embassy/channel: use heapless::Deque.

embassy/Cargo.toml

@@ -42,6 +42,7 @@ embassy-traits  = { version = "0.1.0", path = "../embassy-traits"}
 atomic-polyfill  = "0.1.3"
 critical-section = "0.2.1"
 embedded-hal = "0.2.6"
+heapless = "0.7.5"
 
 [dev-dependencies]
 embassy = { path = ".", features = ["executor-agnostic"] }

embassy/src/channel/mpsc.rs

@@ -40,14 +40,13 @@
 use core::cell::UnsafeCell;
 use core::fmt;
 use core::marker::PhantomData;
-use core::mem::MaybeUninit;
 use core::pin::Pin;
-use core::ptr;
 use core::task::Context;
 use core::task::Poll;
 use core::task::Waker;
 
 use futures::Future;
+use heapless::Deque;
 
 use crate::blocking_mutex::{CriticalSectionMutex, Mutex, NoopMutex, ThreadModeMutex};
 use crate::waitqueue::WakerRegistration;
@@ -446,10 +445,7 @@ impl<T> defmt::Format for TrySendError<T> {
 }
 
 struct ChannelState<T, const N: usize> {
-    buf: [MaybeUninit<UnsafeCell<T>>; N],
-    read_pos: usize,
-    write_pos: usize,
-    full: bool,
+    queue: Deque<T, N>,
     closed: bool,
     receiver_registered: bool,
     senders_registered: u32,
@@ -458,14 +454,9 @@ struct ChannelState<T, const N: usize> {
 }
 
 impl<T, const N: usize> ChannelState<T, N> {
-    const INIT: MaybeUninit<UnsafeCell<T>> = MaybeUninit::uninit();
-
     const fn new() -> Self {
         ChannelState {
-            buf: [Self::INIT; N],
-            read_pos: 0,
-            write_pos: 0,
-            full: false,
+            queue: Deque::new(),
             closed: false,
             receiver_registered: false,
             senders_registered: 0,
@@ -479,17 +470,16 @@ impl<T, const N: usize> ChannelState<T, N> {
     }
 
     fn try_recv_with_context(&mut self, cx: Option<&mut Context<'_>>) -> Result<T, TryRecvError> {
-        if self.read_pos != self.write_pos || self.full {
-            if self.full {
-                self.full = false;
+        if self.queue.is_full() {
             self.senders_waker.wake();
         }
-            let message = unsafe { (self.buf[self.read_pos]).assume_init_mut().get().read() };
-            self.read_pos = (self.read_pos + 1) % self.buf.len();
+
+        if let Some(message) = self.queue.pop_front() {
             Ok(message)
         } else if !self.closed {
-            cx.into_iter()
-                .for_each(|cx| self.set_receiver_waker(&cx.waker()));
+            if let Some(cx) = cx {
+                self.set_receiver_waker(cx.waker());
+            }
             Err(TryRecvError::Empty)
         } else {
             Err(TryRecvError::Closed)
@@ -505,22 +495,21 @@ impl<T, const N: usize> ChannelState<T, N> {
         message: T,
         cx: Option<&mut Context<'_>>,
     ) -> Result<(), TrySendError<T>> {
-        if !self.closed {
-            if !self.full {
-                self.buf[self.write_pos] = MaybeUninit::new(message.into());
-                self.write_pos = (self.write_pos + 1) % self.buf.len();
-                if self.write_pos == self.read_pos {
-                    self.full = true;
+        if self.closed {
+            return Err(TrySendError::Closed(message));
         }
+
+        match self.queue.push_back(message) {
+            Ok(()) => {
                 self.receiver_waker.wake();
+
                 Ok(())
-            } else {
+            }
+            Err(message) => {
                 cx.into_iter()
                     .for_each(|cx| self.set_senders_waker(&cx.waker()));
                 Err(TrySendError::Full(message))
             }
-        } else {
-            Err(TrySendError::Closed(message))
         }
     }
 
@@ -585,16 +574,6 @@ impl<T, const N: usize> ChannelState<T, N> {
     }
 }
 
-impl<T, const N: usize> Drop for ChannelState<T, N> {
-    fn drop(&mut self) {
-        while self.read_pos != self.write_pos || self.full {
-            self.full = false;
-            unsafe { ptr::drop_in_place(self.buf[self.read_pos].as_mut_ptr()) };
-            self.read_pos = (self.read_pos + 1) % N;
-        }
-    }
-}
-
 /// A a bounded mpsc channel for communicating between asynchronous tasks
 /// with backpressure.
 ///
@@ -676,15 +655,7 @@ mod tests {
     use super::*;
 
     fn capacity<T, const N: usize>(c: &ChannelState<T, N>) -> usize {
-        if !c.full {
-            if c.write_pos > c.read_pos {
-                (c.buf.len() - c.write_pos) + c.read_pos
-            } else {
-                (c.buf.len() - c.read_pos) + c.write_pos
-            }
-        } else {
-            0
-        }
+        c.queue.capacity() - c.queue.len()
     }
 
     #[test]