[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: ProDOS Plus

mdj wrote:

On Jun 30, 6:03 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:


mdj wrote:


On Jun 30, 11:50 am, "Bryan Parkoff" <nos...@nospam.com> wrote:



As for actual file system support, it should have P8 and Smartport
compatibility, original HFS and possibly FAT16.



Now the questions arise.



Right.  I think by adding HFS to the list, you've "blown the budget".
This is no longer a simple extension.  FAT16 may also be in this
category.  Even increasing the maximum size of a ProDOS(+) volume
may be well beyond the scope of a "simple extension".



  I try to remember.  Beneath to ProDOS manual states to limit 65,536
blocks per volume.  I think that ProDOS is designed to read only 8 bit width
byte.



The block limit only exists within the ProDOS filesystem itself.
ProDOS 8 V1.5+ can access larger volumes via AppleTalk. See an
AppleTalk reference for a description of the ProDOS Filing Interface
that allows this.


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.


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.

-michael

NadaNet file server for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."