tokio_stream/
iter.rs

1use crate::Stream;
2
3use core::pin::Pin;
4use core::task::{Context, Poll};
5
6/// Stream for the [`iter`](fn@iter) function.
7#[derive(Debug)]
8#[must_use = "streams do nothing unless polled"]
9pub struct Iter<I> {
10    iter: I,
11    #[cfg(not(feature = "rt"))]
12    yield_amt: usize,
13}
14
15impl<I> Unpin for Iter<I> {}
16
17/// Converts an `Iterator` into a `Stream` which is always ready
18/// to yield the next value.
19///
20/// Iterators in Rust don't express the ability to block, so this adapter
21/// simply always calls `iter.next()` and returns that.
22///
23/// ```
24/// # async fn dox() {
25/// use tokio_stream::{self as stream, StreamExt};
26///
27/// let mut stream = stream::iter(vec![17, 19]);
28///
29/// assert_eq!(stream.next().await, Some(17));
30/// assert_eq!(stream.next().await, Some(19));
31/// assert_eq!(stream.next().await, None);
32/// # }
33/// ```
34pub fn iter<I>(i: I) -> Iter<I::IntoIter>
35where
36    I: IntoIterator,
37{
38    Iter {
39        iter: i.into_iter(),
40        #[cfg(not(feature = "rt"))]
41        yield_amt: 0,
42    }
43}
44
45impl<I> Stream for Iter<I>
46where
47    I: Iterator,
48{
49    type Item = I::Item;
50
51    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<I::Item>> {
52        #[cfg(feature = "rt")]
53        {
54            use tokio::task::coop;
55
56            let coop = std::task::ready!(coop::poll_proceed(cx));
57            let item = self.iter.next();
58
59            coop.made_progress();
60
61            Poll::Ready(item)
62        }
63
64        #[cfg(not(feature = "rt"))]
65        {
66            if self.yield_amt >= 32 {
67                self.yield_amt = 0;
68
69                cx.waker().wake_by_ref();
70
71                Poll::Pending
72            } else {
73                let item = self.iter.next();
74
75                self.yield_amt += 1;
76
77                Poll::Ready(item)
78            }
79        }
80    }
81
82    fn size_hint(&self) -> (usize, Option<usize>) {
83        self.iter.size_hint()
84    }
85}
tokio_stream/iter.rs

tokio_stream/
iter.rs
