PPMd compression / decompression. It's a port of the PPMd C-code from 7-Zip to Rust. Only the PPMd7 (PPMdH) with the 7z range coder is ported (as used by the 7z archive format).
Acknowledgement
This port is based on the 7zip version of PPMd by Igor Pavlov, which in turn was based on the PPMd var.H (2001) code by Dmitry Shkarin.
License
The code in this crate is in the public domain as the original code by their authors.