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@@ -0,0 +1,62 @@ +Description + +Tarlz is a small and simple implementation of the tar archiver. By +default tarlz creates, lists and extracts archives in the 'ustar' 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. + +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 diagram below shows the correspondence between tar members (formed +by a header plus optional data) in the tar archive and lzip members in +the resulting multimember tar.lz archive: + +tar ++========+======+========+======+========+======+========+ +| header | data | header | data | header | data | eof | ++========+======+========+======+========+======+========+ + +tar.lz ++===============+===============+===============+========+ +| member | member | member | member | ++===============+===============+===============+========+ + +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. + + +Copyright (C) 2013-2018 Antonio Diaz Diaz. + +This file is free documentation: you have unlimited permission to copy, +distribute and modify it. + +The file Makefile.in is a data file used by configure to produce the +Makefile. It has the same copyright owner and permissions that configure +itself. |