Merge #1118

1118: Atomic ringbuf fixes r=Dirbaio a=Dirbaio

bors r+

Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>

embassy-hal-common/src/atomic_ring_buffer.rs

@@ -82,10 +82,11 @@ impl RingBuffer {
     }
 
     pub fn is_full(&self) -> bool {
+        let len = self.len.load(Ordering::Relaxed);
         let start = self.start.load(Ordering::Relaxed);
         let end = self.end.load(Ordering::Relaxed);
 
-        self.wrap(end + 1) == start
+        len == 0 || self.wrap(end + 1) == start
     }
 
     pub fn is_empty(&self) -> bool {
@@ -134,6 +135,14 @@ impl<'a> Writer<'a> {
         n != 0
     }
 
+    /// Get a buffer where data can be pushed to.
+    ///
+    /// Equivalent to [`Self::push_buf`] but returns a slice.
+    pub fn push_slice(&mut self) -> &mut [u8] {
+        let (data, len) = self.push_buf();
+        unsafe { slice::from_raw_parts_mut(data, len) }
+    }
+
     /// Get a buffer where data can be pushed to.
     ///
     /// Write data to the start of the buffer, then call `push_done` with
@@ -154,7 +163,7 @@ impl<'a> Writer<'a> {
         let end = self.0.end.load(Ordering::Relaxed);
 
         let n = if start <= end {
-            len - end - (start == 0) as usize
+            len - end - (start == 0 && len != 0) as usize
         } else {
             start - end - 1
         };
@@ -203,6 +212,14 @@ impl<'a> Reader<'a> {
         res
     }
 
+    /// Get a buffer where data can be popped from.
+    ///
+    /// Equivalent to [`Self::pop_buf`] but returns a slice.
+    pub fn pop_slice(&mut self) -> &mut [u8] {
+        let (data, len) = self.pop_buf();
+        unsafe { slice::from_raw_parts_mut(data, len) }
+    }
+
     /// Get a buffer where data can be popped from.
     ///
     /// Read data from the start of the buffer, then call `pop_done` with
@@ -328,4 +345,23 @@ mod tests {
             assert_eq!(rb.is_full(), true);
         }
     }
+
+    #[test]
+    fn zero_len() {
+        let rb = RingBuffer::new();
+        unsafe {
+            assert_eq!(rb.is_empty(), true);
+            assert_eq!(rb.is_full(), true);
+
+            rb.writer().push(|buf| {
+                assert_eq!(0, buf.len());
+                0
+            });
+
+            rb.reader().pop(|buf| {
+                assert_eq!(0, buf.len());
+                0
+            });
+        }
+    }
 }