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use crate::Stream;
use core::pin::Pin;
use core::task::{Context, Poll};
/// Stream for the [`iter`](fn@iter) function.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Iter<I> {
iter: I,
yield_amt: usize,
}
impl<I> Unpin for Iter<I> {}
/// Converts an `Iterator` into a `Stream` which is always ready
/// to yield the next value.
///
/// Iterators in Rust don't express the ability to block, so this adapter
/// simply always calls `iter.next()` and returns that.
///
/// ```
/// # async fn dox() {
/// use tokio_stream::{self as stream, StreamExt};
///
/// let mut stream = stream::iter(vec![17, 19]);
///
/// assert_eq!(stream.next().await, Some(17));
/// assert_eq!(stream.next().await, Some(19));
/// assert_eq!(stream.next().await, None);
/// # }
/// ```
pub fn iter<I>(i: I) -> Iter<I::IntoIter>
where
I: IntoIterator,
{
Iter {
iter: i.into_iter(),
yield_amt: 0,
}
}
impl<I> Stream for Iter<I>
where
I: Iterator,
{
type Item = I::Item;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<I::Item>> {
// TODO: add coop back
if self.yield_amt >= 32 {
self.yield_amt = 0;
cx.waker().wake_by_ref();
Poll::Pending
} else {
self.yield_amt += 1;
Poll::Ready(self.iter.next())
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}