test.rs

struct EventKey {
    event_id: u64
}

impl ToMdbValue for EventKey {
    fn to_mdb_value(&self) -> MdbValue {
        let mut key : Vec<u8> = "events:".as_bytes().to_vec();
        let mut buf = [0; 8];
        BigEndian::write_u64(&mut buf, self.event_id);
        for n in &buf {
          key.push(*n);
        }
        return key.to_mdb_value();
    }
}