diff --git a/src/io/mod.rs b/src/io/mod.rs index 93d37d56d..3e44a6b4e 100644 --- a/src/io/mod.rs +++ b/src/io/mod.rs @@ -35,6 +35,7 @@ mod copy; mod flush; mod read_exact; mod read_to_end; +mod read; mod split; mod window; mod write_all; @@ -42,6 +43,7 @@ pub use self::copy::{copy, Copy}; pub use self::flush::{flush, Flush}; pub use self::read_exact::{read_exact, ReadExact}; pub use self::read_to_end::{read_to_end, ReadToEnd}; +pub use self::read::read; pub use self::split::{ReadHalf, WriteHalf}; pub use self::window::Window; pub use self::write_all::{write_all, WriteAll}; diff --git a/src/io/read.rs b/src/io/read.rs new file mode 100644 index 000000000..6798280b7 --- /dev/null +++ b/src/io/read.rs @@ -0,0 +1,51 @@ +use std::mem; + +use futures::{Future, Poll}; + +enum State { + 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 as well as the +/// buffer once the read operation is completed. +pub fn read(rd: R, buf: T) -> Read + 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 { + state: State, +} + +impl Future for Read + 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"), + } + } +}