I agree, thinking in layers is super helpful here. I might prefer the higher-level, simpler API was part of the same project as the low-level API (esp. given the name recognition here), but when it isn't, I can go make my own high-level API.

I'm not a rust user; is there anything preventing someone from making a "base64-simple" crate which uses this base64 crate to make a higher-level API?