Sketch outch rfind

src/stream/double_ended/mod.rs

@@ -1,6 +1,8 @@
 mod nth_back;
+mod rfind;
 
 use nth_back::NthBackFuture;
+use rfind::RFindFuture;
 
 extension_trait! {
     use crate::stream::Stream;
@@ -53,5 +55,17 @@ extension_trait! {
         {
             NthBackFuture::new(self, n)
         }
+
+        fn rfind<P>(
+            &mut self,
+            p: P,
+        ) -> impl Future<Output = Option<Self::Item>> + '_ [RFindFuture<'_, Self, P>]
+        where
+            Self: Unpin + Sized,
+            P: FnMut(&Self::Item) -> bool,
+        {
+            RFindFuture::new(self, p)
+        }
+
     }
 }

src/stream/double_ended/rfind.rs

@@ -0,0 +1,39 @@
+use std::task::{Context, Poll};
+use std::future::Future;
+use std::pin::Pin;
+
+use crate::stream::DoubleEndedStream;
+
+pub struct RFindFuture<'a, S, P> {
+    stream: &'a mut S,
+    p: P,
+}
+
+impl<'a, S, P> RFindFuture<'a, S, P> {
+    pub(super) fn new(stream: &'a mut S, p: P) -> Self {
+        RFindFuture { stream, p }
+    }
+}
+
+impl<S: Unpin, P> Unpin for RFindFuture<'_, S, P> {}
+
+impl<'a, S, P> Future for RFindFuture<'a, S, P>
+where
+    S: DoubleEndedStream + Unpin + Sized,
+    P: FnMut(&S::Item) -> bool,
+{
+    type Output = Option<S::Item>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let item = futures_core::ready!(Pin::new(&mut *self.stream).poll_next_back(cx));
+
+        match item {
+            Some(v) if (&mut self.p)(&v) => Poll::Ready(Some(v)),
+            Some(_) => {
+                cx.waker().wake_by_ref();
+                Poll::Pending
+            }
+            None => Poll::Ready(None),
+        }
+    }
+}