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
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171

use std::io::{self, Read, Write};

use futures::{Async, Poll};
use futures::sync::BiLock;
use bytes::{Buf, BufMut};

use {AsyncRead, AsyncWrite};

/// The readable half of an object returned from `AsyncRead::split`.
#[derive(Debug)]
pub struct ReadHalf<T> {
    handle: BiLock<T>,
}

/// The writable half of an object returned from `AsyncRead::split`.
#[derive(Debug)]
pub struct WriteHalf<T> {
    handle: BiLock<T>,
}

pub fn split<T: AsyncRead + AsyncWrite>(t: T) -> (ReadHalf<T>, WriteHalf<T>) {
    let (a, b) = BiLock::new(t);
    (ReadHalf { handle: a }, WriteHalf { handle: b })
}

fn would_block() -> io::Error {
    io::Error::new(io::ErrorKind::WouldBlock, "would block")
}

impl<T: AsyncRead> Read for ReadHalf<T> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        match self.handle.poll_lock() {
            Async::Ready(mut l) => l.read(buf),
            Async::NotReady => Err(would_block()),
        }
    }
}

impl<T: AsyncRead> AsyncRead for ReadHalf<T> {
    fn read_buf<B: BufMut>(&mut self, buf: &mut B) -> Poll<usize, io::Error> {
        let mut l = try_ready!(wrap_as_io(self.handle.poll_lock()));
        l.read_buf(buf)
    }
}

impl<T: AsyncWrite> Write for WriteHalf<T> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        match self.handle.poll_lock() {
            Async::Ready(mut l) => l.write(buf),
            Async::NotReady => Err(would_block()),
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        match self.handle.poll_lock() {
            Async::Ready(mut l) => l.flush(),
            Async::NotReady => Err(would_block()),
        }
    }
}

impl<T: AsyncWrite> AsyncWrite for WriteHalf<T> {
    fn shutdown(&mut self) -> Poll<(), io::Error> {
        let mut l = try_ready!(wrap_as_io(self.handle.poll_lock()));
        l.shutdown()
    }

    fn write_buf<B: Buf>(&mut self, buf: &mut B) -> Poll<usize, io::Error>
        where Self: Sized,
    {
        let mut l = try_ready!(wrap_as_io(self.handle.poll_lock()));
        l.write_buf(buf)
    }
}

fn wrap_as_io<T>(t: Async<T>) -> Result<Async<T>, io::Error> {
    Ok(t)
}

#[cfg(test)]
mod tests {
    extern crate tokio_current_thread;

    use super::{AsyncRead, AsyncWrite, ReadHalf, WriteHalf};
    use bytes::{BytesMut, IntoBuf};
    use futures::{Async, Poll, future::lazy, future::ok};
    use futures::sync::BiLock;

    use std::io::{self, Read, Write};

    struct RW;

    impl Read for RW {
        fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
            Ok(1)
        }
    }

    impl AsyncRead for RW {}

    impl Write for RW {
        fn write(&mut self, _: &[u8]) -> io::Result<usize> {
            Ok(1)
        }

        fn flush(&mut self) -> io::Result<()> {
            Ok(())
        }
    }

    impl AsyncWrite for RW {
        fn shutdown(&mut self) -> Poll<(), io::Error> {
            Ok(Async::Ready(()))
        }
    }

    #[test]
    fn split_readhalf_translate_wouldblock_to_not_ready() {
        tokio_current_thread::block_on_all(lazy(move || {
            let rw = RW {};
            let (a, b) = BiLock::new(rw);
            let mut rx = ReadHalf { handle: a };

            let mut buf = BytesMut::with_capacity(64);

            // First read is uncontended, should go through.
            assert!(rx.read_buf(&mut buf).unwrap().is_ready());

            // Take lock from write side.
            let lock = b.poll_lock();

            // Second read should be NotReady.
            assert!(!rx.read_buf(&mut buf).unwrap().is_ready());

            drop(lock);

            // Back to uncontended.
            assert!(rx.read_buf(&mut buf).unwrap().is_ready());

            ok::<(), ()>(())
        })).unwrap();
    }

    #[test]
    fn split_writehalf_translate_wouldblock_to_not_ready() {
        tokio_current_thread::block_on_all(lazy(move || {
            let rw = RW {};
            let (a, b) = BiLock::new(rw);
            let mut tx = WriteHalf { handle: a };

            let bufmut = BytesMut::with_capacity(64);
            let mut buf = bufmut.into_buf();

            // First write is uncontended, should go through.
            assert!(tx.write_buf(&mut buf).unwrap().is_ready());

            // Take lock from read side.
            let lock = b.poll_lock();

            // Second write should be NotReady.
            assert!(!tx.write_buf(&mut buf).unwrap().is_ready());

            drop(lock);

            // Back to uncontended.
            assert!(tx.write_buf(&mut buf).unwrap().is_ready());

            ok::<(), ()>(())
        })).unwrap();
    }
}