Add `Application::Executor` associated type

5 files changed, 98 insertions, 0 deletions

diff --git a/futures/src/executor.rs b/futures/src/executor.rs
new file mode 100644
index 00000000..144a41f8
--- /dev/null
+++ b/futures/src/executor.rs
@@ -0,0 +1,36 @@
+//! Choose your preferred executor to power a runtime.
+mod null;
+
+#[cfg(feature = "thread-pool")]
+mod thread_pool;
+
+#[cfg(feature = "thread-pool")]
+pub use thread_pool::ThreadPool;
+
+#[cfg(feature = "tokio")]
+mod tokio;
+
+#[cfg(feature = "async-std")]
+mod async_std;
+
+pub use null::Null;
+
+#[cfg(feature = "tokio")]
+pub use self::tokio::Tokio;
+
+#[cfg(feature = "async-std")]
+pub use self::async_std::AsyncStd;
+
+use futures::Future;
+
+pub trait Executor: Sized {
+    fn new() -> Result<Self, futures::io::Error>
+    where
+        Self: Sized;
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}
diff --git a/futures/src/executor/async_std.rs b/futures/src/executor/async_std.rs
new file mode 100644
index 00000000..b056b23d
--- /dev/null
+++ b/futures/src/executor/async_std.rs
@@ -0,0 +1,15 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub struct AsyncStd;
+
+impl Executor for AsyncStd {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = async_std::task::spawn(future);
+    }
+}
diff --git a/futures/src/executor/null.rs b/futures/src/executor/null.rs
new file mode 100644
index 00000000..722073bb
--- /dev/null
+++ b/futures/src/executor/null.rs
@@ -0,0 +1,13 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub struct Null;
+
+impl Executor for Null {
+    fn new() -> Result<Self, futures::io::Error> {
+        Ok(Self)
+    }
+
+    fn spawn(&self, _future: impl Future<Output = ()> + Send + 'static) {}
+}
diff --git a/futures/src/executor/thread_pool.rs b/futures/src/executor/thread_pool.rs
new file mode 100644
index 00000000..6393d0d5
--- /dev/null
+++ b/futures/src/executor/thread_pool.rs
@@ -0,0 +1,15 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub type ThreadPool = futures::executor::ThreadPool;
+
+impl Executor for futures::executor::ThreadPool {
+    fn new() -> Result<Self, futures::io::Error> {
+        futures::executor::ThreadPool::new()
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        self.spawn_ok(future);
+    }
+}
diff --git a/futures/src/executor/tokio.rs b/futures/src/executor/tokio.rs
new file mode 100644
index 00000000..aafa7e7b
--- /dev/null
+++ b/futures/src/executor/tokio.rs
@@ -0,0 +1,19 @@
+use crate::Executor;
+
+use futures::Future;
+
+pub type Tokio = tokio::runtime::Runtime;
+
+impl Executor for Tokio {
+    fn new() -> Result<Self, futures::io::Error> {
+        tokio::runtime::Runtime::new()
+    }
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
+        let _ = tokio::runtime::Runtime::spawn(self, future);
+    }
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        tokio::runtime::Runtime::enter(self, f)
+    }
+}