CircularBuffer(): get available transactions

This implementation returns the number of available (stored) transactions in the buffer

platform/CircularBuffer.h

@@ -104,7 +104,24 @@ public:
         _full = false;
         core_util_critical_section_exit();
     }
-
+    
+    /** Returns the number of available transactions the buffer contains */
+    CounterType available() {
+        core_util_critical_section_enter();
+        CounterType elements;
+        if (!_full)
+        {
+            if (_head < _tail)
+                elements = BufferSize + _head - _tail;
+            else
+                elements = _head - _tail;
+        }
+        else
+            elements = BufferSize;
+        core_util_critical_section_exit();
+        return elements;
+    }
+    
 private:
     T _pool[BufferSize];
     volatile CounterType _head;