overlay_manager.h

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namespace pr_bgl
{

template <class GCore, class GOver, class OverVertexMap, class OverEdgeMap>
class overlay_manager
{
public:

   GCore & gcore;
   GOver & gover;
   OverVertexMap over_vertex_map;
   OverEdgeMap over_edge_map;
   bool is_applied;
   
   overlay_manager(
         GCore & gcore,
         GOver & gover,
         OverVertexMap over_vertex_map,
         OverEdgeMap over_edge_map):
      gcore(gcore),
      gover(gover),
      over_vertex_map(over_vertex_map),
      over_edge_map(over_edge_map),
      is_applied(false)
   {
   }
   
   // keep track of order of vertices and edges that have been applied
   std::vector<typename boost::graph_traits<GOver>::vertex_descriptor> applied_vertices;
   std::vector<typename boost::graph_traits<GOver>::edge_descriptor> applied_edges;
   
   void apply()
   {
      assert(is_applied == false);
      // copy non-anchor VERTICES first
      typename boost::graph_traits<GOver>::vertex_iterator vi, vi_end;
      for (boost::tie(vi,vi_end)=vertices(gover); vi!=vi_end; ++vi)
      {
         // skip anchor vertices (they're already added, no need to copy anything either)
         if (get(over_vertex_map, *vi) != boost::graph_traits<GCore>::null_vertex())
            continue;
         // ok, need to add this vertex to core graph!
         typename boost::graph_traits<GCore>::vertex_descriptor vcore = add_vertex(gcore);
         put(over_vertex_map, *vi, vcore);
         applied_vertices.push_back(*vi);
         // copy data?
      }
      // next, copy all edges
      typename boost::graph_traits<GOver>::edge_iterator ei, ei_end;
      for (boost::tie(ei,ei_end)=edges(gover); ei!=ei_end; ++ei)
      {
         // ok, need to add this edge to core graph!
         typename boost::graph_traits<GCore>::edge_descriptor ecore
            = add_edge(get(over_vertex_map, source(*ei,gover)),
                       get(over_vertex_map, target(*ei,gover)), gcore).first;
         put(over_edge_map, *ei, ecore);
         applied_edges.push_back(*ei);
         // copy data?
      }
      is_applied = true;
   }
   
   void unapply()
   {
      assert(is_applied == true);
      // remove edges in reverse order
      while (applied_edges.size())
      {
         typename boost::graph_traits<GOver>::edge_descriptor eover = applied_edges.back();
         applied_edges.pop_back();
         // TODO: copy data back?
         typename boost::graph_traits<GCore>::edge_descriptor ecore = get(over_edge_map, eover);
         remove_edge(ecore, gcore);
      }
      // remove vertices in reverse order
      while (applied_vertices.size())
      {
         typename boost::graph_traits<GOver>::vertex_descriptor vover = applied_vertices.back();
         applied_vertices.pop_back();
         // TODO: copy data back?
         typename boost::graph_traits<GCore>::vertex_descriptor vcore = get(over_vertex_map, vover);
         remove_vertex(vcore, gcore);
         // reset vertex pointer so over vertex is known to be a non-anchor vertex
         put(over_vertex_map, vover, boost::graph_traits<GCore>::null_vertex());
      }
      is_applied = false;
   }
};

} // namespace pr_bgl