1 use super::assert_stream;
2 use core::pin::Pin;
3 use futures_core::stream::Stream;
4 use futures_core::task::{Context, Poll};
5
6 /// Stream for the [`iter`] function.
7 #[derive(Debug, Clone)]
8 #[must_use = "streams do nothing unless polled"]
9 pub struct Iter<I> {
10 iter: I,
11 }
12
13 impl<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 /// ```
iter<I>(i: I) -> Iter<I::IntoIter> where I: IntoIterator,29 pub fn iter<I>(i: I) -> Iter<I::IntoIter>
30 where
31 I: IntoIterator,
32 {
33 assert_stream::<I::Item, _>(Iter { iter: i.into_iter() })
34 }
35
36 impl<I> Stream for Iter<I>
37 where
38 I: Iterator,
39 {
40 type Item = I::Item;
41
poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<I::Item>>42 fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<I::Item>> {
43 Poll::Ready(self.iter.next())
44 }
45
size_hint(&self) -> (usize, Option<usize>)46 fn size_hint(&self) -> (usize, Option<usize>) {
47 self.iter.size_hint()
48 }
49 }
50