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Paterson-Listings/3_source_code/86-DOS_1.00/86DOS.ASM
T
Yufeng GaoandRichCini 8065d4d8be Initial commit 
Initial import of the transcribed source code from Tim Paterson's
DOS listings.

Co-authored-by: RichCini <rich.cini@gmail.com>
2026-04-22 01:04:31 +10:00

3622 lines
59 KiB
NASM
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; 86-DOS High-performance operating system for the 8086 version 1.00 04/28/81
; 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
;
; *************************************************************
; Use the switch below to generate code to accept the old 16-byte
; directory entry as well as the new 32-byte entry.
SMALLDIR: EQU 1 ;1 to enable, 0 to disable
; Turn on switch below to allow testing disk code with DEBUG. It sets
; up a different stack for disk I/O (functions > 11) than that used for
; character I/O which effectively makes the DOS re-entrant.
DSKTEST: EQU 0 ;1 to enable, 0 to disable
; 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
MAXCALL:EQU 36
MAXCOM: EQU 41
ESCCH: EQU 1BH
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
ORG 0
DS 12 ;Drive code and name
EXTENT: DS 2
RECSIZ: DS 2 ;Size of record (user settable)
FILSIZ: DS 4 ;Size of file in bytes
FDATE: DS 2 ;Date of last writing
FILDIRBLK:DS 2 ;Location in directory
FIRCLUS:DS 2 ;First cluster of file
LSTCLUS:DS 2 ;Last cluster accessed
CLUSPOS:DS 2 ;Position of last cluster accessed
DIRTYFIL:DS 1 ;File has been written to if <>0
ORG 32
NR: DS 1 ;Next record
RR: DS 3 ;Random record
; 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 13 Zero field (for expansion)
; 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
ORG 0
DRVNUM: DS 1 ;Drive number
SECSIZ: DS 2 ;Size of physical sector in bytes
CLUSMSK:DS 1 ;Sectors/cluster - 1
CLUSSHFT:DS 1 ;Log2 of sectors/cluster
FIRFAT: DS 2 ;Starting record of FATs
FATCNT: DS 1 ;Number of FATs for this drive
MAXENT: DS 2 ;Number of directory entries
DIRSEC: ;Number of dir. sectors (init temporary)
FIRREC: DS 2 ;First sector of first cluster
DSKSIZ: ;Size of disk (temp used during init only)
MAXCLUS:DS 2 ;Number of clusters on drive + 1
FATSIZ: DS 1 ;Number of records occupied by FAT
FIRDIR: DS 2 ;Starting record of directory
IF SMALLDIR
FIRREC1:DS 2 ;First data sector with 16-byte dir. entries
MAXCLUS1:DS 2 ;No. of clusters + 1 with 16-byte dir. entries
FIRREC2:DS 2 ;First data sector with 32-byte dir. entries
MAXCLUS2:DS 2 ;No. of clusters + 1 with 32-byte dir entries
ENDIF
DIRTYFAT:DS 1 ;1=FAT has been changed, -1=never been read
FAT: ;Start of FAT
DIRSIZ: ;-1=small dir. entry, else large
; BIOS entry point defintions
BIOSSEG: EQU 40H
ORG 0
DS 3
BIOSSTAT: DS 3
BIOSIN: DS 3
BIOSOUT: DS 3
BIOSPRINT: DS 3
BIOSAUXIN: DS 3
BIOSAUXOUT: DS 3
BIOSREAD: DS 3
BIOSWRITE: DS 3
BIOSDSKCHG: DS 3
; Location of user registers relative user stack pointer
ORG 0
AXSAVE: DS 2
BXSAVE: DS 2
CXSAVE: DS 2
DXSAVE: DS 2
SISAVE: DS 2
DISAVE: DS 2
BPSAVE: DS 2
DSSAVE: DS 2
ESSAVE: DS 2
IPSAVE: DS 2
CSSAVE: DS 2
FSAVE: DS 2
; Start of code
ORG 0
PUT 100H
JMP DOSINIT
ESCTAB:
DB "SC" ;Copy one char
DB "VN" ;Skip one char
DB "TA" ;Copy to char
DB "WB" ;Skip to char
DB "UH" ;Copy line
DB "HH" ;Kill line (no change in template)
DB "RM" ;Reedit line (new template)
DB "DD" ;Backspace
DB "P@" ;Enter insert mode
DB "QL" ;Exit insert mode
DB ESCCH,ESCCH ;Escape character
DB ESCCH,ESCCH ;End of table
ESCTABLEN:EQU $-ESCTAB
HEADER: DB 13,10,"86-DOS version 1.00"
IF DSKTEST
DB "D"
ENDIF
DB 13,10
DB "Copyright 1980,81 Seattle Computer Products, Inc.",13,10,"$"
QUIT:
MOV AH,0
JP 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
SEG CS
POP [TEMP] ;IP from the CALL 5
PUSHF ;Start re-ordering the stack
DI
PUSH AX ;Save segment
SEG CS
PUSH [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
SEG CS
MOV AX,[SPSAVE]
SEG CS
MOV [NSP],AX
SEG CS
MOV AX,[SSSAVE]
SEG CS
MOV [NSS],AX
POP AX
PUSH AX
ENDIF
SEG CS
MOV [SPSAVE],SP
SEG CS
MOV [SSSAVE],SS
MOV BP,SP
MOV BX,[BP+CSSAVE]
SEG CS
MOV [CSLOC],BX
MOV SP,CS
MOV SS,SP
MOV SP,STACK
EI ;Stack OK now
SEG CS
MOV [FUNC],AH
MOV BL,AH
MOV BH,0
SHL BX
UP
IF DSKTEST
CMP AH,12
JL SAMSTK
MOV SP,TESTSTK
SAMSTK:
ENDIF
SEG CS
CALL [BX+DISPATCH]
LEAVE:
DI
SEG CS
MOV SP,[SPSAVE]
SEG CS
MOV SS,[SSSAVE]
MOV BP,SP
MOV [BP+AXSAVE],AL
IF DSKTEST
SEG CS
MOV AX,[NSP]
SEG CS
MOV [SPSAVE],AX
SEG CS
MOV AX,[NSS]
SEG CS
MOV [SSSAVE],AX
ENDIF
POP AX
POP BX
POP CX
POP DX
POP SI
POP DI
POP BP
POP DS
POP ES
IRET
DISPATCH:
; Standard Functions
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 VERSION
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 CURDRV ;25
DW SETDMA
DW GETFATPT
DW WRTPROT
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
VERSION:
GETIO:
SETIO:
WRTPROT:
GETRDONLY:
SETATTRIB:
USERCODE:
MOV AL,0
RET
READER:
CALL BIOSAUXIN,BIOSSEG
RET
PUNCH:
MOV AL,DL
CALL BIOSAUXOUT,BIOSSEG
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
MOV DI,[DI+BX]
JNC HAVCLUS
SHR DI
SHR DI
SHR DI
SHR DI
STC
HAVCLUS:
RCL BX
AND DI,0FFFH
RET
HURTFAT:
MOV SI,BADMES
CALL OUTMES
JMP ERROR
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
ADD BX,SI
ADD BX,DI
SHR DI
MOV DI,[BX]
JNC ALIGNED
SHL DX
SHL DX
SHL DX
SHL DX
AND DI,0FH
JP PACKIN
ALIGNED:
AND DI,0F000H
PACKIN:
OR DI,DX
MOV [BX],DI
RET
IOCHK:
MOV CX,5 ;Check rest of name but not extension
CMP B,[DI],":"
JNZ NOCOL
INC DI ;Skip over colon
DEC CX
NOCOL:
MOV AL," "
REPE
SCAB ;Make sure rest of name is blanks
JNZ FILSRCH
DEC BL
RET
GETFILE:
; 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
; 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 RET ;Bad file name?
FINDNAME:
MOV AX,CS
MOV DS,AX
MOV SI,IONAME ;List of I/O devices with file names
MOV BX,0FF04H ;BL = number of devices
LOOKIO:
MOV DI,NAME1
MOV CX,3 ;All device names are 3 letters
REPE
CMPB ;Check for name in list
JZ IOCHK ;If first 3 letters OK, check the rest
ADD SI,CX ;Point to next device name
DEC BL
JNZ LOOKIO
FILSRCH: ;Not a device name
CALL STARTSRCH
CONTSRCH:
CALL GETENTRY
JC RET
SRCH:
CMP B,[BX],0E5H
JZ NEXTENT
MOV SI,BX
MOV DI,NAME1
MOV CX,11
WILDCRD:
REPE
CMPB
JZ FOUND
CMP B,[DI-1],"?"
JZ WILDCRD
NEXTENT:
CALL NEXTENTRY
JNC SRCH
RET
FOUND:
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JZ RET
ENDIF
ADD SI,15
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
MOV [LASTENT],AX
MOV CL,4
SHL AX,CL
XOR DX,DX
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JZ SMALENT1
ENDIF
SHL AX
RCL DX ;Account for overflow in last shift
SMALENT1:
MOV BX,[BP+SECSIZ]
AND BL,255-31 ;Must be multiple of 32
DIV AX,BX
MOV BX,DX ;Position within sector
MOV AH,[BP+DRVNUM] ;AL=Directory sector no.
CMP AX,[DIRBUFID]
JZ HAVDIRBUF
PUSH BX
CALL DIRREAD
POP BX
HAVDIRBUF:
MOV DX,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
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGENT3
SUB BX,16
BIGENT3:
ENDIF
CMP BX,DX
JB HAVIT
INC AL ;Next directory sector
PUSH DX ;Save limit
CALL DIRREAD
POP DX
MOV BX,DIRBUF
HAVIT:
CLC
RET
NONE:
CALL CHKDIRWRITE
STC
RET
DELETE: ; System call 19
CALL GETFILE
JC ERRET
CMP BH,-1 ;Check if device name
JZ ERRET ;Can't delete I/O devices
DELFILE:
MOV B,[DIRTYDIR],-1
MOV B,[BX],0E5H
MOV BX,[SI]
LEA 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
CMP BH,-1 ;Check if I/O device name
JZ ERRET ;If so, can't rename it
ADD SI,5
MOV DI,NAME2
CALL LODNAME
CALL FINDNAME
JC ERRET
RENFIL:
MOV B,[DIRTYDIR],-1
MOV DI,BX
MOV SI,NAME2
MOV CX,11
NEWNAM:
LODB
CMP AL,"?"
JZ NOCHG
MOV [DI],AL
NOCHG:
INC DI
LOOP NEWNAM
CALL CONTSRCH
JNC RENFIL
CALL CHKDIRWRITE
XOR AL,AL
RET
ERRET:
MOV AL,-1
RET
MOVNAME:
; Inputs:
; DS, DX point to FCB
; Outputs:
; 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 AX,CS
MOV ES,AX
MOV DI,NAME1
MOV SI,DX
LODB
CALL GETBP
JB RET
LODNAME:
; This entry point copies a file name from DS,SI
; to ES,DI converting to upper case.
MOV CX,11
MOVCHK:
LODB
AND AL,7FH
CMP AL,60H
JLE CASEOK
AND AL,5FH
CASEOK:
CMP AL,20H
JC RET
STOB
LOOP MOVCHK
RET
GETBP:
SEG CS
CMP [NUMDRV],AL
JC RET
CBW
XCHG BP,AX
SHL BP
MOV BP,[BP+CURDRVPT]
RET
OPEN: ;System call 15
PUSH DX
PUSH DS
CALL GETFILE
DOOPEN:
; Enter here to perform OPEN on file already found
; in directory. DS=ES=CS, BX points to directory
; entry in DIRBUF, SI points to First Cluster field, and
; the top of the stack has the address and segment
; of the FCB to be opened. This entry point is used
; by CREATE.
POP ES
POP DI
JC ERRET
CMP BH,-1 ;Check if file is I/O device
JZ OPENDEV ;Special handler if so
MOV AL,[BP+DRVNUM]
INC AL
STOB
ADD DI,11 ;Point to extent field
XOR AX,AX
STOW ;Set extent field to 0
MOV AX,128 ;Default record size
STOW ;Set record size
LODW ;Get starting cluster
MOV DX,AX ;Save it for the moment
MOVW ;Transfer size to FCB
MOVW
MOV AX,[SI-8] ;Get date
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGENT10
SEG ES
MOV [DI-1],0
XOR AX,AX ;Date not available in small entry
BIGENT10:
ENDIF
STOW ;Save date in FCB
MOV AX,[LASTENT]
STOW ;directory location
MOV AX,DX ;Restore starting cluster
STOW ; first cluster
STOW ; last cluster accessed
XOR AX,AX
STOW ; position of last cluster
STOB ; dirty flag
RET
OPENDEV:
SEG ES
MOV [DI+FILDIRBLK],BX ;Use dir. entry number as flag
XOR AL,AL
RET
STARTSRCH:
MOV [LASTENT],-1
FATREAD:
; Inputs:
; DS = CS
; BP = Base of drive parameters
; Function:
; If disk may have been changed, FAT is read in and buffers are
; flagged invalid. If not, no action is taken.
; Outputs:
; AL = 0
; BP unchanged
; All other registers destroyed
MOV AL,[BP+DRVNUM]
CALL BIOSDSKCHG,BIOSSEG ;See what BIOS has to say
MOV AL,[BP+DRVNUM]
OR AH,[BP+DIRTYFAT]
JS NEWDSK ;If either say new disk, then it's so
DEC AH ;Check for AH=1 (disk not changed)
JZ RET
MOV AH,1
CMP AX,[BUFDRVNO] ;Does buffer have dirty sector of this drive?
JZ RET ;If so, disk has not been changed
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 [BUFDRVNO],00FFH
BUFOK:
MOV [DIRBUFID],-1
CALL FIGFAT
NEXTFAT:
PUSH DX
PUSH CX
PUSH BX
PUSH AX
CALL DREAD
OR AL,AL
POP AX
POP BX
POP CX
POP DX
JNZ BADFAT
IF SMALLDIR
MOV DL,AL
LEA SI,[BP+FIRREC1] ;FIRREC and MAXCLUS for 16-byte dir entries
CMP B,[BP+DIRSIZ],-1
JZ SETSIZ
ADD SI,4 ;FIRREC and MAXCLUS for 32-byte entries
SETSIZ:
LODW
MOV [BP+FIRREC],AX
LODW
MOV [BP+MAXCLUS],AX
MOV AL,DL
ENDIF
SUB AL,[BP+FATCNT]
JZ RET
NEG AL
;{Insert error code here. AL=number of bad fats.
;Since one good FAT was read, should include option
;to rewrite all FATs.}
JMP FATWRT
BADFAT:
ADD DX,CX
DEC AL
JNZ NEXTFAT
POP BP
;{Insert error code here. All FATs on drive are bad.}
MOV SI,BADFATMES
CALL HARDERR
JP FATREAD
OKRET1:
MOV AL,0
RET
CLOSE: ;System call 16
MOV DI,DX
CMP B,[DI+FILDIRBLK],-1 ;Check for I/O device
JZ OKRET1 ;Can't close I/O device
TEST B,[DI+DIRTYFIL],-1
JZ OKRET1 ;If not written to, do nothing
MOV AL,[DI] ;Get drive number
CALL GETBP ;Get base of drive parameters
JC BADCLOSEJ
MOV AL,[BP+DRVNUM]
MOV AH,1 ;Look for dirty buffer
SEG CS
CMP AX,[BUFDRVNO]
JNZ FNDDIR
;Write back dirty buffer if on same drive
PUSH DX
PUSH DS
PUSH CS
POP DS
MOV B,[DIRTYBUF],0
MOV BX,[BUFFER]
MOV CX,1
MOV DX,[BUFSECNO]
CALL DWRITE
POP DS
POP DX
FNDDIR:
PUSH DX
PUSH DS
CALL GETFILE
POP ES
POP DI
BADCLOSEJ:
JC BADCLOSE
MOV AX,[LASTENT]
SEG ES
CMP AX,[DI+FILDIRBLK]
JNZ BADCLOSE
SEG ES
MOV CX,[DI+FIRCLUS]
MOV [SI],CX
SEG ES
MOV DX,[DI+FILSIZ]
MOV [SI+2],DX
SEG ES
MOV DX,[DI+FILSIZ+2]
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGENT11
MOV [SI+4],DL
JP SMALLENT2
BIGENT11:
ENDIF
MOV [SI+4],DX
SEG ES
MOV DX,[DI+FDATE]
MOV [SI-2],DX
SMALLENT2:
CALL DIRWRITE
CHKFATWRT:
; Do FATWRT only if FAT is dirty
CMP B,[BP+DIRTYFAT],1
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
MOV B,[BP+DIRTYFAT],0
CALL FIGFAT
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 B,[BP+DIRTYFAT],0
MOV AL,-1
RET
FIGFAT:
; Loads registers with values needed to read or
; write a FAT.
MOV AL,[BP+FATCNT]
LEA 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,DIRBUF
MOV CX,1
RET
CREATE: ;System call 22
CALL MOVNAME
JC ERRET3
MOV DI,NAME1
MOV CX,11
MOV AL,"?"
REPNE
SCAB
JZ ERRET3
PUSH DX
PUSH DS
CALL FINDNAME
JNC EXISTENT
CALL STARTSRCH
CALL GETENTRY
LOOKFRE:
CMP B,[BX],0E5H
JZ FREESPOT
CALL NEXTENTRY
JNC LOOKFRE
POP DS
POP DX
ERRET3:
MOV AL,-1
RET
EXISTENT:
CMP BH,-1 ;Check if file is I/O device
JZ OPENJMP ;If so, no action
XOR CX,CX
MOV [SI+2],CX
MOV AX,[DATE]
IF SMALLDIR
MOV [SI+4],CL
CMP B,[BP+DIRSIZ],-1
JZ SMLENT
MOV [SI+5],CL
MOV [SI-2],AX
SMLENT:
ENDIF
IF 1-SMALLDIR
MOV [SI+4],CX
MOV [SI-2],AX
ENDIF
XCHG CX,[SI]
PUSH SI
PUSH BX
JCXZ WRTBACK
CMP CX,[BP+MAXCLUS]
JA WRTBACK
MOV BX,CX
LEA SI,[BP+FAT]
CALL RELEASE
CALL FATWRT
JP WRTBACK
FREESPOT:
MOV DI,BX
MOV SI,NAME1
MOV CX,5
MOVB
REP
MOVW
XOR AX,AX
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGENT4
PUSH DI
MOV CL,5
JP SMALLENT
BIGENT4:
ENDIF
MOV CL,13
REP
STOB
MOV AX,[DATE]
STOW
XOR AX,AX
PUSH DI
MOV CL,6
SMALLENT:
REP
STOB
PUSH BX
WRTBACK:
CALL DIRWRITE
POP BX
POP SI
OPENJMP:
CLC ;Clear carry so OPEN won't fail
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+DRVNUM]
MOV [DIRBUFID],AX
CALL DIRCOMP
CALL DREAD
POP AX
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.
; Outputs:
; AL = 0 if no error, otherwise non-zero
; BP preserved. All other registers destroyed.
MOV AL,[BP+DRVNUM]
PUSH BP
PUSH BX
PUSH CX
PUSH DX
CALL BIOSREAD,BIOSSEG
POP DX
POP DI
POP BX
POP BP
JC HARDREAD
XOR AL,AL
RET
HARDREAD:
MOV SI,RDERRMES
CALL HARDERR
JP DREAD
CHKDIRWRITE:
TEST B,[DIRTYDIR],-1
JZ RET
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 B,[DIRTYDIR],0
MOV AL,[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.
; Outputs:
; AL = 0 if no error, otherwise non-zero
; BP preserved. All other registers destroyed.
MOV AL,[BP+DRVNUM]
WRTDRV:
PUSH AX
PUSH BP
PUSH BX
PUSH CX
PUSH DX
CALL BIOSWRITE,BIOSSEG
POP DX
POP DI
POP BX
POP BP
POP AX
JC HARDWRITE
XOR AL,AL
RET
HARDWRITE:
MOV SI,WRTERRMES
CALL HARDERR
JP WRTDRV
HARDERR:
SUB DI,CX
ADD DX,DI
CALL SHFTDI7
ADD BX,DI
MOV AH,AL ;Save drive number
CALL OUTMES
GETINSTR:
CALL IN
OR AL,20H
CMP AL,"a"
JZ ERROR
CMP AL,"r"
JZ RETRY
CMP AL,"i"
JZ IGNORE
CMP AL,"c"
JNZ GETINSTR
CONTINUE:
POP AX
MOV AL,1
RET
IGNORE:
POP AX
MOV AL,0
RET
RETRY:
MOV AL,AH ;Restore drive number
RET
ABORT:
SEG CS
MOV DS,[CSLOC]
XOR AX,AX
MOV ES,AX
MOV SI,SAVEXIT
MOV DI,EXIT
MOVW
MOVW
MOVW
MOVW
ERROR:
MOV AX,CS
MOV DS,AX
MOV ES,AX
CALL WRTFATS
XOR AX,AX
DI
MOV SS,[SSSAVE]
MOV SP,[SPSAVE]
MOV DS,AX
MOV SI,EXIT
MOV DI,EXITHOLD
MOVW
MOVW
POP AX
POP BX
POP CX
POP DX
POP SI
POP DI
POP BP
POP DS
POP ES
EI ;Stack OK now
SEG CS
JMP L,[EXITHOLD]
SEQRD: ;System call 20
CALL GETREC
CALL LOAD
JP FINSEQ
SEQWRT: ;System call 21
CALL GETREC
CALL STORE
FINSEQ:
JCXZ SETNREX
ADD AX,1
ADC DX,0
JP SETNREX
RNDRD: ;System call 33
CALL GETRRPOS1
CALL LOAD
JP FINRND
RNDWRT: ;System call 34
CALL GETRRPOS1
CALL STORE
JP FINRND
BLKRD: ;System call 39
CALL GETRRPOS
CALL LOAD
JP FINBLK
BLKWRT: ;System call 40
CALL GETRRPOS
CALL STORE
FINBLK:
LDS SI,[SPSAVE]
MOV [SI+CXSAVE],CX
JCXZ FINRND
ADD AX,1
ADC DX,0
FINRND:
SEG ES
MOV [DI+RR],AX
SEG ES
MOV [DI+RR+2],DL
OR DH,DH
JZ SETNREX
SEG ES
MOV [DI+RR+3],DH ;Save 4 byte of RECPOS only if significant
SETNREX:
MOV CX,AX
AND AL,7FH
SEG ES
MOV [DI+NR],AL
AND CL,80H
SHL CX
RCL DX
MOV AL,CH
MOV AH,DL
SEG ES
MOV [DI+EXTENT],AX
SEG CS
MOV AL,[DSKERR]
RET
GETRRPOS1:
MOV CX,1
GETRRPOS:
MOV DI,DX
MOV AX,[DI+RR]
MOV DX,[DI+RR+2]
RET
NOFILERR:
XOR CX,CX
MOV B,[DSKERR],-2
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
; 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)
; If SETUP detects no records will be transfered, it returns 1 level up
; with CX = 0.
PUSH AX
MOV AL,[DI]
MOV SI,[DI+RECSIZ]
OR SI,SI
JNZ HAVRECSIZ
MOV SI,128
MOV [DI+RECSIZ],SI
HAVRECSIZ:
MOV BX,DS
MOV ES,BX
MOV BX,CS
MOV DS,BX
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 [RECPOS],AX
MOV [RECPOS+2],DX
MOV [FCB],DI
MOV BX,[DMAADD]
MOV [NEXTADD],BX
MOV B,[DSKERR],0
MOV B,[TRANS],0
MOV BX,DX
MUL AX,SI
MOV [BYTPOS],AX
PUSH DX
MOV AX,BX
MUL AX,SI
POP BX
ADD AX,BX
ADC DX,0 ;Ripple carry
JNZ EOFERR
MOV [BYTPOS+2],AX
MOV DX,AX
MOV AX,[BYTPOS]
DIV AX,[BP+SECSIZ]
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 AX,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 stay within 64K
MOV AX,[DMAADD]
NEG AX ;Amount of room left in segment
XOR DX,DX
DIV AX,SI ;How many records will fit?
MUL AX,SI ;Translate that back into bytes
MOV B,[DSKERR],2 ;Flag that trimming took place
MOV CX,AX
JCXZ NOROOM
OK:
LEA SI,[BP+FAT]
RET
EOFERR:
MOV B,[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 AX,[BP+SECSIZ] ;How many whole sectors?
MOV [SECCNT],AX
MOV [BYTCNT2],DX ;Bytes remaining for last sector
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.
SEG ES
MOV BX,[DI+LSTCLUS]
SEG ES
MOV DX,[DI+CLUSPOS]
OR BX,BX
JZ NOCLUS
SUB CX,DX
JNB FINDIT
ADD CX,DX
XOR DX,DX
SEG ES
MOV BX,[DI+FIRCLUS]
FINDIT:
JCXZ RET
SKPCLP:
CALL UNPACK
CMP DI,0FF8H
JAE RET
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
OR AL,AL
JNZ SETBUF
CMP DX,[BUFSECNO]
JNZ GETSEC
MOV AL,[BUFDRVNO]
CMP AL,[BP+DRVNUM]
JZ FINBUF ;Already have it?
GETSEC:
TEST B,[DIRTYBUF],-1
JZ RDSEC
PUSH DX
MOV AL,[BUFDRVNO]
MOV BX,[BUFFER]
MOV CX,1
MOV DX,[BUFSECNO]
CALL WRTDRV
POP DX
RDSEC:
MOV BX,[BUFFER]
MOV CX,1
PUSH DX
CALL DREAD
POP DX
SETBUF:
MOV [BUFSECNO],DX
MOV AL,[BP+DRVNUM]
MOV AH,0
MOV [BUFDRVNO],AX
FINBUF:
MOV B,[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
JNC EVENRD
MOVB
EVENRD:
REP
MOVW
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
JNC EVENWRT
MOVB
EVENWRT:
REP
MOVW
POP ES
POP DS
MOV B,[DIRTYBUF],1
RET
NEXTSEC:
TEST B,[TRANS],-1
JZ CLRET
MOV AL,[SECCLUSPOS]
INC AL
CMP AL,[BP+CLUSMSK]
JBE SAVPOS
MOV BX,[CLUSNUM]
CMP BX,0FF8H
JAE NONEXT
LEA SI,[BP+FAT]
CALL UNPACK
MOV [CLUSNUM],DI
INC [LASTPOS]
MOV AL,0
SAVPOS:
MOV [SECCLUSPOS],AL
CLRET:
CLC
RET
NONEXT:
STC
RET
TRANBUF:
LODB
STOB
CMP AL,13 ;Check for carriage return
JNZ NORMCH
MOV [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]
SEG ES
OR B,[DI+FILDIRBLK],80H ;Mark as no more data available
SETFCBJ:
JMP SETFCB
READDEV:
PUSH ES
LES DI,[DMAADD]
OR BL,BL
JZ READCON
DEC BL
JNZ ENDRDDEV
READAUX:
CALL BIOSAUXIN,BIOSSEG
STOB
CMP AL,1AH
LOOPNZ READAUX
JP ENDRDDEV
READCON:
PUSH CS
POP DS
MOV SI,[CONTPOS]
OR SI,SI
JNZ TRANBUF
CMP B,[CONBUF],128
JZ GETBUF
MOV [CONBUF],0FF80H ;Set up 128-byte buffer with no template
GETBUF:
PUSH CX
PUSH ES
PUSH DI
MOV DX,CONBUF
CALL BUFIN ;Get input buffer
POP DI
POP ES
POP CX
MOV SI,CONBUF+2
CMP B,[SI],1AH ;Check for Ctrl-Z in first character
JNZ TRANBUF
MOV AL,1AH
STOB
MOV AL,10
CALL OUT ;Send linefeed
XOR SI,SI
JP 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
SEG ES
MOV BX,[DI+FILDIRBLK]
CMP BH,-1 ;Check for named device I/O
JZ READDEV
SEG ES
MOV AX,[DI+FILSIZ]
SEG ES
MOV BX,[DI+FILSIZ+2]
SUB AX,[BYTPOS]
SBC BX,[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 B,[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]
CALL DREAD
POP DS
POP CX
POP BX
JCXZ RDLAST
CMP BX,0FF8H
JAE SETFCB
MOV DL,0
INC [LASTPOS] ;We'll be using next cluster
JP RDLP
SETFCB:
MOV SI,[FCB]
MOV AX,[NEXTADD]
MOV DI,AX
SUB AX,[DMAADD] ;Number of bytes transfered
XOR DX,DX
SEG ES
MOV CX,[SI+RECSIZ]
DIV AX,CX ;Number of records
CMP AX,[RECCNT] ;Check if all records transferred
JZ FULLREC
MOV B,[DSKERR],1
OR DX,DX
JZ FULLREC ;If remainder 0, then full record transfered
MOV B,[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
JNC EVENFIL
STOB
EVENFIL:
REP
STOW
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]
SEG ES
MOV [DI+LSTCLUS],AX
MOV AX,[LASTPOS]
SEG ES
MOV [DI+CLUSPOS],AX
ADDREC:
MOV AX,[RECPOS]
MOV DX,[RECPOS+2]
DEC CX
ADD AX,CX ;Update current record position
ADC DX,0
INC CX
RET
RDLAST:
MOV AX,[BYTCNT2]
OR AX,AX
JZ SETFCB
MOV [BYTCNT1],AX
CALL NEXTSEC
JC SETFCB
MOV [BYTSECPOS],0
CALL BUFRD
JP SETFCB
WRTDEV:
PUSH DS
LDS SI,[DMAADD]
AND BL,7FH
OR BL,BL
JZ WRTCON
DEC BL
JZ WRTAUX
WRTLST:
LODB
CMP AL,1AH
JZ ENDWRDEV
CALL BIOSPRINT,BIOSSEG
LOOP WRTLST
JP ENDWRDEV
WRTAUX:
LODB
CALL BIOSAUXOUT,BIOSSEG
CMP AL,1AH
LOOPNZ WRTAUX
JP ENDWRDEV
WRTCON:
LODB
CMP AL,1AH
JZ ENDWRDEV
CALL OUT
LOOP WRTCON
ENDWRDEV:
POP DS
MOV CX,[RECCNT]
MOV DI,[FCB]
JP ADDREC
HAVSTART:
MOV CX,AX
CALL SKPCLP
JCXZ DOWRTJ
CALL ALLOCATE
JNC DOWRTJ
WRTERR:
MOV B,[DSKERR],1
LVDSK:
MOV AX,[RECPOS]
MOV DX,[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
MOV B,[DI+DIRTYFIL],1
SEG CS
MOV BX,[DATE]
MOV [DI+FDATE],BX
CALL SETUP
SEG ES
MOV BX,[DI+FILDIRBLK]
CMP BH,-1
JZ WRTDEV
CALL BREAKDOWN
MOV AX,[BYTPOS]
MOV DX,[BYTPOS+2]
JCXZ WRTEOFJ
DEC CX
ADD AX,CX
ADC DX,0 ;AX:DX=last byte accessed
DIV AX,[BP+SECSIZ] ;AX=last sector accessed
MOV CL,[BP+CLUSSHFT]
SHR AX,CL ;Last cluster to be accessed
PUSH AX
SEG ES
MOV AX,[DI+FILSIZ]
SEG ES
MOV DX,[DI+FILSIZ]
DIV AX,[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
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 B,[TRANS],1 ;A transfer is taking place
MOV DL,[SECCLUSPOS]
MOV BX,[CLUSNUM]
MOV CX,[SECCNT]
WRTLP:
CALL OPTIMIZE
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
JP 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,[BYTPOS]
MOV DX,[BYTPOS+2]
ADC DX,0
MOV CX,DX
MOV DI,[FCB]
SEG ES
CMP AX,[DI+FILSIZ]
SEG ES
SBB CX,[DI+FILSIZ+2]
JB SAMSIZ
SEG ES
MOV [DI+FILSIZ],AX
SEG ES
MOV [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
SBC DX,0
DIV AX,[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,[BYTPOS]
SEG ES
MOV [DI+FILSIZ],AX
MOV AX,[BYTPOS+2]
SEG ES
MOV [DI+FILSIZ+2],AX
XOR CX,CX
RET
RELFILE:
MOV DX,0FFFH
CALL RELBLKS
SETDIRT:
MOV B,[BP+DIRTYFAT],1
JP UPDATE
KILLFIL:
XOR BX,BX
SEG ES
XCHG BX,[DI+FIRCLUS]
OR BX,BX
JZ UPDATE
CALL RELEASE
JP 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
; [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
LEA 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 AX,[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
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
JP 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
MOV CX,1
MOV AL,[DI+NR]
MOV DX,[DI+EXTENT]
SHL AL
SHR DX
RCR AL
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 AX,DX ;AX=max no. of records in file
MOV CX,AX
SUB CX,[RECPOS] ;CX=max no. of records that could be written
JA MAXREC
XOR CX,CX ;If CX was negative, zero it
MAXREC:
STC
RET
TRYOUT:
CALL UNPACK
JZ HAVFRE
TRYIN:
DEC AX
JLE FINDFRE
XCHG AX,BX
CALL UNPACK
JZ HAVFRE
XCHG AX,BX
JP FINDFRE
HAVFRE:
XCHG BX,DX
MOV AX,DX
CALL PACK
MOV BX,AX
LOOP ALLOC
MOV DX,0FFFH
CALL PACK
MOV B,[BP+DIRTYFAT],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 RET
MOV DI,[FCB]
SEG ES
MOV [DI+FIRCLUS],BX
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 RET
MOV AX,DI
CALL PACK
CMP AX,0FF8H
MOV BX,AX
JB RELEASE
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 RET
MOV BX,DI
JP GETEOF
SRCHFRST: ;System call 17
PUSH DX
PUSH DS
CALL GETFILE
SAVPLCE:
; Search-for-next enters here to save place and report
; findings.
POP ES
POP DI
JC KILLSRCH
CMP BH,-1
JZ SRCHDEV
MOV AX,[LASTENT]
SEG ES
MOV [DI+FILDIRBLK],AX
;Information in directory entry must be copied into the first
; 33 bytes starting at the disk transfer address.
MOV SI,BX
LES DI,[DMAADD]
MOV AL,[BP+DRVNUM]
INC AL
STOB ;Set drive number
MOVB ;Copy first character of name
MOV CX,5
REP
MOVW ;Copy remaining 10 characters of name
XOR AX,AX
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGENT5
STOB ;Zero out unused portion
MOV CX,7
REP
STOW ;Zero a total of 15 bytes
MOVW ;Copy first cluster pointer
MOVW ;Copy low word of length
MOVB ;Copy 3rd byte of length
STOB ;4th byte of length must be zero
RET
BIGENT5:
ENDIF
MOV CX,10
REP
MOVW
MOVB
RET
KILLSRCH:
SEG ES
KILLSRCH1:
MOV [DI+FILDIRBLK],-2
MOV AL,-1
RET
SRCHDEV:
SEG ES
MOV [DI+FILDIRBLK],BX
LES DI,[DMAADD]
XOR AX,AX
STOB ;Zero drive byte
SUB SI,3 ;Point to device name
MOVW
MOVB
MOV AX,2020H
MOV CX,4
REP
STOW ;Fill with 8 blanks
XOR AX,AX
MOV CX,10
REP
STOW
STOB
RET
SRCHNXT: ;System call 18
CALL MOVNAME
MOV DI,DX
JC KILLSRCH1
PUSH DX
PUSH DS
MOV AX,[DI+FILDIRBLK]
PUSH CS
POP DS
MOV [LASTENT],AX
CALL CONTSRCH
JMP SAVPLCE
FILESIZE: ;System call 35
PUSH DS
PUSH DX
CALL GETFILE
POP DI
POP ES
MOV AL,-1
JC RET
ADD DI,33 ;Write size in RR field
SEG ES
MOV CX,[DI-33+RECSIZ]
OR CX,CX
JNZ RECOK
MOV CX,128
RECOK:
XOR AX,AX
XOR DX,DX ;Intialize size to zero
CMP BH,-1 ;Check for named I/O device
JZ DEVSIZ
INC SI
INC SI ;Point to length field
MOV AX,[SI+2] ;Get high word of size
IF SMALLDIR
CMP B,[BP+DIRSIZ],-1
JNZ BIGSIZ
MOV AH,0
BIGSIZ:
ENDIF
DIV AX,CX
PUSH AX ;Save high part of result
LODW ;Get low word of size
DIV AX,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:
STOW
MOV AX,DX
STOB
MOV AL,0
CMP CX,64
JAE RET ;Only 3-byte field if RECSIZ >= 64
SEG ES
MOV [DI],AH
RET
SETDMA: ;System call 26
SEG CS
MOV [DMAADD],DX
SEG CS
MOV [DMAADD+2],DS
RET
GETFATPT: ;System call 27
MOV AX,CS
MOV DS,AX
MOV BP,[CURDRVPT]
CALL FATREAD
LEA BX,[BP+FAT]
MOV AL,[BP+CLUSMSK]
INC AL
MOV DX,[BP+MAXCLUS]
DEC DX
MOV B,[BP+DIRTYFAT],1
MOV CX,[BP+SECSIZ]
LDS SI,[SPSAVE]
MOV [SI+BXSAVE],BX
MOV [SI+DXSAVE],DX
MOV [SI+CXSAVE],CX
MOV [SI+DSSAVE],CS
RET
GETDSKPT: ;System call 31
SEG CS
MOV BX,[CURDRVPT]
SEG CS
LDS SI,[SPSAVE]
MOV [SI+BXSAVE],BX
MOV [SI+DSSAVE],CS
RET
DSKRESET: ;System call 13
SEG CS
MOV [DMAADD+2],DS
MOV AX,CS
MOV DS,AX
MOV [DMAADD],80H
MOV AX,[CURDRVPT+2]
MOV [CURDRVPT],AX
WRTFATS:
; DS=CS. Writes back all dirty FATs. All registers destroyed.
MOV CL,[NUMDRV]
MOV CH,0
MOV SI,CURDRVPT+2
WRTFAT:
LODW
PUSH CX
PUSH SI
MOV BP,AX
CALL CHKFATWRT
POP SI
POP CX
LOOP WRTFAT
MOV AX,[BUFDRVNO]
OR AH,AH
JZ RET
CBW
MOV BX,AX
SHL BX
MOV BP,[BX+DRVTAB]
MOV B,[DIRTYBUF],0
MOV DX,[BUFSECNO]
MOV BX,BUFFER
MOV CX,1
JMP DWRITE
CURDRV: ;System call 25
SEG CS
MOV BP,[CURDRVPT]
MOV AL,[BP+DRVNUM]
RET
INUSE: ;System call 24
MOV AX,CS
MOV DS,AX
MOV CL,[NUMDRV]
MOV CH,0
MOV SI,CX
SHL SI
ADD SI,CURDRVPT
MOV BX,0
DOWN
CHKUSE:
LODW
MOV BP,AX
CMP B,[BP+DIRTYFAT],-1 ;Carry set if not equal
RCL BX
LOOP CHKUSE
MOV AL,BL
RET
SETRNDREC: ;System call 36
CALL GETREC
MOV [DI+33],AX
MOV [DI+35],DL
RET
SELDSK: ;System call 14
MOV DH,0
MOV BX,DX
PUSH CS
POP DS
MOV AL,[NUMDRV]
CMP BL,AL
JNB RET
SHL BX
MOV DX,[BX+CURDRVPT+2]
MOV [CURDRVPT],DX
RET
BUFIN: ;System call 10
MOV AX,CS
MOV ES,AX
MOV SI,DX
MOV CH,0
LODW
OR AL,AL
JZ RET
MOV BL,AH
MOV BH,CH
CMP AL,BL
JBE NOEDIT
CMP B,[BX+SI],0DH
JZ EDITON
NOEDIT:
MOV BL,CH
EDITON:
MOV DL,AL
DEC DX
NEWLIN:
SEG CS
MOV AL,[CARPOS]
SEG CS
MOV [STARTPOS],AL
PUSH SI
MOV DI,INBUF
MOV AH,CH
MOV BH,CH
MOV DH,CH
GETCH:
CALL IN
CMP AL,7FH
JZ BACKSP
CMP AL,8
JZ BACKSP
CMP AL,13
JZ ENDLIN
CMP AL,10
JZ PHYCRLF
CMP AL,"X"-"@"
JZ KILNEW
CMP AL,ESCCH
JZ ESC
SAVCH:
CMP DH,DL
JAE GETCH
STOB
INC DH
CALL BUFOUT
OR AH,AH
JNZ GETCH
CMP BH,BL
JAE GETCH
INC SI
INC BH
JP GETCH
ESC:
CALL IN
MOV CL,ESCTABLEN
PUSH DI
MOV DI,ESCTAB
REPNE
SCAB
POP DI
AND CL,0FEH
MOV BP,CX
SEG CS ;To work in init
JMP [BP+ESCFUNC]
ENDLIN:
STOB
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,INBUF
MOV CL,DH
REP
MOVB
RET
CRLF:
MOV AL,13
CALL OUT
MOV AL,10
JMP OUT
PHYCRLF:
CALL CRLF
JP GETCH
KILNEW:
MOV AL,"\"
CALL OUT
POP SI
PUTNEW:
CALL CRLF
SEG CS
MOV AL,[STARTPOS]
CALL TAB
JMP NEWLIN
BACKSP:
OR DH,DH
JZ OLDBAK
CALL BACKUP
SEG ES
MOV AL,[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
DOWN
MOV CL,DH
MOV AL," "
PUSH BX
MOV BL,7
JCXZ FIGTAB
FNDPOS:
SCAB
JNA CHKCNT
SEG ES
CMP B,[DI+1],9
JZ HAVTAB
DEC BL
CHKCNT:
LOOP FNDPOS
FIGTAB:
SEG CS
SUB BL,[STARTPOS]
HAVTAB:
SUB BL,DH
ADD CL,BL
AND CL,7
UP
POP BX
POP DI
JZ OLDBAK
TABBAK:
CALL BACKMES
LOOP TABBAK
JP 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
JP COPYEACH
COPYSTR:
CALL FINDOLD
JP COPYEACH
COPYONE:
MOV CL,1
COPYEACH:
CMP DH,DL
JZ GETCH2
CMP BH,BL
JZ GETCH2
LODB
STOB
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
SCAB
POP DI
POP ES
JNZ NOTFND
NOT CL
ADD CL,BL
SUB CL,BH
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:
MOV AH,-1
JMP GETCH
EXITINS:
MOV AH,0
JMP GETCH
ESCFUNC:
DW GETCH
DW TWOESC
DW EXITINS
DW ENTERINS
DW BACKSP
DW REEDIT
DW KILNEW
DW COPYLIN
DW SKIPSTR
DW COPYSTR
DW SKIPONE
DW COPYONE
BUFOUT:
CMP AL," "
JAE OUT
CMP AL,9
JZ OUT
PUSH AX
MOV AL,"^"
CALL OUT
POP AX
OR AL,40H
JP OUT
CONOUT: ;System call 2
MOV AL,DL
OUT:
CMP AL,20H
JB CTRLOUT
CMP AL,7FH
JZ OUTCH
SEG CS
INC B,[CARPOS]
OUTCH:
CALL BIOSOUT,BIOSSEG
SEG CS
TEST B,[PFLAG],-1
JZ STATCHK
CALL BIOSPRINT,BIOSSEG
STATCHK:
CALL BIOSSTAT,BIOSSEG
JZ RET
INCHK:
CALL BIOSIN,BIOSSEG
CMP AL,'S'-'@'
JNZ NOSTOP
CALL BIOSIN,BIOSSEG
NOSTOP:
CMP AL,'P'-'@'
JZ PRINTON
CMP AL,'N'-'@'
JZ PRINTOFF
CMP AL,'C'-'@'
JNZ RET
; Ctrl-C handler.
; If function 9 or 10 was in progress, a backslash, CR, and LF are printed
; to show line is canceled. 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, except for console output (function 2), which has already output
; its character before the interrupt.
SEG CS
MOV AL,[FUNC] ;Get currently executing function
CMP AL,10 ;Check if buffered line input
JZ CANLIN
CMP AL,9 ;Check if buffered line output
JNZ RESTREG
CANLIN:
MOV AL,"\" ;Display cancel line symbol
CALL OUT
CALL CRLF
RESTREG:
DI ;Prepare to play with stack
SEG CS
MOV SS,[SSSAVE]
SEG CS
MOV SP,[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
CMP AH,2 ;Check if function was console output
JZ SETAL
JMP COMMAND ;Repeat command otherwise
SETAL:
MOV AL,DL
IRET ;Return to user program
PRINTON:
SEG CS
MOV B,[PFLAG],1
RET
PRINTOFF:
SEG CS
MOV B,[PFLAG],0
RET
CTRLOUT:
CMP AL,13
JZ ZERPOS
CMP AL,8
JZ BACKPOS
CMP AL,9
JNZ OUTCHJ
SEG CS
MOV AL,[CARPOS]
OR AL,0F8H
NEG AL
TAB:
PUSH CX
MOV CL,AL
MOV CH,0
TABLP:
MOV AL," "
CALL OUT
LOOP TABLP
POP CX
RET
ZERPOS:
SEG CS
MOV B,[CARPOS],0
OUTCHJ: JMP OUTCH
BACKPOS:
SEG CS
DEC B,[CARPOS]
JMP OUTCH
CONSTAT: ;System call 11
CALL BIOSSTAT,BIOSSEG
JZ RET
OR AL,-1
RET
CONIN: ;System call 1
CALL IN
PUSH AX
CALL OUT
POP AX
RET
IN: ;Internal input routine
CALL INCHK
JZ IN
RET
RAWIO: ;System call 6
MOV AL,DL
CMP AL,-1
JNZ RAWOUT
CALL BIOSSTAT,BIOSSEG
JZ RET
RAWINP: ;System call 7
CALL BIOSIN,BIOSSEG
RET
RAWOUT:
CALL BIOSOUT,BIOSSEG
RET
LIST: ;System call 5
MOV AL,DL
CALL BIOSPRINT,BIOSSEG
RET
PRTBUF: ;System call 9
MOV SI,DX
OUTSTR:
LODB
CMP AL,"$"
JZ RET
CALL OUT
JP OUTSTR
OUTMES: ;String output for internal messages
SEG CS
LODB
CMP AL,"$"
JZ RET
CALL OUT
JP OUTMES
MAKEFCB: ;Interrupt call 41
MOV DL,0 ;Flag--not ambiguous file name
OR AL,AL ;Scan off separators if not zero
JZ NOSCAN
SCAN:
CALL GETLET
JZ SCAN ;Get rid of leading separators (e.g., blanks)
DEC SI ;Point back to first non-separator
NOSCAN:
CMP B,[SI+1],":" ;Check for potential drive specifier
JNZ DEFAULT
CALL GETLET
SUB AL,"@" ;Convert drive letter to binary drive number
JZ NODRV ;Valid drive numbers are 1-15
INC SI
CMP AL,15
JBE HAVDRV
DEC SI
NODRV:
DEC SI ;Invalid drive specifier--back up pointer
DEFAULT:
XOR AL,AL
HAVDRV:
STOB ;Put drive specifier in first byte
MOV CX,8
CALL GETWORD ;Get 8-letter file name
CMP B,[SI],"."
JNZ NODOT
INC SI ;Skip over dot if present
NODOT:
MOV CX,3 ;Get 3-letter extension
CALL GETWORD
SEG CS
LDS BX,[SPSAVE]
MOV [BX+SISAVE],SI
XOR AX,AX
STOW
STOW
MOV AL,DL
RET
GETWORD:
CALL GETLET
JZ FILLNAM ;Exit if invalid character
CMP AL," "
JBE FILLNAM
CMP AL,"*" ;Check for ambiguous file specifier
JNZ NOSTAR
MOV AL,"?"
DEC CX
REP
STOB ;Fill rest of word with "?"
INC CX
NOSTAR:
STOB
CMP AL,"?"
JNZ NOTQ
MOV DL,1 ;Flag ambiguous file name
NOTQ:
LOOP GETWORD
INC SI ;Point to "termination" character
FILLNAM:
MOV AL," "
REP
STOB
DEC SI
RET
GETLET:
LODB
CMP AL,"a"
JB CHK
CMP AL,"z"
JA CHK
SUB AL,20H ;Convert to upper case
CHK:
CMP AL," "
JZ RET
CMP AL,"="
JZ RET
CMP AL,","
JZ RET
CMP AL,";"
JZ RET
CMP AL,"."
JZ RET
CMP AL,":"
JZ RET
CMP AL,9 ;Filter out TABs too
RET
SETVECT: ; Interrupt call 37
XOR BX,BX
MOV ES,BX
MOV BL,AL
SHL BX
SHL BX
SEG ES
MOV [BX],DX
SEG ES
MOV [BX+2],DS
RET
NEWBASE: ; Interrupt call 38
MOV ES,DX
SEG CS
MOV DS,[CSLOC]
XOR SI,SI
MOV DI,SI
MOV CX,80H
REP
MOVW
SETMEM:
; Inputs:
; 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)
; AX,DX,BP unchanged. All other registers destroyed.
XOR CX,CX
MOV DS,CX
MOV ES,DX
MOV SI,EXIT
MOV DI,SAVEXIT
MOVW
MOVW
MOVW
MOVW
SEG CS
MOV CX,[ENDMEM]
SEG ES
MOV [2],CX
SUB CX,DX
CMP CX,MAXDIF
JBE HAVDIF
MOV CX,MAXDIF
HAVDIF:
MOV BX,ENTRYPOINTSEG
SUB BX,CX
SHL CX
SHL CX
SHL CX
SHL CX
MOV DS,DX
MOV [6],CX
MOV [8],BX
MOV [0],20CDH ;"INT INTTAB"
MOV B,[5],LONGCALL
RET
SHFTDI7:
SHL DI
SHL DI
SHL DI
SHL DI
SHL DI
SHL DI
SHL DI
RET
; Default handler for division overflow trap
DIVOV:
XOR DX,DX ;Say no remainder
MOV AX,-1 ;But large quotient
IRET
;***** DATA AREA *****
BADMES: DB 13,10,"Bad FAT",13,10,"$"
BADFATMES:DB 13,10,"All FATs on disk are bad",13,10,"$"
RDERRMES:DB 13,10,"Disk read error",13,10,"$"
WRTERRMES:DB 13,10,"Disk write error",13,10,"$"
IONAME: DB "PRN","LST","AUX","CON"
CARPOS: DB 0
STARTPOS:DB 0
PFLAG: DB 0
DIRTYDIR:DB 0 ;Dirty buffer flag
NUMDRV: DS 1 ;Number of drives
CONTPOS:DW 0
DMAADD: DW 80H ;User's disk transfer address (disp/seg)
DS 2
ENDMEM: DS 2
MAXSEC: DW 0
BUFFER: DS 2
BUFSECNO:DW 0
BUFDRVNO:DB -1
DIRTYBUF:DB 0
DIRBUFID:DW -1
DATE: DS 2
CURDRVPT:DS 2
DRVTAB: DS 30 ;Enough for 15 drives
INBUF: DS 15 ;Only the first part
; Init code overlaps with data area below
INITCODE:
DS 128-15 ;More of INBUF
CONBUF: DS 130 ;The rest of INBUF and console buffer
FUNC: DS 1 ;Currently executing function code
LASTENT:DS 2
EXITHOLD:DS 4
FATBASE:DS 2
NAME1: DS 11 ;File name buffer
NAME2: DS 11
TEMP:
CSLOC: DS 2
SPSAVE: DS 2
SSSAVE: DS 2
SECCLUSPOS:DS 1 ;Position of first sector within cluster
DSKERR: DS 1
TRANS: DS 1
ALIGN
FCB: DS 2 ;Address of user FCB
NEXTADD:DS 2
RECPOS: DS 4
RECCNT: DS 2
LASTPOS:DS 2
CLUSNUM:DS 2
SECPOS: DS 2 ;Position of first sector accessed
VALSEC: DS 2 ;Number of valid (previously written) sectors
BYTSECPOS:DS 2 ;Position of first byte within sector
BYTPOS: DS 4 ;Byte position in file of access
BYTCNT1:DS 2 ;No. of bytes in first sector
BYTCNT2:DS 2 ;No. of bytes in last sector
SECCNT: DS 2 ;No. of whole sectors
DS 60 ;Stack space
STACK:
IF DSKTEST
NSS: DS 2
NSP: DS 2
DS 60
TESTSTK:
ENDIF
DIRBUF:
;Init code below overlaps with data area above
ORG INITCODE
PUT $+100H
MOVFAT:
;This section of code is safe from being overwritten by block move
SEG ES
REP
MOVB
UP
FININIT:
CALL SETMEM ;Set up segment
RET L
DOSINIT:
DI
UP
PUSH CS
POP ES
LODB
SEG ES
MOV [NUMDRV],AL
MOV BX,DRVTAB
MOV DI,MEMSTRT
PERDRV:
SEG ES
MOV [BX],DI
MOV BP,DI
INC BX
INC BX
SEG ES
MOV AL,[DRVCNT]
STOB ;DRVNUM
LODW ;Pointer to DPT
PUSH SI
MOV SI,AX
LODW
STOW ;SECSIZ
MOV DX,AX
SEG ES
CMP AX,[MAXSEC]
JBE NOTMAX
SEG ES
MOV [MAXSEC],AX
NOTMAX:
LODB
DEC AL
STOB ;CLUSMSK
JZ HAVSHFT
CBW
FIGSHFT:
INC AH
SAR AL
JNZ FIGSHFT
MOV AL,AH
HAVSHFT:
STOB ;CLUSSHFT
MOVW ;FIRFAT (= number of reserved sectors)
MOVB ;FATCNT
MOVW ;MAXENT
MOV AX,DX ;SECSIZ again
MOV CL,5
SHR AX,CL
MOV CX,AX ;Directory entries per sector
DEC AX
SEG ES
ADD AX,[BP+MAXENT]
XOR DX,DX
DIV AX,CX
STOW ;DIRSEC (temporarily)
SHR AX ;Divide by two
ADC AX,0 ;Round up
SEG ES
MOV [SDIRSEC],AX ;Number of directory records for small entries
MOVW ;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
SEG ES
DEC [BP+DSKSIZ] ;Damp those oscillations
JP FNDFATSIZ ;Try again
HAVFATSIZ:
STOB ;FATSIZ
SEG ES
MUL AL,[BP+FATCNT] ;Space occupied by all FATs
SEG ES
ADD AX,[BP+FIRFAT]
STOW ;FIRDIR
IF SMALLDIR-1
SEG ES
ADD AX,[BP+DIRSEC]
SEG ES
MOV [BP+FIRREC],AX ;Destroys DIRSEC
CALL FIGMAX
SEG ES
MOV [BP+MAXCLUS],CX
ENDIF
IF SMALLDIR
MOV DX,AX ;Save FIRDIR momentarily
SEG ES
ADD AX,[SDIRSEC] ;Add number of dir. sectors for 16-byte entry
STOW ;FIRREC1
XCHG AX,CX ;Previously computed MAXCLUS
STOW ;MAXCLUS1
XCHG DX,AX
SEG ES
ADD AX,[BP+DIRSEC] ;Add number of dir. sectores for 32-byte entry
STOW ;FIRREC2
CALL FIGMAX
XCHG AX,CX
STOW ;MAXCLUS2
ENDIF
MOV AX,0FFH
STOB ;DIRTYFAT
SEG ES
MOV AL,[BP+FATSIZ]
SEG ES
MUL AX,[BP+SECSIZ]
ADD DI,AX ;Allocate FAT
POP SI ;Restore pointer to init. table
SEG ES
MOV AL,[DRVCNT]
INC AL
SEG ES
MOV [DRVCNT],AL
SEG ES
CMP AL,[NUMDRV]
JAE CONTINIT
JMP PERDRV
CONTINIT:
LODW ;Max. buffer size
SEG ES
MOV BX,[MAXSEC]
MOV AX,DIRBUF
ADD AX,BX
SEG ES
MOV [BUFFER],AX ;Start of buffer
PUSH DI ;Save ending location
ADD DI,BX ;Allocate directory buffer
ADD DI,BX ;Allocate buffer space
ADD DI,ADJFAC+15 ;True start of free space
MOV CL,4
SHR DI,CL ;First free segment
MOV BP,DI
XOR AX,AX
MOV DS,AX
MOV ES,AX
MOV DI,INTBASE
MOV AX,QUIT
STOW ;Set abort address--displacement
MOV AX,CS
MOV B,[ENTRYPOINT],LONGJUMP
MOV [ENTRYPOINT+1],ENTRY
MOV [ENTRYPOINT+3],AX
MOV [0],DIVOV ;Set default divide trap address
MOV [2],AX
MOV CX,9
REP
STOW ;Set 5 segments (skip 2 between each)
MOV [INTBASE+4],COMMAND
MOV [INTBASE+12],IRET ;CTRL-C exit
MOV [INTBASE+16],IRET ;Fatal error exit
MOV AX,BIOSREAD
STOW
MOV AX,BIOSSEG
STOW
STOW ;Add 2 to DI
STOW
MOV [INTBASE+18H],BIOSWRITE
MOV DX,CS
MOV DS,DX
ADD DX,BP
MOV [DMAADD],80H
MOV [DMAADD+2],DX
MOV AX,[DRVTAB]
MOV [CURDRVPT],AX
MOV CX,DX
MOV BX,0FH
MEMSCAN:
INC CX
JZ HAVMEM
MOV DS,CX
MOV AL,[BX]
NOT AL
MOV [BX],AL
CMP AL,[BX]
NOT AL
MOV [BX],AL
JZ MEMSCAN
HAVMEM:
SEG CS
MOV [ENDMEM],CX
XOR CX,CX
MOV DS,CX
MOV [EXIT],100H
MOV [EXIT+2],DX
MOV SI,HEADER
CALL OUTMES
PUSH CS
POP DS
PUSH CS
POP ES
PUSH DX
GETDAT:
MOV SI,DATMES
CALL OUTMES
MOV DX,DATBUF
CALL BUFIN
CALL CRLF
MOV SI,DATBUF+2
MOV DX,12
CALL MYD
JC GETDAT
MOV CL,5
SHL AX,CL
MOV [DATE],AX
MOV DX,31
CALL MYD
JC GETDAT
OR [DATE],AL
MOV DX,2100
CALL MYD
JC GETDAT
SUB AX,80
JC GETDAT
CMP AX,19
JBE SAVYR
SUB AX,1900
JC GETDAT
SAVYR:
SHL AL
OR [DATE+1],AL
;Move the FATs into position and adjust the drive pointer table
POP DX
POP SI
MOV AX,[MAXSEC]
SHL AX ;Allocate two buffers
ADD AX,ADJFAC
JZ FINJMP
MOV DI,DRVTAB
MOV CX,15
ADJLP:
ADD [DI],AX
INC DI
INC DI
LOOP ADJLP
MOV CX,SI
MOV SI,MEMSTRT ;Place to move FATs from
SUB CX,SI ;Total length of FATs
MOV DI,AX
ADD DI,SI ;Place to move FATs to
OR AX,AX
JS MOVJMP
DEC CX
ADD DI,CX
ADD SI,CX
INC CX
DOWN
MOVJMP:
JMP MOVFAT
FINJMP: JMP FININIT
FIGFATSIZ:
SEG ES
MUL AL,[BP+FATCNT]
SEG ES
ADD AX,[BP+FIRFAT]
SEG ES
ADD AX,[SDIRSEC] ;Use small dir. entry to figure FAT size
FIGMAX:
;AX has equivalent of FIRREC
SEG ES
SUB AX,[BP+DSKSIZ]
NEG AX
SEG ES
MOV CL,[BP+CLUSSHFT]
SHR AX,CL
INC AX
MOV CX,AX ;MAXCLUS
INC AX
MOV DX,AX
SHR DX
ADC AX,DX ;Size of FAT in bytes
SEG ES
MOV SI,[BP+SECSIZ]
ADD AX,SI
DEC AX
XOR DX,DX
DIV AX,SI
RET
MYD:
;SI points to input buffer. Get decimal number < DX and return it
;in AX. Carry set on error.
XOR BX,BX
MOV AH,0
GETDIG:
LODB
SUB AL,"0"
JC CHKRET
CMP AL,10
JNC CHKRET
SHL BX
MOV CX,BX
SHL BX
SHL BX
ADD BX,CX
ADD BX,AX
JP GETDIG
CHKRET:
MOV AX,BX
OR AX,AX
STC
JZ RET
CMP DX,AX
RET
DRVCNT: DB 0
DATMES: DB "Enter today's date (m-d-y): $"
DATBUF: DB 12,8,"04-28-81",13
DS 5
SDIRSEC:DS 2
MEMSTRT:
ADJFAC: EQU DIRBUF-MEMSTRT

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