mirror of
https://github.com/microsoft/MS-DOS.git
synced 2024-11-25 23:25:47 +00:00
136 lines
4.0 KiB
NASM
136 lines
4.0 KiB
NASM
; Generic FORMAT module for any ms-dos disk erases the directory,
|
||
; zeros FAT, and marks bad sectors
|
||
|
||
INCLUDE DOST:DOSSYM.ASM
|
||
|
||
CODE SEGMENT PUBLIC 'CODE'
|
||
|
||
ASSUME CS:CODE,DS:CODE,ES:CODE
|
||
|
||
PUBLIC FATID,STARTSECTOR,SWITCHLIST,FREESPACE,FATSPACE
|
||
PUBLIC INIT,DISKFORMAT,BADSECTOR,DONE,WRTFAT,HARDFLAG
|
||
EXTRN SWITCHMAP:WORD,DRIVE:BYTE
|
||
|
||
WRTFAT:
|
||
MOV AH,GET_DPB
|
||
MOV DL,[DRIVE]
|
||
INC DL ;A = 1
|
||
INT 21H ;FORCE A FATREAD
|
||
PUSH CS
|
||
POP DS
|
||
MOV AL,[FATCNT]
|
||
MOV [CURCNT],AL ;SET UP FAT COUNT
|
||
MOV AX,[FATSTART]
|
||
MOV [COUNT],AX
|
||
FATLOOP:
|
||
MOV AL,BYTE PTR DRIVE
|
||
CBW
|
||
MOV CX,[FATSIZE]
|
||
MOV DX,[COUNT]
|
||
MOV BX,[FATSPACE]
|
||
INT 26H
|
||
POP AX
|
||
JC GORET
|
||
MOV CX,[FATSIZE]
|
||
ADD [COUNT],CX
|
||
DEC BYTE PTR [CURCNT]
|
||
JNZ FATLOOP
|
||
CLC ;Good return
|
||
GORET:
|
||
RET
|
||
|
||
FATSIZE DW ?
|
||
FATSTART DW ?
|
||
COUNT DW ?
|
||
STARTSECTOR DW ?
|
||
SPC DB ? ;SECTORS PER CLUSTER
|
||
FATCNT DB ? ;NUMBER OF FATS ON THIS DRIVE
|
||
CURCNT DB ?
|
||
DSKSIZE DW ? ;NUMBER OF SECTORS ON THE DRIVE
|
||
START DW 0 ;CURRENT TEST SECTOR
|
||
|
||
INIT:
|
||
MOV AH,GET_DPB
|
||
MOV DL,[DRIVE]
|
||
INC DL ;A = 1
|
||
INT 21H ;FORCE A FATREAD
|
||
MOV AL,[BX+4] ;SECTORS PER CLUSTER - 1
|
||
INC AL
|
||
MOV CH,AL ;CH = SECTORS PER CLUSTER
|
||
CBW
|
||
MOV BP,[BX+0DH] ;MAXCLUS + 1
|
||
DEC BP
|
||
MUL BP
|
||
MOV BP,AX
|
||
ADD BP,[BX+0BH] ;BP = NUMBER OF SECTORS ON THE DISK
|
||
MOV AL,[BX+0FH] ;GET SIZE OF FAT IN SECTORS
|
||
MOV AH,[BX+8] ;GET NUMBER OF FATS
|
||
MOV DX,[BX+6] ;FIRST SECTOR OF FAT
|
||
MOV CL,[BX+16H] ;FATID BYTE
|
||
MOV SI,[BX+2] ;SECTOR SIZE
|
||
MOV BX,[BX+0BH] ;FIRST SECTOR OF DATA
|
||
PUSH CS
|
||
POP DS
|
||
MOV [FATCNT],AH
|
||
MOV [DSKSIZE],BP
|
||
MOV [SPC],CH
|
||
MOV [FATSTART],DX
|
||
MOV [ENDLOC],CL
|
||
MOV [FATID],CL
|
||
MOV [STARTSECTOR],BX
|
||
XOR AH,AH
|
||
MOV [FATSIZE],AX
|
||
MUL SI ;AX = SIZE OF FAT
|
||
ADD [FREESPACE],AX
|
||
ADD [BUFFER],AX
|
||
MOV AX,BX
|
||
MUL SI
|
||
ADD [FREESPACE],AX ;AX = SIZE OF TEMP BUFFER
|
||
DISKFORMAT:
|
||
DONE:
|
||
XOR AX,AX
|
||
CLC
|
||
RET
|
||
|
||
BADSECTOR:
|
||
MOV DX,[START]
|
||
CMP DX,[DSKSIZE]
|
||
JAE DONE
|
||
|
||
MOV AL,[DRIVE]
|
||
MOV CL,[SPC] ;READ ONE ALLOCATIONS WORTH
|
||
XOR CH,CH
|
||
CMP BYTE PTR [FIRSTFLAG],0
|
||
JZ SETBX
|
||
MOV CX,[STARTSECTOR] ;FIRST TIME THROUGH READ SYSTEM AREA
|
||
MOV BYTE PTR [FIRSTFLAG],0
|
||
MOV DX,[START]
|
||
SETBX: MOV BX,[BUFFER]
|
||
PUSH CX
|
||
INT 25H ;TRY TO READ
|
||
POP AX ;CLEAN UP STACK
|
||
POP CX
|
||
JC GOTBAD ;KEEP LOOKING FOR BADSECTORS
|
||
ADD [START],CX
|
||
JMP BADSECTOR
|
||
|
||
GOTBAD:
|
||
MOV AX,CX
|
||
MOV BX,[START]
|
||
ADD [START],AX ;SET UP FOR NEXT CALL
|
||
CLC
|
||
RET
|
||
|
||
FIRSTFLAG DB 1 ;1 = FIRST CALL TO BADSECTOR
|
||
HARDFLAG DB 1
|
||
FATID DB 0FEH
|
||
SWITCHLIST DB 3,"OVS"
|
||
BUFFER DW ENDLOC
|
||
FREESPACE DW ENDLOC
|
||
FATSPACE DW ENDLOC
|
||
ENDLOC LABEL BYTE
|
||
DB 0FEH,0FFH,0FFH
|
||
|
||
CODE ENDS
|
||
END
|
||
|