Date   : Fri, 07 Jul 2000 03:37:55 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re BBC serial filing system

"Wayne Allen" <wayne@...> wrote:
> I noticed a comment a few messages regarding the writing of a serial
> filing system for the bbc (possibly using xfer) I am going to make some
> attempt at this, so if anyone has any ideas as to what they want it to
 
[snip]
 
Rather than writing a whole new filing system, why not just write a device
driver for an existing filing system?
 
HADFS allows you to access drives other than the standard disk drives. 
There is a support module RSLink which provides a drive via the serial
port, and two host programs RS_Disk1 and RS_Disk2 which run on the host
machine to provide the drives.
 
http://www.mdfsnet.f9.co.uk/Public/Hold/JGH002.ZIP is the HADFS system.
Within it is Extras.S/RSLink - the source for the *RSLink command
             Extras.RS_Disk1 - hosts a ramdisk via the serial link
             Extras.RS_Disk2 - hosts a disk image via the serial link
 
Rewriting RS_Disk2 in the appropriate language will give you the host code
on other systems.
 
Of course, the disadvantage of using the device driver approach is that
the data is stored at the other end within an image file that represents
the disk accessed, not as actual files on the host system's file system. 
Although, HADFSFiler on Archimedes/RISCOS lets you access the HADFS disk
images that RS_Disk2 uses in the same way that DOSFS lets you use DOS disk
images and SparkFS lets you use archive files as disk images.
 
To actually use the host's filing system rather than a disk image stored
on it you need a host filing system that actually deals with files rather
than, effectively, blocks of a device.  ("Give me file 'fred'", instead of
"Give me sector &003345").  There are various already-written options:
 
HostFS written by me which gives you a filing system that is whatever is
at the other end of a connecting link, selectable between serial,
parallel, user, MIDI (if fitted) or 1MHz bus.  If I could just track it
down amongst this pile of disks next to my desk, I'd put it onto my
website.
 
I've also got, somewhere, a skeleton filing system that does nothing but
'be' a filing system.
 
!65Link and LinkFS written by John Kortink gives you a DFS-style filing
system communicating with an Arc/RISCOS via the BBC's user port to the
Arc's Parallel port.  My latest link is www.inter.nl.net/users/J.Kortink
I find it rather limited, the main being that it provides a hosted DFS
rather than hosting whatever the host's filing system is.  If you contact
John he may give you sufficient information to let you develop host code
to run on a non-Arc.
 
-- 
J.G.Harston (JGH BBC PD Library) 70 Camm Street, Walkley, SHEFFIELD S6 3TR
jgh@...                - Running on BBCs & Masters with SJ MDFS FileServer
Z80+6502/CoPro+Tubes/Econet+SJ - - - http://www.mdfsnet.f9.co.uk/User/JGH/