tokio_core/io/
read.rs

1use std::mem;
2
3use futures::{Future, Poll};
4
5enum State<R, T> {
6    Pending {
7        rd: R,
8        buf: T,
9    },
10    Empty,
11}
12
13/// Tries to read some bytes directly into the given `buf` in asynchronous
14/// manner, returning a future type.
15///
16/// The returned future will resolve to both the I/O stream and the buffer
17/// as well as the number of bytes read once the read operation is completed.
18pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
19    where R: ::std::io::Read,
20          T: AsMut<[u8]>
21{
22    Read { state: State::Pending { rd: rd, buf: buf } }
23}
24
25/// A future which can be used to easily read available number of bytes to fill
26/// a buffer.
27///
28/// Created by the [`read`] function.
29#[must_use = "futures do nothing unless polled"]
30pub struct Read<R, T> {
31    state: State<R, T>,
32}
33
34impl<R, T> Future for Read<R, T>
35    where R: ::std::io::Read,
36          T: AsMut<[u8]>
37{
38    type Item = (R, T, usize);
39    type Error = ::std::io::Error;
40
41    fn poll(&mut self) -> Poll<(R, T, usize), ::std::io::Error> {
42        let nread = match self.state {
43            State::Pending { ref mut rd, ref mut buf } => try_nb!(rd.read(&mut buf.as_mut()[..])),
44            State::Empty => panic!("poll a Read after it's done"),
45        };
46
47        match mem::replace(&mut self.state, State::Empty) {
48            State::Pending { rd, buf } => Ok((rd, buf, nread).into()),
49            State::Empty => panic!("invalid internal state"),
50        }
51    }
52}
tokio_core/io/read.rs

tokio_core/io/
read.rs
