50 lines
1.2 KiB
Rust
50 lines
1.2 KiB
Rust
use super::assert_stream;
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use core::pin::Pin;
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use futures_core::stream::Stream;
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use futures_core::task::{Context, Poll};
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/// Stream for the [`iter`] function.
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#[derive(Debug, Clone)]
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#[must_use = "streams do nothing unless polled"]
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pub struct Iter<I> {
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iter: I,
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}
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impl<I> Unpin for Iter<I> {}
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/// Converts an `Iterator` into a `Stream` which is always ready
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/// to yield the next value.
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///
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/// Iterators in Rust don't express the ability to block, so this adapter
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/// simply always calls `iter.next()` and returns that.
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///
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/// ```
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/// # futures::executor::block_on(async {
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/// use futures::stream::{self, StreamExt};
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///
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/// let stream = stream::iter(vec![17, 19]);
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/// assert_eq!(vec![17, 19], stream.collect::<Vec<i32>>().await);
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/// # });
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/// ```
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pub fn iter<I>(i: I) -> Iter<I::IntoIter>
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where
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I: IntoIterator,
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{
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assert_stream::<I::Item, _>(Iter { iter: i.into_iter() })
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}
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impl<I> Stream for Iter<I>
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where
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I: Iterator,
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{
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type Item = I::Item;
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fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<I::Item>> {
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Poll::Ready(self.iter.next())
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.iter.size_hint()
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}
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}
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