Re: [hatari-devel] Max amount of GEMDOS HD file handles?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

I pushed increase to 64 GEMDOS HD handles.

On 28.7.2023 20.45, Thomas Huth wrote:
> Am Thu, 27 Jul 2023 21:06:09 +0300
> schrieb Eero Tamminen <oak@xxxxxxxxxxxxxx>:
>> I'm asking because I came across program needing more than 32 GEMDOS HD
>> handles.
>
> Wow, which program was this?

It was with ScummVM "Illusions" game engine, that currently supports 
only single game:
https://wiki.scummvm.org/index.php?title=Illusions

I.e. something ported from elsewhere, instead of originating on Atari.


> And do you know how many handles it needs?

32 was too little, 64 was enough (to start it).

Note: Miro's ScummVM Atari version includes over fifty game engines [1], 
and only one of them had this issue.

[1] Upstream supports more engines: 
https://wiki.scummvm.org/index.php?title=Engines


On 27.7.2023 22.22, Roger Burrows wrote:
> This raises an interesting issue.  TOS and EmuTOS allow up to 75 non-standard
> handles (6-80 inclusive).  Hatari uses 64-95 for its GEMDOS handles.  So it's
> possible to have different files open on different drives (one GEMDOS and one
> non-GEMDOS), with the same handle.
>
> It is of course extrememly unlikely that this will happen, but it could (I have
> a test program if anyone needs one to verify).  If it *does* happen, I assume
> that I/O to the non-GEMDOS file will quietly be routed by Hatari to the GEMDOS
> file.

Yes, that's likely.


To be safe, the GEMDOS handles *should* start at 81 or higher.

I do not think I've run into another program using more than *32* 
handles (+ few standard ones) within last ~20 years, except with some 
(buggy) GEMDOS test program.

I..e bumping into some real program using more than 64 handles, seems 
fairly theoretical under plain TOS.

Most likely setup triggering that issue would be:
* MiNT kernel build with Helmut's OLDTOSFS (which allows use of GEMDOS 
HD emulation under MiNT), and * user running multiple programs having 
lot of files open on non-GEMDOS HD drives.

Base is not going to be changed though, because it could regress things 
for Atari original programs (I vaguely remember some actually having 
problems with larger file handles).


As there are already several other niche gotchas for GEMDOS HD usage:
https://hatari.tuxfamily.org/doc/manual.html#GEMDOS_based_hard_drive_emulation

I've just added this to the list:
https://git.tuxfamily.org/hatari/hatari.git/commit/


	- Eero