Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!psuvax1!rutgers!uwvax!puff!rt5.cs.wisc.edu!blochowi
From: blochowi@rt5.cs.wisc.edu (Jason Blochowiak)
Newsgroups: comp.sys.apple
Subject: Re: IIgs Software Reboot
Message-ID: <4129@puff.cs.wisc.edu>
Date: 21 Dec 89 03:50:00 GMT
References: <3388@sage.cc.purdue.edu> <0ZWjDCW00WAB00WG8F@andrew.cmu.edu> <4118@puff.cs.wisc.edu>
Sender: news@puff.cs.wisc.edu
Reply-To: blochowi@rt5.cs.wisc.edu (Jason Blochowiak)
Organization: U of Wisconsin CS Dept
Lines: 25

In article <4118@puff.cs.wisc.edu> blochowi@rt7.cs.wisc.edu (Jason Blochowiak) writes:
> [I wrote about looking into adding support for sparse ProDOS files to
>  SmartBoot 8/16, someone else mentioned the problem, and I nuked the whole
>  thing :) ]

	Well, I took a poke at Apple's code briefly, but decided that I didn't
really need to, so I stopped. I then looked at SmartBoot 8/16 to see how it
loaded the files in, and I popped out one of Apple's manuals that details
the way ProDOS stores files. Anyways, SB stops when it gets to a block that's
0, so it'd almost certainly die on a sparse ProDOS file. What would have to be
changed (or, I hope you weren't expecting code :) is: After finding the
appropriate directory entry corresponding to the file being looked for, grab
the BLOCKS_USED field, and hold it somewhere. Then, in the file read routine
(forgot the name or location, but it's pretty obvious), instead of stopping
when you hit a 0 block, you: Look up the current block to be read. If it's a
0, you zero out the target area of memory, increment the target pointer, and
increment the index into the index block. If it's a non-0 block, you read it
in normally, and then decrement the BLOCKS_USED count - if it hits 0, you're
done, otherwise go back to read the next block. Being the lazy guy I am, I
probably won't code this unless I have to... If someone else does decide to
code it, I'd be interested in seeing the result.

--
      Jason Blochowiak - blochowi@garfield.cs.wisc.edu or jason@madnix.uucp
       "Education, like neurosis, begins at home." - Milton R. Sapirstein