Zlib
From Just Solve the File Format Problem
zlib is a data compression library, and a general-purpose data compression format.
The data format uses DEFLATE compression. It is used in many other file formats, and sometimes on its own as a file format. It is defined in RFC 1950.
The zlib format is not the same as gzip format, but they are fairly similar, and both are supported by the zlib library.
