pub struct ControlPacket {
    type_and_flags: u8,
    length: u16,
    variable_header: Option<Vec<u8>>,
    properties: Option<Vec<u8>>,
    payload: Option<Vec<u8>>,
}

impl<'a> From<&'a ControlPacket> for &'a [u8] {
    fn from(packet: &'a ControlPacket) -> &'a [u8] {
        match &packet.payload {
            Some(payload) => payload.as_ref(),
            None => panic!("don't know what to do"),
        }
    }
}