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 Return: nothing 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. SeeAlso: AX=1000h,AX=F800h