🚀 go-pugleaf

In article <dmurdoch.321.727411814@mast.queensu.ca> dmurdoch@mast.queensu.ca (Duncan Murdoch) writes:
>In article <markus.403.727387680@clement.info.umoncton.ca> markus@clement.info.umoncton.ca (PAULIN MARC) writes:
>>In article <C111JG.H5q@ireq.hydro.qc.ca> beaurega@ireq.hydro.qc.ca (Denis
>>Beauregard) writes:
>
>>>Now, about the poster question.  How does UNERASE to retrieve the chain?
>>>It guesses.  A sequential written file (i.e. after saving a text file)
>>>will use the sequential available clusters and the "erased" file entry
>>>still contains the 1st FAT entry position.  
>
>>        Es-tu sur?  It guesses?  You mean it guesses the file position on 
>>the disk?  I doubt it.  What if the file is fragmented?  That's not 
>>sequential.  
>
>Denis was right.  It's easy enough to prove it to yourself:  create two 
>badly fragmented files by writing a program that writes lines to them 
>alternately.  Make sure they're both big, say 100K.  Erase both, and then 
>see if they can be unerased.  Norton will attempt it, but will get them 
>all mixed up.
>
>Your only hope is if you've loaded one of the unerase-helper 
>TSRs or some other program that makes a separate record of erasures
>or of the FAT.
>
>Duncan Murdoch

It is not the only hope.  If the erased file is structured and the
unerase program is intelligent enough, it can guess and improves on
probability of a full unerase.  For example, a dBASE file is made of
columns in which most data is written from the left side of columns.
Using this, a unerase file for a dBASE file can more likely select
the right next cluster.  However, I am not sure if such programs exists.
Don't forget a database will often grow randomly.  In other words,
the "next cluster" may be located before the previous one i.e. file
can be at location 100, 102, 101 while a sequentially written file
would be at 100, 101, 102 or 100, 105, 121.  I took the dBASE example
because it is a common format, usually for a large file, and 
more than the average used by computer illiterate, thus a likely
candidate for an "intelligent" unerase.

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