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Date: Fri, 05 Apr 2002 18:58:38 +0300
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
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To: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
Message-Id: <2110-Fri05Apr2002185837+0300-eliz@is.elta.co.il>
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In-reply-to: <3CAD983A.1B61E2B6@phekda.freeserve.co.uk> (message from Richard
	Dawe on Fri, 05 Apr 2002 13:27:38 +0100)
Subject: Re: FSEXT: grow_table and realloc failure
References: <E16soP7-0000oI-00 AT phekda DOT freeserve DOT co DOT uk> <2110-Fri05Apr2002091207+0300-eliz AT is DOT elta DOT co DOT il> <3CAD72DF DOT ECCADD44 AT phekda DOT freeserve DOT co DOT uk> <8361-Fri05Apr2002142038+0300-eliz AT is DOT elta DOT co DOT il> <3CAD983A DOT 1B61E2B6 AT phekda DOT freeserve DOT co DOT uk>
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> Date: Fri, 05 Apr 2002 13:27:38 +0100
> From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
> 
> Eli Zaretskii wrote:
> [snip]
> > I have no objections to the patch, although it strikes me that it
> > would be easier to have a constant-size table in the first place.
> > After all, the max number of handles we can have is quite small...
> 
> When testing on Windows 98 SE I found that it seemed to max out of filehandles
> at about ~200. Presumably DOS is the limiting factor in the number of
> filehandles?

A DOS program cannot have more than 255 handles available to it, since
the table which gives the SFT entry for each handle allocates a single
byte for the handle.  This gives 256 handles max, but the value FFh is
used for unused handles.  So we are left with 255, including the 5
standard handles.

> If we had SuperDuperDOS that supported > 256 filehandles, then
> we'd hit the limit.

A DOS clone cannot overcome this limit without causing serious
compatibility problems, since the structure of the table that holds
the handles (JFT, the Job File Table) is well documented, and there
are programs that depend on that structure (this includes our own
code in lstat.c and in dbgcom.c).