POC: allow custom executors

embassy-executor/src/arch/wasm.rs

@@ -1,6 +1,9 @@
 #[cfg(feature = "executor-interrupt")]
 compile_error!("`executor-interrupt` is not supported with `arch-wasm`.");
 
+#[cfg(not(feature = "thread-context"))]
+compile_error!("`arch-wasm` requires `thread-context`.");
+
 #[cfg(feature = "executor-thread")]
 pub use thread::*;
 #[cfg(feature = "executor-thread")]
@@ -14,14 +17,13 @@ mod thread {
     use wasm_bindgen::prelude::*;
 
     use crate::raw::util::UninitCell;
-    use crate::raw::{Pender, PenderInner};
+    use crate::raw::{OpaqueThreadContext, Pender, PenderInner};
     use crate::{raw, Spawner};
 
-    /// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
-    pub struct Executor {
-        inner: raw::Executor,
-        ctx: &'static WasmContext,
-        not_send: PhantomData<*mut ()>,
+    #[export_name = "__thread_mode_pender"]
+    fn __thread_mode_pender(context: OpaqueThreadContext) {
+        let signaler: &'static WasmContext = unsafe { std::mem::transmute(context) };
+        let _ = signaler.promise.then(unsafe { signaler.closure.as_mut() });
     }
 
     pub(crate) struct WasmContext {
@@ -29,16 +31,6 @@ mod thread {
         closure: UninitCell<Closure<dyn FnMut(JsValue)>>,
     }
 
-    #[derive(Copy, Clone)]
-    pub(crate) struct ThreadPender(&'static WasmContext);
-
-    impl ThreadPender {
-        #[allow(unused)]
-        pub(crate) fn pend(self) {
-            let _ = self.0.promise.then(unsafe { self.0.closure.as_mut() });
-        }
-    }
-
     impl WasmContext {
         pub fn new() -> Self {
             Self {
@@ -48,14 +40,23 @@ mod thread {
         }
     }
 
+    /// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
+    pub struct Executor {
+        inner: raw::Executor,
+        ctx: &'static WasmContext,
+        not_send: PhantomData<*mut ()>,
+    }
+
     impl Executor {
         /// Create a new Executor.
         pub fn new() -> Self {
             let ctx = &*Box::leak(Box::new(WasmContext::new()));
             Self {
-                inner: raw::Executor::new(Pender(PenderInner::Thread(ThreadPender(ctx)))),
-                not_send: PhantomData,
+                inner: raw::Executor::new(Pender(PenderInner::Thread(OpaqueThreadContext(
+                    ctx as *const _ as usize,
+                )))),
                 ctx,
+                not_send: PhantomData,
             }
         }