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[Libcdio-devel] Re: can files in UDF be fragmented?

From: Thomas Schmitt
Subject: [Libcdio-devel] Re: can files in UDF be fragmented?
Date: Sat, 23 Oct 2010 13:03:21 +0200


i have to correct myself. In previous mail i wrote:

> Quite helpful is  udf_file_entry_[ts].i_alloc_descs  which i
> recognize from ECMA-167 as the extent counter.
> So all is well if this is 1.

The size is counted in bytes and not in descriptor records.
So it is safe if udf_file_entry_t.i_alloc_descs is 8 or 20.
It might be safe with 16, but then one needs to make sure it is
a single "long_ad" and not two "short_ad".

For the interpretation one would have to check:

  udf_file_entry_t.icb_tag.flags & ICBTAG_FLAG_AD_MASK


(I did not check whether all these symbols are public. That approach is
 educating for me, but unappealing for any user of the library.)


For the original topic of this thread:

The extent size of "short_ad" is restricted to 1 GB - 1.
So a reason for fragmentation might already be given if a file is 1 GB
or larger.

Have a nice day :)


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