1 files changed, 101 insertions, 0 deletions
diff --git a/vendor/futures-util/src/stream/stream/then.rs b/vendor/futures-util/src/stream/stream/then.rs
new file mode 100644
index 000000000..d4531d4b9
--- /dev/null
+++ b/vendor/futures-util/src/stream/stream/then.rs
@@ -0,0 +1,101 @@
+use core::fmt;
+use core::pin::Pin;
+use futures_core::future::Future;
+use futures_core::ready;
+use futures_core::stream::{FusedStream, Stream};
+use futures_core::task::{Context, Poll};
+#[cfg(feature = "sink")]
+use futures_sink::Sink;
+use pin_project_lite::pin_project;
+
+pin_project! {
+    /// Stream for the [`then`](super::StreamExt::then) method.
+    #[must_use = "streams do nothing unless polled"]
+    pub struct Then<St, Fut, F> {
+        #[pin]
+        stream: St,
+        #[pin]
+        future: Option<Fut>,
+        f: F,
+    }
+}
+
+impl<St, Fut, F> fmt::Debug for Then<St, Fut, F>
+where
+    St: fmt::Debug,
+    Fut: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Then").field("stream", &self.stream).field("future", &self.future).finish()
+    }
+}
+
+impl<St, Fut, F> Then<St, Fut, F>
+where
+    St: Stream,
+    F: FnMut(St::Item) -> Fut,
+{
+    pub(super) fn new(stream: St, f: F) -> Self {
+        Self { stream, future: None, f }
+    }
+
+    delegate_access_inner!(stream, St, ());
+}
+
+impl<St, Fut, F> FusedStream for Then<St, Fut, F>
+where
+    St: FusedStream,
+    F: FnMut(St::Item) -> Fut,
+    Fut: Future,
+{
+    fn is_terminated(&self) -> bool {
+        self.future.is_none() && self.stream.is_terminated()
+    }
+}
+
+impl<St, Fut, F> Stream for Then<St, Fut, F>
+where
+    St: Stream,
+    F: FnMut(St::Item) -> Fut,
+    Fut: Future,
+{
+    type Item = Fut::Output;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut this = self.project();
+
+        Poll::Ready(loop {
+            if let Some(fut) = this.future.as_mut().as_pin_mut() {
+                let item = ready!(fut.poll(cx));
+                this.future.set(None);
+                break Some(item);
+            } else if let Some(item) = ready!(this.stream.as_mut().poll_next(cx)) {
+                this.future.set(Some((this.f)(item)));
+            } else {
+                break None;
+            }
+        })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let future_len = if self.future.is_some() { 1 } else { 0 };
+        let (lower, upper) = self.stream.size_hint();
+        let lower = lower.saturating_add(future_len);
+        let upper = match upper {
+            Some(x) => x.checked_add(future_len),
+            None => None,
+        };
+        (lower, upper)
+    }
+}
+
+// Forwarding impl of Sink from the underlying stream
+#[cfg(feature = "sink")]
+impl<S, Fut, F, Item> Sink<Item> for Then<S, Fut, F>
+where
+    S: Sink<Item>,
+{
+    type Error = S::Error;
+
+    delegate_sink!(stream, Item);
+}