Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 76 insertions, 0 deletions

diff --git a/third_party/rust/hyper/src/common/lazy.rs b/third_party/rust/hyper/src/common/lazy.rs
new file mode 100644
index 0000000000..2722077303
--- /dev/null
+++ b/third_party/rust/hyper/src/common/lazy.rs
@@ -0,0 +1,76 @@
+use pin_project_lite::pin_project;
+
+use super::{task, Future, Pin, Poll};
+
+pub(crate) trait Started: Future {
+    fn started(&self) -> bool;
+}
+
+pub(crate) fn lazy<F, R>(func: F) -> Lazy<F, R>
+where
+    F: FnOnce() -> R,
+    R: Future + Unpin,
+{
+    Lazy {
+        inner: Inner::Init { func },
+    }
+}
+
+// FIXME: allow() required due to `impl Trait` leaking types to this lint
+pin_project! {
+    #[allow(missing_debug_implementations)]
+    pub(crate) struct Lazy<F, R> {
+        #[pin]
+        inner: Inner<F, R>,
+    }
+}
+
+pin_project! {
+    #[project = InnerProj]
+    #[project_replace = InnerProjReplace]
+    enum Inner<F, R> {
+        Init { func: F },
+        Fut { #[pin] fut: R },
+        Empty,
+    }
+}
+
+impl<F, R> Started for Lazy<F, R>
+where
+    F: FnOnce() -> R,
+    R: Future,
+{
+    fn started(&self) -> bool {
+        match self.inner {
+            Inner::Init { .. } => false,
+            Inner::Fut { .. } | Inner::Empty => true,
+        }
+    }
+}
+
+impl<F, R> Future for Lazy<F, R>
+where
+    F: FnOnce() -> R,
+    R: Future,
+{
+    type Output = R::Output;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
+        let mut this = self.project();
+
+        if let InnerProj::Fut { fut } = this.inner.as_mut().project() {
+            return fut.poll(cx);
+        }
+
+        match this.inner.as_mut().project_replace(Inner::Empty) {
+            InnerProjReplace::Init { func } => {
+                this.inner.set(Inner::Fut { fut: func() });
+                if let InnerProj::Fut { fut } = this.inner.project() {
+                    return fut.poll(cx);
+                }
+                unreachable!()
+            }
+            _ => unreachable!("lazy state wrong"),
+        }
+    }
+}