pub fn uppercase<'a, const N: usize>(code: &str, buffer: &'a mut [u8; N]) -> Option<&'a str> {
let iso_candidate = code.as_bytes();
if iso_candidate.len() == N {
buffer.copy_from_slice(iso_candidate);
buffer.make_ascii_uppercase();
core::str::from_utf8(buffer).ok()
} else {
None
}
}