feat: add RNTuple with inherited structs

dev/make-root/rntuple_class_inheritance.C

@@ -0,0 +1,98 @@
+#include <ROOT/RNTupleModel.hxx>
+#include <ROOT/RNTupleWriter.hxx>
+
+#include <string>
+#include <vector>
+
+using ROOT::RNTupleModel;
+using ROOT::RNTupleWriter;
+
+struct BaseA {
+  int              base_a1;
+  double           base_a2;
+  std::vector<int> base_a3;
+};
+
+struct BaseB {
+  double base_b;
+};
+
+struct Child : public BaseA {
+  int    child_1;
+  double child_2;
+};
+
+struct GrandChild : public Child {
+  int    grandchild_1;
+  double grandchild_2;
+};
+
+struct MultiParent : public BaseA, BaseB {
+  int    multi_parent_1;
+  double multi_parent_2;
+};
+
+struct MultiGrandParent : public Child, MultiParent {
+  int    multi_grand_parent1;
+  double multi_grand_parent2;
+};
+
+void fill_BaseA( BaseA& obj, int i ) {
+  obj.base_a1 = i;
+  obj.base_a2 = i * 0.1;
+  obj.base_a3.clear();
+  for ( int j = 0; j < 3; j++ ) { obj.base_a3.push_back( i * j ); }
+}
+
+void fill_BaseB( BaseB& obj, int i ) { obj.base_b = i * 10.0; }
+
+void fill_Child( Child& obj, int i ) {
+  fill_BaseA( obj, i );
+  obj.child_1 = i * 2;
+  obj.child_2 = i * 20.0;
+}
+
+void fill_GrandChild( GrandChild& obj, int i ) {
+  fill_Child( obj, i );
+  obj.grandchild_1 = i * 3;
+  obj.grandchild_2 = i * 30;
+}
+
+void fill_MultiParent( MultiParent& obj, int i ) {
+  fill_BaseA( obj, i );
+  fill_BaseB( obj, i );
+  obj.multi_parent_1 = i * 4;
+  obj.multi_parent_2 = i * 40.0;
+}
+
+void fill_MultiGrandParent( MultiGrandParent& obj, int i ) {
+  fill_Child( obj, i );
+  fill_MultiParent( obj, i );
+  obj.multi_grand_parent1 = i * 5;
+  obj.multi_grand_parent2 = i * 50.0;
+}
+
+void rntuple_class_inheritance() {
+  std::string fname{ "test_class_inheritance_rntuple_v1-0-0-1.root" };
+
+  auto model = RNTupleModel::Create();
+
+  auto field_child             = model->MakeField<Child>( "child" );
+  auto field_grandchild        = model->MakeField<GrandChild>( "grandchild" );
+  auto field_multi_parent      = model->MakeField<MultiParent>( "multi_parent" );
+  auto field_multi_grandparent = model->MakeField<MultiGrandParent>( "multi_grandparent" );
+
+  auto writer = RNTupleWriter::Recreate( std::move( model ), "rntpl", fname );
+
+  for ( int i = 0; i < 10; i++ )
+  {
+    fill_Child( *field_child, i );
+    fill_GrandChild( *field_grandchild, i );
+    fill_MultiParent( *field_multi_parent, i );
+    fill_MultiGrandParent( *field_multi_grandparent, i );
+
+    writer->Fill();
+  }
+
+  writer.reset();
+}