1 files changed, 73 insertions, 0 deletions
diff --git a/examples/spawn-local.rs b/examples/spawn-local.rs
new file mode 100644
index 0000000..a9da1b4
--- /dev/null
+++ b/examples/spawn-local.rs
@@ -0,0 +1,73 @@
+//! A simple single-threaded executor that can spawn non-`Send` futures.
+
+use std::cell::Cell;
+use std::future::Future;
+use std::rc::Rc;
+
+use async_task::{Runnable, Task};
+
+thread_local! {
+    // A queue that holds scheduled tasks.
+    static QUEUE: (flume::Sender<Runnable>, flume::Receiver<Runnable>) = flume::unbounded();
+}
+
+/// Spawns a future on the executor.
+fn spawn<F, T>(future: F) -> Task<T>
+where
+    F: Future<Output = T> + 'static,
+    T: 'static,
+{
+    // Create a task that is scheduled by pushing itself into the queue.
+    let schedule = |runnable| QUEUE.with(|(s, _)| s.send(runnable).unwrap());
+    let (runnable, task) = async_task::spawn_local(future, schedule);
+
+    // Schedule the task by pushing it into the queue.
+    runnable.schedule();
+
+    task
+}
+
+/// Runs a future to completion.
+fn run<F, T>(future: F) -> T
+where
+    F: Future<Output = T> + 'static,
+    T: 'static,
+{
+    // Spawn a task that sends its result through a channel.
+    let (s, r) = flume::unbounded();
+    spawn(async move { drop(s.send(future.await)) }).detach();
+
+    loop {
+        // If the original task has completed, return its result.
+        if let Ok(val) = r.try_recv() {
+            return val;
+        }
+
+        // Otherwise, take a task from the queue and run it.
+        QUEUE.with(|(_, r)| r.recv().unwrap().run());
+    }
+}
+
+fn main() {
+    let val = Rc::new(Cell::new(0));
+
+    // Run a future that increments a non-`Send` value.
+    run({
+        let val = val.clone();
+        async move {
+            // Spawn a future that increments the value.
+            let task = spawn({
+                let val = val.clone();
+                async move {
+                    val.set(dbg!(val.get()) + 1);
+                }
+            });
+
+            val.set(dbg!(val.get()) + 1);
+            task.await;
+        }
+    });
+
+    // The value should be 2 at the end of the program.
+    dbg!(val.get());
+}