read cell offset and connectivity with flexible index type

dune/vtk/vtkreader.impl.hh

@@ -418,19 +418,33 @@ void VtkReader<Grid,Creator>::readCellsAppended (std::ifstream& input)
 {
   assert(numberOfCells_ > 0);
   auto types_data = dataArray_["types"];
-  auto dataArray_data = dataArray_["offsets"];
+  auto offsets_data = dataArray_["offsets"];
   auto connectivity_data = dataArray_["connectivity"];
 
   assert(types_data.type == Vtk::UINT8);
   readAppended(input, vec_types, types_data.offset);
   assert(vec_types.size() == numberOfCells_);
 
-  assert(dataArray_data.type == Vtk::INT64);
-  readAppended(input, vec_offsets, dataArray_data.offset);
+  if (offsets_data.type == Vtk::INT64)
+    readAppended(input, vec_offsets, offsets_data.offset);
+  else if (offsets_data.type == Vtk::INT32) {
+    std::vector<std::int32_t> offsets;
+    readAppended(input, offsets, offsets_data.offset);
+    vec_offsets.resize(offsets.size());
+    std::copy(offsets.begin(), offsets.end(), vec_offsets.begin());
+  }
+  else { DUNE_THROW(Dune::NotImplemented, "Unsupported DataType in Cell offsets."); }
   assert(vec_offsets.size() == numberOfCells_);
 
-  assert(connectivity_data.type == Vtk::INT64);
-  readAppended(input, vec_connectivity, connectivity_data.offset);
+  if (connectivity_data.type == Vtk::INT64)
+    readAppended(input, vec_connectivity, connectivity_data.offset);
+  else if (connectivity_data.type == Vtk::INT32) {
+    std::vector<std::int32_t> connectivity;
+    readAppended(input, connectivity, connectivity_data.offset);
+    vec_connectivity.resize(connectivity.size());
+    std::copy(connectivity.begin(), connectivity.end(), vec_connectivity.begin());
+  }
+  else { DUNE_THROW(Dune::NotImplemented, "Unsupported DataType in Cell connectivity."); }
   assert(vec_connectivity.size() == std::size_t(vec_offsets.back()));
 
   if (dataArray_.count("global_point_ids") > 0) {