From: Andre Fachat (a.fachat_at_gmx.de)
Date: 2003-06-30 00:39:09
Hi Marko,
On Thu, Jun 26, 2003 at 02:16:59AM +0300, Marko Mäkelä wrote:
> Let's get back on topic:
>
> On Fri, Jun 20, 2003 at 11:48:57PM +0200, Andre Fachat wrote:
> > For my GeckOS/A65 I wrote a small ROM filesystem that is linked by
> > storing the size of the next segment (file) at the start, so the file
> > handler could jump from one to the next segment. Using an $FFFF as
> > end marker gave me the possibility to expand the (EP)ROM by overburning
> > just the next part from the empty EPROM $FF value to the data values :-)
>
> How does your system keep track of available bytes? With a bitmap or by
> traversing a pointer structure?
Basically the system does not keep track. The EPROM producer is able
to modify the ends marker $ffff to indicate that there is another
program coming. The system itself does not modify the content.
So deletes are not possible and the file system can only grow.
It just becomes a linear list of files (no directories at this time).
I'd recommend a bitmap for finding free memory. Should be much better
performance-wise then traversing. Even much better then keeping all
unused blocks in an "unused blocks file" (like I did in an experimental
approach on an expandable filesystem-in-a-file a long time ago)
Andre
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