Got further! Thx Josh!
use std::marker::PhantomData;
use std::pin::Pin;
+use std::mem;
use crate::future::Future;
use crate::stream::Stream;
-use crate::task::{Context, Poll};
+use crate::task::{Context, Poll, ready};
+
+
+pin_project_lite::pin_project! {
/// A stream that yields elements by calling an async closure with the previous value as an
/// argument
///
@@ -17,10 +21,12 @@ where
Fut: Future<Output = Option<T>>,
{
successor: F,
+ #[pin]
future: Option<Fut>,
- next: Option<T>,
+ slot: Option<T>,
_marker: PhantomData<Fut>,
}
+}
/// Creates a new stream where to produce each new element a closure is called with the previous
/// value.
@@ -40,6 +46,7 @@ where
/// });
///
/// pin_utils::pin_mut!(s);
+/// assert_eq!(s.next().await, Some(22));
/// assert_eq!(s.next().await, Some(23));
/// assert_eq!(s.next().await, Some(24));
/// assert_eq!(s.next().await, Some(25));
@@ -58,31 +65,20 @@ where
/// # }) }
///
/// ```
-pub fn successors<F, Fut, T>(start: Option<T>, func: F) -> Successors<F, Fut, T>
+pub fn successors<F, Fut, T>(first: Option<T>, succ: F) -> Successors<F, Fut, T>
where
F: FnMut(T) -> Fut,
Fut: Future<Output = Option<T>>,
T: Copy,
{
Successors {
- successor: func,
+ successor: succ,
future: None,
- next: start,
+ slot: first,
_marker: PhantomData,
}
}
-impl<F, Fut, T> Successors<F, Fut, T>
-where
- F: FnMut(T) -> Fut,
- Fut: Future<Output = Option<T>>,
- T: Copy,
-{
- pin_utils::unsafe_unpinned!(successor: F);
- pin_utils::unsafe_unpinned!(next: Option<T>);
- pin_utils::unsafe_pinned!(future: Option<Fut>);
-}
-
impl<F, Fut, T> Stream for Successors<F, Fut, T>
where
Fut: Future<Output = Option<T>>,
@@ -91,23 +87,23 @@ where
{
type Item = T;
- fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
- if self.next.is_none() {
+ fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+ let mut this = self.project();
+
+ if this.slot.is_none() {
return Poll::Ready(None);
}
- match &self.future {
- None => {
- let x = self.next.unwrap();
- let fut = (self.as_mut().successor())(x);
- self.as_mut().future().set(Some(fut));
- }
- _ => {}
+ if this.future.is_none() {
+ let x = this.slot.unwrap();
+ let fut = (this.successor)(x);
+ this.future.set(Some(fut));
}
- let next = futures_core::ready!(self.as_mut().future().as_pin_mut().unwrap().poll(cx));
- *self.as_mut().next() = next;
- self.as_mut().future().set(None);
+ let mut next = ready!(this.future.as_mut().as_pin_mut().unwrap().poll(cx));
+
+ this.future.set(None);
+ mem::swap(this.slot, &mut next);
Poll::Ready(next)
}
}
