Subject: ext2fs support in RiscOS

From: Phil Norman <[email-masked]>
Date: Fri, 14 Nov 1997 14:44:50 +0000 (GMT)

Hi!

I emailed a few days ago about writing an ext2fs filing system for
RiscOS.  I've recently been doing a little fiddling around with
direct disc access and looking in PRMs about how FileCore does
things, and have had a few problems with finding the armlinux
partitions.

The PRMs say that a second partition should have the following bytes
set with certain values:

	&1fc	format identifier and flags
	&1fd	low byte of start cylinder
	&1fe	high byte of start cylinder

I've written a little BASIC program to read these and print out the
disc address of the correct cylinder, but all three values are read
out as zero.  I've checked the value returned by ADFS_DiscOp,1 (which
tells me how many bytes were not read) and this is zero, and all the
other parameters seem to be right.  I wondered if linux used some
different method of storing its partition info, or maybe just tags
its partition directly at the end of the FileCore one?

Someone said that I'd have problems with all the characters unix can
use and RiscOS can't.  That's not a problem, since I won't be writing
it as a filing system (or at least not initially).  It'll just be a
separate application which looks like the filer (the window redraw
code is already written - I wrote it for another project which never
came to fruition) but uses all the filing system things that unix
does (ie / for directory separator etc).

I doubt I'll be supporting anything other than FileCore, since I
don't have access to anything else for testing, but I'll probably
release the full source of the finished thing, so if anyone wishes to
add anything else they can.

I definately won't be supporting read-write.  Files can be
transferred from ADFS to linux easily enough using mount under linux,
so there really isn't that much point in spending horrendous amounts
of time getting everything to work both ways.

Don't expect anything too soon, but hopefully a RiscOS-side ext2fs
reader should be sorted within a few months or so.  Depends how
complex ext2fs is (probably very complex).

If anyone has any code, suggestions or documentation that might be
useful, please feel free to either email them to me or email me an
ftp/http address if you're using a modem.  I'm using a university
account so large wodges of data aren't a problem.

Thanks in advance for any help,
Phil

-- 
Phil Norman, mailing from Exeter Uni.
Programs available for download from my web page.
email:  [email-masked]
web:    http://newton.ex.ac.uk/general/ug/norman