8 files changed, 216 insertions, 0 deletions
diff --git a/core/src/async_runtime/executor.rs b/core/src/async_runtime/executor.rs
new file mode 100644
index 0000000..9335f12
--- /dev/null
+++ b/core/src/async_runtime/executor.rs
@@ -0,0 +1,100 @@
+use std::{future::Future, panic::catch_unwind, sync::Arc, thread};
+
+use once_cell::sync::OnceCell;
+
+#[cfg(feature = "smol")]
+pub use smol::Executor as SmolEx;
+
+#[cfg(feature = "tokio")]
+pub use tokio::runtime::Runtime;
+
+use super::Task;
+
+#[derive(Clone)]
+pub struct Executor {
+    #[cfg(feature = "smol")]
+    inner: Arc<SmolEx<'static>>,
+    #[cfg(feature = "tokio")]
+    inner: Arc<Runtime>,
+}
+
+impl Executor {
+    pub fn spawn<T: Send + 'static>(
+        &self,
+        future: impl Future<Output = T> + Send + 'static,
+    ) -> Task<T> {
+        self.inner.spawn(future).into()
+    }
+}
+
+static GLOBAL_EXECUTOR: OnceCell<Executor> = OnceCell::new();
+
+/// Returns a single-threaded global executor
+pub fn global_executor() -> Executor {
+    #[cfg(feature = "smol")]
+    fn init_executor() -> Executor {
+        let ex = smol::Executor::new();
+        thread::Builder::new()
+            .name("smol-executor".to_string())
+            .spawn(|| loop {
+                catch_unwind(|| {
+                    smol::block_on(global_executor().inner.run(std::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();
+        Executor {
+            inner: Arc::new(ex),
+        }
+    }
+
+    #[cfg(feature = "tokio")]
+    fn init_executor() -> Executor {
+        let ex = Arc::new(tokio::runtime::Runtime::new().expect("cannot build tokio runtime"));
+        let ex_cloned = ex.clone();
+        thread::Builder::new()
+            .name("tokio-executor".to_string())
+            .spawn(move || {
+                catch_unwind(|| ex_cloned.block_on(std::future::pending::<()>())).ok();
+            })
+            .expect("cannot spawn tokio runtime thread");
+        Executor { inner: ex }
+    }
+
+    GLOBAL_EXECUTOR.get_or_init(init_executor).clone()
+}
+
+#[cfg(feature = "smol")]
+impl From<Arc<smol::Executor<'static>>> for Executor {
+    fn from(ex: Arc<smol::Executor<'static>>) -> Executor {
+        Executor { inner: ex }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl From<Arc<tokio::runtime::Runtime>> for Executor {
+    fn from(rt: Arc<tokio::runtime::Runtime>) -> Executor {
+        Executor { inner: rt }
+    }
+}
+
+#[cfg(feature = "smol")]
+impl From<smol::Executor<'static>> for Executor {
+    fn from(ex: smol::Executor<'static>) -> Executor {
+        Executor {
+            inner: Arc::new(ex),
+        }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl From<tokio::runtime::Runtime> for Executor {
+    fn from(rt: tokio::runtime::Runtime) -> Executor {
+        Executor {
+            inner: Arc::new(rt),
+        }
+    }
+}
diff --git a/core/src/async_runtime/io.rs b/core/src/async_runtime/io.rs
new file mode 100644
index 0000000..161c258
--- /dev/null
+++ b/core/src/async_runtime/io.rs
@@ -0,0 +1,9 @@
+#[cfg(feature = "smol")]
+pub use smol::io::{
+    split, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt, ReadHalf, WriteHalf,
+};
+
+#[cfg(feature = "tokio")]
+pub use tokio::io::{
+    split, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt, ReadHalf, WriteHalf,
+};
diff --git a/core/src/async_runtime/lock.rs b/core/src/async_runtime/lock.rs
new file mode 100644
index 0000000..fc84d1d
--- /dev/null
+++ b/core/src/async_runtime/lock.rs
@@ -0,0 +1,5 @@
+#[cfg(feature = "smol")]
+pub use smol::lock::{Mutex, MutexGuard, OnceCell, RwLock};
+
+#[cfg(feature = "tokio")]
+pub use tokio::sync::{Mutex, MutexGuard, OnceCell, RwLock};
diff --git a/core/src/async_runtime/mod.rs b/core/src/async_runtime/mod.rs
new file mode 100644
index 0000000..d91d01b
--- /dev/null
+++ b/core/src/async_runtime/mod.rs
@@ -0,0 +1,25 @@
+mod executor;
+pub mod io;
+pub mod lock;
+pub mod net;
+mod spawn;
+mod task;
+mod timer;
+
+pub use executor::{global_executor, Executor};
+pub use spawn::spawn;
+pub use task::Task;
+
+#[cfg(test)]
+pub fn block_on<T>(future: impl std::future::Future<Output = T>) -> T {
+    #[cfg(feature = "smol")]
+    let result = smol::block_on(future);
+    #[cfg(feature = "tokio")]
+    let result = tokio::runtime::Builder::new_current_thread()
+        .enable_all()
+        .build()
+        .unwrap()
+        .block_on(future);
+
+    result
+}
diff --git a/core/src/async_runtime/net.rs b/core/src/async_runtime/net.rs
new file mode 100644
index 0000000..5c004ce
--- /dev/null
+++ b/core/src/async_runtime/net.rs
@@ -0,0 +1,12 @@
+pub use std::os::unix::net::SocketAddr;
+
+#[cfg(feature = "smol")]
+pub use smol::net::{
+    unix::{SocketAddr as UnixSocketAddr, UnixListener, UnixStream},
+    TcpListener, TcpStream, UdpSocket,
+};
+
+#[cfg(feature = "tokio")]
+pub use tokio::net::{
+    unix::SocketAddr as UnixSocketAddr, TcpListener, TcpStream, UdpSocket, UnixListener, UnixStream,
+};
diff --git a/core/src/async_runtime/spawn.rs b/core/src/async_runtime/spawn.rs
new file mode 100644
index 0000000..2760982
--- /dev/null
+++ b/core/src/async_runtime/spawn.rs
@@ -0,0 +1,12 @@
+use std::future::Future;
+
+use super::Task;
+
+pub fn spawn<T: Send + 'static>(future: impl Future<Output = T> + Send + 'static) -> Task<T> {
+    #[cfg(feature = "smol")]
+    let result: Task<T> = smol::spawn(future).into();
+    #[cfg(feature = "tokio")]
+    let result: Task<T> = tokio::spawn(future).into();
+
+    result
+}
diff --git a/core/src/async_runtime/task.rs b/core/src/async_runtime/task.rs
new file mode 100644
index 0000000..a681b0f
--- /dev/null
+++ b/core/src/async_runtime/task.rs
@@ -0,0 +1,52 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use crate::error::Error;
+
+pub struct Task<T> {
+    #[cfg(feature = "smol")]
+    inner_task: smol::Task<T>,
+    #[cfg(feature = "tokio")]
+    inner_task: tokio::task::JoinHandle<T>,
+}
+
+impl<T> Task<T> {
+    pub async fn cancel(self) {
+        #[cfg(feature = "smol")]
+        self.inner_task.cancel().await;
+        #[cfg(feature = "tokio")]
+        self.inner_task.abort();
+    }
+}
+
+impl<T> Future for Task<T> {
+    type Output = Result<T, Error>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        #[cfg(feature = "smol")]
+        let result = smol::Task::poll(Pin::new(&mut self.inner_task), cx);
+        #[cfg(feature = "tokio")]
+        let result = tokio::task::JoinHandle::poll(Pin::new(&mut self.inner_task), cx);
+
+        #[cfg(feature = "smol")]
+        return result.map(Ok);
+
+        #[cfg(feature = "tokio")]
+        return result.map_err(|e| e.into());
+    }
+}
+
+#[cfg(feature = "smol")]
+impl<T> From<smol::Task<T>> for Task<T> {
+    fn from(t: smol::Task<T>) -> Task<T> {
+        Task { inner_task: t }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl<T> From<tokio::task::JoinHandle<T>> for Task<T> {
+    fn from(t: tokio::task::JoinHandle<T>) -> Task<T> {
+        Task { inner_task: t }
+    }
+}
diff --git a/core/src/async_runtime/timer.rs b/core/src/async_runtime/timer.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/core/src/async_runtime/timer.rs
@@ -0,0 +1 @@
+