allow default constructed DataAccessors

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project aspires to adhere to [Semantic Versioning](https://semver.org/s
 ## Unreleased 
 
 ### Added
+- Added public default and copy constructor to DataAccessor. Enables more flexibility with initializing DataAccessors from Nodes.
 
 #### General
 - Added Node.name(), Node.path(), Schema.name(), and Schema.path() to Python API.

src/libs/conduit/conduit_data_accessor.cpp

@@ -23,7 +23,7 @@ namespace conduit
 
 //-----------------------------------------------------------------------------
 //
-// -- conduit::DataArray public methods --
+// -- conduit::DataAccessor public methods --
 //
 //-----------------------------------------------------------------------------
 
@@ -34,6 +34,14 @@ DataAccessor<T>::DataAccessor()
   m_dtype()
 {}
 
+//---------------------------------------------------------------------------//
+template <typename T>
+DataAccessor<T>::DataAccessor(const DataAccessor<T> &accessor)
+: m_data(accessor.m_data),
+  m_dtype(accessor.m_dtype)
+{}
+
+
 //---------------------------------------------------------------------------//
 template <typename T> 
 DataAccessor<T>::DataAccessor(void *data, const DataType &dtype)

src/libs/conduit/conduit_data_accessor.hpp

@@ -49,6 +49,10 @@ class CONDUIT_API DataAccessor
 //-----------------------------------------------------------------------------
 // Construction and Destruction
 //-----------------------------------------------------------------------------
+        /// Default constructor
+        DataAccessor();
+        /// Copy constructor
+        DataAccessor(const DataAccessor<T> &accessor);
         /// Access a pointer to raw data according to dtype description.
         DataAccessor(void *data, const DataType &dtype);
         /// Access a const pointer to raw data according to dtype description.
@@ -92,7 +96,6 @@ class CONDUIT_API DataAccessor
 // -- conduit::DataAccessor private data members --
 //
 //-----------------------------------------------------------------------------
-    DataAccessor();
     /// holds data (always external, never allocated)
     void           *m_data;
     /// holds data description

src/tests/conduit/t_conduit_data_accessor.cpp

@@ -186,6 +186,22 @@ TEST(conduit_data_accessor, as_cstyle)
 
 }
 
+//-----------------------------------------------------------------------------
+TEST(conduit_data_accessor, default_construct)
+{
+    index_t_accessor n_acc;
+    Node n;
+    n.set({-1,2,-3,4,-5});
+
+    n_acc = n.value();
+    EXPECT_EQ(n_acc[0],(index_t)(-1));
+    EXPECT_EQ(n_acc[1],(index_t)( 2));
+    EXPECT_EQ(n_acc[2],(index_t)(-3));
+    EXPECT_EQ(n_acc[3],(index_t)( 4));
+    EXPECT_EQ(n_acc[4],(index_t)(-5));
+}
+
+