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page 80,132
;0
title CP/DOS DosOpen mapper
FileAttributeSegment segment word public 'fat'
public FileAttributeTable
FileAttributeTable dw 100 dup(0)
FileAttributeSegment ends
dosxxx segment byte public 'dos'
assume cs:dosxxx,ds:nothing,es:nothing,ss:nothing
;
; ************************************************************************* *
; *
; * MODULE: DosOpen
; *
; * FILE NAME: DosOpen.ASM
; *
; * FUNCTION: This module creates the specified file (if necessary),
; * and opens it. If the file name is a device then the
; * handle returned will be a device handle. The high order
; * byte of the open flag is ignored because PC/DOS does not
; * support a word long open mode. Invalid parameters are
; * reported as general failures because there are no error
; * codes defined at this time.
; *
; * CALLING SEQUENCE:
; *
; * PUSH@ ASCIIZ FileName ; File path name
; * PUSH@ WORD FileHandle ; New file's handle
; * PUSH@ WORD ActionTaken ; Action taken
; * PUSH DWORD FileSize ; File primary allocation
; * PUSH WORD FileAttribute ; File attribute
; * PUSH WORD OpenFlag ; Open function type
; * PUSH WORD OpenMode ; Open mode of the file
; * PUSH@ DWORD 0 ; Reserved (must be zero)
; * CALL DosOpen
; *
; * RETURN SEQUENCE:
; *
; * IF ERROR (AX not = 0)
; *
; * AX = Error Code:
; *
; * o Invalid parameter(s)
; *
; * o Insufficient disk space available
; *
; * o Insufficient resources (i.e., file handles)
; *
; *
; * MODULES CALLED: DOS int 21H function 3DH
; * DOS int 21H function 3EH
; * DOS int 21H function 40H
; * DOS int 21H function 42H
; * DOS int 21H function 43H
; *
; *************************************************************************
;
public DosOpen
.sall
.xlist
include macros.inc
.list
ACT_FileExisted equ 1
ACT_FileCreated equ 2
str struc
old_bp dw ?
return dd ?
resrv34 dd ? ; reserved
OpenMode dw ? ; open mode
OpenFlag dw ? ; open function type (1=Open only if already exist)
OpenFileAttr dw ? ; file attribute
FileSize dd ? ; file allocation size
acttak34 dd ? ; action taken
FileHandlePtr dd ? ; New file handler
FileNamePtr dd ? ; file name pointer
str ends
;
DosOpen proc far
Enter DosOpen ; save registers
sub sp,2 ; allocate space on the stack
SaveArea equ -2
; Check to see if we are trying to open a DASD device. If so, we must do
; something unique as PC-DOS does not support this behavior.
; Return a dummy DASD file handle. This used by IOCTL category 8 option.
test [bp].OpenMode,08000h ; DASD open ?
jz FileOpenRequest ; branch if file open
lds si,[bp].FileNamePtr ; convert device name to upper case
mov al,ds:[si]
cmp al,'a'
jc NoFold
cmp al,'z'+1
jnc NoFold
add al,'A' - 'a'
NoFold:
sub al,'A'
jc BadDASDName ; jump if bad DASD name
cmp al,27
jnc BadDASDName
xor ah,ah ; drive number from 0 to 25
inc ax ; 1 to 26
inc ax ; 2 to 27
neg ax ; -2 to -27
lds si,[bp].FileHandlePtr
mov ds:[si],ax ; save dasd dummy device handle
jmp GoodExit ; in return data area and return
BadDASDName:
mov ax,3 ; set error code
jmp ErrorExit ; return
; Query the file attribute to determine if file exists
FileOpenRequest:
lds dx,dword ptr [bp].FileNamePtr ; load asciiz string address
mov ax,04300h ; query file mode
int 21h ; get file mode
jnc SaveAttribute ; file does exist
cmp ax,00002h ; check if file does not exist error
je dne34 ; go here if does not exist
jmp erret34 ; error return
SaveAttribute:
mov [bp].SaveArea,cx
; File exists - determine what to do
lds si,dword ptr [bp].acttak34 ; Load action taken pointer
mov word ptr[si],ACT_FileExisted ; Indicate that file existed
mov ax,[bp].OpenFlag ; load open flag
and ax,00003h ; mask off the replace and open flags
cmp ax,00003h ; check if both are requested
je nxt134 ; error - invalid parm
cmp ax,00001h ; check if file is to be opened
je opn34 ; file should be opened
cmp ax,00002h ; check if file should be replaced
je creat34 ; file should be replaced
nxt134:;
mov ax,0000ch ; report general
jmp erret34 ; failure
;
opn34:;
; set the file attribute ( *** commented to fix mapper problem Pylee 6/10
;
; lds dx,dword ptr [bp].FileNamePtr ; load asciiz string address
; mov cx,[bp].OpenFileAttr ; load the file attribute
; mov ax,04301h ; change file mode
; int 21h ; get file mode
; jnc nxto34 ; continue good return
; jmp erret34 ; error retrun
nxto34:;
; open the file
lds si,dword ptr [bp].acttak34 ; load action taken pointer
mov word ptr [si],00h ; clear action reported flag
lds dx,dword ptr [bp].FileNamePtr ; load asciiz string address
mov ax,[bp].OpenMode ; load the file mode
mov ah,03dh ; load opcode
int 21h ; open file
jc ErrorExit ; error return
FileWasThere:
lds si,dword ptr [bp].FileHandlePtr ; load file handle address
mov [si],ax ; save file handle
jmp PutAwayAttribute ; normal return
dne34:;
; File does not exist - determine what to do
mov ax,[bp].OpenFlag ; load open flag
and ax,00010h ; check create
cmp ax,00010h ; and open file flag
je creat34 ; go create the file
mov ax,0000ch ; report general failure
jmp erret34 ; if create not requested
creat34:;
; file did not exist so it was created or replacement was requested
lds si,dword ptr [bp].acttak34 ; load action taken pointer
mov word ptr [si],ACT_FileCreated ; file created - action reported
lds dx,dword ptr [bp].FileNamePtr ; load asciiz string address
mov cx,[bp].OpenFileAttr ; set file attribute
mov ah,03ch
int 21h ; create the file
jc erret34 ; error return
lds si,dword ptr [bp].FileHandlePtr ; load file handle address
mov [si],ax ; save file handle
;
; set file length
;
les dx,[bp].FileSize
mov cx,es
mov bx,ax ; load file handle
mov ax,04202h ; load opcode
int 21h ; move file pointer
jc erret34 ; error return
len134:;
lds si,dword ptr [bp].FileHandlePtr ; load file handle address
mov bx,[si] ; load file handle
lds dx,dword ptr [bp].acttak34
sub cx,cx
mov ah,040h
int 21h ; write 0 length record
jc erret34 ; error return
;
len234:;
;
; close and reopen the file to make the length permanent
;
lds si,dword ptr [bp].FileHandlePtr ; load file handle address
mov bx,[si] ; load file handle
mov ah,03eh
int 21h
jc erret34 ; error return
lds dx,dword ptr [bp].FileNamePtr ; load asciiz string address
mov ax,[bp].OpenMode ; load the file mode
mov ah,03dh ;
int 21h ; open the file
jc erret34 ; error return
lds si,dword ptr [bp].FileHandlePtr ; load file handle address
mov [si],ax ; save file handle
PutAwayAttribute: ; save file attribute for other mapper
mov bx,ax ; calls
add bx,bx
mov ax,seg FileAttributeSegment
mov ds,ax
assume ds:FileAttributeSegment
mov ax,[bp].SaveArea
mov FileAttributeTable[bx],ax ; save file attribute
GoodExit:
sub ax,ax ; set good return code
erret34:;
ErrorExit:
add sp,2 ; deallocate space
mexit ; restore registers
ret size str - 6 ; return
DosOpen endp
dosxxx ends
end
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