1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156

use std::io;
use std::net::{SocketAddr, Ipv4Addr, SocketAddrV4};

use futures::{Async, Poll, Stream, Sink, StartSend, AsyncSink};

use super::UdpSocket;

use tokio_codec::{Decoder, Encoder};
use bytes::{BytesMut, BufMut};

/// A unified `Stream` and `Sink` interface to an underlying `UdpSocket`, using
/// the `Encoder` and `Decoder` traits to encode and decode frames.
///
/// Raw UDP sockets work with datagrams, but higher-level code usually wants to
/// batch these into meaningful chunks, called "frames". This method layers
/// framing on top of this socket by using the `Encoder` and `Decoder` traits to
/// handle encoding and decoding of messages frames. Note that the incoming and
/// outgoing frame types may be distinct.
///
/// This function returns a *single* object that is both `Stream` and `Sink`;
/// grouping this into a single object is often useful for layering things which
/// require both read and write access to the underlying object.
///
/// If you want to work more directly with the streams and sink, consider
/// calling `split` on the `UdpFramed` returned by this method, which will break
/// them into separate objects, allowing them to interact more easily.
#[must_use = "sinks do nothing unless polled"]
#[derive(Debug)]
pub struct UdpFramed<C> {
    socket: UdpSocket,
    codec: C,
    rd: BytesMut,
    wr: BytesMut,
    out_addr: SocketAddr,
    flushed: bool,
}

impl<C: Decoder> Stream for UdpFramed<C> {
    type Item = (C::Item, SocketAddr);
    type Error = C::Error;

    fn poll(&mut self) -> Poll<Option<(Self::Item)>, Self::Error> {
        self.rd.reserve(INITIAL_RD_CAPACITY);

        let (n, addr) = unsafe {
            // Read into the buffer without having to initialize the memory.
            let (n, addr) = try_ready!(self.socket.poll_recv_from(self.rd.bytes_mut()));
            self.rd.advance_mut(n);
            (n, addr)
        };
        trace!("received {} bytes, decoding", n);
        let frame_res = self.codec.decode(&mut self.rd);
        self.rd.clear();
        let frame = frame_res?;
        let result = frame.map(|frame| (frame, addr)); // frame -> (frame, addr)
        trace!("frame decoded from buffer");
        Ok(Async::Ready(result))
    }
}

impl<C: Encoder> Sink for UdpFramed<C> {
    type SinkItem = (C::Item, SocketAddr);
    type SinkError = C::Error;

    fn start_send(&mut self, item: Self::SinkItem) -> StartSend<Self::SinkItem, Self::SinkError> {
        trace!("sending frame");

        if !self.flushed {
            match try!(self.poll_complete()) {
                Async::Ready(()) => {},
                Async::NotReady => return Ok(AsyncSink::NotReady(item)),
            }
        }

        let (frame, out_addr) = item;
        self.codec.encode(frame, &mut self.wr)?;
        self.out_addr = out_addr;
        self.flushed = false;
        trace!("frame encoded; length={}", self.wr.len());

        Ok(AsyncSink::Ready)
    }

    fn poll_complete(&mut self) -> Poll<(), C::Error> {
        if self.flushed {
            return Ok(Async::Ready(()))
        }

        trace!("flushing frame; length={}", self.wr.len());
        let n = try_ready!(self.socket.poll_send_to(&self.wr, &self.out_addr));
        trace!("written {}", n);

        let wrote_all = n == self.wr.len();
        self.wr.clear();
        self.flushed = true;

        if wrote_all {
            Ok(Async::Ready(()))
        } else {
            Err(io::Error::new(io::ErrorKind::Other,
                               "failed to write entire datagram to socket").into())
        }
    }

    fn close(&mut self) -> Poll<(), C::Error> {
        try_ready!(self.poll_complete());
        Ok(().into())
    }
}

const INITIAL_RD_CAPACITY: usize = 64 * 1024;
const INITIAL_WR_CAPACITY: usize = 8 * 1024;

impl<C> UdpFramed<C> {
    /// Create a new `UdpFramed` backed by the given socket and codec.
    ///
    /// See struct level documentation for more details.
    pub fn new(socket: UdpSocket, codec: C) -> UdpFramed<C> {
        UdpFramed {
            socket: socket,
            codec: codec,
            out_addr: SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0)),
            rd: BytesMut::with_capacity(INITIAL_RD_CAPACITY),
            wr: BytesMut::with_capacity(INITIAL_WR_CAPACITY),
            flushed: true,
        }
    }

    /// Returns a reference to the underlying I/O stream wrapped by `Framed`.
    ///
    /// # Note
    ///
    /// Care should be taken to not tamper with the underlying stream of data
    /// coming in as it may corrupt the stream of frames otherwise being worked
    /// with.
    pub fn get_ref(&self) -> &UdpSocket {
        &self.socket
    }

    /// Returns a mutable reference to the underlying I/O stream wrapped by
    /// `Framed`.
    ///
    /// # Note
    ///
    /// Care should be taken to not tamper with the underlying stream of data
    /// coming in as it may corrupt the stream of frames otherwise being worked
    /// with.
    pub fn get_mut(&mut self) -> &mut UdpSocket {
        &mut self.socket
    }

    /// Consumes the `Framed`, returning its underlying I/O stream.
    pub fn into_inner(self) -> UdpSocket {
        self.socket
    }
}