[Lzip-bug] Tarlz 0.18 released

[Antonio Diaz Diaz]

I am pleased to announce the release of tarlz 0.18.

Tarlz is a massively parallel (multi-threaded) combined implementation of 
the tar archiver and the lzip compressor. Tarlz uses the compression library 
lzlib.

Tarlz creates, lists, and extracts archives in a simplified and safer 
variant of the POSIX pax format compressed in lzip format, keeping the 
alignment between tar members and lzip members. The resulting multimember 
tar.lz archive is fully backward compatible with standard tar tools like GNU 
tar, which treat it like any other tar.lz archive. Tarlz can append files to 
the end of such compressed archives.

Keeping the alignment between tar members and lzip members has two 
advantages. It adds an indexed lzip layer on top of the tar archive, making 
it possible to decode the archive safely in parallel. It also minimizes the 
amount of data lost in case of corruption. Compressing a tar archive with 
plzip may even double the amount of files lost for each lzip member damaged 
because it does not keep the members aligned.

Tarlz can create tar archives with five levels of compression granularity: 
per file (--no-solid), per block (--bsolid, default), per directory 
(--dsolid), appendable solid (--asolid), and solid (--solid). It can also 
create uncompressed tar archives.

Of course, compressing each file (or each directory) individually can't 
achieve a compression ratio as high as compressing solidly the whole tar 
archive, but it has the following advantages:

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

    * New members can be appended to the archive (by removing the EOF
      member), and unwanted members can be deleted from the archive.
      Just like 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, the option '--keep-damaged' can be
      used to recover as much data as possible from each damaged member,
      and lziprecover can be used to recover some 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 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/

The sha256sum is:
fcd0ea54c1c9128af812eaa16bb462ee5e9bc9e000b9259c27169ae1f41e4554 
tarlz-0.18.tar.lz


Changes in version 0.18:

  * The new option '--check-lib', which compares the version of lzlib used 
to compile tarlz with the version actually being used at run time, has been 
added.

  * Multi-threaded '-x, --extract' has been implemented. See chapters 
'Internal structure of tarlz' and 'Limitations of parallel tar decoding' in 
the manual for details.

  * The header <sys/sysmacros.h> is now not #included when compiling on OS2.

  * The new section 'Limitations of multi-threaded extraction' has been 
added to the manual.


Please send bug reports and suggestions to lzip-bug@nongnu.org


Regards,
Antonio Diaz, tarlz author and maintainer.
Self-determination is a human right. Free Catalan political prisoners.
--
If you care about interoperability and long-term archiving, please help me 
replace xz with lzip. See http://www.nongnu.org/lzip/lzip_benchmark.html#xz1
http://www.nongnu.org/lzip/manual/lzip_manual.html#Quality-assurance and
http://www.nongnu.org/lzip/xz_inadequate.html Thanks.