Code shared from the Rust Playground

playground.rs

use std::fmt;

fn main() -> Result<(), &'static str> {
    let b = vec![0x64, 0x61, 0x76, 0x65];
    println!("{}", b.to_hex());
    Ok(())
}

trait ToHex {
    fn to_hex(&self) -> String;
}

impl<T: fmt::LowerHex> ToHex for T {
    fn to_hex(&self) -> String {
        format!("{:x}", self)
    }
}

impl ToHex for [u8] {
    fn to_hex(&self) -> String {
        use core::fmt::Write;
        let mut ret = String::with_capacity(2 * self.len());

        for ch in self {
            write!(ret, "{:02X}", ch).expect("writing to string");
        }
        ret
    }
}