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use crate::stream::StreamExt; use core::pin::Pin; use futures_core::future::{FusedFuture, Future}; use futures_core::ready; use futures_core::stream::Stream; use futures_core::task::{Context, Poll}; /// Future for the [`into_future`](super::StreamExt::into_future) method. #[derive(Debug)] #[must_use = "futures do nothing unless you `.await` or poll them"] pub struct StreamFuture<St> { stream: Option<St>, } impl<St: Stream + Unpin> StreamFuture<St> { pub(super) fn new(stream: St) -> Self { Self { 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() } /// Acquires a pinned 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_pin_mut(self: Pin<&mut Self>) -> Option<Pin<&mut St>> { self.get_mut().stream.as_mut().map(Pin::new) } /// 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> FusedFuture for StreamFuture<St> { fn is_terminated(&self) -> bool { self.stream.is_none() } } impl<St: Stream + Unpin> Future for StreamFuture<St> { type Output = (Option<St::Item>, St); fn poll( mut self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Self::Output> { let item = { let s = self.stream.as_mut().expect("polling StreamFuture twice"); ready!(s.poll_next_unpin(cx)) }; let stream = self.stream.take().unwrap(); Poll::Ready((item, stream)) } }