udp: add into_parts to RecvDgram

tokio-udp/src/recv_dgram.rs

@@ -30,6 +30,36 @@ impl<T> RecvDgram<T> {
         let inner = RecvDgramInner { socket: socket, buffer: buffer };
         RecvDgram { state: Some(inner) }
     }
+
+    /// Consume the `RecvDgram`, returning the socket and buffer.
+    ///
+    /// ```
+    /// # extern crate tokio_udp;
+    ///
+    /// use tokio_udp::UdpSocket;
+    ///
+    /// # pub fn main() {
+    ///
+    /// let socket = UdpSocket::bind(&([127, 0, 0, 1], 0).into()).unwrap();
+    /// let mut buffer = vec![0; 4096];
+    ///
+    /// let future = socket.recv_dgram(buffer);
+    ///
+    /// // ... polling `future` ... giving up (e.g. after timeout)
+    ///
+    /// let (socket, buffer) = future.into_parts();
+    ///
+    /// # }
+    /// ```
+    /// # Panics
+    ///
+    /// If called after the future has completed.
+    pub fn into_parts(mut self) -> (UdpSocket, T) {
+        let state = self.state
+            .take()
+            .expect("into_parts called after completion");
+        (state.socket, state.buffer)
+    }
 }
 
 impl<T> Future for RecvDgram<T>