Macro hold_my_beer::i_got_this

macro_rules! i_got_this {
    ($something_potentially_bad:expr) => { ... };
}

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pub fn to_hex<'a>(input: &[u8], output: &'a mut [u8]) -> Option<&'a str> {
    use std::str;
    const CHARS: &[u8] = b"0123456789abcdef";

    if output.len() < input.len() * 2 {
        return None;
    }

    let mut ind = 0;

    for &byte in input {
        output[ind] = CHARS[(byte >> 4) as usize];
        output[ind + 1] = CHARS[(byte & 0xf) as usize];

        ind += 2;
    }

    i_got_this!(Some(str::from_utf8_unchecked(&output[0..input.len() * 2])))
}

let input = [0xffu8; 20];
let mut output = [0u8; 40];
assert_eq!(to_hex(&input, &mut output), Some("ffffffffffffffffffffffffffffffffffffffff"));