65 lines
1.6 KiB
Rust
65 lines
1.6 KiB
Rust
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use crate::fmt;
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use crate::future::Future;
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use crate::pin::Pin;
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use crate::task::{Context, Poll};
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/// Creates a future that wraps a function returning `Poll`.
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///
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/// Polling the future delegates to the wrapped function.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(future_poll_fn)]
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/// # async fn run() {
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/// use core::future::poll_fn;
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/// use core::task::{Context, Poll};
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///
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/// fn read_line(_cx: &mut Context<'_>) -> Poll<String> {
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/// Poll::Ready("Hello, World!".into())
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/// }
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///
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/// let read_future = poll_fn(read_line);
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/// assert_eq!(read_future.await, "Hello, World!".to_owned());
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/// # };
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/// ```
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#[unstable(feature = "future_poll_fn", issue = "72302")]
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pub fn poll_fn<T, F>(f: F) -> PollFn<F>
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where
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F: FnMut(&mut Context<'_>) -> Poll<T>,
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{
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PollFn { f }
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}
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/// A Future that wraps a function returning `Poll`.
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///
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/// This `struct` is created by the [`poll_fn`] function. See its
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/// documentation for more.
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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#[unstable(feature = "future_poll_fn", issue = "72302")]
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pub struct PollFn<F> {
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f: F,
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}
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#[unstable(feature = "future_poll_fn", issue = "72302")]
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impl<F> Unpin for PollFn<F> {}
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#[unstable(feature = "future_poll_fn", issue = "72302")]
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impl<F> fmt::Debug for PollFn<F> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("PollFn").finish()
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}
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}
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#[unstable(feature = "future_poll_fn", issue = "72302")]
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impl<T, F> Future for PollFn<F>
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where
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F: FnMut(&mut Context<'_>) -> Poll<T>,
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{
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type Output = T;
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fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
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(&mut self.f)(cx)
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}
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}
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