RhodeCode

    ///

    /// This function gives back true if the given arc is valid,

    /// ie. it is a real arc of the graph.

    ///

    /// \warning A removed arc (using Snapshot) could become valid again

    /// when new edges are added to the graph.

    bool valid(Arc a) const { return Parent::valid(a); }

    /// \brief Edge validity check

    ///

    /// This function gives back true if the given edge is valid,

    /// ie. it is a real edge of the graph.

    ///

    /// \warning A removed edge (using Snapshot) could become valid again

    /// when new edges are added to the graph.

    bool valid(Edge e) const { return Parent::valid(e); }

    ///Clear the graph.

    ///Erase all the nodes and edges from the graph.

    ///

    void clear() {

      Parent::clear();

    }

  public:

    class Snapshot;

  protected:

    void saveSnapshot(Snapshot &s)

    {

      s._graph = this;

      s.node_num = nodes.size();

      s.arc_num = arcs.size();

    }

    void restoreSnapshot(const Snapshot &s)

    {

      while(s.arc_num<arcs.size()) {

        int n=arcs.size()-1;

        Edge arc=edgeFromId(n/2);

        Parent::notifier(Edge()).erase(arc);

        std::vector<Arc> dir;

        dir.push_back(arcFromId(n));

        dir.push_back(arcFromId(n-1));

        Parent::notifier(Arc()).erase(dir);

        arcs.pop_back();

        arcs.pop_back();

      }

      while(s.node_num<nodes.size()) {

        int n=nodes.size()-1;

        Node node = nodeFromId(n);

        Parent::notifier(Node()).erase(node);

        nodes.pop_back();

      }

    }

  public:

    ///Class to make a snapshot of the digraph and to restrore to it later.

    ///Class to make a snapshot of the digraph and to restrore to it later.

    ///

    ///The newly added nodes and arcs can be removed using the

    ///restore() function.

    ///

    ///\note After you restore a state, you cannot restore

    ///a later state, in other word you cannot add again the arcs deleted

    ///by restore() using another one Snapshot instance.

    ///

    ///\warning If you do not use correctly the snapshot that can cause

    ///either broken program, invalid state of the digraph, valid but

    ///not the restored digraph or no change. Because the runtime performance

    ///the validity of the snapshot is not stored.

    class Snapshot

    {

      SmartGraph *_graph;

    protected:

      friend class SmartGraph;

      unsigned int node_num;

      unsigned int arc_num;

    public:

      ///Default constructor.

      ///Default constructor.

      ///To actually make a snapshot you must call save().

      ///

      Snapshot() : _graph(0) {}

      ///Constructor that immediately makes a snapshot

      ///This constructor immediately makes a snapshot of the digraph.

      ///\param graph The digraph we make a snapshot of.

      Snapshot(SmartGraph &graph) {

        graph.saveSnapshot(*this);