DynamicVector, FieldVector: add `data` member function

dune/common/dynvector.hh

@@ -156,6 +156,18 @@ namespace Dune {
       return _data[i];
     }
 
+    //! return pointer to underlying array
+    K* data() noexcept
+    {
+      return _data.data();
+    }
+
+    //! return pointer to underlying array
+    const K* data() const noexcept
+    {
+      return _data.data();
+    }
+
     const container_type &container () const { return _data; }
     container_type &container () { return _data; }
   };

dune/common/fvector.hh

@@ -196,6 +196,18 @@ namespace Dune {
       DUNE_ASSERT_BOUNDS(i < SIZE);
       return _data[i];
     }
+
+    //! return pointer to underlying array
+    K* data() noexcept
+    {
+      return _data.data();
+    }
+
+    //! return pointer to underlying array
+    const K* data() const noexcept
+    {
+      return _data.data();
+    }
   };
 
   /** \brief Read a FieldVector from an input stream
@@ -333,6 +345,18 @@ namespace Dune {
       return _data;
     }
 
+    //! return pointer to underlying array
+    K* data() noexcept
+    {
+      return &_data;
+    }
+
+    //! return pointer to underlying array
+    const K* data() const noexcept
+    {
+      return &_data;
+    }
+
     //===== conversion operator
 
     /** \brief Conversion operator */

dune/common/test/fvectortest.cc

@@ -128,6 +128,7 @@ struct FieldVectorMainTestCommons
     if (w.size() > 0) {
       FVECTORTEST_ASSERT(!w.empty());
       FVECTORTEST_ASSERT(std::addressof(w[0]) == std::addressof(w.front()));
+      FVECTORTEST_ASSERT(std::addressof(w[0]) == w.data());
       FVECTORTEST_ASSERT(std::addressof(w[d-1]) == std::addressof(w.back()));
     }
   }