| use std::mem; |
| |
| use futures::{Future, Poll}; |
| |
| 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: ::std::io::Read, |
| 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. |
| pub struct Read<R, T> { |
| state: State<R, T>, |
| } |
| |
| impl<R, T> Future for Read<R, T> |
| where R: ::std::io::Read, |
| T: AsMut<[u8]> |
| { |
| type Item = (R, T, usize); |
| type Error = ::std::io::Error; |
| |
| fn poll(&mut self) -> Poll<(R, T, usize), ::std::io::Error> { |
| let nread = match self.state { |
| State::Pending { ref mut rd, ref mut buf } => try_nb!(rd.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"), |
| } |
| } |
| } |