[Lzip-bug] Tarlz 0.6 released

[Antonio Diaz Diaz]

I am pleased to announce the release of tarlz 0.6.

Tarlz is a small and simple implementation of the tar archiver. By 
default tarlz creates, lists and extracts archives in a simplified posix 
pax format compressed with lzip on a per file basis. Tarlz can append 
files to the end of such compressed archives.

Each tar member is compressed in its own lzip member, as well as the 
end-of-file blocks. This same method works for any tar format (gnu, 
ustar, posix) and is fully backward compatible with standard tar tools 
like GNU tar, which treat the resulting multimember tar.lz archive like 
any other tar.lz archive.

Tarlz can create tar archives with four levels of compression 
granularity; per file, per directory, appendable solid, and solid.

Of course, compressing each file (or each directory) individually is 
less efficient than compressing the whole tar archive, but it has the 
following advantages:

   * The resulting multimember tar.lz archive can be decompressed in
     parallel with plzip, multiplying the decompression speed.

   * New members can be appended to the archive (by removing the eof
     member) just like to an uncompressed tar archive.

   * It is a safe posix-style backup format. In case of corruption,
     tarlz can extract all the undamaged members from the tar.lz
     archive, skipping over the damaged members, just like the standard
     (uncompressed) tar. Moreover, lziprecover can be used to recover at
     least part of the contents of the damaged members.

   * A multimember tar.lz archive is usually smaller than the
     corresponding solidly compressed tar.gz archive, except when
     individually compressing files smaller than about 32 KiB.

Note that the posix pax format has a serious flaw. The metadata stored 
in pax extended records are not protected by any kind of check sequence. 
Because of this, tarlz protects the extended records with a CRC in a way 
compatible with standard tar tools.

The diagram below shows the correspondence between each tar member 
(formed by one or two headers plus optional data) in the tar archive and 
each lzip member in the resulting multimember tar.lz archive:

tar
+========+======+=================+===============+========+======+========+
| header | data | extended header | extended data | header | data |   eof  |
+========+======+=================+===============+========+======+========+

tar.lz
+===============+=================================================+========+
|     member    |                      member                     | member |
+===============+=================================================+========+

Tarlz is intended as a showcase project for the maintainers of real tar 
programs to evaluate the format and perhaps implement it in their tools.


The homepage is at http://www.nongnu.org/lzip/tarlz.html

An online manual for tarlz can be found at 
http://www.nongnu.org/lzip/manual/tarlz_manual.html

The sources can be downloaded from
http://download.savannah.gnu.org/releases/lzip/tarlz/tarlz-0.6.tar.lz

The sha256sum is:
579279518be4623a8f1512bf35293765cc2b66ebf244a4bcd37b309c8c08f237 
tarlz-0.6.tar.lz


Changes in version 0.6:

  * The new option '-A, --concatenate', which appends tar.lz archives 
to the end of a tar.lz archive, has been added.

  * The option '--ignore-crc' has been replaced with '--missing-crc' to 
improve backwards compatibility with the pax format. Missing CRCs are 
now ignored by default and only reported as errors if '--missing-crc' is 
specified.

  * Tarlz now tests that uid, gid, mtime, devmajor and devminor are in 
ustar range when adding members to an archive.

  * The configure script now accepts appending options to CXXFLAGS 
using the syntax 'CXXFLAGS+=OPTIONS'.

  * 'make dist' now uses tarlz to create the source tarball.


Please send bug reports and suggestions to address@hidden


Regards,
Antonio Diaz, tarlz author and maintainer.

--
If you are distributing software in xz format, please consider using 
lzip instead. See http://www.nongnu.org/lzip/lzip_benchmark.html#xz1 and 
http://www.nongnu.org/lzip/xz_inadequate.html