add data interface to buffer adaptor

Author: wolfv

include/xtensor-python/pybuffer_adaptor.hpp

@@ -66,6 +66,9 @@ namespace xt
         const_reverse_iterator crbegin() const;
         const_reverse_iterator crend() const;
 
+        pointer data();
+        const_pointer data() const;
+
     private:
 
         pointer p_data;
@@ -258,6 +261,18 @@ namespace xt
     {
         return rend();
     }
+
+    template <class T>
+    inline auto pybuffer_adaptor<T>::data() -> pointer
+    {
+        return p_data;
+    }
+
+    template <class T>
+    inline auto pybuffer_adaptor<T>::data() const -> const_pointer
+    {
+        return p_data;
+    }
 
     template<class T>
     inline bool operator==(const pybuffer_adaptor<T>& x, const pybuffer_adaptor<T>& y)