Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!mcsun!ukc!mucs!cns!usenet
From: rogersh%p2h@uk.ac.man.cs
Newsgroups: comp.sys.acorn,eunet.micro.acorn
Subject: Re: DOS/UNIX/etc <-> ADFS Filename Mapping
Message-ID: <1991Jan16.103434.797@cns.umist.ac.uk>
Date: 16 Jan 91 10:34:34 GMT
References: <7850@castle.ed.ac.uk>
Sender: usenet@cns.umist.ac.uk (News System)
Organization: Murder Inc.
Lines: 69

In article <7850@castle.ed.ac.uk> as@castle.ed.ac.uk (A Stevens) writes:
>One serious complication when porting code or file-structures
>to and from the Arch is its unfortunate combination
>of short (10 char) filenames and an absence of filename extensions.
>
>To convert filenames from DOS (effectively 11 chars if you
>count the extension) or UNIX or VMS some kind of transformation
>has to be performed.  The catch is not that this is impossible,
>just that there are so many different ways to do it,
>so programs tend not work in the same way.

	I have already had to tackle this problem. Basically there are
several stages to converting a UNIX filename (or MSDOS since apart from
the delimiter there is no difference) to ADFS.

1) Sort out the directory info. This means dealing with things like:

	.././../.info
	/.././../info
	/etc/../tmp/info

	etc. At this stage it is also necessary to do something about
 characters in the filenames. The method I use is to convert all filenames
with certain common UNIX/MSDOS single character extensions (e.g. x.c, x.s,
x.h) to s.x, c.x, etc. and otherwise just convert the '.' to a '_' along
with all other ADFS-illegal characters '#$@' etc. E.g.

	info.Z				@.Z.info
	info.tmp			@.info_tmp
	/.././etc/../tmp/info		$.tmp.info
	tmp/sort.c			@.tmp.c.sort
	../Makefile_src			@.^.Makefile_src
	./124$$.etc			@.124___etc

2) Sort out long names in the resulting path. This is done by first removing
vowels except from the first letter. E.g.

	Makefile_tmp			Mkfile_tmp
	Afternoon_test_data		Aftrnn_tst_dt

	Then if the component is still too long chop out sufficient characters
from the 2cnd character onwards:

	Aftrnn_tst_dt			Ann_tst_dt

	This has the result of in almost all cases preserving uniqueness
with multiple filenames with the same root and different extensions, but also
preserves the maximum meaning in the filename due to the selective removal
of vowels first.

3) Check if we ought to create a directory for a single character suffix
filename. If the file is to be opened for creation (perhaps implicitly)
then we need to create the directory. Otherwise the access operation merely
fails and we don't need to bother (indeed if we did it would waste disk
space).

	Unfortunately 3) implies that the conversion needs to be integrated
into a set of common file access routines. In unixlib it is called by open(),
creat(), stat(), etc. and performs filename conversion transparent to the
user. There is a global flag which can turn conversion on and off, and the
routine can also be called directly. Starting any unixlib program with
the environment variable UNIX set, automatically sets conversion on, else
by default it is off.


[ H.J.Rogers (INTERNET: rogersh%p4%cs.man.ac.uk@cunyvm.cuny.edu)       ]
[    ,_,     (BITNET/EARN: rogersh%p4%cs.man.ac.uk@UKACRL.BITNET)      ]
[  :-(_)-o   (UUCP: ...!uunet!cunyvm.cuny.edu!cs.man.ac.uk!p4!rogersh) ]
[   _} {_    (JANET: rogersh%p4@uk.ac.man.cs)                          ]