use failure::Error;
use std::char;

fn bytes_from_hex_str(hex: &str) -> Result<Vec<u8>, Error> {
    let mut bytes = vec![];

    for i in (0..hex.len()).step_by(2) {
        let byte = u8::from_str_radix(&hex[i..=(i + 1)], 16)?;
        bytes.push(byte);
    }

    Ok(bytes)
}


fn main() {
    let s = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736".to_string();

    let bytes = bytes_from_hex_str(&s).expect("must work");
    for c in b"0123456789abcdef" {
        let phrase = bytes.iter().map(|&b|
            format!("{}", char::from_u32( (b ^ c) as u32 ).unwrap() )).collect::<String>();
        println!("{} - {}", c, phrase);
    }
}