blob: 3d1ed5a61e4508d00cd02e2f658717604ca06c85 [file] [log] [blame]
use core::marker::Unpin;
use core::mem::PinMut;
use futures_core::stream::Stream;
use futures_core::task::{self, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// A stream which "fuse"s a stream once it's terminated.
///
/// Normally streams can behave unpredictably when used after they have already
/// finished, but `Fuse` continues to return `None` from `poll` forever when
/// finished.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Fuse<St> {
stream: St,
done: bool,
}
impl<St: Unpin> Unpin for Fuse<St> {}
impl<St: Stream> Fuse<St> {
unsafe_pinned!(stream: St);
unsafe_unpinned!(done: bool);
pub(super) fn new(stream: St) -> Fuse<St> {
Fuse { stream, done: false }
}
/// Returns whether the underlying stream has finished or not.
///
/// If this method returns `true`, then all future calls to poll are
/// guaranteed to return `None`. If this returns `false`, then the
/// underlying stream is still in use.
pub fn is_done(&self) -> bool {
self.done
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
&self.stream
}
/// 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.
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
/// Acquires a mutable pinned 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.
#[allow(needless_lifetimes)] // https://github.com/rust-lang/rust/issues/52675
pub fn get_pin_mut<'a>(self: PinMut<'a, Self>) -> PinMut<'a, St> {
unsafe { PinMut::map_unchecked(self, |x| x.get_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.
pub fn into_inner(self) -> St {
self.stream
}
}
impl<S: Stream> Stream for Fuse<S> {
type Item = S::Item;
fn poll_next(
mut self: PinMut<Self>,
cx: &mut task::Context,
) -> Poll<Option<S::Item>> {
if *self.done() {
return Poll::Ready(None);
}
let item = ready!(self.stream().poll_next(cx));
if item.is_none() {
*self.done() = true;
}
Poll::Ready(item)
}
}
// Forwarding impl of Sink from the underlying stream
impl<S: Stream + Sink> Sink for Fuse<S> {
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
delegate_sink!(stream);
}