Perform same len fix for iterators

src/ring_buffer/mod.rs

@@ -207,7 +207,7 @@ where
         let tail = self.tail.load_relaxed().into();
 
         if head > tail {
-            head - tail
+            self.capacity().into() + 1 - head + tail
         } else {
             tail - head
         }

tests/tsan.rs

@@ -172,3 +172,21 @@ fn len_properly_wraps() {
     rb.enqueue(4).unwrap();
     assert_eq!(rb.len(), 3);
 }
+
+#[test]
+fn iterator_properly_wraps() {
+    type N = U3;
+    let mut rb: RingBuffer<u8, N> = RingBuffer::new();
+
+    rb.enqueue(1).unwrap();
+    rb.dequeue();
+    rb.enqueue(2).unwrap();
+    rb.enqueue(3).unwrap();
+    rb.enqueue(4).unwrap();
+    let expected = [2, 3, 4];
+    let mut actual = [0, 0, 0];
+    for (idx, el) in rb.iter().enumerate() {
+        actual[idx] = *el;
+    }
+    assert_eq!(expected, actual)
+}