Re: ProDOS Plus

[mdj <mdj.mdj@gmail.com>]

On Jul 1, 5:09 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:

> >>At the file level, the ProDOS limit is 16MB (3-byte byte pointer).
> >>That limit is probably not too constraining.
>
> > I can't imagine a dataset > 16mb that would be useful on an b bit
> > machine :-)
>
> Exactly.
>
> However, I've actually used such large files as sparse "containers"
> for multiple data streams of nearly unlimited length (say, 16 streams,
> any of which might grow to a megabyte in some worst case).
>
> Mapping all 16 to a single file accessed with byte offsets greatly
> reduces the OS buffer requirements.

Yep. Sparse files is one of the more innovative concepts in ProDOS,
and was used in many larger productivity applications. The most
typical being the dictionary files of word processors with spell
checkers.

Of course, the fact that it supports 3 different file organisation
models is one of the reasons the file handling code is so large :-S

> >>Appletalk file sharing presents only a file level to ProDOS, since the
> >>remote volume is managed by the server.
>
> > The point is, the necessary indirection between the OS's Filing
> > Interface an Filesystem implementation exists. I got the feeling some
> > here thought it necessary to replace ProDOS 8 to manage this feat, but
> > that's not necessary at all, you can just plug another filesystem in.
>
> True, if you finesse some details, like file attributes in a FAT
> filesystem.

The attributes are always going to be the problem here, unless you
decide to implement HFS, in which case it would "just work". The only
finessing would be 'genericizing' non-Apple II files to be accessible
as binary blobs.

Matt