Format of SHARE.EXE hooks (DOS 3.1-6.00):
Offset Size Description )
(offsets from first system file table--pointed at by ListOfLists+04h)
-3Ch DWORD pointer to FAR routine for ???
Note: not called by MS-DOS 3.3, set to 0000h:0000h by
SHARE 3.3+
-38h DWORD pointer to FAR routine called on opening file
on call, internal DOS location points at filename
(see #01687 at AX=5D06h)
Return: CF clear if successful
CF set on error
AX = DOS error code (24h)
(see #01680 at AH=59h/BX=0000h)
Note: SHARE directly accesses DOS-internal data to get name of
file just opened
-34h DWORD pointer to FAR routine called on closing file
ES:DI -> system file table
Note: does something to every Record Lock Record for file
-30h DWORD pointer to FAR routine to close all files for given computer
(called by AX=5D03h)
-2Ch DWORD pointer to FAR routine to close all files for given process
(called by AX=5D04h)
-28h DWORD pointer to FAR routine to close file by name
(called by AX=5D02h)
DS:SI -> DOS parameter list (see #01686 at AX=5D00h)
DPL's DS:DX -> name of file to close
Return: CF clear if successful
CF set on error
AX = DOS error code (03h)
(see #01680 at AH=59h/BX=0000h)
-24h DWORD pointer to FAR routine to lock region of file
call with BX = file handle
---DOS 3.x---
CX:DX = starting offset
SI:AX = size
---DOS 4.0+ ---
DS:DX -> lock range
DWORD start offset
DWORD size in bytes
Return: CF set on error
AL = DOS error code (21h) (see #01680 at AH=59h)
Note: not called if file is marked as remote
-20h DWORD pointer to FAR routine to unlock region of file
call with BX = file handle
---DOS 3.x---
CX:DX = starting offset
SI:AX = size
---DOS 4.0+ ---
DS:DX -> lock range
DWORD start offset
DWORD size in bytes
Return: CF set on error
AL = DOS error code (21h) (see #01680 at AH=59h)
Note: not called if file is marked as remote
-1Ch DWORD pointer to FAR routine to check if file region is locked
call with ES:DI -> system file table entry for file
CX = length of region from current position in file
Return: CF set if any portion of region locked
AX = 0021h
-18h DWORD pointer to FAR routine to get open file list entry
(called by AX=5D05h)
call with DS:SI -> DOS parameter list (see #01686 at AX=5D00h)
DPL's BX = index of sharing record
DPL's CX = index of SFT in SFT chain of sharing rec
Return: CF set on error or not loaded
AX = DOS error code (12h) (see #01680 at AH=59h)
CF clear if successful
ES:DI -> filename
CX = number of locks owned by specified SFT
BX = network machine number
DX destroyed
-14h DWORD pointer to FAR routine for updating FCB from SFT???
call with DS:SI -> unopened FCB
ES:DI -> system file table entry
Return: BL = C0h???
Note: copies following fields from SFT to FCB:
starting cluster of file 0Bh 1Ah
sharing record offset 33h 1Ch
file attribute 04h 1Eh
-10h DWORD pointer to FAR routine to get first cluster of FCB file ???
call with ES:DI -> system file table entry
DS:SI -> FCB
Return: CF set if SFT closed or sharing record offsets
mismatched
CF clear if successful
BX = starting cluster number from FCB
-0Ch DWORD pointer to FAR routine to close file if duplicate for process
DS:SI -> system file table
Return: AX = number of handle in JFT which already uses SFT
Note: called during open/create of a file
Note: if SFT was opened with inheritance enabled and sharing
mode 111, does something to all other SFTs owned by
same process which have the same file open mode and
sharing record
-08h DWORD pointer to FAR routine for closing file
Note: closes various handles referring to file most-recently
opened
-04h DWORD pointer to FAR routine to update directory info in related SFT
entries
call with ES:DI -> system file table entry for file (see #01641)
AX = subfunction (apply to each related SFT)
00h: update time stamp (offset 0Dh) and date
stamp (offset 0Fh)
01h: update file size (offset 11h) and starting
cluster (offset 0Bh). Sets last-accessed
cluster fields to start of file if file
never accessed
02h: as function 01h, but last-accessed fields
always changed
03h: do both functions 00h and 02h
Note: follows ptr at offset 2Bh in system file table entries
Note: NOP if opened with no-inherit or via FCB
Notes: most of the above hooks (except -04h, -14h, -18h, and -3Ch) assume
either that SS=DOS DS or SS=DS=DOS DS and directly access
DOS-internal data
sharing hooks are not supported by DR DOS 5-6; they appear to be
supported by Novell DOS 7, with a segment of 0000h indicating the
DOS data segment
SeeAlso: #01637,#01638