tokio_io/io/
read.rs

1use std::io;
2use std::mem;
3
4use futures::{Future, Poll};
5
6use AsyncRead;
7
8#[derive(Debug)]
9enum State<R, T> {
10    Pending { rd: R, buf: T },
11    Empty,
12}
13
14/// Tries to read some bytes directly into the given `buf` in asynchronous
15/// manner, returning a future type.
16///
17/// The returned future will resolve to both the I/O stream and the buffer
18/// as well as the number of bytes read once the read operation is completed.
19pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
20where
21    R: AsyncRead,
22    T: AsMut<[u8]>,
23{
24    Read {
25        state: State::Pending { rd: rd, buf: buf },
26    }
27}
28
29/// A future which can be used to easily read available number of bytes to fill
30/// a buffer.
31///
32/// Created by the [`read`] function.
33#[derive(Debug)]
34pub struct Read<R, T> {
35    state: State<R, T>,
36}
37
38impl<R, T> Future for Read<R, T>
39where
40    R: AsyncRead,
41    T: AsMut<[u8]>,
42{
43    type Item = (R, T, usize);
44    type Error = io::Error;
45
46    fn poll(&mut self) -> Poll<(R, T, usize), io::Error> {
47        let nread = match self.state {
48            State::Pending {
49                ref mut rd,
50                ref mut buf,
51            } => try_ready!(rd.poll_read(&mut buf.as_mut()[..])),
52            State::Empty => panic!("poll a Read after it's done"),
53        };
54
55        match mem::replace(&mut self.state, State::Empty) {
56            State::Pending { rd, buf } => Ok((rd, buf, nread).into()),
57            State::Empty => panic!("invalid internal state"),
58        }
59    }
60}
tokio_io/io/read.rs

tokio_io/io/
read.rs
