blob: 4c5a96652ece3d787313c1898274ea30471398a4 [file] [log] [blame]
use std::io;
use std::mem;
use futures::{Future, Poll};
use AsyncRead;
#[derive(Debug)]
enum State<R, T> {
Pending {
rd: R,
buf: T,
},
Empty,
}
/// Tries to read some bytes directly into the given `buf` in asynchronous
/// manner, returning a future type.
///
/// The returned future will resolve to both the I/O stream and the buffer
/// as well as the number of bytes read once the read operation is completed.
pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
where R: AsyncRead,
T: AsMut<[u8]>
{
Read { state: State::Pending { rd: rd, buf: buf } }
}
/// A future which can be used to easily read available number of bytes to fill
/// a buffer.
///
/// Created by the [`read`] function.
#[derive(Debug)]
pub struct Read<R, T> {
state: State<R, T>,
}
impl<R, T> Future for Read<R, T>
where R: AsyncRead,
T: AsMut<[u8]>
{
type Item = (R, T, usize);
type Error = io::Error;
fn poll(&mut self) -> Poll<(R, T, usize), io::Error> {
let nread = match self.state {
State::Pending { ref mut rd, ref mut buf } => try_ready!(rd.poll_read(&mut buf.as_mut()[..])),
State::Empty => panic!("poll a Read after it's done"),
};
match mem::replace(&mut self.state, State::Empty) {
State::Pending { rd, buf } => Ok((rd, buf, nread).into()),
State::Empty => panic!("invalid internal state"),
}
}
}