Merge pull request #415 from k-nasa/stream_from_iter

Add stream::from_iter

src/stream/from_iter.rs

@@ -0,0 +1,50 @@
+use std::pin::Pin;
+
+use pin_project_lite::pin_project;
+
+use crate::stream::Stream;
+use crate::task::{Context, Poll};
+
+pin_project! {
+    /// A stream that created from iterator
+    ///
+    /// This stream is created by the [`from_iter`] function.
+    /// See it documentation for more.
+    ///
+    /// [`from_iter`]: fn.from_iter.html
+    #[derive(Debug)]
+    pub struct FromIter<I> {
+        iter: I,
+    }
+}
+
+/// # Examples
+///```
+/// # async_std::task::block_on(async {
+/// #
+/// use async_std::prelude::*;
+/// use async_std::stream;
+///
+/// let mut s = stream::from_iter(vec![0, 1, 2, 3]);
+///
+/// assert_eq!(s.next().await, Some(0));
+/// assert_eq!(s.next().await, Some(1));
+/// assert_eq!(s.next().await, Some(2));
+/// assert_eq!(s.next().await, Some(3));
+/// assert_eq!(s.next().await, None);
+/// #
+/// # })
+///````
+pub fn from_iter<I: IntoIterator>(iter: I) -> FromIter<<I as std::iter::IntoIterator>::IntoIter> {
+    FromIter {
+        iter: iter.into_iter(),
+    }
+}
+
+impl<I: Iterator> Stream for FromIter<I> {
+    type Item = I::Item;
+
+    fn poll_next(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        Poll::Ready(self.iter.next())
+    }
+}

src/stream/mod.rs

@@ -302,6 +302,7 @@
 
 pub use empty::{empty, Empty};
 pub use from_fn::{from_fn, FromFn};
+pub use from_iter::{from_iter, FromIter};
 pub use once::{once, Once};
 pub use repeat::{repeat, Repeat};
 pub use repeat_with::{repeat_with, RepeatWith};
@@ -313,6 +314,7 @@ pub(crate) mod stream;
 
 mod empty;
 mod from_fn;
+mod from_iter;
 mod once;
 mod repeat;
 mod repeat_with;