1 files changed, 92 insertions, 0 deletions
diff --git a/vendor/futures-util/src/future/try_maybe_done.rs b/vendor/futures-util/src/future/try_maybe_done.rs
new file mode 100644
index 000000000..24044d2c2
--- /dev/null
+++ b/vendor/futures-util/src/future/try_maybe_done.rs
@@ -0,0 +1,92 @@
+//! Definition of the TryMaybeDone combinator
+
+use super::assert_future;
+use core::mem;
+use core::pin::Pin;
+use futures_core::future::{FusedFuture, Future, TryFuture};
+use futures_core::ready;
+use futures_core::task::{Context, Poll};
+
+/// A future that may have completed with an error.
+///
+/// This is created by the [`try_maybe_done()`] function.
+#[derive(Debug)]
+pub enum TryMaybeDone<Fut: TryFuture> {
+    /// A not-yet-completed future
+    Future(/* #[pin] */ Fut),
+    /// The output of the completed future
+    Done(Fut::Ok),
+    /// The empty variant after the result of a [`TryMaybeDone`] has been
+    /// taken using the [`take_output`](TryMaybeDone::take_output) method,
+    /// or if the future returned an error.
+    Gone,
+}
+
+impl<Fut: TryFuture + Unpin> Unpin for TryMaybeDone<Fut> {}
+
+/// Wraps a future into a `TryMaybeDone`
+pub fn try_maybe_done<Fut: TryFuture>(future: Fut) -> TryMaybeDone<Fut> {
+    assert_future::<Result<(), Fut::Error>, _>(TryMaybeDone::Future(future))
+}
+
+impl<Fut: TryFuture> TryMaybeDone<Fut> {
+    /// Returns an [`Option`] containing a mutable reference to the output of the future.
+    /// The output of this method will be [`Some`] if and only if the inner
+    /// future has completed successfully and [`take_output`](TryMaybeDone::take_output)
+    /// has not yet been called.
+    #[inline]
+    pub fn output_mut(self: Pin<&mut Self>) -> Option<&mut Fut::Ok> {
+        unsafe {
+            match self.get_unchecked_mut() {
+                TryMaybeDone::Done(res) => Some(res),
+                _ => None,
+            }
+        }
+    }
+
+    /// Attempt to take the output of a `TryMaybeDone` without driving it
+    /// towards completion.
+    #[inline]
+    pub fn take_output(self: Pin<&mut Self>) -> Option<Fut::Ok> {
+        match &*self {
+            Self::Done(_) => {}
+            Self::Future(_) | Self::Gone => return None,
+        }
+        unsafe {
+            match mem::replace(self.get_unchecked_mut(), Self::Gone) {
+                TryMaybeDone::Done(output) => Some(output),
+                _ => unreachable!(),
+            }
+        }
+    }
+}
+
+impl<Fut: TryFuture> FusedFuture for TryMaybeDone<Fut> {
+    fn is_terminated(&self) -> bool {
+        match self {
+            Self::Future(_) => false,
+            Self::Done(_) | Self::Gone => true,
+        }
+    }
+}
+
+impl<Fut: TryFuture> Future for TryMaybeDone<Fut> {
+    type Output = Result<(), Fut::Error>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        unsafe {
+            match self.as_mut().get_unchecked_mut() {
+                TryMaybeDone::Future(f) => match ready!(Pin::new_unchecked(f).try_poll(cx)) {
+                    Ok(res) => self.set(Self::Done(res)),
+                    Err(e) => {
+                        self.set(Self::Gone);
+                        return Poll::Ready(Err(e));
+                    }
+                },
+                TryMaybeDone::Done(_) => {}
+                TryMaybeDone::Gone => panic!("TryMaybeDone polled after value taken"),
+            }
+        }
+        Poll::Ready(Ok(()))
+    }
+}