title: How to read a specific number of bytes from a stream?
body: <p>I have a struct with a <code>BufStream&lt;T&gt;</code> where <code>T: Read+Write</code>.
  The <code>BufStream</code> can be a <code>TcpStream</code> and I'd like to read n bytes from it.
  Not a fixed amount of bytes in a predefined buffer, but I have a string/stream which indicates the number of bytes to read next.</p>
  
  <p>Is there a nice way to do that?</p>