1use super::assert_stream;
2use core::pin::Pin;
3use futures_core::stream::{FusedStream, Stream};
4use futures_core::task::{Context, Poll};
5
6/// Stream for the [`repeat`] function.
7#[derive(Debug, Clone)]
8#[must_use = "streams do nothing unless polled"]
9pub struct Repeat<T> {
10 item: T,
11}
12
13/// Create a stream which produces the same item repeatedly.
14///
15/// The stream never terminates. Note that you likely want to avoid
16/// usage of `collect` or such on the returned stream as it will exhaust
17/// available memory as it tries to just fill up all RAM.
18///
19/// ```
20/// # futures::executor::block_on(async {
21/// use futures::stream::{self, StreamExt};
22///
23/// let stream = stream::repeat(9);
24/// assert_eq!(vec![9, 9, 9], stream.take(3).collect::<Vec<i32>>().await);
25/// # });
26/// ```
27pub fn repeat<T>(item: T) -> Repeat<T>
28where
29 T: Clone,
30{
31 assert_stream::<T, _>(Repeat { item })
32}
33
34impl<T> Unpin for Repeat<T> {}
35
36impl<T> Stream for Repeat<T>
37where
38 T: Clone,
39{
40 type Item = T;
41
42 fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
43 Poll::Ready(Some(self.item.clone()))
44 }
45
46 fn size_hint(&self) -> (usize, Option<usize>) {
47 (usize::MAX, None)
48 }
49}
50
51impl<T> FusedStream for Repeat<T>
52where
53 T: Clone,
54{
55 fn is_terminated(&self) -> bool {
56 false
57 }
58}
59