Date   : Wed, 19 Aug 2009 00:08:48 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Level 4 FS Y2K query

I've been away for a week, so am catching up on posts...
 
Michael Firth wrote:
> You stated 1 Jan 1981, so I'm not sure I have understood you
> correctly. Since 1981 is the year Econet year counting started
> - as years are an offset 'since 1981' - and starting at 1 Jan,
> it suggests a default to me, notifying no date was found at all?
> 
> If RISC OS was in control, a year of 1901 should be displayed. It
> seems L4 does something? Cuurently I have no L4 running on a A5000
> e.g., to check this out. So I can't reproduce this.
 
Rick Murray wrote:
> Is that possible over Econet? 1901 isn't a valid date.
 
Exactly. How would L4 fit a date of 1900 into a 7-bit offset from
1981? If the datestamp on the file on the underlying filing system
that is exported by L4 is outside the range that NetFS can pass to
a client, then L4 can't pass it and has to pass something, so it
passes 01-Jan-1981. Actually, you should be more surprised it
doesn't return 00-00-1981.
 
Sprow wrote:
> The top 24 bits of the attributes are private to the filing system. Some
 
Not really, byte 2 and byte 3 are defined as the object's
modification date. Whether a filing system implements them or not
depends on that particular filing system.
 
>   byte 0 = common FS attributes [...]
 
To clarify terminology, the word at X%!14 is "attributes", the byte
at X%?14 is "access". An object's "attributes" consists of "access"
and "moddate" where implemented.
 
> [...] per AUG
 
Note that a HUGE amount of documentation gets these wrong. It has
been propagated to a huge extent that each bit represents "can't"
do something. This is wrong, each bit represents access bit
"present". The default access of WR/WR is &33. <See
beebwiki.jonripley.com/File_access>.
 
Johan Heuseveldt wrote:
> So RISC OS is at its end - unless the 40 bits field is extended to
> 48, or even more - somewhere in:
 
RISC OS 5-byte time runs from 1900 to 2248. &5000000000 was last
November as noted in my tagline for a few weeks.
 
By odd coincedence, &4000000000 was in 1987, more or less the start
of the RISC OS era.
 
> Running a file server /needs/ this awareness. So it's a real
> pitty Acorn got it wrong, or at least not up to standards.
 
That's why my SoftMDFS stores metadata in an extra metadata file on
fiesystems that don't support enough metadata natively. It means
you can export a DOS filesystem if you want and still get full
load, exec, create/modify date&time and account numbers :)
 
Johan Heuseveldt wrote:
> There is a bit for 'Execute Only'. I have the feeling this was in
> use for only a small amount of time. Is it still (officially) in use?
 
Yes, bit 2 (owner) and bit 6 (public), see
http://beebwiki.jonripley.com/File_access
 
Some filing systems never return 'E' set, some filing systems
always return 'E' as a copy of 'R', some filing systems allow 'E'
and 'R' to be used independantly. ADFS, HADFS and HDFS implement
'E'. ADFS on RISC OS stores and returns 'E' but FileSwitch ignores
it. NFS* and UnixFS on RISC OS translate 'E' inwards and outwards
to the unix 'X' bits.
 
RISC OS FileSwitch ignores 'E', but it is there and can be tested
for by applications. For instance, there's a RISC OS ftp server
(whose name I can't remember) that uses the 'E' bits.
 
(*NFS to connect to a Unix server, not NetFS to connect to an
Econet server)
 
Rick Murray wrote:
> True, but can you not - on a FileStore - set a bit of code with a
> load/exec address, and also say WHEN the file was written?
 
Yes, on any file server than serves a file system that stores them
seperately, such as Level2, Level3, FileStore, FDFS, HDFS, MDFS,
SoftMDFS.
 
> Is that possible under Level4? The attributes of the host system IS
> important, as it is the host that is making the limitation.
 
No, as Level4 doesn't serve a filing system that stores them
seperately, unless Level4 serves a mount onto another file server -
I've done this occasionally for testing ;)
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
In 1939 $50 of groceries would fill three station wagons. Today I
can lift $50 of groceries with one hand. I must have got stronger.