frame: added bool function returning whether the frame is allocated or not

app/codec/frame.cpp

@@ -145,6 +145,11 @@ void Frame::allocate()
   }
 }
 
+bool Frame::is_allocated() const
+{
+  return !data_.isEmpty();
+}
+
 void Frame::destroy()
 {
   data_.clear();

app/codec/frame.h

@@ -109,6 +109,11 @@ public:
    */
   void allocate();
 
+  /**
+   * @brief Return whether the frame is allocated or not
+   */
+  bool is_allocated() const;
+
   /**
    * @brief Destroy a memory buffer allocated with allocate()
    */