Category: disk I/O enhancements
Flags: Undocumented function
INT 2F - DR DOS 6.0+ FDOS EXTENSIONS - INSTALL FDOS HOOK (SHARE / DELWATCH)
AX = 1001h
DX:BX -> new FDOS stub entry function
Notes: the default handler for the pointer set by this call under DELWATCH
simply returns with CF set
In Digital Research terminology FDOS is the part of the BDOS kernel
(IBMDOS.COM) responsible for the file system and related tasks, and
its functionality is also used by the BDOS kernel itself. However,
for reasons of performance and code size, it uses direct calling.
This interrupt allows external components like SHARE file locking or
DELWATCH delete tracking software to hook into the internal backdoor
INT 2F/AH=10h/AL<=09h chain in the kernel, so that they can actually
allows the kernel to ensure that several conditions are met when
passing control to these registered components including proper
maintaining A20, re-enterancy, or critical section mutexing
(e.g. getting the disk sub-system queue "MXdisk").
The default handler in the BDOS just sets the carry flag and returns.
Currently known clients to this shared interface are DR DOS 6.0
SHARE 1.xx, DR DOS 6.0+ DELWATCH 1.00+, which both chain onto
the same call far address, and the version of AddStor's SuperStor
which is bundled with DR DOS 6.0
However, the DR PalmDOS, and Novell DOS 7 - DR-DOS 7.03 SHARE 2.00-2.05
do not use this function to hook into the system. Instead they fix up
the share stubs directly. DR PalmDOS SHARE 2.00 uses the stubs at
Table !!! INT 21/AH=52h, while Novell DOS 7 - DR-DOS 7.03
SHARE 2.01-2.05 use the private set of share stubs at Table !!! at
INT 21/AX=4458h). Future releases may possibly again fix up the
share stubs at INT 21/AH=52h.