🚀 go-pugleaf

In article <markus.409.727646157@clement.info.umoncton.ca>,
markus@clement.info.umoncton.ca (PAULIN MARC) wrote:
> 
> In article <rol-190193093304@90.222.1.80> rol@grasp1.univ-lyon1.fr (Paul Rolland) writes:
> >From: rol@grasp1.univ-lyon1.fr (Paul Rolland)
> >Subject: Re: Unerase - how does it wor
> >Date: 19 Jan 93 08:31:55 GMT
> 
> >The key, at this point, is to do supposition... Imagine that your disk is
> >not fragmented. THen, your file TOTO is stored in contiguous clusters, and
> >you have :
> >'correct'
> >---------
> >FAT:   Entry number:     Content of this entry
> >             3                      4
> >             4                      5
> >             5                    0xfff
> 
> >When it is cleared, you have :
> >FAT:   Entry number:     Content of this entry
> >             3                      0
> >             4                      0
> >             5                      0
> >So, if you undelete a file, you check the FAT to see if you have enough
> >CONTIGUOUS free clusters starting at the first one allocated to the file,
> >and you allocate them to the file you are restoring, rewriting the FAT so
> >that it is like the one marked 'correct'.
> 
> 
> 	Ok.  And what if you have more contiguous space than the actual file 
> size?  UNERASE will bring back a file larger than its original size?  If so, 
> unfragmenting can cause UNERASING problems too.

Nice remarks... This tends to prove that you have read my complete post :)
No, in fact, you point out something I've completely forgotten (well, it
seems that). When you unerase a file, you have the length of the file which
is still present in the directory entry. Using this length, you can
determine how many clusters are required (just by dividing the length of
the
file (in byte) by the length of a cluster (in byte too) and then adding 1
*IF* there is a remainder). For example, let's imagin you have a cluster
size
that is 2048 bytes. If your file is 10000 bytes, you will have 10000/2048=4
and you add 1, so you'll need 5 clusters. If your file is 4096, you'll
need 4096/2048 = 2, and you*don't* add 1, so you need 2 free clusters to
*try* to undelete !
But you're right, unfragmenting can cause UNERASING problem for these
reasons:
  - First, unfragmenter move clusters, and usually rewrite on the clusters
of
your lost files, 
  - Second, they sometines clear unused entry in the directories, and an
erased files is often considered as unused. Thus, you have no more
information
on your file, and can't unerase it.

Hope that now it is a bit more clear.

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THIS SHOULD BE PART OF THE FAQ !!!!!!!!!!
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Paul Rolland

A bug can be changed to a feature by documenting it. Developpers know !