Rust pipe from Read to Write

pipe.rs

use std::io::prelude::*;

// Feedback welcome

fn pipe(source: &mut Read, dest: &mut Write) -> std::io::Result<usize> {
	let mut buf = [0; 512];
	let mut bytes_read: usize = 0;
	let mut bytes_written: usize = 0;
	let mut total_bytes: usize = 0;
	loop {
		if bytes_read == 0 {
			match source.read(&mut buf) {
				Err(e) => return Err(e),
				Ok(n) => {
					if n == 0 {
						break;
					} else {
						bytes_read = n;
					}
				}
			}
		}

		if bytes_written < bytes_read {
			match dest.write(&buf[bytes_written .. bytes_read]) {
				Err(e) => return Err(e),
				Ok(n) => {
					bytes_written += n;
					total_bytes += n;
				}
			}
		}

		if bytes_written == bytes_read {
			bytes_read = 0;
			bytes_written = 0;
		}
	}

	return Ok(total_bytes);
}