1 files changed, 84 insertions, 0 deletions
diff --git a/vendor/futures-util/src/future/try_select.rs b/vendor/futures-util/src/future/try_select.rs
new file mode 100644
index 000000000..4d0b7ff13
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+++ b/vendor/futures-util/src/future/try_select.rs
@@ -0,0 +1,84 @@
+use crate::future::{Either, TryFutureExt};
+use core::pin::Pin;
+use futures_core::future::{Future, TryFuture};
+use futures_core::task::{Context, Poll};
+
+/// Future for the [`try_select()`] function.
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+#[derive(Debug)]
+pub struct TrySelect<A, B> {
+    inner: Option<(A, B)>,
+}
+
+impl<A: Unpin, B: Unpin> Unpin for TrySelect<A, B> {}
+
+/// Waits for either one of two differently-typed futures to complete.
+///
+/// This function will return a new future which awaits for either one of both
+/// futures to complete. The returned future will finish with both the value
+/// resolved and a future representing the completion of the other work.
+///
+/// Note that this function consumes the receiving futures and returns a
+/// wrapped version of them.
+///
+/// Also note that if both this and the second future have the same
+/// success/error type you can use the `Either::factor_first` method to
+/// conveniently extract out the value at the end.
+///
+/// # Examples
+///
+/// ```
+/// use futures::future::{self, Either, Future, FutureExt, TryFuture, TryFutureExt};
+///
+/// // A poor-man's try_join implemented on top of select
+///
+/// fn try_join<A, B, E>(a: A, b: B) -> impl TryFuture<Ok=(A::Ok, B::Ok), Error=E>
+///      where A: TryFuture<Error = E> + Unpin + 'static,
+///            B: TryFuture<Error = E> + Unpin + 'static,
+///            E: 'static,
+/// {
+///     future::try_select(a, b).then(|res| -> Box<dyn Future<Output = Result<_, _>> + Unpin> {
+///         match res {
+///             Ok(Either::Left((x, b))) => Box::new(b.map_ok(move |y| (x, y))),
+///             Ok(Either::Right((y, a))) => Box::new(a.map_ok(move |x| (x, y))),
+///             Err(Either::Left((e, _))) => Box::new(future::err(e)),
+///             Err(Either::Right((e, _))) => Box::new(future::err(e)),
+///         }
+///     })
+/// }
+/// ```
+pub fn try_select<A, B>(future1: A, future2: B) -> TrySelect<A, B>
+where
+    A: TryFuture + Unpin,
+    B: TryFuture + Unpin,
+{
+    super::assert_future::<
+        Result<Either<(A::Ok, B), (B::Ok, A)>, Either<(A::Error, B), (B::Error, A)>>,
+        _,
+    >(TrySelect { inner: Some((future1, future2)) })
+}
+
+impl<A: Unpin, B: Unpin> Future for TrySelect<A, B>
+where
+    A: TryFuture,
+    B: TryFuture,
+{
+    #[allow(clippy::type_complexity)]
+    type Output = Result<Either<(A::Ok, B), (B::Ok, A)>, Either<(A::Error, B), (B::Error, A)>>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let (mut a, mut b) = self.inner.take().expect("cannot poll Select twice");
+        match a.try_poll_unpin(cx) {
+            Poll::Ready(Err(x)) => Poll::Ready(Err(Either::Left((x, b)))),
+            Poll::Ready(Ok(x)) => Poll::Ready(Ok(Either::Left((x, b)))),
+            Poll::Pending => match b.try_poll_unpin(cx) {
+                Poll::Ready(Err(x)) => Poll::Ready(Err(Either::Right((x, a)))),
+                Poll::Ready(Ok(x)) => Poll::Ready(Ok(Either::Right((x, a)))),
+                Poll::Pending => {
+                    self.inner = Some((a, b));
+                    Poll::Pending
+                }
+            },
+        }
+    }
+}