Show u8 slice in hex representation

Question

I need to convert &[u8] to a hex representation. For example [ A9, 45, FF, 00 ... ].

The trait std::fmt::UpperHex is not i

Answer 1

Since the accepted answer doesn't work on Rust 1.0 stable, here's my attempt. Should be allocationless and thus reasonably fast. This is basically a formatter for [u8], but because of the coherence rules, we must wrap [u8] to a self-defined type ByteBuf(&[u8]) to use it:

struct ByteBuf<'a>(&'a [u8]);

impl<'a> std::fmt::LowerHex for ByteBuf<'a> {
    fn fmt(&self, fmtr: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
        for byte in self.0 {
            try!( fmtr.write_fmt(format_args!("{:02x}", byte)));
        }
        Ok(())
    }
}

Usage:

let buff = [0_u8; 24];
println!("{:x}", ByteBuf(&buff));