1 files changed, 55 insertions, 0 deletions
diff --git a/futures/src/executor.rs b/futures/src/executor.rs
new file mode 100644
index 00000000..c2b9cc72
--- /dev/null
+++ b/futures/src/executor.rs
@@ -0,0 +1,55 @@
+//! Choose your preferred executor to power a runtime.
+mod null;
+
+#[cfg(feature = "thread-pool")]
+mod thread_pool;
+
+#[cfg(feature = "tokio")]
+mod tokio;
+
+#[cfg(feature = "async-std")]
+mod async_std;
+
+#[cfg(target_arch = "wasm32")]
+mod wasm_bindgen;
+
+pub use null::Null;
+
+#[cfg(feature = "thread-pool")]
+pub use thread_pool::ThreadPool;
+
+#[cfg(feature = "tokio")]
+pub use self::tokio::Tokio;
+
+#[cfg(feature = "async-std")]
+pub use self::async_std::AsyncStd;
+
+#[cfg(target_arch = "wasm32")]
+pub use wasm_bindgen::WasmBindgen;
+
+use futures::Future;
+
+/// A type that can run futures.
+pub trait Executor: Sized {
+    /// Creates a new [`Executor`].
+    ///
+    /// [`Executor`]: trait.Executor.html
+    fn new() -> Result<Self, futures::io::Error>
+    where
+        Self: Sized;
+
+    /// Spawns a future in the [`Executor`].
+    ///
+    /// [`Executor`]: trait.Executor.html
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
+
+    /// Runs the given closure inside the [`Executor`].
+    ///
+    /// Some executors, like `tokio`, require some global state to be in place
+    /// before creating futures. This method can be leveraged to set up this
+    /// global state, call a function, restore the state, and obtain the result
+    /// of the call.
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}