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

// Copyright 2019 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use crate::{connection::Endpoint, muxing::{StreamMuxer, StreamMuxerEvent}};

use futures::prelude::*;
use parking_lot::Mutex;
use std::{io, pin::Pin, sync::atomic::{AtomicBool, Ordering}, task::Context, task::Poll};

/// Implementation of `StreamMuxer` that allows only one substream on top of a connection,
/// yielding the connection itself.
///
/// Applying this muxer on a connection doesn't read or write any data on the connection itself.
/// Most notably, no protocol is negotiated.
pub struct SingletonMuxer<TSocket> {
    /// The inner connection.
    inner: Mutex<TSocket>,
    /// If true, a substream has been produced and any further attempt should fail.
    substream_extracted: AtomicBool,
    /// Our local endpoint. Always the same value as was passed to `new`.
    endpoint: Endpoint,
}

impl<TSocket> SingletonMuxer<TSocket> {
    /// Creates a new `SingletonMuxer`.
    ///
    /// If `endpoint` is `Dialer`, then only one outbound substream will be permitted.
    /// If `endpoint` is `Listener`, then only one inbound substream will be permitted.
    pub fn new(inner: TSocket, endpoint: Endpoint) -> Self {
        SingletonMuxer {
            inner: Mutex::new(inner),
            substream_extracted: AtomicBool::new(false),
            endpoint,
        }
    }
}

/// Substream of the `SingletonMuxer`.
pub struct Substream {}
/// Outbound substream attempt of the `SingletonMuxer`.
pub struct OutboundSubstream {}

impl<TSocket> StreamMuxer for SingletonMuxer<TSocket>
where
    TSocket: AsyncRead + AsyncWrite + Unpin,
{
    type Substream = Substream;
    type OutboundSubstream = OutboundSubstream;
    type Error = io::Error;

    fn poll_event(&self, _: &mut Context<'_>) -> Poll<Result<StreamMuxerEvent<Self::Substream>, io::Error>> {
        match self.endpoint {
            Endpoint::Dialer => return Poll::Pending,
            Endpoint::Listener => {}
        }

        if !self.substream_extracted.swap(true, Ordering::Relaxed) {
            Poll::Ready(Ok(StreamMuxerEvent::InboundSubstream(Substream {})))
        } else {
            Poll::Pending
        }
    }

    fn open_outbound(&self) -> Self::OutboundSubstream {
        OutboundSubstream {}
    }

    fn poll_outbound(&self, _: &mut Context<'_>, _: &mut Self::OutboundSubstream) -> Poll<Result<Self::Substream, io::Error>> {
        match self.endpoint {
            Endpoint::Listener => return Poll::Pending,
            Endpoint::Dialer => {}
        }

        if !self.substream_extracted.swap(true, Ordering::Relaxed) {
            Poll::Ready(Ok(Substream {}))
        } else {
            Poll::Pending
        }
    }

    fn destroy_outbound(&self, _: Self::OutboundSubstream) {
    }

    fn read_substream(&self, cx: &mut Context<'_>, _: &mut Self::Substream, buf: &mut [u8]) -> Poll<Result<usize, io::Error>> {
        AsyncRead::poll_read(Pin::new(&mut *self.inner.lock()), cx, buf)
    }

    fn write_substream(&self, cx: &mut Context<'_>, _: &mut Self::Substream, buf: &[u8]) -> Poll<Result<usize, io::Error>> {
        AsyncWrite::poll_write(Pin::new(&mut *self.inner.lock()), cx, buf)
    }

    fn flush_substream(&self, cx: &mut Context<'_>, _: &mut Self::Substream) -> Poll<Result<(), io::Error>> {
        AsyncWrite::poll_flush(Pin::new(&mut *self.inner.lock()), cx)
    }

    fn shutdown_substream(&self, cx: &mut Context<'_>, _: &mut Self::Substream) -> Poll<Result<(), io::Error>> {
        AsyncWrite::poll_close(Pin::new(&mut *self.inner.lock()), cx)
    }

    fn destroy_substream(&self, _: Self::Substream) {
    }

    fn close(&self, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
        // The `StreamMuxer` trait requires that `close()` implies `flush_all()`.
        self.flush_all(cx)
    }

    fn flush_all(&self, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
        AsyncWrite::poll_flush(Pin::new(&mut *self.inner.lock()), cx)
    }
}