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Re: [Libcdio-devel] Hindsight is 2020 - Let's sort multiextents at last

From: Thomas Schmitt
Subject: Re: [Libcdio-devel] Hindsight is 2020 - Let's sort multiextents at last
Date: Sun, 24 May 2020 15:36:17 +0200


branch pragmatic-multiextent-2020 has now passed all my experiments
which master would pass.
Insofar i propose to merge it.


There is a substantial problem with the size assessment of DVD and BD
media, though. A fully fomatted DVD+RW of 2,295,104 blocks gets assessed
as having only 431,849 blocks (and MSF being 95:59:74).
The macro check_lsn in lib/driver/read.c then prevents reading of any
block beyond that wrong small size.

Since large.iso is a multi-session ISO, its root directory lies above
the wrong size and src/cd-info reports no ISO directory tree but also no
error message.
(The lack of error message is caused by check_lsn only issuing a cdio_info
 message which src/cd-info does not show. src/cd-info itself tries to
 issue an error message on failure of iso9660_fs_readdir() by a call
 named report(). It does not show up.)

I assume that the size misperception comes from use of MSF oriented
inquiries or conversions which are inapproriate with block counts in
the millions.

I will try to find out where it goes wrong with gnu_linux.c.
Depending on the results, this issue might need fixing in each of the
operating system drivers.

Have a nice day :)


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