Add support for checkpointing to VTKSequenceWriter

In order to support checkpointing, we need to be able to set an initial list of already written times and to read that list from the writer.

dune/grid/io/file/vtk/vtksequencewriter.hh

@@ -39,13 +39,15 @@ namespace Dune {
      *                   piece as well as the parallel collection file.
      */
     VTKSequenceWriter ( std::shared_ptr<VTKWriter<GridView> > vtkWriter,
-                        const std::string& name )
+                        const std::string& name,
+                        const std::vector<double>& timesteps = std::vector<double>())
       : VTKSequenceWriterBase<GridView>(vtkWriter,
                                         name,
                                         "",
                                         "",
                                         vtkWriter->gridView_.comm().rank(),
-                                        vtkWriter->gridView_.comm().size())
+                                        vtkWriter->gridView_.comm().size(),
+                                        timesteps)
     {}
 
     /** \brief Constructor with a given VTKWriter or SubsamplingVTKWriter
@@ -68,13 +70,15 @@ namespace Dune {
     VTKSequenceWriter ( std::shared_ptr<VTKWriter<GridView> > vtkWriter,
                         const std::string& name,
                         const std::string& path,
-                        const std::string& extendpath )
+                        const std::string& extendpath,
+                        const std::vector<double>& timesteps = std::vector<double>())
       : VTKSequenceWriterBase<GridView>(vtkWriter,
                                         name,
                                         path,
                                         extendpath,
                                         vtkWriter->gridView_.comm().rank(),
-                                        vtkWriter->gridView_.comm().size())
+                                        vtkWriter->gridView_.comm().size(),
+                                        timesteps)
     {}
 
     /** \brief Constructor creating its own VTKWriter object
@@ -87,10 +91,12 @@ namespace Dune {
                                  const std::string& name,
                                  const std::string& path,
                                  const std::string& extendpath,
-                                 VTK::DataMode dm = VTK::conforming )
+                                 VTK::DataMode dm = VTK::conforming,
+                                 const std::vector<double>& timesteps = std::vector<double>())
       : VTKSequenceWriterBase<GridView>(std::make_shared<VTKWriter<GridView> >(gridView,dm),
                                         name,path,extendpath,
-                                        gridView.comm().rank(), gridView.comm().size())
+                                        gridView.comm().rank(), gridView.comm().size(),
+                                        timesteps)
     {}
 
     ~VTKSequenceWriter() {}