1 files changed, 86 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/compat/executor.rs b/third_party/rust/futures-util/src/compat/executor.rs
new file mode 100644
index 0000000000..ea0c67a0ae
--- /dev/null
+++ b/third_party/rust/futures-util/src/compat/executor.rs
@@ -0,0 +1,86 @@
+use super::{Compat, Future01CompatExt};
+use crate::{
+    future::{FutureExt, TryFutureExt, UnitError},
+    task::SpawnExt,
+};
+use futures_01::future::{ExecuteError as ExecuteError01, Executor as Executor01};
+use futures_01::Future as Future01;
+use futures_task::{FutureObj, Spawn as Spawn03, SpawnError as SpawnError03};
+
+/// A future that can run on a futures 0.1
+/// [`Executor`](futures_01::future::Executor).
+pub type Executor01Future = Compat<UnitError<FutureObj<'static, ()>>>;
+
+/// Extension trait for futures 0.1 [`Executor`](futures_01::future::Executor).
+pub trait Executor01CompatExt: Executor01<Executor01Future> + Clone + Send + 'static {
+    /// Converts a futures 0.1 [`Executor`](futures_01::future::Executor) into a
+    /// futures 0.3 [`Spawn`](futures_task::Spawn).
+    ///
+    /// ```
+    /// # if cfg!(miri) { return; } // Miri does not support epoll
+    /// use futures::task::SpawnExt;
+    /// use futures::future::{FutureExt, TryFutureExt};
+    /// use futures_util::compat::Executor01CompatExt;
+    /// use tokio::executor::DefaultExecutor;
+    ///
+    /// # let (tx, rx) = futures::channel::oneshot::channel();
+    ///
+    /// let spawner = DefaultExecutor::current().compat();
+    /// let future03 = async move {
+    ///     println!("Running on the pool");
+    ///     spawner.spawn(async {
+    ///         println!("Spawned!");
+    ///         # tx.send(42).unwrap();
+    ///     }).unwrap();
+    /// };
+    ///
+    /// let future01 = future03.unit_error().boxed().compat();
+    ///
+    /// tokio::run(future01);
+    /// # futures::executor::block_on(rx).unwrap();
+    /// ```
+    fn compat(self) -> Executor01As03<Self>
+    where
+        Self: Sized;
+}
+
+impl<Ex> Executor01CompatExt for Ex
+where
+    Ex: Executor01<Executor01Future> + Clone + Send + 'static,
+{
+    fn compat(self) -> Executor01As03<Self> {
+        Executor01As03 { executor01: self }
+    }
+}
+
+/// Converts a futures 0.1 [`Executor`](futures_01::future::Executor) into a
+/// futures 0.3 [`Spawn`](futures_task::Spawn).
+#[derive(Debug, Clone)]
+pub struct Executor01As03<Ex> {
+    executor01: Ex,
+}
+
+impl<Ex> Spawn03 for Executor01As03<Ex>
+where
+    Ex: Executor01<Executor01Future> + Clone + Send + 'static,
+{
+    fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError03> {
+        let future = future.unit_error().compat();
+
+        self.executor01.execute(future).map_err(|_| SpawnError03::shutdown())
+    }
+}
+
+#[allow(single_use_lifetimes)] // https://github.com/rust-lang/rust/issues/55058
+impl<Sp, Fut> Executor01<Fut> for Compat<Sp>
+where
+    for<'a> &'a Sp: Spawn03,
+    Fut: Future01<Item = (), Error = ()> + Send + 'static,
+{
+    fn execute(&self, future: Fut) -> Result<(), ExecuteError01<Fut>> {
+        (&self.inner)
+            .spawn(future.compat().map(|_| ()))
+            .expect("unable to spawn future from Compat executor");
+        Ok(())
+    }
+}