Package lz4 implements reading and writing lz4 compressed data (a frame), as specified in http://fastcompression.blogspot.fr/2013/04/lz4-streaming-format-final.html. Although the block level compression and decompression functions are exposed and are fully compatible with the lz4 block format definition, they are low level and should not be used directly. For a complete description of an lz4 compressed block, see: http://fastcompression.blogspot.fr/2011/05/lz4-explained.html See https://github.com/Cyan4973/lz4 for the reference C implementation.