core: add the option to create a new task group without providing an

executor & remove GlobalExecutor type

1 files changed, 30 insertions, 0 deletions

diff --git a/core/src/async_util/executor.rs b/core/src/async_util/executor.rs
new file mode 100644
index 0000000..3e7aa06
--- /dev/null
+++ b/core/src/async_util/executor.rs
@@ -0,0 +1,30 @@
+use std::{panic::catch_unwind, sync::Arc, thread};
+
+use async_lock::OnceCell;
+use smol::Executor as SmolEx;
+
+static GLOBAL_EXECUTOR: OnceCell<Arc<smol::Executor<'_>>> = OnceCell::new();
+
+/// A pointer to an Executor
+pub type Executor<'a> = Arc<SmolEx<'a>>;
+
+/// Returns a single-threaded global executor
+pub(crate) fn global_executor() -> Executor<'static> {
+    fn init_executor() -> Executor<'static> {
+        let ex = smol::Executor::new();
+        thread::Builder::new()
+            .spawn(|| loop {
+                catch_unwind(|| {
+                    smol::block_on(global_executor().run(smol::future::pending::<()>()))
+                })
+                .ok();
+            })
+            .expect("cannot spawn executor thread");
+        // Prevent spawning another thread by running the process driver on this
+        // thread. see https://github.com/smol-rs/smol/blob/master/src/spawn.rs
+        ex.spawn(async_process::driver()).detach();
+        Arc::new(ex)
+    }
+
+    GLOBAL_EXECUTOR.get_or_init_blocking(init_executor).clone()
+}