forked from mirror/async-std
bac74c2d7f
* Add future::poll_fn * Replace all uses of poll_fn with the new one * Remove some uses of futures * Simplify ReadDir and DirEntry * Remove some use of futures from File * Use futures subcrates * Fix imports in docs * Remove futures-util dependency * Remove futures-executor-preview * Refactor * Require more features in the futures-preview crate
49 lines
1,008 B
Rust
49 lines
1,008 B
Rust
use std::pin::Pin;
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use crate::future::Future;
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use crate::task::{Context, Poll};
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/// Creates a new future wrapping around a function returning [`Poll`].
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///
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/// Polling the returned 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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/// # fn main() { async_std::task::block_on(async {
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/// #
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/// use async_std::future;
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/// use async_std::task::{Context, Poll};
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///
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/// fn poll_greeting(_: &mut Context<'_>) -> Poll<String> {
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/// Poll::Ready("hello world".to_string())
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/// }
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///
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/// assert_eq!(future::poll_fn(poll_greeting).await, "hello world");
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/// #
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/// # }) }
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/// ```
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pub async fn poll_fn<F, T>(f: F) -> T
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where
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F: FnMut(&mut Context<'_>) -> Poll<T>,
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{
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let fut = PollFn { f };
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fut.await
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}
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struct PollFn<F> {
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f: F,
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}
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impl<F> Unpin for PollFn<F> {}
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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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