ROT13 stdin to stdout in Rust

rot13.rs

use std::io;

// Get the ROT13ed equivalent of char
fn rot13(c: char) -> char {
    let base = match c {
        'a'..'z' => 'a' as u8,
        'A'..'Z' => 'A' as u8,
        _ => return c
    };

    let ord = c as u8 - base;
    let rot = (ord + 13) % 26;
    (rot + base) as char
}

// ROT13 stdin and write to stdout
fn main() {
    let mut reader = io::stdin();
    let mut output = io::stdout();

    for x in reader.chars() {
        let res = output.write_char(rot13(x.unwrap()));
        if res.is_err() {
            break;
        }
    }
}