use {Future, Poll, Async};
use stream::Stream;
/// A combinator used to temporarily convert a stream into a future.
///
/// This future is returned by the `Stream::into_future` method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct StreamFuture<S> {
stream: Option<S>,
}
pub fn new<S: Stream>(s: S) -> StreamFuture<S> {
StreamFuture { stream: Some(s) }
}
impl<S> StreamFuture<S> {
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
///
/// This method returns an `Option` to account for the fact that `StreamFuture`'s
/// implementation of `Future::poll` consumes the underlying stream during polling
/// in order to return it to the caller of `Future::poll` if the stream yielded
/// an element.
pub fn get_ref(&self) -> Option<&S> {
self.stream.as_ref()
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
///
/// This method returns an `Option` to account for the fact that `StreamFuture`'s
/// implementation of `Future::poll` consumes the underlying stream during polling
/// in order to return it to the caller of `Future::poll` if the stream yielded
/// an element.
pub fn get_mut(&mut self) -> Option<&mut S> {
self.stream.as_mut()
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
///
/// This method returns an `Option` to account for the fact that `StreamFuture`'s
/// implementation of `Future::poll` consumes the underlying stream during polling
/// in order to return it to the caller of `Future::poll` if the stream yielded
/// an element.
pub fn into_inner(self) -> Option<S> {
self.stream
}
}
impl<S: Stream> Future for StreamFuture<S> {
type Item = (Option<S::Item>, S);
type Error = (S::Error, S);
fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
let item = {
let s = self.stream.as_mut().expect("polling StreamFuture twice");
match s.poll() {
Ok(Async::NotReady) => return Ok(Async::NotReady),
Ok(Async::Ready(e)) => Ok(e),
Err(e) => Err(e),
}
};
let stream = self.stream.take().unwrap();
match item {
Ok(e) => Ok(Async::Ready((e, stream))),
Err(e) => Err((e, stream)),
}
}
}