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MS-DOS/v1.25/source/MSDOS.ASM
Rich Turner fce0f75959 MS-DOS v1.25 Release
2018-09-21 17:51:26 -07:00

4031 lines
108 KiB
NASM
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; 86-DOS High-performance operating system for the 8086 version 1.25
; by Tim Paterson
; ****************** Revision History *************************
; >> EVERY change must noted below!! <<
;
; 0.34 12/29/80 General release, updating all past customers
; 0.42 02/25/81 32-byte directory entries added
; 0.56 03/23/81 Variable record and sector sizes
; 0.60 03/27/81 Ctrl-C exit changes, including register save on user stack
; 0.74 04/15/81 Recognize I/O devices with file names
; 0.75 04/17/81 Improve and correct buffer handling
; 0.76 04/23/81 Correct directory size when not 2^N entries
; 0.80 04/27/81 Add console input without echo, Functions 7 & 8
; 1.00 04/28/81 Renumber for general release
; 1.01 05/12/81 Fix bug in `STORE'
; 1.10 07/21/81 Fatal error trapping, NUL device, hidden files, date & time,
; RENAME fix, general cleanup
; 1.11 09/03/81 Don't set CURRENT BLOCK to 0 on open; fix SET FILE SIZE
; 1.12 10/09/81 Zero high half of CURRENT BLOCK after all (CP/M programs don't)
; 1.13 10/29/81 Fix classic "no write-through" error in buffer handling
; 1.20 12/31/81 Add time to FCB; separate FAT from DPT; Kill SMALLDIR;
; Add FLUSH and MAPDEV calls; allow disk mapping in DSKCHG;
; Lots of smaller improvements
; 1.21 01/06/82 HIGHMEM switch to run DOS in high memory
; 1.22 01/12/82 Add VERIFY system call to enable/disable verify after write
; 1.23 02/11/82 Add defaulting to parser; use variable escape character
; Don't zero extent field in IBM version (back to 1.01!)
; 1.24 03/01/82 Restore fcn. 27 to 1.0 level; add fcn. 28
; 1.25 03/03/82 Put marker (00) at end of directory to speed searches
;
; *************************************************************
; Interrupt Entry Points:
; INTBASE: ABORT
; INTBASE+4: COMMAND
; INTBASE+8: BASE EXIT ADDRESS
; INTBASE+C: CONTROL-C ABORT
; INTBASE+10H: FATAL ERROR ABORT
; INTBASE+14H: BIOS DISK READ
; INTBASE+18H: BIOS DISK WRITE
; INTBASE+40H: Long jump to CALL entry point
IF IBM
ESCCH EQU 0
CANCEL EQU 1BH ;Cancel with ESC
TOGLINS EQU TRUE ;One key toggles insert mode
TOGLPRN EQU TRUE ;One key toggles printer echo
NUMDEV EQU 6 ;Include "COM1" as I/O device name
ZEROEXT EQU TRUE
ELSE
ESCCH EQU 1BH
CANCEL EQU "X"-"@" ;Cancel with Ctrl-X
TOGLINS EQU FALSE ;Separate keys for insert mode on and off
TOGLPRN EQU FALSE ;Separate keys for printer echo on and off
NUMDEV EQU 5 ;Number of I/O device names
ZEROEXT EQU FALSE
ENDIF
MAXCALL EQU 36
MAXCOM EQU 46
INTBASE EQU 80H
INTTAB EQU 20H
ENTRYPOINTSEG EQU 0CH
ENTRYPOINT EQU INTBASE+40H
CONTC EQU INTTAB+3
EXIT EQU INTBASE+8
LONGJUMP EQU 0EAH
LONGCALL EQU 9AH
MAXDIF EQU 0FFFH
SAVEXIT EQU 10
; Field definition for FCBs
FCBLOCK STRUC
DB 12 DUP (?) ;Drive code and name
EXTENT DW ?
RECSIZ DW ? ;Size of record (user settable)
FILSIZ DW ? ;Size of file in bytes
DRVBP DW ? ;BP for SEARCH FIRST and SEARCH NEXT
FDATE DW ? ;Date of last writing
FTIME DW ? ;Time of last writing
DEVID DB ? ;Device ID number, bits 0-5
;bit 7=0 for file, bit 7=1 for I/O device
;If file, bit 6=0 if dirty
;If I/O device, bit 6=0 if EOF (input)
FIRCLUS DW ? ;First cluster of file
LSTCLUS DW ? ;Last cluster accessed
CLUSPOS DW ? ;Position of last cluster accessed
DB ? ;Forces NR to offset 32
NR DB ? ;Next record
RR DB 3 DUP (?) ;Random record
FCBLOCK ENDS
FILDIRENT = FILSIZ ;Used only by SEARCH FIRST and SEARCH NEXT
; Description of 32-byte directory entry (same as returned by SEARCH FIRST
; and SEARCH NEXT, functions 17 and 18).
;
; Location bytes Description
;
; 0 11 File name and extension ( 0E5H if empty)
; 11 1 Attributes. Bits 1 or 2 make file hidden
; 12 10 Zero field (for expansion)
; 22 2 Time. Bits 0-4=seconds/2, bits 5-10=minute, 11-15=hour
; 24 2 Date. Bits 0-4=day, bits 5-8=month, bits 9-15=year-1980
; 26 2 First allocation unit ( < 4080 )
; 28 4 File size, in bytes (LSB first, 30 bits max.)
;
; The File Allocation Table uses a 12-bit entry for each allocation unit on
; the disk. These entries are packed, two for every three bytes. The contents
; of entry number N is found by 1) multiplying N by 1.5; 2) adding the result
; to the base address of the Allocation Table; 3) fetching the 16-bit word at
; this address; 4) If N was odd (so that N*1.5 was not an integer), shift the
; word right four bits; 5) mask to 12 bits (AND with 0FFF hex). Entry number
; zero is used as an end-of-file trap in the OS and as a flag for directory
; entry size (if SMALLDIR selected). Entry 1 is reserved for future use. The
; first available allocation unit is assigned entry number two, and even
; though it is the first, is called cluster 2. Entries greater than 0FF8H are
; end of file marks; entries of zero are unallocated. Otherwise, the contents
; of a FAT entry is the number of the next cluster in the file.
; Field definition for Drive Parameter Block
DPBLOCK STRUC
DEVNUM DB ? ;I/O driver number
DRVNUM DB ? ;Physical Unit number
SECSIZ DW ? ;Size of physical sector in bytes
CLUSMSK DB ? ;Sectors/cluster - 1
CLUSSHFT DB ? ;Log2 of sectors/cluster
FIRFAT DW ? ;Starting record of FATs
FATCNT DB ? ;Number of FATs for this drive
MAXENT DW ? ;Number of directory entries
FIRREC DW ? ;First sector of first cluster
MAXCLUS DW ? ;Number of clusters on drive + 1
FATSIZ DB ? ;Number of records occupied by FAT
FIRDIR DW ? ;Starting record of directory
FAT DW ? ;Pointer to start of FAT
DPBLOCK ENDS
DPBSIZ EQU 20 ;Size of the structure in bytes
DIRSEC = FIRREC ;Number of dir. sectors (init temporary)
DSKSIZ = MAXCLUS ;Size of disk (temp used during init only)
;The following are all of the segments used
;They are declared in the order that they should be placed in the executable
CODE SEGMENT
CODE ENDS
CONSTANTS SEGMENT BYTE
CONSTANTS ENDS
DATA SEGMENT WORD
DATA ENDS
DOSGROUP GROUP CODE,CONSTANTS,DATA
SEGBIOS SEGMENT
SEGBIOS ENDS
; BOIS entry point definitions
IF IBM
BIOSSEG EQU 60H
ENDIF
IF NOT IBM
BIOSSEG EQU 40H
ENDIF
SEGBIOS SEGMENT AT BIOSSEG
ORG 0
DB 3 DUP (?) ;Reserve room for jump to init code
BIOSSTAT DB 3 DUP (?) ;Console input status check
BIOSIN DB 3 DUP (?) ;Get console character
BIOSOUT DB 3 DUP (?) ;Output console character
BIOSPRINT DB 3 DUP (?) ;Output to printer
BIOSAUXIN DB 3 DUP (?) ;Get byte from auxilliary
BIOSAUXOUT DB 3 DUP (?) ;Output byte to auxilliary
BIOSREAD DB 3 DUP (?) ;Disk read
BIOSWRITE DB 3 DUP (?) ;Disk write
BIOSDSKCHG DB 3 DUP (?) ;Dsik-change status
BIOSSETDATE DB 3 DUP (?) ;Set date
BIOSSETTIME DB 3 DUP (?) ;Set time
BIOSGETTIME DB 3 DUP (?) ;Get time and date
BIOSFLUSH DB 3 DUP (?) ;Clear console input buffer
BIOSMAPDEV DB 3 DUP (?) ;Dynamic disk table mapper
SEGBIOS ENDS
; Location of user registers relative user stack pointer
STKPTRS STRUC
AXSAVE DW ?
BXSAVE DW ?
CXSAVE DW ?
DXSAVE DW ?
SISAVE DW ?
DISAVE DW ?
BPSAVE DW ?
DSSAVE DW ?
ESSAVE DW ?
IPSAVE DW ?
CSSAVE DW ?
FSAVE DW ?
STKPTRS ENDS
; Start of code
CODE SEGMENT
ASSUME CS:DOSGROUP,DS:DOSGROUP,ES:DOSGROUP,SS:DOSGROUP
ORG 0
CODSTRT EQU $
JMP DOSINIT
ESCCHAR DB ESCCH ;Lead-in character for escape sequences
ESCTAB:
IF NOT IBM
DB "S" ;Copy one char
DB "V" ;Skip one char
DB "T" ;Copy to char
DB "W" ;Skip to char
DB "U" ;Copy line
DB "E" ;Kill line (no change in template)
DB "J" ;Reedit line (new template)
DB "D" ;Backspace
DB "P" ;Enter insert mode
DB "Q" ;Exit insert mode
DB "R" ;Escape character
DB "R" ;End of table
ENDIF
IF IBM
DB 64 ;Crtl-Z - F6
DB 77 ;Copy one char - -->
DB 59 ;Copy one char - F1
DB 83 ;Skip one char - DEL
DB 60 ;Copy to char - F2
DB 62 ;Skip to char - F4
DB 61 ;Copy line - F3
DB 61 ;Kill line (no change to template ) - Not used
DB 63 ;Reedit line (new template) - F5
DB 75 ;Backspace - <--
DB 82 ;Enter insert mode - INS (toggle)
DB 65 ;Escape character - F7
DB 65 ;End of table
ENDIF
ESCTABLEN EQU $-ESCTAB
IF NOT IBM
HEADER DB 13,10,"MS-DOS version 1.25"
IF HIGHMEM
DB "H"
ENDIF
IF DSKTEST
DB "D"
ENDIF
DB 13,10
DB "Copyright 1981,82 Microsoft, Inc.",13,10,"$"
ENDIF
QUIT:
MOV AH,0
JMP SHORT SAVREGS
COMMAND: ;Interrupt call entry point
CMP AH,MAXCOM
JBE SAVREGS
BADCALL:
MOV AL,0
IRET: IRET
ENTRY: ;System call entry point and dispatcher
POP AX ;IP from the long call at 5
POP AX ;Segment from the long call at 5
POP CS:[TEMP] ;IP from the CALL 5
PUSHF ;Start re-ordering the stack
CLI
PUSH AX ;Save segment
PUSH CS:[TEMP] ;Stack now ordered as if INT had been used
CMP CL,MAXCALL ;This entry point doesn't get as many calls
JA BADCALL
MOV AH,CL
SAVREGS:
PUSH ES
PUSH DS
PUSH BP
PUSH DI
PUSH SI
PUSH DX
PUSH CX
PUSH BX
PUSH AX
IF DSKTEST
MOV AX,CS:[SPSAVE]
MOV CS:[NSP],AX
MOV AX,CS:[SSSAVE]
MOV CS:[NSS],AX
POP AX
PUSH AX
ENDIF
MOV CS:[SPSAVE],SP
MOV CS:[SSSAVE],SS
MOV SP,CS
MOV SS,SP
REDISP:
MOV SP,OFFSET DOSGROUP:IOSTACK
STI ;Stack OK now
MOV BL,AH
MOV BH,0
SHL BX,1
CLD
CMP AH,12
JLE SAMSTK
MOV SP,OFFSET DOSGROUP:DSKSTACK
SAMSTK:
CALL CS:[BX+DISPATCH]
LEAVE:
CLI
MOV SP,CS:[SPSAVE]
MOV SS,CS:[SSSAVE]
MOV BP,SP
MOV BYTE PTR [BP.AXSAVE],AL
IF DSKTEST
MOV AX,CS:[NSP]
MOV CS:[SPSAVE],AX
MOV AX,CS:[NSS]
MOV CS:[SSSAVE],AX
ENDIF
POP AX
POP BX
POP CX
POP DX
POP SI
POP DI
POP BP
POP DS
POP ES
IRET
; Standard Functions
DISPATCH DW ABORT ;0
DW CONIN
DW CONOUT
DW READER
DW PUNCH
DW LIST ;5
DW RAWIO
DW RAWINP
DW IN
DW PRTBUF
DW BUFIN ;10
DW CONSTAT
DW FLUSHKB
DW DSKRESET
DW SELDSK
DW OPEN ;15
DW CLOSE
DW SRCHFRST
DW SRCHNXT
DW DELETE
DW SEQRD ;20
DW SEQWRT
DW CREATE
DW RENAME
DW INUSE
DW GETDRV ;25
DW SETDMA
DW GETFATPT
DW GETFATPTDL
DW GETRDONLY
DW SETATTRIB ;30
DW GETDSKPT
DW USERCODE
DW RNDRD
DW RNDWRT
DW FILESIZE ;35
DW SETRNDREC
; Extended Functions
DW SETVECT
DW NEWBASE
DW BLKRD
DW BLKWRT ;40
DW MAKEFCB
DW GETDATE
DW SETDATE
DW GETTIME
DW SETTIME ;45
DW VERIFY
INUSE:
GETIO:
SETIO:
GETRDONLY:
SETATTRIB:
USERCODE:
MOV AL,0
RET
VERIFY:
AND AL,1
MOV CS:VERFLG,AL
RET
FLUSHKB:
PUSH AX
CALL FAR PTR BIOSFLUSH
POP AX
MOV AH,AL
CMP AL,1
JZ REDISPJ
CMP AL,6
JZ REDISPJ
CMP AL,7
JZ REDISPJ
CMP AL,8
JZ REDISPJ
CMP AL,10
JZ REDISPJ
MOV AL,0
RET
REDISPJ:JMP REDISP
READER:
AUXIN:
CALL STATCHK
CALL FAR PTR BIOSAUXIN
RET
PUNCH:
MOV AL,DL
AUXOUT:
PUSH AX
CALL STATCHK
POP AX
CALL FAR PTR BIOSAUXOUT
RET
UNPACK:
; Inputs:
; DS = CS
; BX = Cluster number
; BP = Base of drive parameters
; SI = Pointer to drive FAT
; Outputs:
; DI = Contents of FAT for given cluster
; Zero set means DI=0 (free cluster)
; No other registers affected. Fatal error if cluster too big.
CMP BX,[BP.MAXCLUS]
JA HURTFAT
LEA DI,[SI+BX]
SHR BX,1
MOV DI,[DI+BX]
JNC HAVCLUS
SHR DI,1
SHR DI,1
SHR DI,1
SHR DI,1
STC
HAVCLUS:
RCL BX,1
AND DI,0FFFH
RET
HURTFAT:
PUSH AX
MOV AH,80H ;Signal Bad FAT to INT 24H handler
MOV DI,0FFFH ;In case INT 24H returns (it shouldn't)
CALL FATAL
POP AX ;Try to ignore bad FAT
RET
PACK:
; Inputs:
; DS = CS
; BX = Cluster number
; DX = Data
; SI = Pointer to drive FAT
; Outputs:
; The data is stored in the FAT at the given cluster.
; BX,DX,DI all destroyed
; No other registers affected
MOV DI,BX
SHR BX,1
ADD BX,SI
ADD BX,DI
SHR DI,1
MOV DI,[BX]
JNC ALIGNED
SHL DX,1
SHL DX,1
SHL DX,1
SHL DX,1
AND DI,0FH
JMP SHORT PACKIN
ALIGNED:
AND DI,0F000H
PACKIN:
OR DI,DX
MOV [BX],DI
RET
DEVNAME:
MOV SI,OFFSET DOSGROUP:IONAME ;List of I/O devices with file names
MOV BH,NUMDEV ;BH = number of device names
LOOKIO:
MOV DI,OFFSET DOSGROUP:NAME1
MOV CX,4 ;All devices are 4 letters
REPE CMPSB ;Check for name in list
JZ IOCHK ;If first 3 letters OK, check for the rest
ADD SI,CX ;Point to next device name
DEC BH
JNZ LOOKIO
CRET:
STC ;Not found
RET
IOCHK:
IF IBM
CMP BH,NUMDEV ;Is it the first device?
JNZ NOTCOM1
MOV BH,2 ;Make it the same as AUX
NOTCOM1:
ENDIF
NEG BH
MOV CX,2 ;Check rest of name but not extension
MOV AX,2020H
REPE SCASW ;Make sure rest of name is blanks
JNZ CRET
RET1: RET ;Zero set so CREATE works
GETFILE:
; Same as GETNAME except ES:DI points to FCB on successful return
CALL MOVNAME
JC RET1
PUSH DX
PUSH DS
CALL FINDNAME
POP ES
POP DI
RET2: RET
GETNAME:
; Inputs:
; DS,DX point to FCB
; Function:
; Find file name in disk directory. First byte is
; drive number (0=current disk). "?" matches any
; character.
; Outputs:
; Carry set if file not found
; ELSE
; Zero set if attributes match (always except when creating)
; BP = Base of drive parameters
; DS = CS
; ES = CS
; BX = Pointer into directory buffer
; SI = Pointer to First Cluster field in directory entry
; [DIRBUF] has directory record with match
; [NAME1] has file name
; All other registers destroyed.
CALL MOVNAME
JC RET2 ;Bad file name?
FINDNAME:
MOV AX,CS
MOV DS,AX
CALL DEVNAME
JNC RET2
CALL STARTSRCH
CONTSRCH:
CALL GETENTRY
JC RET2
SRCH:
MOV AH,BYTE PTR [BX]
OR AH,AH ;End of directory?
JZ FREE
CMP AH,[DELALL] ;Free entry?
JZ FREE
MOV SI,BX
MOV DI,OFFSET DOSGROUP:NAME1
MOV CX,11
WILDCRD:
REPE CMPSB
JZ FOUND
CMP BYTE PTR [DI-1],"?"
JZ WILDCRD
NEXTENT:
CALL NEXTENTRY
JNC SRCH
RET3: RET
FREE:
CMP [ENTFREE],-1 ;Found a free entry before?
JNZ TSTALL ;If so, ignore this one
MOV CX,[LASTENT]
MOV [ENTFREE],CX
TSTALL:
CMP AH,[DELALL] ;At end of directory?
JZ NEXTENT ;No - continue search
STC ;Report not found
RET
FOUND:
;Check if attributes allow finding it
MOV AH,[ATTRIB] ;Attributes of search
NOT AH
AND AH,[SI] ;Compare with attributes of file
ADD SI,15
AND AH,6 ;Only look at bits 1 and 2
JZ RET3
TEST BYTE PTR [CREATING],-1 ;Pass back mismatch if creating
JZ NEXTENT ;Otherwise continue searching
RET
GETENTRY:
; Inputs:
; [LASTENT] has previously searched directory entry
; Function:
; Locates next sequential directory entry in preparation for search
; Outputs:
; Carry set if none
; ELSE
; AL = Current directory block
; BX = Pointer to next directory entry in [DIRBUF]
; DX = Pointer to first byte after end of DIRBUF
; [LASTENT] = New directory entry number
MOV AX,[LASTENT]
INC AX ;Start with next entry
CMP AX,[BP.MAXENT]
JAE NONE
GETENT:
MOV [LASTENT],AX
MOV CL,4
SHL AX,CL
XOR DX,DX
SHL AX,1
RCL DX,1 ;Account for overflow in last shift
MOV BX,[BP.SECSIZ]
AND BL,255-31 ;Must be multiple of 32
DIV BX
MOV BX,DX ;Position within sector
MOV AH,[BP.DEVNUM] ;AL=Directory sector no.
CMP AX,[DIRBUFID]
JZ HAVDIRBUF
PUSH BX
CALL DIRREAD
POP BX
HAVDIRBUF:
MOV DX,OFFSET DOSGROUP:DIRBUF
ADD BX,DX
ADD DX,[BP.SECSIZ]
RET
NEXTENTRY:
; Inputs:
; Same as outputs of GETENTRY, above
; Function:
; Update AL, BX, and [LASTENT] for next directory entry.
; Carry set if no more.
MOV DI,[LASTENT]
INC DI
CMP DI,[BP.MAXENT]
JAE NONE
MOV [LASTENT],DI
ADD BX,32
CMP BX,DX
JB HAVIT
INC AL ;Next directory sector
PUSH DX ;Save limit
CALL DIRREAD
POP DX
MOV BX,OFFSET DOSGROUP:DIRBUF
HAVIT:
CLC
RET
NONE:
CALL CHKDIRWRITE
STC
RET4: RET
DELETE: ; System call 19
CALL MOVNAME
MOV AL,-1
JC RET4
MOV AL,CS:[ATTRIB]
AND AL,6 ;Look only at hidden bits
CMP AL,6 ;Both must be set
JNZ NOTALL
MOV CX,11
MOV AL,"?"
MOV DI,OFFSET DOSGROUP:NAME1
REPE SCASB ;See if name is *.*
JNZ NOTALL
MOV BYTE PTR CS:[DELALL],0 ;DEL *.* - flag deleting all
NOTALL:
CALL FINDNAME
MOV AL,-1
JC RET4
OR BH,BH ;Check if device name
JS RET4 ;Can't delete I/O devices
DELFILE:
MOV BYTE PTR [DIRTYDIR],-1
MOV AH,[DELALL]
MOV BYTE PTR [BX],AH
MOV BX,[SI]
MOV SI,[BP.FAT]
OR BX,BX
JZ DELNXT
CMP BX,[BP.MAXCLUS]
JA DELNXT
CALL RELEASE
DELNXT:
CALL CONTSRCH
JNC DELFILE
CALL FATWRT
CALL CHKDIRWRITE
XOR AL,AL
RET
RENAME: ;System call 23
CALL MOVNAME
JC ERRET
ADD SI,5
MOV DI,OFFSET DOSGROUP:NAME2
CALL LODNAME
JC ERRET ;Report error if second name invalid
CALL FINDNAME
JC ERRET
OR BH,BH ;Check if I/O device name
JS ERRET ;If so, can't rename it
MOV SI,OFFSET DOSGROUP:NAME1
MOV DI,OFFSET DOSGROUP:NAME3
MOV CX,6 ;6 words (12 bytes)--include attribute byte
REP MOVSW ;Copy name to search for
RENFIL:
MOV DI,OFFSET DOSGROUP:NAME1
MOV SI,OFFSET DOSGROUP:NAME2
MOV CX,11
NEWNAM:
LODSB
CMP AL,"?"
JNZ NOCHG
MOV AL,[BX]
NOCHG:
STOSB
INC BX
LOOP NEWNAM
MOV BYTE PTR [DI],6 ;Stop duplicates with any attributes
CALL DEVNAME ;Check if giving it a device name
JNC RENERR
PUSH [LASTENT] ;Save position of match
MOV [LASTENT],-1 ;Search entire directory for duplicate
CALL CONTSRCH ;See if new name already exists
POP AX
JNC RENERR ;Error if found
CALL GETENT ;Re-read matching entry
MOV DI,BX
MOV SI,OFFSET DOSGROUP:NAME1
MOV CX,5
MOVSB
REP MOVSW ;Replace old name with new one
MOV BYTE PTR [DIRTYDIR],-1 ;Flag change in directory
MOV SI,OFFSET DOSGROUP:NAME3
MOV DI,OFFSET DOSGROUP:NAME1
MOV CX,6 ;Include attribute byte
REP MOVSW ;Copy name back into search buffer
CALL CONTSRCH
JNC RENFIL
CALL CHKDIRWRITE
XOR AL,AL
RET
RENERR:
CALL CHKDIRWRITE
ERRET:
MOV AL,-1
RET5: RET
MOVNAME:
; Inputs:
; DS, DX point to FCB or extended FCB
; Outputs:
; DS:DX point to normal FCB
; ES = CS
; If file name OK:
; BP has base of driver parameters
; [NAME1] has name in upper case
; All registers except DX destroyed
; Carry set if bad file name or drive
MOV CS:WORD PTR [CREATING],0E500H ;Not creating, not DEL *.*
MOV AX,CS
MOV ES,AX
MOV DI,OFFSET DOSGROUP:NAME1
MOV SI,DX
LODSB
MOV CS:[EXTFCB],AL ;Set flag if extended FCB in use
MOV AH,0 ;Set default attributes
CMP AL,-1 ;Is it an extended FCB?
JNZ HAVATTRB
ADD DX,7 ;Adjust to point to normal FCB
ADD SI,6 ;Point to drive select byte
MOV AH,[SI-1] ;Get attribute byte
LODSB ;Get drive select byte
HAVATTRB:
MOV CS:[ATTRIB],AH ;Save attributes
CALL GETTHISDRV
LODNAME:
; This entry point copies a file name from DS,SI
; to ES,DI converting to upper case.
CMP BYTE PTR [SI]," " ;Don't allow blank as first letter
STC ;In case of error
JZ RET5
MOV CX,11
MOVCHK:
CALL GETLET
JB RET5
JNZ STOLET ;Is it a delimiter?
CMP AL," " ;This is the only delimiter allowed
STC ;In case of error
JNZ RET5
STOLET:
STOSB
LOOP MOVCHK
CLC ;Got through whole name - no error
RET6: RET
GETTHISDRV:
CMP CS:[NUMDRV],AL
JC RET6
DEC AL
JNS PHYDRV
MOV AL,CS:[CURDRV]
PHYDRV:
MOV CS:[THISDRV],AL
RET
OPEN: ;System call 15
CALL GETFILE
DOOPEN:
; Enter here to perform OPEN on file already found
; in directory. DS=CS, BX points to directory
; entry in DIRBUF, SI points to First Cluster field, and
; ES:DI point to the FCB to be opened. This entry point
; is used by CREATE.
JC ERRET
OR BH,BH ;Check if file is I/O device
JS OPENDEV ;Special handler if so
MOV AL,[THISDRV]
INC AX
STOSB
XOR AX,AX
IF ZEROEXT
ADD DI,11
STOSW ;Zero low byte of extent field if IBM only
ENDIF
IF NOT ZEROEXT
ADD DI,12 ;Point to high half of CURRENT BLOCK field
STOSB ;Set it to zero (CP/M programs set low byte)
ENDIF
MOV AL,128 ;Default record size
STOSW ;Set record size
LODSW ;Get starting cluster
MOV DX,AX ;Save it for the moment
MOVSW ;Transfer size to FCB
MOVSW
MOV AX,[SI-8] ;Get date
STOSW ;Save date in FCB
MOV AX,[SI-10] ;Get time
STOSW ;Save it in FCB
MOV AL,[BP.DEVNUM]
OR AL,40H
STOSB
MOV AX,DX ;Restore starting cluster
STOSW ; first cluster
STOSW ; last cluster accessed
XOR AX,AX
STOSW ; position of last cluster
RET
OPENDEV:
ADD DI,13 ;point to 2nd half of extent field
XOR AX,AX
STOSB ;Set it to zero
MOV AL,128
STOSW ;Set record size to 128
XOR AX,AX
STOSW
STOSW ;Set current size to zero
CALL DATE16
STOSW ;Date is todays
XCHG AX,DX
STOSW ;Use current time
MOV AL,BH ;Get device number
STOSB
XOR AL,AL ;No error
RET
FATERR:
XCHG AX,DI ;Put error code in DI
MOV AH,2 ;While trying to read FAT
MOV AL,[THISDRV] ;Tell which drive
CALL FATAL1
JMP SHORT FATREAD
STARTSRCH:
MOV AX,-1
MOV [LASTENT],AX
MOV [ENTFREE],AX
FATREAD:
; Inputs:
; DS = CS
; Function:
; If disk may have been changed, FAT is read in and buffers are
; flagged invalid. If not, no action is taken.
; Outputs:
; BP = Base of drive parameters
; Carry set if invalid drive returned by MAPDEV
; All other registers destroyed
MOV AL,[THISDRV]
XOR AH,AH ;Set default response to zero & clear carry
CALL FAR PTR BIOSDSKCHG ;See what BIOS has to say
JC FATERR
CALL GETBP
MOV AL,[THISDRV] ;Use physical unit number
MOV SI,[BP.FAT]
OR AH,[SI-1] ;Dirty byte for FAT
JS NEWDSK ;If either say new disk, then it's so
JNZ MAPDRV
MOV AH,1
CMP AX,WORD PTR [BUFDRVNO] ;Does buffer have dirty sector of this drive?
JZ MAPDRV
NEWDSK:
CMP AL,[BUFDRVNO] ;See if buffer is for this drive
JNZ BUFOK ;If not, don't touch it
MOV [BUFSECNO],0 ;Flag buffers invalid
MOV WORD PTR [BUFDRVNO],00FFH
BUFOK:
MOV [DIRBUFID],-1
CALL FIGFAT
NEXTFAT:
PUSH AX
CALL DSKREAD
POP AX
JC BADFAT
SUB AL,[BP.FATCNT]
JZ NEWFAT
CALL FATWRT
NEWFAT:
MOV SI,[BP.FAT]
MOV AL,[BP.DEVNUM]
MOV AH,[SI] ;Get first byte of FAT
OR AH,0F8H ;Put in range
CALL FAR PTR BIOSMAPDEV
MOV AH,0
MOV [SI-2],AX ;Set device no. and reset dirty bit
MAPDRV:
MOV AL,[SI-2] ;Get device number
GETBP:
MOV BP,[DRVTAB] ;Just in case drive isn't valid
AND AL,3FH ;Mask out dirty bit
CMP AL,[NUMIO]
CMC
JC RET7
PUSH AX
MOV AH,DPBSIZ
MUL AH
ADD BP,AX
POP AX
RET7: RET
BADFAT:
MOV CX,DI
ADD DX,CX
DEC AL
JNZ NEXTFAT
CALL FIGFAT ;Reset registers
CALL DREAD ;Try first FAT once more
JMP SHORT NEWFAT
OKRET1:
MOV AL,0
RET
CLOSE: ;System call 16
MOV DI,DX
CMP BYTE PTR [DI],-1 ;Check for extended FCB
JNZ NORMFCB3
ADD DI,7
NORMFCB3:
TEST BYTE PTR [DI.DEVID],0C0H ;Allow only dirty files
JNZ OKRET1 ;can't close if I/O device, or not writen
MOV AL,[DI] ;Get physical unit number
DEC AL ;Make zero = drive A
MOV AH,1 ;Look for dirty buffer
CMP AX,CS:WORD PTR [BUFDRVNO]
JNZ FNDDIR
;Write back dirty buffer if on same drive
PUSH DX
PUSH DS
PUSH CS
POP DS
MOV BYTE PTR [DIRTYBUF],0
MOV BX,[BUFFER]
MOV CX,1
MOV DX,[BUFSECNO]
MOV BP,[BUFDRVBP]
CALL DWRITE
POP DS
POP DX
FNDDIR:
CALL GETFILE
BADCLOSEJ:
JC BADCLOSE
MOV CX,ES:[DI.FIRCLUS]
MOV [SI],CX
MOV DX,ES:WORD PTR [DI.FILSIZ]
MOV [SI+2],DX
MOV DX,ES:WORD PTR [DI.FILSIZ+2]
MOV [SI+4],DX
MOV DX,ES:[DI.FDATE]
MOV [SI-2],DX
MOV DX,ES:[DI.FTIME]
MOV [SI-4],DX
CALL DIRWRITE
CHKFATWRT:
; Do FATWRT only if FAT is dirty and uses same I/O driver
MOV SI,[BP.FAT]
MOV AL,[BP.DEVNUM]
MOV AH,1
CMP [SI-2],AX ;See if FAT dirty and uses same driver
JNZ OKRET
FATWRT:
; Inputs:
; DS = CS
; BP = Base of drive parameter table
; Function:
; Write the FAT back to disk and reset FAT
; dirty bit.
; Outputs:
; AL = 0
; BP unchanged
; All other registers destroyed
CALL FIGFAT
MOV BYTE PTR [BX-1],0
EACHFAT:
PUSH DX
PUSH CX
PUSH BX
PUSH AX
CALL DWRITE
POP AX
POP BX
POP CX
POP DX
ADD DX,CX
DEC AL
JNZ EACHFAT
OKRET:
MOV AL,0
RET
BADCLOSE:
MOV SI,[BP.FAT]
MOV BYTE PTR [SI-1],0
MOV AL,-1
RET
FIGFAT:
; Loads registers with values needed to read or
; write a FAT.
MOV AL,[BP.FATCNT]
MOV BX,[BP.FAT]
MOV CL,[BP.FATSIZ] ;No. of records occupied by FAT
MOV CH,0
MOV DX,[BP.FIRFAT] ;Record number of start of FATs
RET
DIRCOMP:
; Prepare registers for directory read or write
CBW
ADD AX,[BP.FIRDIR]
MOV DX,AX
MOV BX,OFFSET DOSGROUP:DIRBUF
MOV CX,1
RET
CREATE: ;System call 22
CALL MOVNAME
JC ERRET3
MOV DI,OFFSET DOSGROUP:NAME1
MOV CX,11
MOV AL,"?"
REPNE SCASB
JZ ERRET3
MOV CS:BYTE PTR [CREATING],-1
PUSH DX
PUSH DS
CALL FINDNAME
JNC EXISTENT
MOV AX,[ENTFREE] ;First free entry found in FINDNAME
CMP AX,-1
JZ ERRPOP
CALL GETENT ;Point at that free entry
JMP SHORT FREESPOT
ERRPOP:
POP DS
POP DX
ERRET3:
MOV AL,-1
RET
EXISTENT:
JNZ ERRPOP ;Error if attributes don't match
OR BH,BH ;Check if file is I/O device
JS OPENJMP ;If so, no action
MOV CX,[SI] ;Get pointer to clusters
JCXZ FREESPOT
CMP CX,[BP.MAXCLUS]
JA FREESPOT
PUSH BX
MOV BX,CX
MOV SI,[BP.FAT]
CALL RELEASE ;Free any data already allocated
CALL FATWRT
POP BX
FREESPOT:
MOV DI,BX
MOV SI,OFFSET DOSGROUP:NAME1
MOV CX,5
MOVSB
REP MOVSW
MOV AL,[ATTRIB]
STOSB
XOR AX,AX
MOV CL,5
REP STOSW
CALL DATE16
XCHG AX,DX
STOSW
XCHG AX,DX
STOSW
XOR AX,AX
PUSH DI
MOV CL,6
SMALLENT:
REP STOSB
PUSH BX
CALL DIRWRITE
POP BX
POP SI
OPENJMP:
CLC ;Clear carry so OPEN won't fail
POP ES
POP DI
JMP DOOPEN
DIRREAD:
; Inputs:
; DS = CS
; AL = Directory block number
; BP = Base of drive parameters
; Function:
; Read the directory block into DIRBUF.
; Outputs:
; AX,BP unchanged
; All other registers destroyed.
PUSH AX
CALL CHKDIRWRITE
POP AX
PUSH AX
MOV AH,[BP.DEVNUM]
MOV [DIRBUFID],AX
CALL DIRCOMP
CALL DREAD
POP AX
RET8: RET
DREAD:
; Inputs:
; BX,DS = Transfer address
; CX = Number of sectors
; DX = Absolute record number
; BP = Base of drive parameters
; Function:
; Calls BIOS to perform disk read. If BIOS reports
; errors, will call HARDERR for further action.
; BP preserved. All other registers destroyed.
CALL DSKREAD
JNC RET8
MOV CS:BYTE PTR [READOP],0
CALL HARDERR
CMP AL,1 ;Check for retry
JZ DREAD
RET ;Ignore otherwise
HARDERR:
;Hard disk error handler. Entry conditions:
; DS:BX = Original disk transfer address
; DX = Original logical sector number
; CX = Number of sectors to go (first one gave the error)
; AX = Hardware error code
; DI = Original sector transfer count
; BP = Base of drive parameters
; [READOP] = 0 for read, 1 for write
XCHG AX,DI ;Error code in DI, count in AX
SUB AX,CX ;Number of sectors successfully transferred
ADD DX,AX ;First sector number to retry
PUSH DX
MUL [BP.SECSIZ] ;Number of bytes transferred
POP DX
ADD BX,AX ;First address for retry
MOV AH,0 ;Flag disk section in error
CMP DX,[BP.FIRFAT] ;In reserved area?
JB ERRINT
INC AH ;Flag for FAT
CMP DX,[BP.FIRDIR] ;In FAT?
JB ERRINT
INC AH
CMP DX,[BP.FIRREC] ;In directory?
JB ERRINT
INC AH ;Must be in data area
ERRINT:
SHL AH,1 ;Make room for read/write bit
OR AH,CS:[READOP]
FATAL:
MOV AL,[BP.DRVNUM] ;Get drive number
FATAL1:
PUSH BP ;The only thing we preserve
MOV CS:[CONTSTK],SP
CLI ;Prepare to play with stack
MOV SS,CS:[SSSAVE]
MOV SP,CS:[SPSAVE] ;User stack pointer restored
INT 24H ;Fatal error interrupt vector
MOV CS:[SPSAVE],SP
MOV CS:[SSSAVE],SS
MOV SP,CS
MOV SS,SP
MOV SP,CS:[CONTSTK]
STI
POP BP
CMP AL,2
JZ ERROR
RET
DSKREAD:
MOV AL,[BP.DEVNUM]
PUSH BP
PUSH BX
PUSH CX
PUSH DX
CALL FAR PTR BIOSREAD
POP DX
POP DI
POP BX
POP BP
RET9: RET
CHKDIRWRITE:
TEST BYTE PTR [DIRTYDIR],-1
JZ RET9
DIRWRITE:
; Inputs:
; DS = CS
; AL = Directory block number
; BP = Base of drive parameters
; Function:
; Write the directory block into DIRBUF.
; Outputs:
; BP unchanged
; All other registers destroyed.
MOV BYTE PTR [DIRTYDIR],0
MOV AL,BYTE PTR [DIRBUFID]
CALL DIRCOMP
DWRITE:
; Inputs:
; BX,DS = Transfer address
; CX = Number of sectors
; DX = Absolute record number
; BP = Base of drive parameters
; Function:
; Calls BIOS to perform disk write. If BIOS reports
; errors, will call HARDERR for further action.
; BP preserved. All other registers destroyed.
MOV AL,[BP.DEVNUM]
MOV AH,CS:VERFLG
PUSH BP
PUSH BX
PUSH CX
PUSH DX
CALL FAR PTR BIOSWRITE
POP DX
POP DI
POP BX
POP BP
JNC RET9
MOV CS:BYTE PTR [READOP],1
CALL HARDERR
CMP AL,1 ;Check for retry
JZ DWRITE
RET
ABORT:
LDS SI,CS:DWORD PTR [SPSAVE]
MOV DS,[SI.CSSAVE]
XOR AX,AX
MOV ES,AX
MOV SI,SAVEXIT
MOV DI,EXIT
MOVSW
MOVSW
MOVSW
MOVSW
MOVSW
MOVSW
ERROR:
MOV AX,CS
MOV DS,AX
MOV ES,AX
CALL WRTFATS
XOR AX,AX
CLI
MOV SS,[SSSAVE]
MOV SP,[SPSAVE]
MOV DS,AX
MOV SI,EXIT
MOV DI,OFFSET DOSGROUP:EXITHOLD
MOVSW
MOVSW
POP AX
POP BX
POP CX
POP DX
POP SI
POP DI
POP BP
POP DS
POP ES
STI ;Stack OK now
JMP CS:DWORD PTR [EXITHOLD]
SEQRD: ;System call 20
CALL GETREC
CALL LOAD
JMP SHORT FINSEQ
SEQWRT: ;System call 21
CALL GETREC
CALL STORE
FINSEQ:
JCXZ SETNREX
ADD AX,1
ADC DX,0
JMP SHORT SETNREX
RNDRD: ;System call 33
CALL GETRRPOS1
CALL LOAD
JMP SHORT FINRND
RNDWRT: ;System call 34
CALL GETRRPOS1
CALL STORE
JMP SHORT FINRND
BLKRD: ;System call 39
CALL GETRRPOS
CALL LOAD
JMP SHORT FINBLK
BLKWRT: ;System call 40
CALL GETRRPOS
CALL STORE
FINBLK:
LDS SI,DWORD PTR [SPSAVE]
MOV [SI.CXSAVE],CX
JCXZ FINRND
ADD AX,1
ADC DX,0
FINRND:
MOV ES:WORD PTR [DI.RR],AX
MOV ES:[DI.RR+2],DL
OR DH,DH
JZ SETNREX
MOV ES:[DI.RR+3],DH ;Save 4 byte of RECPOS only if significant
SETNREX:
MOV CX,AX
AND AL,7FH
MOV ES:[DI.NR],AL
AND CL,80H
SHL CX,1
RCL DX,1
MOV AL,CH
MOV AH,DL
MOV ES:[DI.EXTENT],AX
MOV AL,CS:[DSKERR]
RET
GETRRPOS1:
MOV CX,1
GETRRPOS:
MOV DI,DX
CMP BYTE PTR [DI],-1
JNZ NORMFCB1
ADD DI,7
NORMFCB1:
MOV AX,WORD PTR [DI.RR]
MOV DX,WORD PTR [DI.RR+2]
RET
NOFILERR:
XOR CX,CX
MOV BYTE PTR [DSKERR],4
POP BX
RET
SETUP:
; Inputs:
; DS:DI point to FCB
; DX:AX = Record position in file of disk transfer
; CX = Record count
; Outputs:
; DS = CS
; ES:DI point to FCB
; BL = DEVID from FCB
; CX = No. of bytes to transfer
; BP = Base of drive parameters
; SI = FAT pointer
; [RECCNT] = Record count
; [RECPOS] = Record position in file
; [FCB] = DI
; [NEXTADD] = Displacement of disk transfer within segment
; [SECPOS] = Position of first sector
; [BYTPOS] = Byte position in file
; [BYTSECPOS] = Byte position in first sector
; [CLUSNUM] = First cluster
; [SECCLUSPOS] = Sector within first cluster
; [DSKERR] = 0 (no errors yet)
; [TRANS] = 0 (No transfers yet)
; [THISDRV] = Physical drive unit number
; If SETUP detects no records will be transfered, it returns 1 level up
; with CX = 0.
PUSH AX
MOV AL,[DI]
DEC AL
MOV CS:[THISDRV],AL
MOV AL,[DI.DEVID]
MOV SI,[DI.RECSIZ]
OR SI,SI
JNZ HAVRECSIZ
MOV SI,128
MOV [DI.RECSIZ],SI
HAVRECSIZ:
PUSH DS
POP ES ;Set ES to DS
PUSH CS
POP DS ;Set DS to CS
OR AL,AL ;Is it a device?
JNS NOTDEVICE
MOV AL,0 ;Fake in drive 0 so we can get SP
NOTDEVICE:
CALL GETBP
POP AX
JC NOFILERR
CMP SI,64 ;Check if highest byte of RECPOS is significant
JB SMALREC
MOV DH,0 ;Ignore MSB if record >= 64 bytes
SMALREC:
MOV [RECCNT],CX
MOV WORD PTR [RECPOS],AX
MOV WORD PTR [RECPOS+2],DX
MOV [FCB],DI
MOV BX,[DMAADD]
MOV [NEXTADD],BX
MOV BYTE PTR [DSKERR],0
MOV BYTE PTR [TRANS],0
MOV BX,DX
MUL SI
MOV WORD PTR [BYTPOS],AX
PUSH DX
MOV AX,BX
MUL SI
POP BX
ADD AX,BX
ADC DX,0 ;Ripple carry
JNZ EOFERR
MOV WORD PTR [BYTPOS+2],AX
MOV DX,AX
MOV AX,WORD PTR [BYTPOS]
MOV BX,[BP.SECSIZ]
CMP DX,BX ;See if divide will overflow
JNC EOFERR
DIV BX
MOV [SECPOS],AX
MOV [BYTSECPOS],DX
MOV DX,AX
AND AL,[BP.CLUSMSK]
MOV [SECCLUSPOS],AL
MOV AX,CX ;Record count
MOV CL,[BP.CLUSSHFT]
SHR DX,CL
MOV [CLUSNUM],DX
MUL SI ;Multiply by bytes per record
MOV CX,AX
ADD AX,[DMAADD] ;See if it will fit in one segment
ADC DX,0
JZ OK ;Must be less than 64K
MOV AX,[DMAADD]
NEG AX ;Amount of room left in segment
JNZ PARTSEG ;All 64K available?
DEC AX ;If so, reduce by one
PARTSEG:
XOR DX,DX
DIV SI ;How many records will fit?
MOV [RECCNT],AX
MUL SI ;Translate that back into bytes
MOV BYTE PTR [DSKERR],2 ;Flag that trimming took place
MOV CX,AX
JCXZ NOROOM
OK:
MOV BL,ES:[DI.DEVID]
MOV SI,[BP.FAT]
RET
EOFERR:
MOV BYTE PTR [DSKERR],1
XOR CX,CX
NOROOM:
POP BX ;Kill return address
RET
BREAKDOWN:
;Inputs:
; DS = CS
; CX = Length of disk transfer in bytes
; BP = Base of drive parameters
; [BYTSECPOS] = Byte position witin first sector
;Outputs:
; [BYTCNT1] = Bytes to transfer in first sector
; [SECCNT] = No. of whole sectors to transfer
; [BYTCNT2] = Bytes to transfer in last sector
;AX, BX, DX destroyed. No other registers affected.
MOV AX,[BYTSECPOS]
MOV BX,CX
OR AX,AX
JZ SAVFIR ;Partial first sector?
SUB AX,[BP.SECSIZ]
NEG AX ;Max number of bytes left in first sector
SUB BX,AX ;Subtract from total length
JAE SAVFIR
ADD AX,BX ;Don't use all of the rest of the sector
XOR BX,BX ;And no bytes are left
SAVFIR:
MOV [BYTCNT1],AX
MOV AX,BX
XOR DX,DX
DIV [BP.SECSIZ] ;How many whole sectors?
MOV [SECCNT],AX
MOV [BYTCNT2],DX ;Bytes remaining for last sector
RET10: RET
FNDCLUS:
; Inputs:
; DS = CS
; CX = No. of clusters to skip
; BP = Base of drive parameters
; SI = FAT pointer
; ES:DI point to FCB
; Outputs:
; BX = Last cluster skipped to
; CX = No. of clusters remaining (0 unless EOF)
; DX = Position of last cluster
; DI destroyed. No other registers affected.
MOV BX,ES:[DI.LSTCLUS]
MOV DX,ES:[DI.CLUSPOS]
OR BX,BX
JZ NOCLUS
SUB CX,DX
JNB FINDIT
ADD CX,DX
XOR DX,DX
MOV BX,ES:[DI.FIRCLUS]
FINDIT:
JCXZ RET10
SKPCLP:
CALL UNPACK
CMP DI,0FF8H
JAE RET10
XCHG BX,DI
INC DX
LOOP SKPCLP
RET
NOCLUS:
INC CX
DEC DX
RET
BUFSEC:
; Inputs:
; AL = 0 if buffer must be read, 1 if no pre-read needed
; BP = Base of drive parameters
; [CLUSNUM] = Physical cluster number
; [SECCLUSPOS] = Sector position of transfer within cluster
; [BYTCNT1] = Size of transfer
; Function:
; Insure specified sector is in buffer, flushing buffer before
; read if necessary.
; Outputs:
; SI = Pointer to buffer
; DI = Pointer to transfer address
; CX = Number of bytes
; [NEXTADD] updated
; [TRANS] set to indicate a transfer will occur
MOV DX,[CLUSNUM]
MOV BL,[SECCLUSPOS]
CALL FIGREC
MOV [PREREAD],AL
CMP DX,[BUFSECNO]
JNZ GETSEC
MOV AL,[BUFDRVNO]
CMP AL,[THISDRV]
JZ FINBUF ;Already have it?
GETSEC:
XOR AL,AL
XCHG [DIRTYBUF],AL ;Read dirty flag and reset it
OR AL,AL
JZ RDSEC
PUSH DX
PUSH BP
MOV BP,[BUFDRVBP]
MOV BX,[BUFFER]
MOV CX,1
MOV DX,[BUFSECNO]
CALL DWRITE
POP BP
POP DX
RDSEC:
TEST BYTE PTR [PREREAD],-1
JNZ SETBUF
XOR AX,AX
MOV [BUFSECNO],AX ;Set buffer valid in case of disk error
DEC AX
MOV [BUFDRVNO],AL
MOV BX,[BUFFER]
MOV CX,1
PUSH DX
CALL DREAD
POP DX
SETBUF:
MOV [BUFSECNO],DX
MOV AL,[THISDRV]
MOV [BUFDRVNO],AL
MOV [BUFDRVBP],BP
FINBUF:
MOV BYTE PTR [TRANS],1 ;A transfer is taking place
MOV DI,[NEXTADD]
MOV SI,DI
MOV CX,[BYTCNT1]
ADD SI,CX
MOV [NEXTADD],SI
MOV SI,[BUFFER]
ADD SI,[BYTSECPOS]
RET
BUFRD:
XOR AL,AL ;Pre-read necessary
CALL BUFSEC
PUSH ES
MOV ES,[DMAADD+2]
SHR CX,1
JNC EVENRD
MOVSB
EVENRD:
REP MOVSW
POP ES
RET
BUFWRT:
MOV AX,[SECPOS]
INC AX ;Set for next sector
MOV [SECPOS],AX
CMP AX,[VALSEC] ;Has sector been written before?
MOV AL,1
JA NOREAD ;Skip preread if SECPOS>VALSEC
MOV AL,0
NOREAD:
CALL BUFSEC
XCHG DI,SI
PUSH DS
PUSH ES
PUSH CS
POP ES
MOV DS,[DMAADD+2]
SHR CX,1
JNC EVENWRT
MOVSB
EVENWRT:
REP MOVSW
POP ES
POP DS
MOV BYTE PTR [DIRTYBUF],1
RET
NEXTSEC:
TEST BYTE PTR [TRANS],-1
JZ CLRET
MOV AL,[SECCLUSPOS]
INC AL
CMP AL,[BP.CLUSMSK]
JBE SAVPOS
MOV BX,[CLUSNUM]
CMP BX,0FF8H
JAE NONEXT
MOV SI,[BP.FAT]
CALL UNPACK
MOV [CLUSNUM],DI
INC [LASTPOS]
MOV AL,0
SAVPOS:
MOV [SECCLUSPOS],AL
CLRET:
CLC
RET
NONEXT:
STC
RET
TRANBUF:
LODSB
STOSB
CMP AL,13 ;Check for carriage return
JNZ NORMCH
MOV BYTE PTR [SI],10
NORMCH:
CMP AL,10
LOOPNZ TRANBUF
JNZ ENDRDCON
CALL OUT ;Transmit linefeed
XOR SI,SI
OR CX,CX
JNZ GETBUF
OR AL,1 ;Clear zero flag--not end of file
ENDRDCON:
MOV [CONTPOS],SI
ENDRDDEV:
MOV [NEXTADD],DI
POP ES
JNZ SETFCBJ ;Zero set if Ctrl-Z found in input
MOV DI,[FCB]
AND ES:BYTE PTR [DI.DEVID],0FFH-40H ;Mark as no more data available
SETFCBJ:
JMP SETFCB
READDEV:
PUSH ES
LES DI,DWORD PTR [DMAADD]
INC BL
JZ READCON
INC BL
JNZ ENDRDDEV
READAUX:
CALL AUXIN
STOSB
CMP AL,1AH
LOOPNZ READAUX
JMP SHORT ENDRDDEV
READCON:
PUSH CS
POP DS
MOV SI,[CONTPOS]
OR SI,SI
JNZ TRANBUF
CMP BYTE PTR [CONBUF],128
JZ GETBUF
MOV WORD PTR [CONBUF],0FF80H ;Set up 128-byte buffer with no template
GETBUF:
PUSH CX
PUSH ES
PUSH DI
MOV DX,OFFSET DOSGROUP:CONBUF
CALL BUFIN ;Get input buffer
POP DI
POP ES
POP CX
MOV SI,2 + OFFSET DOSGROUP:CONBUF
CMP BYTE PTR [SI],1AH ;Check for Ctrl-Z in first character
JNZ TRANBUF
MOV AL,1AH
STOSB
MOV AL,10
CALL OUT ;Send linefeed
XOR SI,SI
JMP SHORT ENDRDCON
RDERR:
XOR CX,CX
JMP WRTERR
RDLASTJ:JMP RDLAST
LOAD:
; Inputs:
; DS:DI point to FCB
; DX:AX = Position in file to read
; CX = No. of records to read
; Outputs:
; DX:AX = Position of last record read
; CX = No. of bytes read
; ES:DI point to FCB
; LSTCLUS, CLUSPOS fields in FCB set
CALL SETUP
OR BL,BL ;Check for named device I/O
JS READDEV
MOV AX,ES:WORD PTR [DI.FILSIZ]
MOV BX,ES:WORD PTR [DI.FILSIZ+2]
SUB AX,WORD PTR [BYTPOS]
SBB BX,WORD PTR [BYTPOS+2]
JB RDERR
JNZ ENUF
OR AX,AX
JZ RDERR
CMP AX,CX
JAE ENUF
MOV CX,AX
ENUF:
CALL BREAKDOWN
MOV CX,[CLUSNUM]
CALL FNDCLUS
OR CX,CX
JNZ RDERR
MOV [LASTPOS],DX
MOV [CLUSNUM],BX
CMP [BYTCNT1],0
JZ RDMID
CALL BUFRD
RDMID:
CMP [SECCNT],0
JZ RDLASTJ
CALL NEXTSEC
JC SETFCB
MOV BYTE PTR [TRANS],1 ;A transfer is taking place
ONSEC:
MOV DL,[SECCLUSPOS]
MOV CX,[SECCNT]
MOV BX,[CLUSNUM]
RDLP:
CALL OPTIMIZE
PUSH DI
PUSH AX
PUSH DS
MOV DS,[DMAADD+2]
PUSH DX
PUSH BX
PUSHF ;Save carry flag
CALL DREAD
POPF ;Restore carry flag
POP DI ;Initial transfer address
POP AX ;First sector transfered
POP DS
JC NOTBUFFED ;Was one of those sectors in the buffer?
CMP BYTE PTR [DIRTYBUF],0 ;Is buffer dirty?
JZ NOTBUFFED ;If not no problem
;We have transfered in a sector from disk when a dirty copy of it is in the buffer.
;We must transfer the sector from the buffer to correct memory address
SUB AX,[BUFSECNO] ;How many sectors into the transfer?
NEG AX
MOV CX,[BP.SECSIZ]
MUL CX ;How many bytes into the transfer?
ADD DI,AX
MOV SI,[BUFFER]
PUSH ES
MOV ES,[DMAADD+2] ;Get disk transfer segment
SHR CX,1
REP MOVSW
JNC EVENMOV
MOVSB
EVENMOV:
POP ES
NOTBUFFED:
POP CX
POP BX
JCXZ RDLAST
CMP BX,0FF8H
JAE SETFCB
MOV DL,0
INC [LASTPOS] ;We'll be using next cluster
JMP SHORT RDLP
SETFCB:
MOV SI,[FCB]
MOV AX,[NEXTADD]
MOV DI,AX
SUB AX,[DMAADD] ;Number of bytes transfered
XOR DX,DX
MOV CX,ES:[SI.RECSIZ]
DIV CX ;Number of records
CMP AX,[RECCNT] ;Check if all records transferred
JZ FULLREC
MOV BYTE PTR [DSKERR],1
OR DX,DX
JZ FULLREC ;If remainder 0, then full record transfered
MOV BYTE PTR [DSKERR],3 ;Flag partial last record
SUB CX,DX ;Bytes left in last record
PUSH ES
MOV ES,[DMAADD+2]
XCHG AX,BX ;Save the record count temporarily
XOR AX,AX ;Fill with zeros
SHR CX,1
JNC EVENFIL
STOSB
EVENFIL:
REP STOSW
XCHG AX,BX ;Restore record count to AX
POP ES
INC AX ;Add last (partial) record to total
FULLREC:
MOV CX,AX
MOV DI,SI ;ES:DI point to FCB
SETCLUS:
MOV AX,[CLUSNUM]
MOV ES:[DI.LSTCLUS],AX
MOV AX,[LASTPOS]
MOV ES:[DI.CLUSPOS],AX
ADDREC:
MOV AX,WORD PTR [RECPOS]
MOV DX,WORD PTR [RECPOS+2]
JCXZ RET28 ;If no records read, don't change position
DEC CX
ADD AX,CX ;Update current record position
ADC DX,0
INC CX
RET28: RET
RDLAST:
MOV AX,[BYTCNT2]
OR AX,AX
JZ SETFCB
MOV [BYTCNT1],AX
CALL NEXTSEC
JC SETFCB
MOV [BYTSECPOS],0
CALL BUFRD
JMP SHORT SETFCB
WRTDEV:
PUSH DS
LDS SI,DWORD PTR [DMAADD]
OR BL,40H
INC BL
JZ WRTCON
INC BL
JZ WRTAUX
INC BL
JZ ENDWRDEV ;Done if device is NUL
WRTLST:
LODSB
CMP AL,1AH
JZ ENDWRDEV
CALL LISTOUT
LOOP WRTLST
JMP SHORT ENDWRDEV
WRTAUX:
LODSB
CALL AUXOUT
CMP AL,1AH
LOOPNZ WRTAUX
JMP SHORT ENDWRDEV
WRTCON:
LODSB
CMP AL,1AH
JZ ENDWRDEV
CALL OUT
LOOP WRTCON
ENDWRDEV:
POP DS
MOV CX,[RECCNT]
MOV DI,[FCB]
JMP SHORT ADDREC
HAVSTART:
MOV CX,AX
CALL SKPCLP
JCXZ DOWRTJ
CALL ALLOCATE
JNC DOWRTJ
WRTERR:
MOV BYTE PTR [DSKERR],1
LVDSK:
MOV AX,WORD PTR [RECPOS]
MOV DX,WORD PTR [RECPOS+2]
MOV DI,[FCB]
RET
DOWRTJ: JMP DOWRT
WRTEOFJ:
JMP WRTEOF
STORE:
; Inputs:
; DS:DI point to FCB
; DX:AX = Position in file of disk transfer
; CX = Record count
; Outputs:
; DX:AX = Position of last record written
; CX = No. of records written
; ES:DI point to FCB
; LSTCLUS, CLUSPOS fields in FCB set
CALL SETUP
CALL DATE16
MOV ES:[DI.FDATE],AX
MOV ES:[DI.FTIME],DX
OR BL,BL
JS WRTDEV
AND BL,3FH ;Mark file as dirty
MOV ES:[DI.DEVID],BL
CALL BREAKDOWN
MOV AX,WORD PTR [BYTPOS]
MOV DX,WORD PTR [BYTPOS+2]
JCXZ WRTEOFJ
DEC CX
ADD AX,CX
ADC DX,0 ;AX:DX=last byte accessed
DIV [BP.SECSIZ] ;AX=last sector accessed
MOV CL,[BP.CLUSSHFT]
SHR AX,CL ;Last cluster to be accessed
PUSH AX
MOV AX,ES:WORD PTR [DI.FILSIZ]
MOV DX,ES:WORD PTR [DI.FILSIZ+2]
DIV [BP.SECSIZ]
OR DX,DX
JZ NORNDUP
INC AX ;Round up if any remainder
NORNDUP:
MOV [VALSEC],AX ;Number of sectors that have been written
POP AX
MOV CX,[CLUSNUM] ;First cluster accessed
CALL FNDCLUS
MOV [CLUSNUM],BX
MOV [LASTPOS],DX
SUB AX,DX ;Last cluster minus current cluster
JZ DOWRT ;If we have last clus, we must have first
JCXZ HAVSTART ;See if no more data
PUSH CX ;No. of clusters short of first
MOV CX,AX
CALL ALLOCATE
POP AX
JC WRTERR
MOV CX,AX
MOV DX,[LASTPOS]
INC DX
DEC CX
JZ NOSKIP
CALL SKPCLP
NOSKIP:
MOV [CLUSNUM],BX
MOV [LASTPOS],DX
DOWRT:
CMP [BYTCNT1],0
JZ WRTMID
MOV BX,[CLUSNUM]
CALL BUFWRT
WRTMID:
MOV AX,[SECCNT]
OR AX,AX
JZ WRTLAST
ADD [SECPOS],AX
CALL NEXTSEC
MOV BYTE PTR [TRANS],1 ;A transfer is taking place
MOV DL,[SECCLUSPOS]
MOV BX,[CLUSNUM]
MOV CX,[SECCNT]
WRTLP:
CALL OPTIMIZE
JC NOTINBUF ;Is one of the sectors buffered?
MOV [BUFSECNO],0 ;If so, invalidate the buffer since we're
MOV WORD PTR [BUFDRVNO],0FFH ; completely rewritting it
NOTINBUF:
PUSH DI
PUSH AX
PUSH DS
MOV DS,[DMAADD+2]
CALL DWRITE
POP DS
POP CX
POP BX
JCXZ WRTLAST
MOV DL,0
INC [LASTPOS] ;We'll be using next cluster
JMP SHORT WRTLP
WRTLAST:
MOV AX,[BYTCNT2]
OR AX,AX
JZ FINWRT
MOV [BYTCNT1],AX
CALL NEXTSEC
MOV [BYTSECPOS],0
CALL BUFWRT
FINWRT:
MOV AX,[NEXTADD]
SUB AX,[DMAADD]
ADD AX,WORD PTR [BYTPOS]
MOV DX,WORD PTR [BYTPOS+2]
ADC DX,0
MOV CX,DX
MOV DI,[FCB]
CMP AX,ES:WORD PTR [DI.FILSIZ]
SBB CX,ES:WORD PTR [DI.FILSIZ+2]
JB SAMSIZ
MOV ES:WORD PTR [DI.FILSIZ],AX
MOV ES:WORD PTR [DI.FILSIZ+2],DX
SAMSIZ:
MOV CX,[RECCNT]
JMP SETCLUS
WRTERRJ:JMP WRTERR
WRTEOF:
MOV CX,AX
OR CX,DX
JZ KILLFIL
SUB AX,1
SBB DX,0
DIV [BP.SECSIZ]
MOV CL,[BP.CLUSSHFT]
SHR AX,CL
MOV CX,AX
CALL FNDCLUS
JCXZ RELFILE
CALL ALLOCATE
JC WRTERRJ
UPDATE:
MOV DI,[FCB]
MOV AX,WORD PTR [BYTPOS]
MOV ES:WORD PTR [DI.FILSIZ],AX
MOV AX,WORD PTR [BYTPOS+2]
MOV ES:WORD PTR [DI.FILSIZ+2],AX
XOR CX,CX
JMP ADDREC
RELFILE:
MOV DX,0FFFH
CALL RELBLKS
SETDIRT:
MOV BYTE PTR [SI-1],1
JMP SHORT UPDATE
KILLFIL:
XOR BX,BX
XCHG BX,ES:[DI.FIRCLUS]
OR BX,BX
JZ UPDATE
CALL RELEASE
JMP SHORT SETDIRT
OPTIMIZE:
; Inputs:
; DS = CS
; BX = Physical cluster
; CX = No. of records
; DL = sector within cluster
; BP = Base of drives parameters
; [NEXTADD] = transfer address
; Outputs:
; AX = No. of records remaining
; BX = Transfer address
; CX = No. or records to be transferred
; DX = Physical sector address
; DI = Next cluster
; Carry clear if a sector to transfer is in the buffer
; Carry set otherwise
; [CLUSNUM] = Last cluster accessed
; [NEXTADD] updated
; BP unchanged. Note that segment of transfer not set.
PUSH DX
PUSH BX
MOV AL,[BP.CLUSMSK]
INC AL ;Number of sectors per cluster
MOV AH,AL
SUB AL,DL ;AL = Number of sectors left in first cluster
MOV DX,CX
MOV SI,[BP.FAT]
MOV CX,0
OPTCLUS:
;AL has number of sectors available in current cluster
;AH has number of sectors available in next cluster
;BX has current physical cluster
;CX has number of sequential sectors found so far
;DX has number of sectors left to transfer
;SI has FAT pointer
CALL UNPACK
ADD CL,AL
ADC CH,0
CMP CX,DX
JAE BLKDON
MOV AL,AH
INC BX
CMP DI,BX
JZ OPTCLUS
DEC BX
FINCLUS:
MOV [CLUSNUM],BX ;Last cluster accessed
SUB DX,CX ;Number of sectors still needed
PUSH DX
MOV AX,CX
MUL [BP.SECSIZ] ;Number of sectors times sector size
MOV SI,[NEXTADD]
ADD AX,SI ;Adjust by size of transfer
MOV [NEXTADD],AX
POP AX ;Number of sectors still needed
POP DX ;Starting cluster
SUB BX,DX ;Number of new clusters accessed
ADD [LASTPOS],BX
POP BX ;BL = sector postion within cluster
CALL FIGREC
MOV BX,SI
;Now let's see if any of these sectors are already in the buffer
CMP [BUFSECNO],DX
JC RET100 ;If DX > [BUFSECNO] then not in buffer
MOV SI,DX
ADD SI,CX ;Last sector + 1
CMP [BUFSECNO],SI
CMC
JC RET100 ;If SI <= [BUFSECNO] then not in buffer
PUSH AX
MOV AL,[BP.DEVNUM]
CMP AL,[BUFDRVNO] ;Is buffer for this drive?
POP AX
JZ RET100 ;If so, then we match
STC ;No match
RET100: RET
BLKDON:
SUB CX,DX ;Number of sectors in cluster we don't want
SUB AH,CL ;Number of sectors in cluster we accepted
DEC AH ;Adjust to mean position within cluster
MOV [SECCLUSPOS],AH
MOV CX,DX ;Anyway, make the total equal to the request
JMP SHORT FINCLUS
FIGREC:
;Inputs:
; DX = Physical cluster number
; BL = Sector postion within cluster
; BP = Base of drive parameters
;Outputs:
; DX = physical sector number
;No other registers affected.
PUSH CX
MOV CL,[BP.CLUSSHFT]
DEC DX
DEC DX
SHL DX,CL
OR DL,BL
ADD DX,[BP.FIRREC]
POP CX
RET
GETREC:
; Inputs:
; DS:DX point to FCB
; Outputs:
; CX = 1
; DX:AX = Record number determined by EXTENT and NR fields
; DS:DI point to FCB
; No other registers affected.
MOV DI,DX
CMP BYTE PTR [DI],-1 ;Check for extended FCB
JNZ NORMFCB2
ADD DI,7
NORMFCB2:
MOV CX,1
MOV AL,[DI.NR]
MOV DX,[DI.EXTENT]
SHL AL,1
SHR DX,1
RCR AL,1
MOV AH,DL
MOV DL,DH
MOV DH,0
RET
ALLOCATE:
; Inputs:
; DS = CS
; ES = Segment of FCB
; BX = Last cluster of file (0 if null file)
; CX = No. of clusters to allocate
; DX = Position of cluster BX
; BP = Base of drive parameters
; SI = FAT pointer
; [FCB] = Displacement of FCB within segment
; Outputs:
; IF insufficient space
; THEN
; Carry set
; CX = max. no. of records that could be added to file
; ELSE
; Carry clear
; BX = First cluster allocated
; FAT is fully updated including dirty bit
; FIRCLUS field of FCB set if file was null
; SI,BP unchanged. All other registers destroyed.
PUSH [SI]
PUSH DX
PUSH CX
PUSH BX
MOV AX,BX
ALLOC:
MOV DX,BX
FINDFRE:
INC BX
CMP BX,[BP.MAXCLUS]
JLE TRYOUT
CMP AX,1
JG TRYIN
POP BX
MOV DX,0FFFH
CALL RELBLKS
POP AX ;No. of clusters requested
SUB AX,CX ;AX=No. of clusters allocated
POP DX
POP [SI]
INC DX ;Position of first cluster allocated
ADD AX,DX ;AX=max no. of cluster in file
MOV DL,[BP.CLUSMSK]
MOV DH,0
INC DX ;DX=records/cluster
MUL DX ;AX=max no. of records in file
MOV CX,AX
SUB CX,WORD PTR [RECPOS] ;CX=max no. of records that could be written
JA MAXREC
XOR CX,CX ;If CX was negative, zero it
MAXREC:
STC
RET11: RET
TRYOUT:
CALL UNPACK
JZ HAVFRE
TRYIN:
DEC AX
JLE FINDFRE
XCHG AX,BX
CALL UNPACK
JZ HAVFRE
XCHG AX,BX
JMP SHORT FINDFRE
HAVFRE:
XCHG BX,DX
MOV AX,DX
CALL PACK
MOV BX,AX
LOOP ALLOC
MOV DX,0FFFH
CALL PACK
MOV BYTE PTR [SI-1],1
POP BX
POP CX ;Don't need this stuff since we're successful
POP DX
CALL UNPACK
POP [SI]
XCHG BX,DI
OR DI,DI
JNZ RET11
MOV DI,[FCB]
MOV ES:[DI.FIRCLUS],BX
RET12: RET
RELEASE:
; Inputs:
; DS = CS
; BX = Cluster in file
; SI = FAT pointer
; BP = Base of drive parameters
; Function:
; Frees cluster chain starting with [BX]
; AX,BX,DX,DI all destroyed. Other registers unchanged.
XOR DX,DX
RELBLKS:
; Enter here with DX=0FFFH to put an end-of-file mark
; in the first cluster and free the rest in the chain.
CALL UNPACK
JZ RET12
MOV AX,DI
CALL PACK
CMP AX,0FF8H
MOV BX,AX
JB RELEASE
RET13: RET
GETEOF:
; Inputs:
; BX = Cluster in a file
; SI = Base of drive FAT
; DS = CS
; Outputs:
; BX = Last cluster in the file
; DI destroyed. No other registers affected.
CALL UNPACK
CMP DI,0FF8H
JAE RET13
MOV BX,DI
JMP SHORT GETEOF
SRCHFRST: ;System call 17
CALL GETFILE
SAVPLCE:
; Search-for-next enters here to save place and report
; findings.
JC KILLSRCH
OR BH,BH
JS SRCHDEV
MOV AX,[LASTENT]
MOV ES:[DI.FILDIRENT],AX
MOV ES:[DI.DRVBP],BP
;Information in directory entry must be copied into the first
; 33 bytes starting at the disk transfer address.
MOV SI,BX
LES DI,DWORD PTR [DMAADD]
MOV AX,00FFH
CMP AL,[EXTFCB]
JNZ NORMFCB
STOSW
INC AL
STOSW
STOSW
MOV AL,[ATTRIB]
STOSB
NORMFCB:
MOV AL,[THISDRV]
INC AL
STOSB ;Set drive number
MOV CX,16
REP MOVSW ;Copy remaining 10 characters of name
XOR AL,AL
RET
KILLSRCH:
KILLSRCH1 EQU KILLSRCH+1
;The purpose of the KILLSRCH1 label is to provide a jump label to the following
; instruction which leaves out the segment override.
MOV WORD PTR ES:[DI.FILDIRENT],-1
MOV AL,-1
RET
SRCHDEV:
MOV ES:[DI.FILDIRENT],BX
LES DI,DWORD PTR [DMAADD]
XOR AX,AX
STOSB ;Zero drive byte
SUB SI,4 ;Point to device name
MOVSW
MOVSW
MOV AX,2020H
STOSB
STOSW
STOSW
STOSW ;Fill with 8 blanks
XOR AX,AX
MOV CX,10
REP STOSW
STOSB
RET14: RET
SRCHNXT: ;System call 18
CALL MOVNAME
MOV DI,DX
JC NEAR PTR KILLSRCH1
MOV BP,[DI.DRVBP]
MOV AX,[DI.FILDIRENT]
OR AX,AX
JS NEAR PTR KILLSRCH1
PUSH DX
PUSH DS
PUSH CS
POP DS
MOV [LASTENT],AX
CALL CONTSRCH
POP ES
POP DI
JMP SAVPLCE
FILESIZE: ;System call 35
CALL GETFILE
MOV AL,-1
JC RET14
ADD DI,33 ;Write size in RR field
MOV CX,ES:[DI.RECSIZ-33]
OR CX,CX
JNZ RECOK
MOV CX,128
RECOK:
XOR AX,AX
XOR DX,DX ;Intialize size to zero
OR BH,BH ;Check for named I/O device
JS DEVSIZ
INC SI
INC SI ;Point to length field
MOV AX,[SI+2] ;Get high word of size
DIV CX
PUSH AX ;Save high part of result
LODSW ;Get low word of size
DIV CX
OR DX,DX ;Check for zero remainder
POP DX
JZ DEVSIZ
INC AX ;Round up for partial record
JNZ DEVSIZ ;Propagate carry?
INC DX
DEVSIZ:
STOSW
MOV AX,DX
STOSB
MOV AL,0
CMP CX,64
JAE RET14 ;Only 3-byte field if RECSIZ >= 64
MOV ES:[DI],AH
RET
SETDMA: ;System call 26
MOV CS:[DMAADD],DX
MOV CS:[DMAADD+2],DS
RET
NOSUCHDRV:
MOV AL,-1
RET
GETFATPT: ;System call 27
MOV DL,0 ;Use default drive
GETFATPTDL: ;System call 28
PUSH CS
POP DS
MOV AL,DL
CALL GETTHISDRV
JC NOSUCHDRV
CALL FATREAD
MOV BX,[BP.FAT]
MOV AL,[BP.CLUSMSK]
INC AL
MOV DX,[BP.MAXCLUS]
DEC DX
MOV CX,[BP.SECSIZ]
LDS SI,DWORD PTR [SPSAVE]
MOV [SI.BXSAVE],BX
MOV [SI.DXSAVE],DX
MOV [SI.CXSAVE],CX
MOV [SI.DSSAVE],CS
RET
GETDSKPT: ;System call 31
PUSH CS
POP DS
MOV AL,[CURDRV]
MOV [THISDRV],AL
CALL FATREAD
LDS SI,DWORD PTR [SPSAVE]
MOV [SI.BXSAVE],BP
MOV [SI.DSSAVE],CS
RET
DSKRESET: ;System call 13
PUSH CS
POP DS
WRTFATS:
; DS=CS. Writes back all dirty FATs. All registers destroyed.
XOR AL,AL
XCHG AL,[DIRTYBUF]
OR AL,AL
JZ NOBUF
MOV BP,[BUFDRVBP]
MOV DX,[BUFSECNO]
MOV BX,[BUFFER]
MOV CX,1
CALL DWRITE
NOBUF:
MOV CL,[NUMIO]
MOV CH,0
MOV BP,[DRVTAB]
WRTFAT:
PUSH CX
CALL CHKFATWRT
POP CX
ADD BP,DPBSIZ
LOOP WRTFAT
RET
GETDRV: ;System call 25
MOV AL,CS:[CURDRV]
RET15: RET
SETRNDREC: ;System call 36
CALL GETREC
MOV [DI+33],AX
MOV [DI+35],DL
CMP [DI.RECSIZ],64
JAE RET15
MOV [DI+36],DH ;Set 4th byte only if record size < 64
RET16: RET
SELDSK: ;System call 14
MOV AL,CS:[NUMDRV]
CMP DL,AL
JNB RET17
MOV CS:[CURDRV],DL
RET17: RET
BUFIN: ;System call 10
MOV AX,CS
MOV ES,AX
MOV SI,DX
MOV CH,0
LODSW
OR AL,AL
JZ RET17
MOV BL,AH
MOV BH,CH
CMP AL,BL
JBE NOEDIT
CMP BYTE PTR [BX+SI],0DH
JZ EDITON
NOEDIT:
MOV BL,CH
EDITON:
MOV DL,AL
DEC DX
NEWLIN:
MOV AL,CS:[CARPOS]
MOV CS:[STARTPOS],AL
PUSH SI
MOV DI,OFFSET DOSGROUP:INBUF
MOV AH,CH
MOV BH,CH
MOV DH,CH
GETCH:
CALL IN
CMP AL,"F"-"@" ;Ignore ^F
JZ GETCH
CMP AL,CS:ESCCHAR
JZ ESC
CMP AL,7FH
JZ BACKSP
CMP AL,8
JZ BACKSP
CMP AL,13
JZ ENDLIN
CMP AL,10
JZ PHYCRLF
CMP AL,CANCEL
JZ KILNEW
SAVCH:
CMP DH,DL
JAE BUFFUL
STOSB
INC DH
CALL BUFOUT
OR AH,AH
JNZ GETCH
CMP BH,BL
JAE GETCH
INC SI
INC BH
JMP SHORT GETCH
BUFFUL:
MOV AL,7
CALL OUT
JMP SHORT GETCH
ESC:
CALL IN
MOV CL,ESCTABLEN
PUSH DI
MOV DI,OFFSET DOSGROUP:ESCTAB
REPNE SCASB
POP DI
SHL CX,1
MOV BP,CX
JMP [BP+OFFSET DOSGROUP:ESCFUNC]
ENDLIN:
STOSB
CALL OUT
POP DI
MOV [DI-1],DH
INC DH
COPYNEW:
MOV BP,ES
MOV BX,DS
MOV ES,BX
MOV DS,BP
MOV SI,OFFSET DOSGROUP:INBUF
MOV CL,DH
REP MOVSB
RET
CRLF:
MOV AL,13
CALL OUT
MOV AL,10
JMP OUT
PHYCRLF:
CALL CRLF
JMP SHORT GETCH
KILNEW:
MOV AL,"\"
CALL OUT
POP SI
PUTNEW:
CALL CRLF
MOV AL,CS:[STARTPOS]
CALL TAB
JMP NEWLIN
BACKSP:
OR DH,DH
JZ OLDBAK
CALL BACKUP
MOV AL,ES:[DI]
CMP AL," "
JAE OLDBAK
CMP AL,9
JZ BAKTAB
CALL BACKMES
OLDBAK:
OR AH,AH
JNZ GETCH1
OR BH,BH
JZ GETCH1
DEC BH
DEC SI
GETCH1:
JMP GETCH
BAKTAB:
PUSH DI
DEC DI
STD
MOV CL,DH
MOV AL," "
PUSH BX
MOV BL,7
JCXZ FIGTAB
FNDPOS:
SCASB
JNA CHKCNT
CMP ES:BYTE PTR [DI+1],9
JZ HAVTAB
DEC BL
CHKCNT:
LOOP FNDPOS
FIGTAB:
SUB BL,CS:[STARTPOS]
HAVTAB:
SUB BL,DH
ADD CL,BL
AND CL,7
CLD
POP BX
POP DI
JZ OLDBAK
TABBAK:
CALL BACKMES
LOOP TABBAK
JMP SHORT OLDBAK
BACKUP:
DEC DH
DEC DI
BACKMES:
MOV AL,8
CALL OUT
MOV AL," "
CALL OUT
MOV AL,8
JMP OUT
TWOESC:
MOV AL,ESCCH
JMP SAVCH
COPYLIN:
MOV CL,BL
SUB CL,BH
JMP SHORT COPYEACH
COPYSTR:
CALL FINDOLD
JMP SHORT COPYEACH
COPYONE:
MOV CL,1
COPYEACH:
MOV AH,0
CMP DH,DL
JZ GETCH2
CMP BH,BL
JZ GETCH2
LODSB
STOSB
CALL BUFOUT
INC BH
INC DH
LOOP COPYEACH
GETCH2:
JMP GETCH
SKIPONE:
CMP BH,BL
JZ GETCH2
INC BH
INC SI
JMP GETCH
SKIPSTR:
CALL FINDOLD
ADD SI,CX
ADD BH,CL
JMP GETCH
FINDOLD:
CALL IN
MOV CL,BL
SUB CL,BH
JZ NOTFND
DEC CX
JZ NOTFND
PUSH ES
PUSH DS
POP ES
PUSH DI
MOV DI,SI
INC DI
REPNE SCASB
POP DI
POP ES
JNZ NOTFND
NOT CL
ADD CL,BL
SUB CL,BH
RET30: RET
NOTFND:
POP BP
JMP GETCH
REEDIT:
MOV AL,"@"
CALL OUT
POP DI
PUSH DI
PUSH ES
PUSH DS
CALL COPYNEW
POP DS
POP ES
POP SI
MOV BL,DH
JMP PUTNEW
ENTERINS:
IF TOGLINS
NOT AH
JMP GETCH
ENDIF
IF NOT TOGLINS
MOV AH,-1
JMP GETCH
EXITINS:
MOV AH,0
JMP GETCH
ENDIF
ESCFUNC DW GETCH
DW TWOESC
IF NOT TOGLINS
DW EXITINS
ENDIF
DW ENTERINS
DW BACKSP
DW REEDIT
DW KILNEW
DW COPYLIN
DW SKIPSTR
DW COPYSTR
DW SKIPONE
DW COPYONE
IF IBM
DW COPYONE
DW CTRLZ
CTRLZ:
MOV AL,"Z"-"@"
JMP SAVCH
ENDIF
BUFOUT:
CMP AL," "
JAE OUT
CMP AL,9
JZ OUT
PUSH AX
MOV AL,"^"
CALL OUT
POP AX
OR AL,40H
JMP SHORT OUT
NOSTOP:
CMP AL,"P"-"@"
JZ INCHK
IF NOT TOGLPRN
CMP AL,"N"-"@"
JZ INCHK
ENDIF
CMP AL,"C"-"@"
JZ INCHK
RET
CONOUT: ;System call 2
MOV AL,DL
OUT:
CMP AL,20H
JB CTRLOUT
CMP AL,7FH
JZ OUTCH
INC CS:BYTE PTR [CARPOS]
OUTCH:
PUSH AX
CALL STATCHK
POP AX
CALL FAR PTR BIOSOUT
TEST CS:BYTE PTR [PFLAG],-1
JZ RET18
CALL FAR PTR BIOSPRINT
RET18: RET
STATCHK:
CALL FAR PTR BIOSSTAT
JZ RET18
CMP AL,'S'-'@'
JNZ NOSTOP
CALL FAR PTR BIOSIN ;Eat Cntrl-S
INCHK:
CALL FAR PTR BIOSIN
CMP AL,'P'-'@'
JZ PRINTON
IF NOT TOGLPRN
CMP AL,'N'-'@'
JZ PRINTOFF
ENDIF
CMP AL,'C'-'@'
JNZ RET18
; Ctrl-C handler.
; "^C" and CR/LF is printed. Then the user registers are restored and the
; user CTRL-C handler is executed. At this point the top of the stack has
; 1) the interrupt return address should the user CTRL-C handler wish to
; allow processing to continue; 2) the original interrupt return address
; to the code that performed the function call in the first place. If the
; user CTRL-C handler wishes to continue, it must leave all registers
; unchanged and IRET. The function that was interrupted will simply be
; repeated.
MOV AL,3 ;Display "^C"
CALL BUFOUT
CALL CRLF
CLI ;Prepare to play with stack
MOV SS,CS:[SSSAVE]
MOV SP,CS:[SPSAVE] ;User stack now restored
POP AX
POP BX
POP CX
POP DX
POP SI
POP DI
POP BP
POP DS
POP ES ;User registers now restored
INT CONTC ;Execute user Ctrl-C handler
JMP COMMAND ;Repeat command otherwise
PRINTON:
IF TOGLPRN
NOT CS:BYTE PTR [PFLAG]
RET
ENDIF
IF NOT TOGLPRN
MOV CS:BYTE PTR [PFLAG],1
RET
PRINTOFF:
MOV CS:BYTE PTR [PFLAG],0
RET
ENDIF
CTRLOUT:
CMP AL,13
JZ ZERPOS
CMP AL,8
JZ BACKPOS
CMP AL,9
JNZ OUTCHJ
MOV AL,CS:[CARPOS]
OR AL,0F8H
NEG AL
TAB:
PUSH CX
MOV CL,AL
MOV CH,0
JCXZ POPTAB
TABLP:
MOV AL," "
CALL OUT
LOOP TABLP
POPTAB:
POP CX
RET19: RET
ZERPOS:
MOV CS:BYTE PTR [CARPOS],0
OUTCHJ: JMP OUTCH
BACKPOS:
DEC CS:BYTE PTR [CARPOS]
JMP OUTCH
CONSTAT: ;System call 11
CALL STATCHK
MOV AL,0
JZ RET19
OR AL,-1
RET
CONIN: ;System call 1
CALL IN
PUSH AX
CALL OUT
POP AX
RET
IN: ;System call 8
CALL INCHK
JZ IN
RET29: RET
RAWIO: ;System call 6
MOV AL,DL
CMP AL,-1
JNZ RAWOUT
LDS SI,DWORD PTR CS:[SPSAVE] ;Get pointer to register save area
CALL FAR PTR BIOSSTAT
JNZ RESFLG
OR BYTE PTR [SI.FSAVE],40H ;Set user's zero flag
XOR AL,AL
RET
RESFLG:
AND BYTE PTR [SI.FSAVE],0FFH-40H ;Reset user's zero flag
RAWINP: ;System call 7
CALL FAR PTR BIOSIN
RET
RAWOUT:
CALL FAR PTR BIOSOUT
RET
LIST: ;System call 5
MOV AL,DL
LISTOUT:
PUSH AX
CALL STATCHK
POP AX
CALL FAR PTR BIOSPRINT
RET20: RET
PRTBUF: ;System call 9
MOV SI,DX
OUTSTR:
LODSB
CMP AL,"$"
JZ RET20
CALL OUT
JMP SHORT OUTSTR
OUTMES: ;String output for internal messages
LODS CS:BYTE PTR [SI]
CMP AL,"$"
JZ RET20
CALL OUT
JMP SHORT OUTMES
MAKEFCB: ;Interrupt call 41
DRVBIT EQU 2
NAMBIT EQU 4
EXTBIT EQU 8
MOV DL,0 ;Flag--not ambiguous file name
TEST AL,DRVBIT ;Use current drive field if default?
JNZ DEFDRV
MOV BYTE PTR ES:[DI],0 ;No - use default drive
DEFDRV:
INC DI
MOV CX,8
TEST AL,NAMBIT ;Use current name fiels as defualt?
XCHG AX,BX ;Save bits in BX
MOV AL," "
JZ FILLB ;If not, go fill with blanks
ADD DI,CX
XOR CX,CX ;Don't fill any
FILLB:
REP STOSB
MOV CL,3
TEST BL,EXTBIT ;Use current extension as default
JZ FILLB2
ADD DI,CX
XOR CX,CX
FILLB2:
REP STOSB
XCHG AX,CX ;Put zero in AX
STOSW
STOSW ;Initialize two words after to zero
SUB DI,16 ;Point back at start
TEST BL,1 ;Scan off separators if not zero
JZ SKPSPC
CALL SCANB ;Peel off blanks and tabs
CALL DELIM ;Is it a one-time-only delimiter?
JNZ NOSCAN
INC SI ;Skip over the delimiter
SKPSPC:
CALL SCANB ;Always kill preceding blanks and tabs
NOSCAN:
CALL GETLET
JBE NODRV ;Quit if termination character
CMP BYTE PTR[SI],":" ;Check for potential drive specifier
JNZ NODRV
INC SI ;Skip over colon
SUB AL,"@" ;Convert drive letter to binary drive number
JBE BADDRV ;Valid drive numbers are 1-15
CMP AL,CS:[NUMDRV]
JBE HAVDRV
BADDRV:
MOV DL,-1
HAVDRV:
STOSB ;Put drive specifier in first byte
INC SI
DEC DI ;Counteract next two instructions
NODRV:
DEC SI ;Back up
INC DI ;Skip drive byte
MOV CX,8
CALL GETWORD ;Get 8-letter file name
CMP BYTE PTR [SI],"."
JNZ NODOT
INC SI ;Skip over dot if present
MOV CX,3 ;Get 3-letter extension
CALL MUSTGETWORD
NODOT:
LDS BX,CS:DWORD PTR [SPSAVE]
MOV [BX.SISAVE],SI
MOV AL,DL
RET
NONAM:
ADD DI,CX
DEC SI
RET
GETWORD:
CALL GETLET
JBE NONAM ;Exit if invalid character
DEC SI
MUSTGETWORD:
CALL GETLET
JBE FILLNAM
JCXZ MUSTGETWORD
DEC CX
CMP AL,"*" ;Check for ambiguous file specifier
JNZ NOSTAR
MOV AL,"?"
REP STOSB
NOSTAR:
STOSB
CMP AL,"?"
JNZ MUSTGETWORD
OR DL,1 ;Flag ambiguous file name
JMP MUSTGETWORD
FILLNAM:
MOV AL," "
REP STOSB
DEC SI
RET21: RET
SCANB:
LODSB
CALL SPCHK
JZ SCANB
DEC SI
RET
GETLET:
;Get a byte from [SI], convert it to upper case, and compare for delimiter.
;ZF set if a delimiter, CY set if a control character (other than TAB).
LODSB
AND AL,7FH
CMP AL,"a"
JB CHK
CMP AL,"z"
JA CHK
SUB AL,20H ;Convert to upper case
CHK:
CMP AL,"."
JZ RET21
CMP AL,'"'
JZ RET21
CMP AL,"/"
JZ RET21
CMP AL,"["
JZ RET21
CMP AL,"]"
JZ RET21
IF IBM
DELIM:
ENDIF
CMP AL,":" ;Allow ":" as separator in IBM version
JZ RET21
IF NOT IBM
DELIM:
ENDIF
CMP AL,"+"
JZ RET101
CMP AL,"="
JZ RET101
CMP AL,";"
JZ RET101
CMP AL,","
JZ RET101
SPCHK:
CMP AL,9 ;Filter out tabs too
JZ RET101
;WARNING! " " MUST be the last compare
CMP AL," "
RET101: RET
SETVECT: ; Interrupt call 37
XOR BX,BX
MOV ES,BX
MOV BL,AL
SHL BX,1
SHL BX,1
MOV ES:[BX],DX
MOV ES:[BX+2],DS
RET
NEWBASE: ; Interrupt call 38
MOV ES,DX
LDS SI,CS:DWORD PTR [SPSAVE]
MOV DS,[SI.CSSAVE]
XOR SI,SI
MOV DI,SI
MOV AX,DS:[2]
MOV CX,80H
REP MOVSW
SETMEM:
; Inputs:
; AX = Size of memory in paragraphs
; DX = Segment
; Function:
; Completely prepares a program base at the
; specified segment.
; Outputs:
; DS = DX
; ES = DX
; [0] has INT 20H
; [2] = First unavailable segment ([ENDMEM])
; [5] to [9] form a long call to the entry point
; [10] to [13] have exit address (from INT 22H)
; [14] to [17] have ctrl-C exit address (from INT 23H)
; [18] to [21] have fatal error address (from INT 24H)
; DX,BP unchanged. All other registers destroyed.
XOR CX,CX
MOV DS,CX
MOV ES,DX
MOV SI,EXIT
MOV DI,SAVEXIT
MOVSW
MOVSW
MOVSW
MOVSW
MOVSW
MOVSW
MOV ES:[2],AX
SUB AX,DX
CMP AX,MAXDIF
JBE HAVDIF
MOV AX,MAXDIF
HAVDIF:
MOV BX,ENTRYPOINTSEG
SUB BX,AX
SHL AX,1
SHL AX,1
SHL AX,1
SHL AX,1
MOV DS,DX
MOV DS:[6],AX
MOV DS:[8],BX
MOV DS:[0],20CDH ;"INT INTTAB"
MOV DS:(BYTE PTR [5]),LONGCALL
RET
DATE16:
PUSH CX
CALL READTIME
SHL CL,1 ;Minutes to left part of byte
SHL CL,1
SHL CX,1 ;Push hours and minutes to left end
SHL CX,1
SHL CX,1
SHR DH,1 ;Count every two seconds
OR CL,DH ;Combine seconds with hours and minutes
MOV DX,CX
POP CX
MOV AX,WORD PTR [MONTH] ;Fetch month and year
SHL AL,1 ;Push month to left to make room for day
SHL AL,1
SHL AL,1
SHL AL,1
SHL AX,1
OR AL,[DAY]
RET22: RET
FOURYEARS EQU 3*365+366
READTIME:
;Gets time in CX:DX. Figures new date if it has changed.
;Uses AX, CX, DX.
CALL FAR PTR BIOSGETTIME
CMP AX,[DAYCNT] ;See if day count is the same
JZ RET22
CMP AX,FOURYEARS*30 ;Number of days in 120 years
JAE RET22 ;Ignore if too large
MOV [DAYCNT],AX
PUSH SI
PUSH CX
PUSH DX ;Save time
XOR DX,DX
MOV CX,FOURYEARS ;Number of days in 4 years
DIV CX ;Compute number of 4-year units
SHL AX,1
SHL AX,1
SHL AX,1 ;Multiply by 8 (no. of half-years)
MOV CX,AX ;<240 implies AH=0
MOV SI,OFFSET DOSGROUP:YRTAB ;Table of days in each year
CALL DSLIDE ;Find out which of four years we're in
SHR CX,1 ;Convert half-years to whole years
JNC SK ;Extra half-year?
ADD DX,200
SK:
CALL SETYEAR
MOV CL,1 ;At least at first month in year
MOV SI,OFFSET DOSGROUP:MONTAB ;Table of days in each month
CALL DSLIDE ;Find out which month we're in
MOV [MONTH],CL
INC DX ;Remainder is day of month (start with one)
MOV [DAY],DL
CALL WKDAY ;Set day of week
POP DX
POP CX
POP SI
RET23: RET
DSLIDE:
MOV AH,0
DSLIDE1:
LODSB ;Get count of days
CMP DX,AX ;See if it will fit
JB RET23 ;If not, done
SUB DX,AX
INC CX ;Count one more month/year
JMP SHORT DSLIDE1
SETYEAR:
;Set year with value in CX. Adjust length of February for this year.
MOV BYTE PTR [YEAR],CL
CHKYR:
TEST CL,3 ;Check for leap year
MOV AL,28
JNZ SAVFEB ;28 days if no leap year
INC AL ;Add leap day
SAVFEB:
MOV [MONTAB+1],AL ;Store for February
RET
;Days in year
YRTAB DB 200,166 ;Leap year
DB 200,165
DB 200,165
DB 200,165
;Days of each month
MONTAB DB 31 ;January
DB 28 ;February--reset each time year changes
DB 31 ;March
DB 30 ;April
DB 31 ;May
DB 30 ;June
DB 31 ;July
DB 31 ;August
DB 30 ;September
DB 31 ;October
DB 30 ;November
DB 31 ;December
GETDATE: ;Function call 42
PUSH CS
POP DS
CALL READTIME ;Check for rollover to next day
MOV AX,[YEAR]
MOV BX,WORD PTR [DAY]
LDS SI,DWORD PTR [SPSAVE] ;Get pointer to user registers
MOV [SI.DXSAVE],BX ;DH=month, DL=day
ADD AX,1980 ;Put bias back
MOV [SI.CXSAVE],AX ;CX=year
MOV AL,CS:[WEEKDAY]
RET24: RET
SETDATE: ;Function call 43
MOV AL,-1 ;Be ready to flag error
SUB CX,1980 ;Fix bias in year
JC RET24 ;Error if not big enough
CMP CX,119 ;Year must be less than 2100
JA RET24
OR DH,DH
JZ RET24
OR DL,DL
JZ RET24 ;Error if either month or day is 0
CMP DH,12 ;Check against max. month
JA RET24
PUSH CS
POP DS
CALL CHKYR ;Set Feb. up for new year
MOV AL,DH
MOV BX,OFFSET DOSGROUP:MONTAB-1
XLAT ;Look up days in month
CMP AL,DL
MOV AL,-1 ;Restore error flag, just in case
JB RET24 ;Error if too many days
CALL SETYEAR
MOV WORD PTR [DAY],DX ;Set both day and month
SHR CX,1
SHR CX,1
MOV AX,FOURYEARS
MOV BX,DX
MUL CX
MOV CL,BYTE PTR [YEAR]
AND CL,3
MOV SI,OFFSET DOSGROUP:YRTAB
MOV DX,AX
SHL CX,1 ;Two entries per year, so double count
CALL DSUM ;Add up the days in each year
MOV CL,BH ;Month of year
MOV SI,OFFSET DOSGROUP:MONTAB
DEC CX ;Account for months starting with one
CALL DSUM ;Add up days in each month
MOV CL,BL ;Day of month
DEC CX ;Account for days starting with one
ADD DX,CX ;Add in to day total
XCHG AX,DX ;Get day count in AX
MOV [DAYCNT],AX
CALL FAR PTR BIOSSETDATE
WKDAY:
MOV AX,[DAYCNT]
XOR DX,DX
MOV CX,7
INC AX
INC AX ;First day was Tuesday
DIV CX ;Compute day of week
MOV [WEEKDAY],DL
XOR AL,AL ;Flag OK
RET25: RET
DSUM:
MOV AH,0
JCXZ RET25
DSUM1:
LODSB
ADD DX,AX
LOOP DSUM1
RET
GETTIME: ;Function call 44
PUSH CS
POP DS
CALL READTIME
LDS SI,DWORD PTR [SPSAVE] ;Get pointer to user registers
MOV [SI.DXSAVE],DX
MOV [SI.CXSAVE],CX
XOR AL,AL
RET26: RET
SETTIME: ;Function call 45
;Time is in CX:DX in hours, minutes, seconds, 1/100 sec.
MOV AL,-1 ;Flag in case of error
CMP CH,24 ;Check hours
JAE RET26
CMP CL,60 ;Check minutes
JAE RET26
CMP DH,60 ;Check seconds
JAE RET26
CMP DL,100 ;Check 1/100's
JAE RET26
CALL FAR PTR BIOSSETTIME
XOR AL,AL
RET
; Default handler for division overflow trap
DIVOV:
PUSH SI
PUSH AX
MOV SI,OFFSET DOSGROUP:DIVMES
CALL OUTMES
POP AX
POP SI
INT 23H ;Use Ctrl-C abort on divide overflow
IRET
CODSIZ EQU $-CODSTRT ;Size of code segment
CODE ENDS
;***** DATA AREA *****
CONSTANTS SEGMENT BYTE
ORG 0
CONSTRT EQU $ ;Start of constants segment
IONAME:
IF NOT IBM
DB "PRN ","LST ","NUL ","AUX ","CON "
ENDIF
IF IBM
DB "COM1","PRN ","LPT1","NUL ","AUX ","CON "
ENDIF
DIVMES DB 13,10,"Divide overflow",13,10,"$"
CARPOS DB 0
STARTPOS DB 0
PFLAG DB 0
DIRTYDIR DB 0 ;Dirty buffer flag
NUMDRV DB 0 ;Number of drives
NUMIO DB ? ;Number of disk tables
VERFLG DB 0 ;Initialize with verify off
CONTPOS DW 0
DMAADD DW 80H ;User's disk transfer address (disp/seg)
DW ?
ENDMEM DW ?
MAXSEC DW 0
BUFFER DW ?
BUFSECNO DW 0
BUFDRVNO DB -1
DIRTYBUF DB 0
BUFDRVBP DW ?
DIRBUFID DW -1
DAY DB 0
MONTH DB 0
YEAR DW 0
DAYCNT DW -1
WEEKDAY DB 0
CURDRV DB 0 ;Default to drive A
DRVTAB DW 0 ;Address of start of DPBs
DOSLEN EQU CODSIZ+($-CONSTRT) ;Size of CODE + CONSTANTS segments
CONSTANTS ENDS
DATA SEGMENT WORD
; Init code overlaps with data area below
ORG 0
INBUF DB 128 DUP (?)
CONBUF DB 131 DUP (?) ;The rest of INBUF and console buffer
LASTENT DW ?
EXITHOLD DB 4 DUP (?)
FATBASE DW ?
NAME1 DB 11 DUP (?) ;File name buffer
ATTRIB DB ?
NAME2 DB 11 DUP (?)
NAME3 DB 12 DUP (?)
EXTFCB DB ?
;WARNING - the following two items are accessed as a word
CREATING DB ?
DELALL DB ?
TEMP LABEL WORD
SPSAVE DW ?
SSSAVE DW ?
CONTSTK DW ?
SECCLUSPOS DB ? ;Position of first sector within cluster
DSKERR DB ?
TRANS DB ?
PREREAD DB ? ;0 means preread; 1 means optional
READOP DB ?
THISDRV DB ?
EVEN
FCB DW ? ;Address of user FCB
NEXTADD DW ?
RECPOS DB 4 DUP (?)
RECCNT DW ?
LASTPOS DW ?
CLUSNUM DW ?
SECPOS DW ? ;Position of first sector accessed
VALSEC DW ? ;Number of valid (previously written) sectors
BYTSECPOS DW ? ;Position of first byte within sector
BYTPOS DB 4 DUP (?) ;Byte position in file of access
BYTCNT1 DW ? ;No. of bytes in first sector
BYTCNT2 DW ? ;No. of bytes in last sector
SECCNT DW ? ;No. of whole sectors
ENTFREE DW ?
DB 80H DUP (?) ;Stack space
IOSTACK LABEL BYTE
DB 80H DUP (?)
DSKSTACK LABEL BYTE
IF DSKTEST
NSS DW ?
NSP DW ?
ENDIF
DIRBUF LABEL WORD
;Init code below overlaps with data area above
ORG 0
MOVFAT:
;This section of code is safe from being overwritten by block move
REP MOVS BYTE PTR [DI],[SI]
CLD
MOV ES:[DMAADD+2],DX
MOV SI,[DRVTAB] ;Address of first DPB
MOV AL,-1
MOV CL,[NUMIO] ;Number of DPBs
FLGFAT:
MOV DI,ES:[SI.FAT] ;get pointer to FAT
DEC DI ;Point to dirty byte
STOSB ;Flag as unused
ADD SI,DPBSIZ ;Point to next DPB
LOOP FLGFAT
MOV AX,[ENDMEM]
CALL SETMEM ;Set up segment
XXX PROC FAR
RET
XXX ENDP
DOSINIT:
CLI
CLD
PUSH CS
POP ES
MOV ES:[ENDMEM],DX
LODSB ;Get no. of drives & no. of I/O drivers
MOV ES:[NUMIO],AL
MOV DI,OFFSET DOSGROUP:MEMSTRT
PERDRV:
MOV BP,DI
MOV AL,ES:[DRVCNT]
STOSB ;DEVNUM
LODSB ;Physical unit no.
STOSB ;DRVNUM
CMP AL,15
JA BADINIT
CBW ;Index into FAT size table
SHL AX,1
ADD AX,OFFSET DOSGROUP:FATSIZTAB
XCHG BX,AX
LODSW ;Pointer to DPT
PUSH SI
MOV SI,AX
LODSW
STOSW ;SECSIZ
MOV DX,AX
CMP AX,ES:[MAXSEC]
JBE NOTMAX
MOV ES:[MAXSEC],AX
NOTMAX:
LODSB
DEC AL
STOSB ;CLUSMSK
JZ HAVSHFT
CBW
FIGSHFT:
INC AH
SAR AL,1
JNZ FIGSHFT
MOV AL,AH
HAVSHFT:
STOSB ;CLUSSHFT
MOVSW ;FIRFAT (= number of reserved sectors)
MOVSB ;FATCNT
MOVSW ;MAXENT
MOV AX,DX ;SECSIZ again
MOV CL,5
SHR AX,CL
MOV CX,AX ;Directory entries per sector
DEC AX
ADD AX,ES:[BP.MAXENT]
XOR DX,DX
DIV CX
STOSW ;DIRSEC (temporarily)
MOVSW ;DSKSIZ (temporarily)
FNDFATSIZ:
MOV AL,1
MOV DX,1
GETFATSIZ:
PUSH DX
CALL FIGFATSIZ
POP DX
CMP AL,DL ;Compare newly computed FAT size with trial
JZ HAVFATSIZ ;Has sequence converged?
CMP AL,DH ;Compare with previous trial
MOV DH,DL
MOV DL,AL ;Shuffle trials
JNZ GETFATSIZ ;Continue iterations if not oscillating
DEC WORD PTR ES:[BP.DSKSIZ] ;Damp those oscillations
JMP SHORT FNDFATSIZ ;Try again
BADINIT:
MOV SI,OFFSET DOSGROUP:BADMES
CALL OUTMES
STI
HLT
HAVFATSIZ:
STOSB ;FATSIZ
MUL ES:BYTE PTR[BP.FATCNT] ;Space occupied by all FATs
ADD AX,ES:[BP.FIRFAT]
STOSW ;FIRDIR
ADD AX,ES:[BP.DIRSEC]
MOV ES:[BP.FIRREC],AX ;Destroys DIRSEC
CALL FIGMAX
MOV ES:[BP.MAXCLUS],CX
MOV AX,BX ;Pointer into FAT size table
STOSW ;Allocate space for FAT pointer
MOV AL,ES:[BP.FATSIZ]
XOR AH,AH
MUL ES:[BP.SECSIZ]
CMP AX,ES:[BX] ;Bigger than already allocated
JBE SMFAT
MOV ES:[BX],AX
SMFAT:
POP SI ;Restore pointer to init. table
MOV AL,ES:[DRVCNT]
INC AL
MOV ES:[DRVCNT],AL
CMP AL,ES:[NUMIO]
JAE CONTINIT
JMP PERDRV
BADINITJ:
JMP BADINIT
CONTINIT:
PUSH CS
POP DS
;Calculate true address of buffers, FATs, free space
MOV BP,[MAXSEC]
MOV AX,OFFSET DOSGROUP:DIRBUF
ADD AX,BP
MOV [BUFFER],AX ;Start of buffer
ADD AX,BP
MOV [DRVTAB],AX ;Start of DPBs
SHL BP,1 ;Two sectors - directory and buffer
ADD BP,DI ;Allocate buffer space
ADD BP,ADJFAC ;True address of FATs
PUSH BP
MOV SI,OFFSET DOSGROUP:FATSIZTAB
MOV DI,SI
MOV CX,16
TOTFATSIZ:
INC BP ;Add one for Dirty byte
INC BP ;Add one for I/O device number
LODSW ;Get size of this FAT
XCHG AX,BP
STOSW ;Save address of this FAT
ADD BP,AX ;Compute size of next FAT
CMP AX,BP ;If size was zero done
LOOPNZ TOTFATSIZ
MOV AL,15
SUB AL,CL ;Compute number of FATs used
MOV [NUMDRV],AL
XOR AX,AX ;Set zero flag
REPZ SCASW ;Make sure all other entries are zero
JNZ BADINITJ
ADD BP,15 ;True start of free space
MOV CL,4
SHR BP,CL ;First free segment
MOV DX,CS
ADD DX,BP
MOV BX,0FH
MOV CX,[ENDMEM]
CMP CX,1 ;Use memory scan?
JNZ SETEND
MOV CX,DX ;Start scanning just after DOS
MEMSCAN:
INC CX
JZ SETEND
MOV DS,CX
MOV AL,[BX]
NOT AL
MOV [BX],AL
CMP AL,[BX]
NOT AL
MOV [BX],AL
JZ MEMSCAN
SETEND:
IF HIGHMEM
SUB CX,BP
MOV BP,CX ;Segment of DOS
MOV DX,CS ;Program segment
ENDIF
IF NOT HIGHMEM
MOV BP,CS
ENDIF
; BP has segment of DOS (whether to load high or run in place)
; DX has program segment (whether after DOS or overlaying DOS)
; CX has size of memory in paragraphs (reduced by DOS size if HIGHMEM)
MOV CS:[ENDMEM],CX
IF HIGHMEM
MOV ES,BP
XOR SI,SI
MOV DI,SI
MOV CX,(DOSLEN+1)/2
PUSH CS
POP DS
REP MOVSW ;Move DOS to high memory
ENDIF
XOR AX,AX
MOV DS,AX
MOV ES,AX
MOV DI,INTBASE
MOV AX,OFFSET DOSGROUP:QUIT
STOSW ;Set abort address--displacement
MOV AX,BP
MOV BYTE PTR DS:[ENTRYPOINT],LONGJUMP
MOV WORD PTR DS:[ENTRYPOINT+1],OFFSET DOSGROUP:ENTRY
MOV WORD PTR DS:[ENTRYPOINT+3],AX
MOV WORD PTR DS:[0],OFFSET DOSGROUP:DIVOV ;Set default divide trap address
MOV DS:[2],AX
MOV CX,9
REP STOSW ;Set 5 segments (skip 2 between each)
MOV WORD PTR DS:[INTBASE+4],OFFSET DOSGROUP:COMMAND
MOV WORD PTR DS:[INTBASE+12],OFFSET DOSGROUP:IRET ;Ctrl-C exit
MOV WORD PTR DS:[INTBASE+16],OFFSET DOSGROUP:IRET ;Fatal error exit
MOV AX,OFFSET BIOSREAD
STOSW
MOV AX,BIOSSEG
STOSW
STOSW ;Add 2 to DI
STOSW
MOV WORD PTR DS:[INTBASE+18H],OFFSET BIOSWRITE
MOV WORD PTR DS:[EXIT],100H
MOV WORD PTR DS:[EXIT+2],DX
IF NOT IBM
MOV SI,OFFSET DOSGROUP:HEADER
CALL OUTMES
ENDIF
PUSH CS
POP DS
PUSH CS
POP ES
;Move the FATs into position
MOV AL,[NUMIO]
CBW
XCHG AX,CX
MOV DI,OFFSET DOSGROUP:MEMSTRT.FAT
FATPOINT:
MOV SI,WORD PTR [DI] ;Get address within FAT address table
MOVSW ;Set address of this FAT
ADD DI,DPBSIZ-2 ;Point to next DPB
LOOP FATPOINT
POP CX ;True address of first FAT
MOV SI,OFFSET DOSGROUP:MEMSTRT ;Place to move DPBs from
MOV DI,[DRVTAB] ;Place to move DPBs to
SUB CX,DI ;Total length of DPBs
CMP DI,SI
JBE MOVJMP ;Are we moving to higher or lower memory?
DEC CX ;Move backwards to higher memory
ADD DI,CX
ADD SI,CX
INC CX
STD
MOVJMP:
MOV ES,BP
JMP MOVFAT
FIGFATSIZ:
MUL ES:BYTE PTR[BP.FATCNT]
ADD AX,ES:[BP.FIRFAT]
ADD AX,ES:[BP.DIRSEC]
FIGMAX:
;AX has equivalent of FIRREC
SUB AX,ES:[BP.DSKSIZ]
NEG AX
MOV CL,ES:[BP.CLUSSHFT]
SHR AX,CL
INC AX
MOV CX,AX ;MAXCLUS
INC AX
MOV DX,AX
SHR DX,1
ADC AX,DX ;Size of FAT in bytes
MOV SI,ES:[BP.SECSIZ]
ADD AX,SI
DEC AX
XOR DX,DX
DIV SI
RET
BADMES:
DB 13,10,"INIT TABLE BAD",13,10,"$"
FATSIZTAB:
DW 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
DRVCNT DB 0
MEMSTRT LABEL WORD
ADJFAC EQU DIRBUF-MEMSTRT
DATA ENDS
END

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