PPMd compression/decompression library

 PPM(Prediction by partial matching) is a compression algorithm which has
 several variations of implementations. PPMd is the implementation by Dmitry
 Shkarin. It is used in the RAR and by 7-Zip as one of several possible methods.
 .
 ppmd, aka. ppmd-cffi, is a python bindings with PPMd implementation by C
 language. The C codes are derived from p7zip, portable 7-zip implementation.
 ppmd-cffi support PPMd ver.H and PPMd ver.I.