; **************************************************************************
; EMPTY - This code contains:
;             - TUOX boot record code, which doesn't load system,
;               but prints a message "Non system disk(ette)"
;             - code to store boot record to disk(ette)
;
; Modified by Petr Smidak, member of 1999 Bootstrap group, after
; old Bootstrap group(s)
;
;								8.5.1999
; **************************************************************************

Ideal
model TINY
P386		; few 386 instruction, but not registers (so far)

DataSeg
; 0:7C00h = address where BIOS loads boot record
	STACK_TOP	= 7C00H
	SHIFT		= 7C00H - 103H	; PSP = 100H bytes, JMP BOOT_BEGIN = 3 bytes
	FIRST_MODUL	= 0700H		; Address where to load first module
					; First module = Loader

org 100h

CodeSeg
STARTUPCODE
	JMP     BOOT_BEGIN

; TUOX boot record begins here
; Some is the same as MS-DOS (version 4.0 or higher) boot record
; Every value named in sectors is relative to boot sector
; Boot sector relative number is 0.
Boot_Start:
	JMP	SHORT @@Start	; Jump over data
	NOP			; Near jump expected, short one used
				; so we need one extra byte here

VersionID	db	'TUOX2.0',0	; Company and version
BytesPerSec	dw	?	; the most frequently 512B per sector
		db	?	; Unused
StartImageSecs	dw	?	; First available sector for image
LoaderSize	db	?	; Size of LOADER in sectors
SizeImageSec	dw	?	; Image size in sectors
TotalSectors	dw	?	; Total sector number on the disk
FormatID	db	?	; F0 = floppy, F8 = harddisk
LoaderDataSec	dw	?	; First sector of LOADER
SectorsPerCyl	dw	?	; Sectors per track (cylinder)
Sides		dw	?	; Number of sides (heads) on disk(ette)
		dw	?	; Unused
		dw	?	; Unused
		dd	?	; Unused
DriveNo		db	?	; 0 = 1st floppy, 80h = 1st harddisk
		db	?	; Unused
		db	?	; Unused
VolumeSerialNo	db	1,2,3,4	; Volume serial number 0102-0304
VolumeLabel	db	'TUOX NonSys'	; Volume label (max. 11 chars)
		db      8 dup (?)	; 8 bytes
; Boot record end (total 62 bytes)

; Here come the variables that TUOX needs
RAMDiskSize	dw	?	; Size of memory block reserved for RAM disk
				; in paragraphs (1MB-16B)
; Boot main code
@@Start:
; init segments except ES
	CLI
	XOR     AX, AX
	MOV	es, ax
	MOV     SS, AX
	MOV     SP, STACK_TOP   ; Stack initiation
	MOV     DS, AX
	STI

	mov	si, offset NotBootMsg + SHIFT
	CALL	WriteString	; Print error message
	XOR	AH, AH		; BIOS keyboard service
	INT	16H		; Wait for key stroke
	INT	19H		; Try to load boot sector again


proc WriteString near		; Print an ASCIIZ string at DS:SI
@@Write_Begin:
	LODSB			; Next character
	OR	AL, AL
	JZ	@@Write_End	; AL=0 => end of ASCIIZ string
	MOV	AH, 0EH		; BIOS service - write character
	MOV	BL, 0FFH	; Char's attribute
	INT	10H
	JMP	SHORT @@Write_Begin
@@Write_End:
	RET
endp WriteString


NotBootMsg	db	13,10, 'TUOX Boot: Non-System disk', 13, 10
		db	'Press any key to reboot...', 13, 10, 0
@@BootCode_End:

BOOT_BEGIN:
; get command line to buffer 'cmd'
	mov	si, 80h
	movzx	cx, [BYTE ds:si]	; CX = velikost
	inc	cx

	mov	di, offset cmd
	cld
	rep	movsb

; transmission 'cmd' to big letters
	cld
	mov	ax, offset cmd
	mov	si, ax
	mov	di, ax
	mov	cx, 80h
cik:	lodsb
	cmp	al, 'a'
	jb	neeee
	cmp	al, 'z'
	ja	neeee
	sub	al, 'a'-'A'
neeee:	stosb
	loop	cik

; go to main writing code
	jmp	main


PROC	str2num
; Transmission of hexadecimal string to real number
; input  : AX = string offset (one or two characters)
; output : BX = wanted number
;	   CF = 1, if transmission gone wrong
	mov	bx, 0
	cld
	clc
	mov	si, ax
	mov	di, ax
	mov	ax, 0
	mov	cx, 2		; max 2 characters
cak:	lodsb

	cmp	al,'0'		; AL must be '0'-'9' or 'A'-'F'
	jb	tr_err
	cmp	al,'9'
	jb	number
	cmp	al,'A'
	jb	tr_err
	cmp	al,'F'
	ja	tr_err

; transmission of characters 'A'-'F' to number
	sub	al,55	; 'A'=65 => 65-55=10, (10 decimal is A hexadec.)
	shl	bx,4
	add	bx,ax
	loop	cak

	jmp	finish

; transmission of characters '0'-'9' to number
number:	sub	al,48	; '0'=48 => 48-48=0
	shl	bx,4
	add	bx,ax
	loop	cak

	jmp	finish

; wrong input
tr_err:	stc
finish:	
	ret
ENDP	str2num


main:
; cmd+2 = 1st character of command line
	mov	al, [BYTE cmd + 2]
	mov	si, offset HelpMsg
	cmp	al, 0		; when no parameters
	je	ParDrvErr
	cmp	al, '?'		; or given '?', then
	jne	ParDrvOk	; print help

ParDrvErr:
	call	WriteString
	jmp	main_end
ParDrvOk:
	mov	ax, offset cmd + 2	; first parameter = drive
	call	str2num
	mov	[BYTE DRIVE], bl

	cmp	bl, 7Fh
	ja	@@ReadMBR		; Don't read MBR when writing
	mov	[BYTE HEAD], 0		; to floppy
	mov	[WORD CYLSEC], 1
	jmp	@@ReadBoot

@@ReadMBR:
; cmd+5 = 4th character of command line
	mov	al, [BYTE cmd + 5]
	mov	si, offset HelpMsg
	cmp	al, 0			; if partition parameter not
	je	@@Do_Write		; specified
	cmp	al, '1'			; or not in range 1 to 4
	jb	@@Do_Write		; print help
	cmp	al, '4'
	ja	@@Do_Write

	mov	bx, offset MBRbuffer
	mov	dl, [BYTE DRIVE]
	mov	dh, 0		; MBR Head
	mov	cx, 3
@@TryReadMBR:
	push	cx
	mov	cx, 1		; MBR Cylinder & Sector
	mov	ax, 0201H	; read MBR to buffer
	int	13h
	pop	cx
	jnc	@@ReadMBROK
	loop	@@TryReadMBR
	mov	si, offset DiskReadErrMBR
	jmp	@@Do_Write

@@ReadMBROK:
	mov	ax, offset cmd + 5
	call	str2num

; get parameters of given partition
	mov	ax, bx
	mov	bx, 16
	mul	bx
	sub	ax, bx
	add	ax, 1beh
	mov	di, ax
	add	di, 1
	mov	cl, [BYTE MBRbuffer + di]
	mov	[BYTE HEAD], cl			; BeginHead
	add	di, 1
	mov	cx, [WORD MBRbuffer + di]
	mov	[WORD CYLSEC], cx		; BeginCylSec


; Read original boot record before update
@@ReadBoot:
	MOV	BX, OFFSET BootBuffer
	MOV	DL, [BYTE DRIVE]
	MOV	DH, [BYTE HEAD]		; BeginHead = boot sector Head
	MOV	CX, 3
@@TryRead:
	PUSH	CX
	MOV	CX, [WORD CYLSEC]	; boot sector Cylinder & Sector
	MOV	AX, 0201H		; read boot to buffer
	INT	13H
	POP	CX
	JNC	@@ReadOK
	LOOP	@@TryRead
	MOV	SI, OFFSET DiskReadErr
	JMP	@@Do_Write
@@ReadOK:
	MOV	SI, OFFSET Boot_Start
	MOV	DI, OFFSET BootBuffer
	MOV	CX, 11
	REP	MOVSB		; write my boot to buffer, but
	ADD	SI, 27		; skip disk parameters 12-38 byte
	ADD	DI, 27
	MOV	CX, 472/2
	REP	MOVSW
	MOV	AX, 0AA55H	; End of boot sector signature
	STOSW
	MOV	CX, 3
@@TryWrite:
	PUSH	CX
	MOV	DL, [BYTE DRIVE]
	MOV	DH, [BYTE HEAD]
	MOV	CX, [WORD CYLSEC]
	MOV	AX, 0301H
	MOV	BX, OFFSET BootBuffer
	INT	13H		; Write buffer to boot sector
	POP	CX
	JNC	@@Write_OK
	LOOP	@@TryWrite
	MOV	SI, OFFSET WriteErrorMsg
	JMP	SHORT @@Do_Write
@@Write_OK:
	MOV	SI, OFFSET WriteOKMsg
@@Do_Write:
	CALL	WriteString
main_end:
EXITCODE

HelpMsg	db	'Boot Record Writer by Petr Smidak & friends '
	db	'from TUOX Bootstrap group, 1999', 13,10,13,10
	db	'Empty Boot record Code. IT DOES NOT LOAD TUOX.', 13,10,13,10
	db	'EMPTY.COM [? | <DRIVE [PARTITION]>]', 13,10,13,10
	db	'Parameters :',13,10
	db	'  ? - this help message', 13,10
	db	'  DRIVE = hexadecimal number', 13,10
	db	'          (0 = first floppy drive, '
	db	'1 = second floppy drive, ...', 13,10
	db	'           80 = first harddisk, '
	db	'81 = second harddisk, ...)', 13,10
	db	'  PARTITION = partition number on choosed drive (1-4)', 13,10
	db	'      This has no effect, if drive < 80 (hexa)', 13,10,0
WriteErrorMsg	db	'Boot Writing Error.', 13,10,0
DiskReadErr	db	'Boot Reading Error.', 13,10,0
WriteOKMsg	db	'Boot Record Was Successfully Written.', 13,10
		db	'Load System Files Now.', 13,10,0
DiskReadErrMBR	db	'MBR Reading Error.', 13,10,0
DRIVE		db	?
PARTBEG		dw	?
HEAD		db	?
CYLSEC		dw	?
hex		db	'0123456789ABCDEF'	; hexa znaky
cmd		db	8 dup(0), 78h dup(?)	; argumenty z PSP
BootBuffer	db	512 dup(?)
MBRbuffer	db	512 dup(?)
  
ends
end