Commit 8f2ed48

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add stream::peekable

peek() implementation is still missing

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Lines changed: 33 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -44,6 +44,7 @@ mod min_by;`
`44`	`44`	`mod next;`
`45`	`45`	`mod nth;`
`46`	`46`	`mod partial_cmp;`
	`47`	`+mod peekable;`
`47`	`48`	`mod scan;`
`48`	`49`	`mod skip;`
`49`	`50`	`mod skip_while;`
`@@ -80,6 +81,7 @@ pub use filter::Filter;`
`80`	`81`	`pub use fuse::Fuse;`
`81`	`82`	`pub use inspect::Inspect;`
`82`	`83`	`pub use map::Map;`
	`84`	`+pub use peekable::Peekable;`
`83`	`85`	`pub use scan::Scan;`
`84`	`86`	`pub use skip::Skip;`
`85`	`87`	`pub use skip_while::SkipWhile;`
`@@ -984,6 +986,37 @@ extension_trait! {`
`984`	`986`	`}`
`985`	`987`	`}`
`986`	`988`
	`989`	`+ #[doc = r#"`
	`990`	`+ ## Examples`
	`991`	`+`
	`992`	+ ```
	`993`	`+ # fn main() { async_std::task::block_on(async {`
	`994`	`+ #`
	`995`	`+ use std::collections::VecDeque;`
	`996`	`+`
	`997`	`+ use async_std::prelude::*;`
	`998`	`+`
	`999`	`+ let s: VecDeque<usize> = vec![1, 2, 3].into_iter().collect();`
	`1000`	`+ let mut s = s.peekable();`
	`1001`	`+`
	`1002`	`+ assert_eq!(s.next().await, Some(1));`
	`1003`	`+ assert_eq!(s.peek().await, Some(1));`
	`1004`	`+ assert_eq!(s.next().await, Some(2));`
	`1005`	`+ assert_eq!(s.next().await, Some(3));`
	`1006`	`+ assert_eq!(s.next().await, None);`
	`1007`	`+ #`
	`1008`	`+ # }) }`
	`1009`	+ ```
	`1010`	`+ "#]`
	`1011`	`+ #[inline]`
	`1012`	`+ fn peekable(self) -> Peekable<Self>`
	`1013`	`+ where`
	`1014`	`+ Self: Sized,`
	`1015`	`+ {`
	`1016`	`+ Peekable::new(self)`
	`1017`	`+ }`
	`1018`	`+`
	`1019`	`+`
`987`	`1020`	`#[doc = r#"`
`988`	`1021`	A stream adaptor similar to [`fold`] that holds internal state and produces a new
`989`	`1022`	`stream.`

Lines changed: 49 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,49 @@`
	`1`	`+use std::pin::Pin;`
	`2`	`+`
	`3`	`+use crate::stream::Stream;`
	`4`	`+use crate::task::{Context, Poll};`
	`5`	`+`
	`6`	`+#[doc(hidden)]`
	`7`	`+#[allow(missing_debug_implementations)]`
	`8`	`+pub struct Peekable<S: Stream> {`
	`9`	`+ stream: S,`
	`10`	`+ peeked: Option<Option<S::Item>>,`
	`11`	`+}`
	`12`	`+`
	`13`	`+`
	`14`	`+impl<S> Peekable<S>`
	`15`	`+where`
	`16`	`+ S: Stream,`
	`17`	`+{`
	`18`	`+ pin_utils::unsafe_pinned!(stream: S);`
	`19`	`+ pin_utils::unsafe_unpinned!(peeked: Option<Option<S::Item>>);`
	`20`	`+`
	`21`	`+ pub(crate) fn new(stream: S) -> Self {`
	`22`	`+ Peekable{`
	`23`	`+ stream: stream,`
	`24`	`+ peeked: None,`
	`25`	`+ }`
	`26`	`+ }`
	`27`	`+`
	`28`	`+ pub fn peek(&mut self) -> Poll<Option<&S::Item>> {`
	`29`	`+ Poll::Ready(None)`
	`30`	`+ }`
	`31`	`+`
	`32`	`+}`
	`33`	`+`
	`34`	`+impl<S> Stream for Peekable<S>`
	`35`	`+where`
	`36`	`+ S: Stream,`
	`37`	`+{`
	`38`	`+ type Item = S::Item;`
	`39`	`+`
	`40`	`+ fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {`
	`41`	`+ match &self.peeked {`
	`42`	`+ Some(_) => Poll::Ready(self.as_mut().peeked().take().unwrap()) ,`
	`43`	`+ None => {`
	`44`	`+ let next = futures_core::ready!(self.as_mut().stream().poll_next(cx));`
	`45`	`+ Poll::Ready(next)`
	`46`	`+ }`
	`47`	`+ }`
	`48`	`+ }`
	`49`	`+}`

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