3 files changed, 138 insertions, 33 deletions

diff --git a/embassy-sync/src/pubsub/mod.rs b/embassy-sync/src/pubsub/mod.rs
index adbf8cf02..af3d6db2a 100644
--- a/embassy-sync/src/pubsub/mod.rs
+++ b/embassy-sync/src/pubsub/mod.rs
@@ -248,13 +248,6 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
         })
     }
 
-    fn space(&self) -> usize {
-        self.inner.lock(|s| {
-            let s = s.borrow();
-            s.queue.capacity() - s.queue.len()
-        })
-    }
-
     fn unregister_subscriber(&self, subscriber_next_message_id: u64) {
         self.inner.lock(|s| {
             let mut s = s.borrow_mut();
@@ -268,6 +261,26 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
             s.unregister_publisher()
         })
     }
+
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
+    fn free_capacity(&self) -> usize {
+        self.free_capacity()
+    }
+
+    fn len(&self) -> usize {
+        self.len()
+    }
+
+    fn is_empty(&self) -> bool {
+        self.is_empty()
+    }
+
+    fn is_full(&self) -> bool {
+        self.is_full()
+    }
 }
 
 /// Internal state for the PubSub channel
@@ -439,8 +452,22 @@ trait SealedPubSubBehavior<T> {
     /// Publish a message immediately
     fn publish_immediate(&self, message: T);
 
-    /// The amount of messages that can still be published without having to wait or without having to lag the subscribers
-    fn space(&self) -> usize;
+    /// Returns the maximum number of elements the channel can hold.
+    fn capacity(&self) -> usize;
+
+    /// Returns the free capacity of the channel.
+    ///
+    /// This is equivalent to `capacity() - len()`
+    fn free_capacity(&self) -> usize;
+
+    /// Returns the number of elements currently in the channel.
+    fn len(&self) -> usize;
+
+    /// Returns whether the channel is empty.
+    fn is_empty(&self) -> bool;
+
+    /// Returns whether the channel is full.
+    fn is_full(&self) -> bool;
 
     /// Let the channel know that a subscriber has dropped
     fn unregister_subscriber(&self, subscriber_next_message_id: u64);
@@ -588,6 +615,7 @@ mod tests {
         assert_eq!(pub0.try_publish(0), Ok(()));
         assert_eq!(pub0.try_publish(0), Ok(()));
         assert_eq!(pub0.try_publish(0), Ok(()));
+        assert!(pub0.is_full());
         assert_eq!(pub0.try_publish(0), Err(0));
 
         drop(sub0);
@@ -620,32 +648,42 @@ mod tests {
     }
 
     #[futures_test::test]
-    async fn correct_space() {
+    async fn correct_len() {
         let channel = PubSubChannel::<NoopRawMutex, u32, 4, 4, 4>::new();
 
         let mut sub0 = channel.subscriber().unwrap();
         let mut sub1 = channel.subscriber().unwrap();
         let pub0 = channel.publisher().unwrap();
 
-        assert_eq!(pub0.space(), 4);
+        assert!(sub0.is_empty());
+        assert!(sub1.is_empty());
+        assert!(pub0.is_empty());
+        assert_eq!(pub0.free_capacity(), 4);
+        assert_eq!(pub0.len(), 0);
 
         pub0.publish(42).await;
 
-        assert_eq!(pub0.space(), 3);
+        assert_eq!(pub0.free_capacity(), 3);
+        assert_eq!(pub0.len(), 1);
 
         pub0.publish(42).await;
 
-        assert_eq!(pub0.space(), 2);
+        assert_eq!(pub0.free_capacity(), 2);
+        assert_eq!(pub0.len(), 2);
 
         sub0.next_message().await;
         sub0.next_message().await;
 
-        assert_eq!(pub0.space(), 2);
+        assert_eq!(pub0.free_capacity(), 2);
+        assert_eq!(pub0.len(), 2);
 
         sub1.next_message().await;
-        assert_eq!(pub0.space(), 3);
+        assert_eq!(pub0.free_capacity(), 3);
+        assert_eq!(pub0.len(), 1);
+
         sub1.next_message().await;
-        assert_eq!(pub0.space(), 4);
+        assert_eq!(pub0.free_capacity(), 4);
+        assert_eq!(pub0.len(), 0);
     }
 
     #[futures_test::test]
@@ -656,29 +694,29 @@ mod tests {
         let mut sub0 = channel.subscriber().unwrap();
         let mut sub1 = channel.subscriber().unwrap();
 
-        assert_eq!(4, pub0.space());
+        assert_eq!(4, pub0.free_capacity());
 
         pub0.publish(1).await;
         pub0.publish(2).await;
 
-        assert_eq!(2, channel.space());
+        assert_eq!(2, channel.free_capacity());
 
         assert_eq!(1, sub0.try_next_message_pure().unwrap());
         assert_eq!(2, sub0.try_next_message_pure().unwrap());
 
-        assert_eq!(2, channel.space());
+        assert_eq!(2, channel.free_capacity());
 
         drop(sub0);
 
-        assert_eq!(2, channel.space());
+        assert_eq!(2, channel.free_capacity());
 
         assert_eq!(1, sub1.try_next_message_pure().unwrap());
 
-        assert_eq!(3, channel.space());
+        assert_eq!(3, channel.free_capacity());
 
         drop(sub1);
 
-        assert_eq!(4, channel.space());
+        assert_eq!(4, channel.free_capacity());
     }
 
     struct CloneCallCounter(usize);
diff --git a/embassy-sync/src/pubsub/publisher.rs b/embassy-sync/src/pubsub/publisher.rs
index e1edc9eb9..26e2c63b7 100644
--- a/embassy-sync/src/pubsub/publisher.rs
+++ b/embassy-sync/src/pubsub/publisher.rs
@@ -43,12 +43,31 @@ impl<'a, PSB: PubSubBehavior<T> + ?Sized, T: Clone> Pub<'a, PSB, T> {
         self.channel.publish_with_context(message, None)
     }
 
-    /// The amount of messages that can still be published without having to wait or without having to lag the subscribers
+    /// Returns the maximum number of elements the ***channel*** can hold.
+    pub fn capacity(&self) -> usize {
+        self.channel.capacity()
+    }
+
+    /// Returns the free capacity of the ***channel***.
     ///
-    /// *Note: In the time between checking this and a publish action, other publishers may have had time to publish something.
-    /// So checking doesn't give any guarantees.*
-    pub fn space(&self) -> usize {
-        self.channel.space()
+    /// This is equivalent to `capacity() - len()`
+    pub fn free_capacity(&self) -> usize {
+        self.channel.free_capacity()
+    }
+
+    /// Returns the number of elements currently in the ***channel***.
+    pub fn len(&self) -> usize {
+        self.channel.len()
+    }
+
+    /// Returns whether the ***channel*** is empty.
+    pub fn is_empty(&self) -> bool {
+        self.channel.is_empty()
+    }
+
+    /// Returns whether the ***channel*** is full.
+    pub fn is_full(&self) -> bool {
+        self.channel.is_full()
     }
 }
 
@@ -124,12 +143,31 @@ impl<'a, PSB: PubSubBehavior<T> + ?Sized, T: Clone> ImmediatePub<'a, PSB, T> {
         self.channel.publish_with_context(message, None)
     }
 
-    /// The amount of messages that can still be published without having to wait or without having to lag the subscribers
+    /// Returns the maximum number of elements the ***channel*** can hold.
+    pub fn capacity(&self) -> usize {
+        self.channel.capacity()
+    }
+
+    /// Returns the free capacity of the ***channel***.
     ///
-    /// *Note: In the time between checking this and a publish action, other publishers may have had time to publish something.
-    /// So checking doesn't give any guarantees.*
-    pub fn space(&self) -> usize {
-        self.channel.space()
+    /// This is equivalent to `capacity() - len()`
+    pub fn free_capacity(&self) -> usize {
+        self.channel.free_capacity()
+    }
+
+    /// Returns the number of elements currently in the ***channel***.
+    pub fn len(&self) -> usize {
+        self.channel.len()
+    }
+
+    /// Returns whether the ***channel*** is empty.
+    pub fn is_empty(&self) -> bool {
+        self.channel.is_empty()
+    }
+
+    /// Returns whether the ***channel*** is full.
+    pub fn is_full(&self) -> bool {
+        self.channel.is_full()
     }
 }
 
diff --git a/embassy-sync/src/pubsub/subscriber.rs b/embassy-sync/src/pubsub/subscriber.rs
index f420a75f0..2e2bd26a9 100644
--- a/embassy-sync/src/pubsub/subscriber.rs
+++ b/embassy-sync/src/pubsub/subscriber.rs
@@ -65,10 +65,39 @@ impl<'a, PSB: PubSubBehavior<T> + ?Sized, T: Clone> Sub<'a, PSB, T> {
         }
     }
 
-    /// The amount of messages this subscriber hasn't received yet
+    /// The amount of messages this subscriber hasn't received yet. This is like [Self::len] but specifically
+    /// for this subscriber.
     pub fn available(&self) -> u64 {
         self.channel.available(self.next_message_id)
     }
+
+    /// Returns the maximum number of elements the ***channel*** can hold.
+    pub fn capacity(&self) -> usize {
+        self.channel.capacity()
+    }
+
+    /// Returns the free capacity of the ***channel***.
+    ///
+    /// This is equivalent to `capacity() - len()`
+    pub fn free_capacity(&self) -> usize {
+        self.channel.free_capacity()
+    }
+
+    /// Returns the number of elements currently in the ***channel***.
+    /// See [Self::available] for how many messages are available for this subscriber.
+    pub fn len(&self) -> usize {
+        self.channel.len()
+    }
+
+    /// Returns whether the ***channel*** is empty.
+    pub fn is_empty(&self) -> bool {
+        self.channel.is_empty()
+    }
+
+    /// Returns whether the ***channel*** is full.
+    pub fn is_full(&self) -> bool {
+        self.channel.is_full()
+    }
 }
 
 impl<'a, PSB: PubSubBehavior<T> + ?Sized, T: Clone> Drop for Sub<'a, PSB, T> {