pub const fn num_to_hex_digit(x: u8) -> u8 {
match x {
0..=9 => b'0' + x,
10..=15 => b'a' + (x - 10),
_ => panic!("invalid hex number"),
}
}
pub const fn num_from_dec_digit(d: u8) -> u8 {
match d {
b'0'..=b'9' => d - b'0',
_ => panic!("invalid dec digit"),
}
}