move dummy executor out to wiggle:: for reuse

crates/wiggle/src/lib.rs

@@ -953,3 +953,40 @@ impl From<GuestError> for Trap {
         Trap::String(err.to_string())
     }
 }
+
+pub unsafe fn run_in_dummy_executor<F: std::future::Future>(future: F) -> F::Output {
+    use std::pin::Pin;
+    use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+
+    let mut f = Pin::from(Box::new(future));
+    let waker = dummy_waker();
+    let mut cx = Context::from_waker(&waker);
+    match f.as_mut().poll(&mut cx) {
+        Poll::Ready(val) => return val,
+        Poll::Pending => {
+            panic!("Cannot wait on pending future: must enable wiggle \"async\" future and execute on an async Store")
+        }
+    }
+
+    fn dummy_waker() -> Waker {
+        return unsafe { Waker::from_raw(clone(5 as *const _)) };
+
+        unsafe fn clone(ptr: *const ()) -> RawWaker {
+            assert_eq!(ptr as usize, 5);
+            const VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake_by_ref, drop);
+            RawWaker::new(ptr, &VTABLE)
+        }
+
+        unsafe fn wake(ptr: *const ()) {
+            assert_eq!(ptr as usize, 5);
+        }
+
+        unsafe fn wake_by_ref(ptr: *const ()) {
+            assert_eq!(ptr as usize, 5);
+        }
+
+        unsafe fn drop(ptr: *const ()) {
+            assert_eq!(ptr as usize, 5);
+        }
+    }
+}