Example of calling Rust from C
via: https://blog.rust-lang.org/2015/04/24/Rust-Once-Run-Everywhere.html
https://doc.rust-lang.org/std/ffi/index.html
https://doc.rust-lang.org/std/ffi/struct.CString.html#method.from_raw
https://users.rust-lang.org/t/correct-way-to-implement-a-function-which-returns-a-c-string/315