split `embassy-util` into `embassy-futures`, `embassy-sync`.

1 files changed, 33 insertions, 0 deletions

diff --git a/embassy-sync/src/waitqueue/multi_waker.rs b/embassy-sync/src/waitqueue/multi_waker.rs
new file mode 100644
index 000000000..325d2cb3a
--- /dev/null
+++ b/embassy-sync/src/waitqueue/multi_waker.rs
@@ -0,0 +1,33 @@
+use core::task::Waker;
+
+use super::WakerRegistration;
+
+/// Utility struct to register and wake multiple wakers.
+pub struct MultiWakerRegistration<const N: usize> {
+    wakers: [WakerRegistration; N],
+}
+
+impl<const N: usize> MultiWakerRegistration<N> {
+    /// Create a new empty instance
+    pub const fn new() -> Self {
+        const WAKER: WakerRegistration = WakerRegistration::new();
+        Self { wakers: [WAKER; N] }
+    }
+
+    /// Register a waker. If the buffer is full the function returns it in the error
+    pub fn register<'a>(&mut self, w: &'a Waker) -> Result<(), &'a Waker> {
+        if let Some(waker_slot) = self.wakers.iter_mut().find(|waker_slot| !waker_slot.occupied()) {
+            waker_slot.register(w);
+            Ok(())
+        } else {
+            Err(w)
+        }
+    }
+
+    /// Wake all registered wakers. This clears the buffer
+    pub fn wake(&mut self) {
+        for waker_slot in self.wakers.iter_mut() {
+            waker_slot.wake()
+        }
+    }
+}