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Subject: Re: Status report
From: Paul Suade (paul.suade_at_laposte.net)
Date: 2002-05-08

>So it would seem to me, following this (perhaps flawed) logic, that we
>could get by by only moving the first portion of the cluster of the new
>file to a new location and linking back to the second cluster through the
>FAT32 addressing. (Hmmm, maybe that's how fragmentation got started...)

What are you saying ? to share some clusters between two files ? there is no
way to know if a cluster is shared between files so it is strictly forbidden to
do so and there is chance that some fat tools would consider such "duplicated"
cluster chain as being corrupted.

>We would lose a lot of space depending on how often this was done between
>defrags (which I think would have to be run fairly often if this was used a
>lot), but I *think* it would mean that we would only have to copy the
>contents of one cluster to a new cluster, and not rewrite the whole file.

Anyway, the minimal size of a file is cluster unit. And because the file starts
always on a cluster alignment. So if you split inside a cluster, the new file
have no way to tell us where the first content of the file begins in the first
cluster of the file. So you are forced to shift bytes in the first sector. But
shifting bytes in the first sectors would also need to shift bytes of the
following clusters.

Supposedly it is possible to fill the gap with a fake header of something like
it in the mp3 file (i'm not a connoisseur), but you will still need to copy all
the clusters, so finally to "rewrite" the whole file.

Page was last modified "Jan 10 2012" The Rockbox Crew
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