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
42 lines
865 B
Rust
42 lines
865 B
Rust
use std::pin::Pin;
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use crate::task::{Context, Poll};
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/// Creates a stream that yields a single item.
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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::prelude::*;
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/// use async_std::stream;
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///
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/// let mut s = stream::once(7);
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///
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/// assert_eq!(s.next().await, Some(7));
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/// assert_eq!(s.next().await, None);
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/// #
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/// # }) }
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/// ```
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pub fn once<T>(t: T) -> Once<T> {
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Once { value: Some(t) }
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}
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/// A stream that yields a single item.
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///
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/// This stream is constructed by the [`once`] function.
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///
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/// [`once`]: fn.once.html
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#[derive(Debug)]
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pub struct Once<T> {
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value: Option<T>,
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}
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impl<T: Unpin> futures_core::stream::Stream for Once<T> {
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type Item = T;
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fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<T>> {
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Poll::Ready(self.value.take())
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}
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}
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