Libwandio is a software library written in C that provides an API for
transparent reading and writing of files using a variety of supported
compression methods.  Provided pthreads are available, I/O performance
will be improved by doing any compression and/or decompression using a
separate thread.

Libwandio supports the popular compression methods (zlib, bzip2, LZMA,
write-only LZO) and HTTP transport (read-only).

WWW: http://research.wand.net.nz/software/libwandio.php