add file-version utility

dune/gmsh4/utility/version.hh

+#pragma once
+
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <vector>
+
+#include <dune/common/exceptions.hh>
+#include "string.hh"
+
+namespace Dune
+{
+  namespace Gmsh4
+  {
+    /// Return a version tuple identifying the .msh file format version
+    inline std::vector<int> fileVersion(std::string filename)
+    {
+      std::ifstream file(filename, std::ios_base::in);
+      std::string section;
+      file >> section;
+
+      if (section != "$MeshFormat")
+        DUNE_THROW(Dune::IOError, "Invalid header of msh file.");
+
+      std::string version;
+      int file_type = -1;
+      int data_size = -1;
+      file >> version >> file_type >> data_size;
+
+      if (std::stod(version) <= 0.0)
+        DUNE_THROW(Dune::IOError, "Invalid version number in msh file.");
+
+      if (file_type != 0 and file_type != 1)
+        DUNE_THROW(Dune::IOError, "Invalid file-type: 0 for ASCII mode, 1 for binary mode.");
+
+      if (data_size < 4 || data_size > 16)
+        DUNE_THROW(Dune::IOError, "Invalid data-size range: should be in {4, 16}");
+
+      std::vector<int> version_tuple;
+      split(version.begin(), version.end(), '.', [&](auto first, auto last) {
+        version_tuple.push_back(std::stoi(std::string{first,last}));
+      });
+
+      return version_tuple;
+    }
+  }
+}

src/gmsh4reader.cc

@@ -19,6 +19,7 @@
 #include <dune/gmsh4/gmsh4reader.hh>
 #include <dune/gmsh4/gridcreators/continuousgridcreator.hh>
 #include <dune/gmsh4/gridcreators/discontinuousgridcreator.hh>
+#include <dune/gmsh4/utility/version.hh>
 
 #include <dune/alugrid/grid.hh>
 
@@ -34,6 +35,10 @@ int main(int argc, char** argv)
   using GridType = Dune::ALUGrid<2,2,Dune::simplex,Dune::conforming>;
   using GridView = typename GridType::LeafGridView;
   {
+    auto ver = Gmsh4::fileVersion(GRID_PATH "/square.msh");
+    if (ver[0] != 4)
+      DUNE_THROW(Dune::Exception, "Wrong .msh file version");
+
     auto gridPtr = Gmsh4Reader<GridType>::createGridFromFile(GRID_PATH "/square.msh");
     auto& grid = *gridPtr;
 
@@ -50,6 +55,10 @@ int main(int argc, char** argv)
   }
 
   {
+    auto ver = Gmsh4::fileVersion(GRID_PATH "/square_part2.msh");
+    if (ver[0] != 4)
+      DUNE_THROW(Dune::Exception, "Wrong .msh file version");
+
     auto gridPtr = Gmsh4Reader<GridType>::createGridFromFile(GRID_PATH "/square_part2.msh");
     auto& grid = *gridPtr;