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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: Fri, 22 Oct 2010 12:20:52 +0200


> Thomas - you do have commit rights to libcdio, so if you want to fix the
> faulty code, by all means do so. Or if you want to make a patch and send
> that to me and/or have me double check, I'd be happy to do that.

I would try ... if i had a test case.

Obviously the existing code is aware of multi-extent files.
The bug which i believe to see and the obvious unimplemented handling
of extent boundaries tell me that nobody ever tested libcdio with
such UDF images.
Do such images exist at all in real life ?
(I'd look at Blu-ray movie discs for files >= 4 GB. On DVD they are
 unlikely to find.)

I myself am still very clueless about UDF. 
It is all 4 times more complicated than in ECMA-119 plus Rock Ridge.
Even the simple things are explained awkwardly.


How about you put remarks at both spots in the code and change the
rather riddling warning message:

-        printf("Warning: don't know how to handle yet\n" );
+        fprintf(stderr,
+        "libcdio: Warning: Encountered UDF file with multiple extents.\n");
+        fprintf(stderr, "libcdio: Cannot handle this properly yet.\n");

Next would be to test whether subtracting i_offset from *pi_max_size
is the right thing to do.
If i am wrong, then this would break well working use cases.

But if i am right then it would at least cause the warning to pop up
at the appropriate occasions.
Currently it looks as if the test is too lax and will often allow to
read over the end of an extend.

Do we have testers for vanilla UDF reading via libcdio ?

Have a nice day :)


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