RhodeCode

/// \ingroup nauty_group

/// \file

/// \brief Nauty file reader.

namespace lemon {

  /// \ingroup nauty_group

  ///

  /// \brief Nauty file reader

  ///

  /// The \e geng program is in the \e gtools suite of the nauty

  /// package. This tool can generate all non-isomorphic undirected

  /// graphs with given node number from several classes (for example,

  /// general, connected, biconnected, triangle-free, 4-cycle-free,

  /// bipartite and graphs with given edge number and degree

  /// constraints). This function reads a \e nauty \e graph6 \e format

  /// line from the given stream and builds it in the given graph.

  ///

  /// The site of nauty package: http://cs.anu.edu.au/~bdm/nauty/

  ///

  /// For example, the number of all non-isomorphic connected graphs

  /// can be computed with following code.

  ///\code

  /// int num = 0;

  /// SmartGraph graph;

  ///   if (pc.run()) ++num;

  /// }

  /// std::cout << "Number of planar graphs: " << num << std::endl;

  ///\endcode

  ///

  /// The nauty files are quite huge, therefore instead of the direct

  /// file generation the pipelining is recommended.

  ///\code

  /// ./geng -c 10 | ./num_of_pg

  ///\endcode

  template <typename Graph>

    graph.clear();

    std::string line;

    if (getline(is, line)) {

      int index = 0;

      int n;

      if (line[index] == '>') {

        index += 10;

      }

      char c = line[index++]; c -= 63;

      if (c != 63) {

        n = int(c);

      } else {

        c = line[index++]; c -= 63;

        n = (int(c) << 12);

        c = line[index++]; c -= 63;

        n |= (int(c) << 6);

        c = line[index++]; c -= 63;

        n |= int(c);

      }