Update futures-util to 0.3.21 am: 737dc97288 am: b9180251b3

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-util/+/2004175

Change-Id: I30785daabcfc58d3479c32b9aff9cc4130c3bfe0

1 files changed, 53 insertions, 0 deletions

diff --git a/src/stream/stream/count.rs b/src/stream/stream/count.rs
new file mode 100644
index 0000000..513cab7
--- /dev/null
+++ b/src/stream/stream/count.rs
@@ -0,0 +1,53 @@
+use core::fmt;
+use core::pin::Pin;
+use futures_core::future::{FusedFuture, Future};
+use futures_core::ready;
+use futures_core::stream::{FusedStream, Stream};
+use futures_core::task::{Context, Poll};
+use pin_project_lite::pin_project;
+
+pin_project! {
+    /// Future for the [`count`](super::StreamExt::count) method.
+    #[must_use = "futures do nothing unless you `.await` or poll them"]
+    pub struct Count<St> {
+        #[pin]
+        stream: St,
+        count: usize
+    }
+}
+
+impl<St> fmt::Debug for Count<St>
+where
+    St: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Count").field("stream", &self.stream).field("count", &self.count).finish()
+    }
+}
+
+impl<St: Stream> Count<St> {
+    pub(super) fn new(stream: St) -> Self {
+        Self { stream, count: 0 }
+    }
+}
+
+impl<St: FusedStream> FusedFuture for Count<St> {
+    fn is_terminated(&self) -> bool {
+        self.stream.is_terminated()
+    }
+}
+
+impl<St: Stream> Future for Count<St> {
+    type Output = usize;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let mut this = self.project();
+
+        Poll::Ready(loop {
+            match ready!(this.stream.as_mut().poll_next(cx)) {
+                Some(_) => *this.count += 1,
+                None => break *this.count,
+            }
+        })
+    }
+}