That code looks like it could (and should, IMO) be refactored to put the unsafe code in more contained locations, e.g. the &[u8] could be manipulated into a (&[

That code looks like it could (and should, IMO) be refactored to put the unsafe code in more contained locations, e.g. the &[u8] could be manipulated into a (&[u64], &[u8]) pair (with the main sequence of values, and the trailing ones). Rust unfortunately can't stop people writing code that makes life hard for themselves.