63 lines
2.6 KiB
Text
63 lines
2.6 KiB
Text
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Description
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Tarlz is a small and simple implementation of the tar archiver. By
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default tarlz creates, lists and extracts archives in the 'ustar' format
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compressed with lzip on a per file basis. Tarlz can append files to the
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end of such compressed archives.
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Each tar member is compressed in its own lzip member, as well as the
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end-of-file blocks. This same method works for any tar format (gnu,
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ustar, posix) and is fully backward compatible with standard tar tools
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like GNU tar, which treat the resulting multimember tar.lz archive like
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any other tar.lz archive.
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Tarlz can create tar archives with four levels of compression
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granularity; per file, per directory, appendable solid, and solid.
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Tarlz is intended as a showcase project for the maintainers of real tar
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programs to evaluate the format and perhaps implement it in their tools.
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The diagram below shows the correspondence between tar members (formed
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by a header plus optional data) in the tar archive and lzip members in
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the resulting multimember tar.lz archive:
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tar
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+========+======+========+======+========+======+========+
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| header | data | header | data | header | data | eof |
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+========+======+========+======+========+======+========+
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tar.lz
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+===============+===============+===============+========+
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| member | member | member | member |
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+===============+===============+===============+========+
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Of course, compressing each file (or each directory) individually is
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less efficient than compressing the whole tar archive, but it has the
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following advantages:
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* The resulting multimember tar.lz archive can be decompressed in
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parallel with plzip, multiplying the decompression speed.
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* New members can be appended to the archive (by removing the eof
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member) just like to an uncompressed tar archive.
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* It is a safe posix-style backup format. In case of corruption,
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tarlz can extract all the undamaged members from the tar.lz
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archive, skipping over the damaged members, just like the standard
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(uncompressed) tar. Moreover, lziprecover can be used to recover at
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least part of the contents of the damaged members.
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* A multimember tar.lz archive is usually smaller than the
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corresponding solidly compressed tar.gz archive, except when
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individually compressing files smaller than about 32 KiB.
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Copyright (C) 2013-2018 Antonio Diaz Diaz.
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This file is free documentation: you have unlimited permission to copy,
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distribute and modify it.
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The file Makefile.in is a data file used by configure to produce the
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Makefile. It has the same copyright owner and permissions that configure
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itself.
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