Move tokio::net module into tokio tcp/udp crates (#224)

tokio-udp/src/recv_dgram.rs

@@ -0,0 +1,52 @@
+use super::socket::UdpSocket;
+
+use std::io;
+use std::net::SocketAddr;
+
+use futures::{Async, Future, Poll};
+
+/// A future used to receive a datagram from a UDP socket.
+///
+/// This is created by the `UdpSocket::recv_dgram` method.
+#[must_use = "futures do nothing unless polled"]
+#[derive(Debug)]
+pub struct RecvDgram<T> {
+    /// None means future was completed
+    state: Option<RecvDgramInner<T>>
+}
+
+/// A struct is used to represent the full info of RecvDgram.
+#[derive(Debug)]
+struct RecvDgramInner<T> {
+    /// Rx socket
+    socket: UdpSocket,
+    /// The received data will be put in the buffer
+    buffer: T
+}
+
+impl<T> RecvDgram<T> {
+    /// Create a new future to receive UDP Datagram
+    pub(crate) fn new(socket: UdpSocket, buffer: T) -> RecvDgram<T> {
+        let inner = RecvDgramInner { socket: socket, buffer: buffer };
+        RecvDgram { state: Some(inner) }
+    }
+}
+
+impl<T> Future for RecvDgram<T>
+    where T: AsMut<[u8]>,
+{
+    type Item = (UdpSocket, T, usize, SocketAddr);
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, io::Error> {
+        let (n, addr) = {
+            let ref mut inner =
+                self.state.as_mut().expect("RecvDgram polled after completion");
+
+            try_ready!(inner.socket.poll_recv_from(inner.buffer.as_mut()))
+        };
+
+        let inner = self.state.take().unwrap();
+        Ok(Async::Ready((inner.socket, inner.buffer, n, addr)))
+    }
+}