hextodecimal.rs

pub(crate) fn parse_hex(buffer: &[u8]) -> Result<usize, ()> {
    let mut output = 0;

    let buf_len = buffer.len();
    for (idx, chr) in buffer.iter().copied().enumerate() {
        let shl = 4 * (buf_len - idx - 1);
        match chr {
            alpha @ b'a'..=b'f' => {
                output += (10_usize + (alpha - b'a') as usize) << shl;
            }

            digit @ b'0'..=b'9' => {
                output += ((digit - b'0') as usize) << shl;
            }

            _ => return Err(()),
        }
    }

    Ok(output)
}