filename chars in FCB to space
			INC		HL				; ...
			LD		C,' '			; ...
			XOR		A				; ...
P2FL2		LD		(HL),C			; ...
			INC		HL				; ...
			INC		A				; ...
			CP		8+3				; ...
			JP		NZ,P2FL2		; ...

			EX		DE,HL			; Get file entry pointer back in HL
	
			LD		A,(HL)			; Obtain first char of ProDOS dirent
			AND		0FH				; Mask to obtain length of the name
			LD		C,A				; Stash source character count in C
			LD		DE,(DMAADDR)	; Initialize DE as write pointer
			LD		A,B				; Move drive number to A
			LD		(DE),A			; Write drive number
			LD		B,0				; Use B to count chars written
P2FL3		INC		HL				; Advance source pointer
			INC		DE				; Advance destination pointer
			LD		A,C				; Get count of chars remaining
			CP		0				; If none left ...
			JP		Z,P2FS3			; We are done
			LD		A,B				; Get count of chars written
			CP		8+3				; If 8+3 chars have been written ...
			JP		Z,P2FS3			; We are done
			LD		A,(HL)			; Read character
			CP		'.'				; See if it is a period
			JP		Z,P2FS2			; Prepare to copy the extension
			LD		(DE),A			; Write character
			INC		B				; Increment count of chars written
P2FS1		DEC		C				; Decrement count of chars remaining
			JP		P2FL3			; Loop

			; Initialize DE, B to start processing the extension
P2FS2		LD		DE,(DMAADDR)	; Destination is start of extension
			INC		DE				;
			INC		DE				;
			INC		DE				;
			INC		DE				;
			INC		DE				;
			INC		DE				;
			INC		DE				;
			INC		DE				;
			LD		B,8				; 8 chars have been written
			JP		P2FS1			; Jump back into the read-write loop

			; Handle file size info
P2FS3		LD		DE,(DMAADDR)	; Pointer to start of FCB
			LD		IX,PATHBUF		; Destination buffer
			CALL	FCB2PATH		; Populate PATHLEN and PATH from new FCB
			LD		HL,GFIMLI		; Pass address of 6502 JSR instruction
			CALL	PRODOS			; Invoke ProDOS MLI
			CP		0				; See if there was an error
			JP		NZ,P2FERR		; Handle error
			LD		HL,(GFIMLIBU)	; Obtain the blocks used field
			ADD		HL,HL			; Mult x 4 to get 128 byte records
			ADD		HL,HL			; ...
			CALL	RECS2EXRC		; Puts extent in B, recs in A
			LD		DE,(DMAADDR)	; Pointer to start of FCB
			PUSH	DE				; Copy into IX
			POP		IX				; ...
			LD		(IX+0CH),B		; Store num extents in EX field of FCB
			LD		(IX+0FH),A		; Store num recs in RC field of FCB
			RET	
P2FERR		LD		DE,(DMAADDR)	; Pointer to start of FCB
			PUSH	DE				; Copy into IX
			POP		IX				; ...
			LD		A,0				; If error, set num extents to zero
			LD		(IX+0CH),A		; Store in EX field of FCB
			LD		A,0				; If error, set record count to zero
			LD		(IX+0FH),A		; Store in RC field of FCB
			RET	

; Read 512 byte block of directory
; Used by F_SFIRST and F_SNEXT
; Trashes HL + registers trashed by F_READ (best to assume all of them!)
; Returns A=0 for success, A=0FFH on error
RDDIRBLK	LD		HL,(DMAADDR)	; Save existing DMA address
			PUSH	HL				; ...

			; Read first 512 byte block of directory
			LD		DE,DFCB			; Use this FCB to open the directory
			LD		HL,DIRBUF1		; Set DMAADDR to point to DIRBUF1
			LD		(DMAADDR),HL	; ...
			CALL	F_READ			; Read first record of directory
			CP		0				; See if there was an error
			JP		NZ,RDBS1		; If so, quit with error code

			LD		DE,DFCB			; Use this FCB to open the directory
			LD		HL,DIRBUF2		; Set DMAADDR to point to DIRBUF2
			LD		(DMAADDR),HL	; ...
			CALL	F_READ			; Read second record of directory
			CP		0				; See if there was an error
			JP		NZ,RDBS1		; If so, quit with error code

			LD		DE,DFCB			; Use this FCB to open the directory
			LD		HL,DIRBUF3		; Set DMAADDR to point to DIRBUF3
			LD		(DMAADDR),HL	; ...
			CALL	F_READ			; Read third record of directory
			CP		0				; See if there was an error
			JP		NZ,RDBS1		; If so, quit with error code

			LD		DE,DFCB			; Use this FCB to open the directory
			LD		HL,DIRBUF4		; Set DMAADDR to point to DIRBUF4
			LD		(DMAADDR),HL	; ...
			CALL	F_READ			; Read fourth record of directory
			CP		0				; See if there was an error
			JP		NZ,RDBS1		; If so, quit with error code

			XOR		A				; Return code for success
			JP		RDBS2			; Successful return

RDBS1		LD		A,0FFH			; Error return code

RDBS2		POP		HL				; Reset DMA address as we found it
			LD		(DMAADDR),HL	; ...
			RET

; Match FCBs
; Used by CHKDIRENT
; DE is the address of the FCB describing the file to look for
; Compare with FCB at DMAADDR already created by PATH2FCB
; Returns A=0 if entry matches, A=FFH if no match
; Trashes A,BC,DE,HL
MATCHFCB	INC		DE				; Skip over drive byte in FCB
			LD		HL,(DMAADDR)	; Will read FCB at DMAADDR pointer
			INC		HL				; Skip over drive byte in FCB
			LD		C,0				; Initialize character counter
MFL1		LD		A,(DE)			; Load byte of search pattern

			CP		'?'				; Is it '?' wildcard?
			JP		Z,MFS1			; If so, automatic char match
			LD		B,(HL)			; Load byte of match candidate

			CP		B				; See if the characters match
			JP		NZ,MFS2			; If not, then no match
MFS1		INC		DE				; Advance source pointer
			INC		HL				; Advance match candidate pointer
			INC		C				; Increment counter
			LD		A,8+3			; Compare character counter
			CP		C				; ...
			JP		NZ,MFL1			; Loop if characters left
			XOR		A				; We have a match
			RET						;
MFS2		LD		A,0FFH			; No match
			RET

; Compare a ProDOS directory file entry to see if it matches
; Used by F_SFIRST and F_SNEXT
; DE is the address of the FCB describing the file to look for
; HL points to the first file entry in the ProDOS directory
; Returns A=0 if entry matches, A=FFH if no match
CHKDIRENT	LD		B,0				; Hardcode drive A: MATCHFCB ignores it
			LD		A,(HL)			; Get first byte of file entry
			AND		0FH				; Mask to get the filename length
			CP		0				; If zero ...
			JP		Z,CDES1			; File is deleted - no match
			PUSH	HL				; Preserve HL
			PUSH	DE				; Preserve DE
			CALL	PATH2FCB		; Create FCB in DMA buffer
			POP		DE				; Recover DE
			POP		HL
			PUSH	HL
			PUSH	DE
			CALL	MATCHFCB		; Compare search FCB w/ FCB in DMA buffer
			POP		DE
			POP		HL				; Restore HL
			CP		0				; Does it match?
			JP		Z,CDES2			; If so, return
CDES1		LD		A,0FFH			; No match
			RET						;
CDES2		XOR		A				; Match
			RET

; Search a 512 byte block of a ProDOS directory for a matching file entry
; Used by F_SFIRST and F_SNEXT
; DE is the address of the FCB describing the file to look for
; CDBPTR points to the next ProDOS file entry to parse
; CDBCOUNT is set to the number of file entries already parsed in this block
; Returns A=0 if entry matches, A=FFH if no match
CHKDIRBLK	LD		A,(CDBCOUNT)	; File entry counter
			LD		HL,(CDBPTR)		; Pointer to next file entry
CDBL1		CALL	CHKDIRENT		; Match the file entry at HL
			EX		AF,AF'			; Stash return code for now
			LD		BC,FILEENTSZ	; Advance to next file entry
			ADD		HL,BC			; ...
			LD		(CDBPTR),HL		; Store the pointer
			LD		A,(CDBCOUNT)	; File entry counter
			INC		A				; Increment count of file entries
			LD		(CDBCOUNT),A	; Store the counter
			EX		AF,AF'			; Get return code back in A
			CP		0				; Was it a match?
			JP		Z,CDBS1			; If so, we are done
			LD		A,(CDBCOUNT)	; Get the counter back
			CP		ENTPERBLK		; Done all of them in this block?
			JP		NZ,CDBL1		; If not, loop
			LD		A,0FFH			; No match
			RET						;
CDBS1		XOR		A				; Match
			RET

; The following variables are used to preserve state between calls
CDBPTR		DEFW	0000H			; Stores pointer to next file entry
CDBCOUNT	DEFB	0				; Stores file entry counter

; Find IOBUF address for a file reference number
; Scan through FRN1, FRN2, FRN3, FRN4 to find the file reference number in A
; If found, return FRN slot# 1,2,3,4 in A, I/O buffer address in HL
; If not found, return A=0FFH
; Trashes B
GETIOADDR	LD		B,A				; Stash file ref number into B
			LD		A,(FRN1)		; Does it match FRN1?
			CP		B				; ...
			JP		Z,GIOAS1		; ...
			LD		A,(FRN2)		; Does it match FRN2?
			CP		B				; ...
			JP		Z,GIOAS2		; ...
			LD		A,(FRN3)		; Does it match FRN3?
			CP		B				; ...
			JP		Z,GIOAS3		; ...
			LD		A,(FRN4)		; Does it match FRN4?
			CP		B				; ...
			JP		Z,GIOAS4		; ...
			LD		A,0FFH			; No match, return A=0FFH
			RET						; ...
GIOAS1		LD		HL,IOBUF1		; Address of I/O buf 1 -> HL
			LD		A,1				; FRN slot 1
			RET
GIOAS2		LD		HL,IOBUF2		; Address of I/O buf 2 -> HL
			LD		A,2				; FRN slot 2
			RET
GIOAS3		LD		HL,IOBUF3		; Address of I/O buf 3 -> HL
			LD		A,3				; FRN slot 3
			RET
GIOAS4		LD		HL,IOBUF4		; Address of I/O buf 4 -> HL
			LD		A,4				; FRN slot 4
			RET

; Convert length in bytes to the number of 128 byte records
; Length in bytes is passed in HL
; Length in records is returned in A
; Only works for files whose size in multiple of 128 bytes
LEN2RECS	LD      A,H				; Most significant byte of length
			SLA     A				; Shift left to make space
			LD      B,A				; Stash in B for now
			LD      A,L				; Least significant byte of length
			AND     80H				; Keep most significant bit, mask off others
			SRA     A				; Move to LSB (shift seven times)
			SRA     A				; ...
			SRA     A				; ...
			SRA     A				; ...
			SRA     A				; ...
			SRA     A				; ...
			SRA     A				; ...
			OR      B				; Leaves file length in records in A
			RET

; Convert pos in extent/recs format to a linear position in 128 byte records
; Extent number is passed in B
; Records within the extent is passed in A
; Returns the length in records in HL - HL = (B*128)+A
EXRC2RECS	LD		L,B				; Extent number in LSB of HL
			LD		H,0				; ...
			ADD		HL,HL			; Shift left seven times
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			LD		B,0				; Put recs in this extent in BC
			LD		C,A				; ...
			ADD		HL,BC			; Now we have total offset in records
			RET

; Convert random record number of 128 byte records to length in bytes
; Length in records is passed in HL
; Returns the length in bytes in HL
RRN2LEN		ADD		HL,HL			; Shift left seven times
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			ADD		HL,HL			; ...
			RET

; Convert position in terms of random record number to extent/recs
; Length in records in passed in HL
; Returns extent number in B and records within extent in A
RECS2EXRC	SLA		H				; 7 MS-bits of extent number
			BIT		7,L				; See if MS-bit of L is set
			JP		Z,R2ERS1		; If set ...
			INC		H				; ... set LSB of extent number
R2ERS1		LD		B,H				; Return extent in B
			LD		A,L				; Now for the recs in the extent
			AND		7FH				; Just need to mask out MS-bit
			RET

; Convert pos in extent/recs format to a linear position in bytes
; Extent number is passed in B
; Records within the extent is passed in A
; Returns the length in bytes in HL - HL = ((B*128)+A)*128
EXRC2LEN	CALL	EXRC2RECS		; Does most of the work
			CALL	RRN2LEN			; Does the rest!
			RET

; Convert value in HL into an HEX ASCII string, pointed to by DE
; Courtesy of http://map.grauw.nl/sources/external/z80bits.html#5.2
; Trashes A
NUM2HEX		LD		A,H				;
			CALL	N2H1			;
			LD		A,H				;
			CALL	N2H2			;
			LD		A,L				;
			CALL	N2H1			;
			LD		A,L				;
			JR		N2H2			;
N2H1		RRA						;
			RRA						;
			RRA						;
			RRA						;
N2H2		OR		0F0H			;
			DAA						;
			ADD		A,0A0H			;
			ADC		A,40H			;
			LD		(DE),A			;
			INC		DE				;
			RET

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Additional private scratch space for BDOS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; ProDOS Parameter Lists
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; Parameter list for ProDOS CREATE call
FMMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0C0H			; ProDOS CREATE call
			DEFW	FMMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FMMLIPL		DEFB	7				; ProDOS PL: Seven parameters
FMMLIP		DEFW	PATHBUF+OFFSET	; ProDOS PL: Pointer to path in 6502 addr
FMMLIA		DEFB	0C3H			; ProDOS PL: Access (0C3H full access)
FMMLIT		DEFB	0				; ProDOS PL: File type (0 means typeless)
FMMLIAT		DEFW	0000H			; ProDOS PL: Aux file type (always 0000H)
FMMLIS		DEFB	1				; ProDOS PL: Storage type (1 for file)
FMMLICD		DEFW	0000H			; ProDOS PL: Create date (always 0000H)
FMMLICT		DEFW	0000H			; ProDOS PL: Create time (always 0000H)

; Parameter list for ProDOS DESTROY call
FDMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0C1H			; ProDOS DESTROY call
			DEFW	FDMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FDMLIPL		DEFB	1				; ProDOS PL: Seven parameters
FDMLIP		DEFW	PATHBUF+OFFSET	; ProDOS PL: Pointer to path in 6502 addr

; Parameter list for ProDOS RENAME call
FRNMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0C2H			; ProDOS RENAME call
			DEFW	FRNMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FRNMLIPL	DEFB	2				; ProDOS PL: Two parameters
FRNMLIP1	DEFW	PATHBUF+OFFSET	; ProDOS PL: Pointer to path in 6502 addr
FRNMLIP2	DEFW	PATHBUF2+OFFSET	; ProDOS PL: Pointer to path in 6502 addr

; Parameter list for ProDOS GET_FILE_INFO call
GFIMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0C4H			; ProDOS GET_FILE_INFO call
			DEFW	GFIMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
GFIMLIPL	DEFB	0AH				; ProDOS PL: Ten parameters
GFIMLIP		DEFW	PATHBUF+OFFSET	; ProDOS PL: Pointer to path in 6502 addr
GFIMLIAC	DEFB	0				; ProDOS PL: Access
GFIMLIT		DEFB	0				; ProDOS PL: File type
GFIMLIAT	DEFW	0000H			; ProDOS PL: Aux type
GFIMLIS		DEFB	1				; ProDOS PL: Storage type
GFIMLIBU	DEFW	0000H			; ProDOS PL: Blocks used
GFIMLIMD	DEFW	0000H			; ProDOS PL: Modification date
GFIMLIMT	DEFW	0000H			; ProDOS PL: Modification time
GFIMLICD	DEFW	0000H			; ProDOS PL: Create date
GFIMLICT	DEFW	0000H			; ProDOS PL: Create time

; Parameter list for ProDOS OPEN call
FOMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0C8H			; ProDOS OPEN call
			DEFW	FOMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FOMLIPL		DEFB	3				; ProDOS PL: Three parameters
FOMLIP		DEFW	PATHBUF+OFFSET	; ProDOS PL: pointer to path in 6502 addr
FOMLII		DEFW	0000H			; ProDOS PL: pointer to IO buffer
FOMLIN		DEFB	0				; ProDOS PL: File reference number

; Parameter list for ProDOS READ call
FRMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0CAH			; ProDOS READ call
			DEFW	FRMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FRMLIPL		DEFB	4				; ProDOS PL: Four parameters
FRMLIN		DEFB	0				; ProDOS PL: File reference number
FRMLIDB		DEFW	0000H			; ProDOS PL: Data buffer
FRMLIRC		DEFW	128				; ProDOS PL: Request count (bytes to read)
FRMLITC		DEFW	0000H			; ProDOS PL: Number of bytes transferred

; Parameter list for ProDOS WRITE call
FWMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0CBH			; ProDOS WRITE call
			DEFW	FWMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FWMLIPL		DEFB	4				; ProDOS PL: Four parameters
FWMLIN		DEFB	0				; ProDOS PL: File reference number
FWMLIDB		DEFW	0000H			; ProDOS PL: Data buffer
FWMLIRC		DEFW	128				; ProDOS PL: Request count (bytes to read)
FWMLITC		DEFW	0000H			; ProDOS PL: Number of bytes transferred

; Parameter list for ProDOS CLOSE call
FCMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0CCH			; ProDOS CLOSE call
			DEFW	FCMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FCMLIPL		DEFB	1				; ProDOS PB: One parameter
FCMLIN		DEFB	0				; ProDOS PB: File reference number

; Parameter list for ProDOS FLUSH call
FLMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0CDH			; ProDOS FLUSH call
			DEFW	FLMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
FLMLIPL		DEFB	1				; ProDOS PL: One parameter
FLMLIN		DEFB	0				; ProDOS PL: File ref num (0 = all files)

; Parameter list for ProDOS SET_MARK call
SMMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code		
			DEFB	0CEH			; ProDOS SET_MARK call
			DEFW	SMMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
SMMLIPL		DEFB	2				; ProDOS PL: Two parameters
SMMLIN		DEFB	0				; ProDOS PL: File reference number
SMMLIP1		DEFB	0				; ProDOS PL: Position (LSB)
SMMLIP2		DEFB	0				; ProDOS PL: Position
SMMLIP3		DEFB	0				; ProDOS PL: Position (MSB)

; Parameter list for ProDOS SET_EOF call
SEMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code
			DEFB	0D0H			; ProDOS SET_EOF call
			DEFW	SEMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
SEMLIPL		DEFB	2				; ProDOS PL: Two parameters
SEMLIN		DEFB	0				; ProDOS PL: File reference number
SEMLIE1		DEFB	0				; ProDOS PL: EOF position (LS-byte)
SEMLIE2		DEFB	0				; ProDOS PL: EOF position
SEMLIE3		DEFB	0				; ProDOS PL: EOF position (MS-byte)

; Parameter list for ProDOS GET_EOF call
GEMLI		DEFB	20H,00H,0BFH	; JSR $BF00 in 6502 code
			DEFB	0D1H			; ProDOS GET_EOF call
			DEFW	GEMLIPL+OFFSET	; Pointer to parm list in 6502 addr space
			DEFB	60H				; RTS in 6502 code
GEMLIPL		DEFB	2				; ProDOS PL: Two parameters
GEMLIN		DEFB	0				; ProDOS PL: File reference number
GEMLIE1		DEFB	0				; ProDOS PL: EOF position (LS-byte)
GEMLIE2		DEFB	0				; ProDOS PL: EOF position
GEMLIE3		DEFB	0				; ProDOS PL: EOF position (MS-byte)

; FCB used for opening ProDOS directory corresponding to drive
DFCB								; File control block for directory
DFCBDRV		DEFB	00H				; FCB Drive (0 current, 1 A:, 2 B: etc)
DFCBNAM		DEFM	'           '	; FCB filename and extension (all spaces)
DFCBEX		DEFB	00H				; FCB extent field
DFCBS1		DEFB	00H				; FCB S1 field
DFCBS2		DEFB	00H				; FCB S2 field
DFCBRC		DEFB	00H				; FCB RC field
DFCBMAP		DEFS	16				; Map of blocks in file
DFCBSR		DEFB	0				; FCB seq record number
DFCBRR		DEFB	0,0,0			; FCB rand record number

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; End of ProDOS Parameter Lists
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; Drive parameter block (CP/M 2.2 format)
; See Johnson-Laird Pg 33-34
DPB			DEFW	32				; # 128 byte records per track (for Disk II)
			DEFB	3				; Block shift (1024 byte allocation blocks)
			DEFB	7				; Block mask (1024 byte allocation blocks)
			DEFB	0				; Extent mask (1024 byte alocation blocks)
			DEFW	1023			; # allocation blocks on disk (1MB)
			DEFW	255				; # directory entries 
			DEFB	0				; Directory allocation bitmap byte 1
			DEFB	0				; Directory allocation bitmap byte 2
			DEFW	0				; Checksum vector size
			DEFW	0				; # of reserved tracks

; Fake allocation vector (2048 allocation blocks / 8 = 256 bytes)
ALLOCVEC	DEFS	256				; TODO: This is a waste of memory
									; Get rid of it?

; 64 byte buffer for storing a file path as a Pascal style string
PATHBUF
PATHLEN		DEFB	0
PATH		DEFS	64

; 64 byte buffer for storing a second file path as a Pascal style string
PATHBUF2
PATHLEN2	DEFB	0
PATH2		DEFS	64

; Record file reference numbers for each I/O buffer
; Or 0 if no file is using the buffer
FRN1		DEFB	0
FRN2		DEFB	0
FRN3		DEFB	0
FRN4		DEFB	0

; Buffer for printing hex numbers to console
HEXBUF		DEFB	0,0,0,0,'$'

; 512 byte buffer for reading directories (used by F_SFIRST and F_SNEXT)
DIRBUF
DIRBUF1		DEFS	128
DIRBUF2		DEFS	128
DIRBUF3		DEFS	128
DIRBUF4		DEFS	128

; Four 1024 byte ProDOS I/O buffers
; These must start on a page boundary
; ProDOS occupies the space from $BF00 up (in 6502 addresses)
; 6502 code is loaded at $B800 for now
; So in theory the I/O buffers could go from $A800-$B800 (09800H base)


			;ORG		9000H	; Try this - WORKS
			ORG		9800H	; Try this - WORKS
IOBUF1		DEFS	1024
IOBUF2		DEFS	1024
IOBUF3		DEFS	1024
IOBUF4		DEFS	1024

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;