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[Bug-tar] Robustness of tar.gz files?

From: Juhana Sadeharju
Subject: [Bug-tar] Robustness of tar.gz files?
Date: Tue, 2 Oct 2007 19:39:51 +0300

Hello. I have large tar.gz packages in archive DVDs.
What if the file gets corrupted? Is the whole file
useless? For example, what happens if one byte is
altered short after the begin?

It looks like somebody should design and implement
a robust package format in any case.

Some observations:
 -zcat seems to not recognize compression if the begin
is cut off
 -tar cannot find the file headers even we would have

If tar.gz and tar.bz2 are a far from robust, should I use
zip, rar, 7z packages? Probably not, because cutting off
two bytes at the end of a zip package made the whole zip
file useless. The two bytes at the end had no real use as
I recovered the file by taking the two bytes from another
zip package. Most likely rar, 7z and other formats are as
fragile as zip.

I have some design notes for better tar.gz/bz2:
 -gzip equipped with bzip2 style blocks
 -tar aligned to bzip2 style blocks
 -start of each tar-block would contain header which tells
what file and at what offset the data (at the begin of the
block) belongs to

For example, if I pack multiple audiofiles to tar.gz and shoot
the disc with a shotgun, I'm able to recover pieces of the
audiofiles at the correct offsets:
  audio.wav ------AAAA-----AAAA----AAAAAAAA-----------AAAAAA--AAAAAAA
where A is correctly recovered audio and -- are unrecoverable


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