use core::marker;
use {Async, Poll};
use stream::Stream;
/// A stream which is just a shim over an underlying instance of `Iterator`.
///
/// This stream will never block and is always ready.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct IterOk<I, E> {
iter: I,
_marker: marker::PhantomData<fn() -> E>,
}
/// 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.
///
/// ```rust
/// use futures::*;
///
/// let mut stream = stream::iter_ok::<_, ()>(vec![17, 19]);
/// assert_eq!(Ok(Async::Ready(Some(17))), stream.poll());
/// assert_eq!(Ok(Async::Ready(Some(19))), stream.poll());
/// assert_eq!(Ok(Async::Ready(None)), stream.poll());
/// ```
pub fn iter_ok<I, E>(i: I) -> IterOk<I::IntoIter, E>
where I: IntoIterator,
{
IterOk {
iter: i.into_iter(),
_marker: marker::PhantomData,
}
}
impl<I, E> Stream for IterOk<I, E>
where I: Iterator,
{
type Item = I::Item;
type Error = E;
fn poll(&mut self) -> Poll<Option<I::Item>, E> {
Ok(Async::Ready(self.iter.next()))
}
}