This the unix port of the Amiga XPK library.

The XPK system consists of a master library (libxpkmaster.so) and several
(un)packer sublibraries (libxpkXXXX.so). Application programs only use the
master library directly: the master library takes care of loading and using 
the sublibraries. Each sublibrary implements one type of compression. 

There are different libraries for different types of data. When unpacking the 
applications do not need to know which library was used to pack the data - 
the appropriate library needs to be installed.

WWW: http://www.jormas.com/~vesuri/xpk/