blob: 395be52334fa0c884720c098f561147afb71b8e9 [file] [log] [blame]
use core::marker::Unpin;
use core::mem::PinMut;
use futures_core::future::Future;
use futures_core::stream::Stream;
use futures_core::task::{self, Poll};
/// 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<St> {
stream: Option<St>,
}
impl<St: Stream + Unpin> Unpin for StreamFuture<St> {}
impl<St: Stream + Unpin> StreamFuture<St> {
pub(super) fn new(stream: St) -> StreamFuture<St> {
StreamFuture { stream: Some(stream) }
}
/// 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<&St> {
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 St> {
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<St> {
self.stream
}
}
impl<St: Stream + Unpin> Future for StreamFuture<St> {
type Output = (Option<St::Item>, St);
fn poll(
mut self: PinMut<Self>,
cx: &mut task::Context
) -> Poll<Self::Output> {
let item = {
let s = self.stream.as_mut().expect("polling StreamFuture twice");
ready!(PinMut::new(s).poll_next(cx))
};
let stream = self.stream.take().unwrap();
Poll::Ready((item, stream))
}
}