1use super::assert_stream;
2use core::pin::Pin;
3use futures_core::stream::Stream;
4use futures_core::task::{Context, Poll};
5
6/// Stream for the [`iter`] function.
7#[derive(Debug, Clone)]
8#[must_use = "streams do nothing unless polled"]
9pub struct Iter<I> {
10 iter: I,
11}
12
13impl<I> Unpin for Iter<I> {}
14
15/// Converts an `Iterator` into a `Stream` which is always ready
16/// to yield the next value.
17///
18/// Iterators in Rust don't express the ability to block, so this adapter
19/// simply always calls `iter.next()` and returns that.
20///
21/// ```
22/// # futures::executor::block_on(async {
23/// use futures::stream::{self, StreamExt};
24///
25/// let stream = stream::iter(vec![17, 19]);
26/// assert_eq!(vec![17, 19], stream.collect::<Vec<i32>>().await);
27/// # });
28/// ```
29pub fn iter<I>(i: I) -> Iter<I::IntoIter>
30where
31 I: IntoIterator,
32{
33 assert_stream::<I::Item, _>(Iter { iter: i.into_iter() })
34}
35
36impl<I> Stream for Iter<I>
37where
38 I: Iterator,
39{
40 type Item = I::Item;
41
42 fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<I::Item>> {
43 Poll::Ready(self.iter.next())
44 }
45
46 fn size_hint(&self) -> (usize, Option<usize>) {
47 self.iter.size_hint()
48 }
49}
50