Latin-1 is actually the first 256 code points from Unicode. So, you can do that in Rust by casting u8 (the Latin-1 bytes) into char (Unicode scalar values). That's unintuitive perhaps because of course in C that wouldn't do anything useful since the char type isn't Unicode, but in Rust that's exactly what you wanted.
In this environment you might very well not need actual uppercase/ lowercase but only the ASCII subset. Accordingly Rust provides that too, which is far less to carry around than the Unicode case rules. Since the ASCII case change can always be performed in situ (if you can modify the data) Rust provides that too if it's what you want.
In this environment you might very well not need actual uppercase/ lowercase but only the ASCII subset. Accordingly Rust provides that too, which is far less to carry around than the Unicode case rules. Since the ASCII case change can always be performed in situ (if you can modify the data) Rust provides that too if it's what you want.