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boost/graph/named_graph.hpp

// Copyright (C) 2007 Douglas Gregor

// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

// Provides support for named vertices in graphs, allowing one to more
// easily associate unique external names (URLs, city names, employee
// ID numbers, etc.) with the vertices of a graph.
#ifndef BOOST_GRAPH_NAMED_GRAPH_HPP
#define BOOST_GRAPH_NAMED_GRAPH_HPP

#include <boost/config.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/optional.hpp>
#include <boost/throw_exception.hpp>
#include <stdexcept> // for std::runtime_error

namespace boost { namespace graph {

/*******************************************************************
 * User-customized traits                                          *
 *******************************************************************/

/**
 * @brief Trait used to extract the internal vertex name from a vertex
 * property.
 *
 * To enable the use of internal vertex names in a graph type,
 * specialize the @c internal_vertex_name trait for your graph
 * property (e.g., @c a City class, which stores information about the
 * vertices in a road map).
 */
template<typename VertexProperty>
struct internal_vertex_name
{
  /**
   *  The @c type field provides a function object that extracts a key
   *  from the @c VertexProperty. The function object type must have a
   *  nested @c result_type that provides the type of the key. For
   *  more information, see the @c KeyExtractor concept in the
   *  Boost.MultiIndex documentation: @c type must either be @c void
   *  (if @c VertexProperty does not have an internal vertex name) or
   *  a model of @c KeyExtractor.
   */
  typedef void type;
};

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
/**
 * Extract the internal vertex name from a @c property structure by
 * looking at its base.
 */
template<typename Tag, typename T, typename Base>
struct internal_vertex_name<property<Tag, T, Base> >
  : internal_vertex_name<Base> { };
#endif

/**
 * Construct an instance of @c VertexProperty directly from its
 * name. This function object should be used within the @c
 * internal_vertex_constructor trait.
 */
template<typename VertexProperty>
struct vertex_from_name
{
private:
  typedef typename internal_vertex_name<VertexProperty>::type extract_name_type;

  typedef typename remove_cv<
            typename remove_reference<
              typename extract_name_type::result_type>::type>::type
    vertex_name_type;

public:
  typedef vertex_name_type argument_type;
  typedef VertexProperty result_type;

  VertexProperty operator()(const vertex_name_type& name)
  {
    return VertexProperty(name);
  }
};

/**
 * Throw an exception whenever one tries to construct a @c
 * VertexProperty instance from its name.
 */
template<typename VertexProperty>
struct cannot_add_vertex
{
private:
  typedef typename internal_vertex_name<VertexProperty>::type extract_name_type;

  typedef typename remove_cv<
            typename remove_reference<
              typename extract_name_type::result_type>::type>::type
    vertex_name_type;

public:
  typedef vertex_name_type argument_type;
  typedef VertexProperty result_type;

  VertexProperty operator()(const vertex_name_type& name)
  {
      boost::throw_exception(std::runtime_error("add_vertex: "
                                                "unable to create a vertex from its name"));
  }
};

/**
 * @brief Trait used to construct an instance of a @c VertexProperty,
 * which is a class type that stores the properties associated with a
 * vertex in a graph, from just the name of that vertex property. This
 * operation is used when an operation is required to map from a
 * vertex name to a vertex descriptor (e.g., to add an edge outgoing
 * from that vertex), but no vertex by the name exists. The function
 * object provided by this trait will be used to add new vertices
 * based only on their names. Since this cannot be done for arbitrary
 * types, the default behavior is to throw an exception when this
 * routine is called, which requires that all named vertices be added
 * before adding any edges by name.
 */
template<typename VertexProperty>
struct internal_vertex_constructor
{
  /**
   * The @c type field provides a function object that constructs a
   * new instance of @c VertexProperty from the name of the vertex (as
   * determined by @c internal_vertex_name). The function object shall
   * accept a vertex name and return a @c VertexProperty. Predefined
   * options include:
   *
   *   @c vertex_from_name<VertexProperty>: construct an instance of
   *   @c VertexProperty directly from the name.
   *
   *   @c cannot_add_vertex<VertexProperty>: the default value, which
   *   throws an @c std::runtime_error if one attempts to add a vertex
   *   given just the name.
   */
  typedef cannot_add_vertex<VertexProperty> type;
};

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
/**
 * Extract the internal vertex constructor from a @c property structure by
 * looking at its base.
 */
template<typename Tag, typename T, typename Base>
struct internal_vertex_constructor<property<Tag, T, Base> >
  : internal_vertex_constructor<Base> { };
#endif

/*******************************************************************
 * Named graph-specific metafunctions                              *
 *******************************************************************/
namespace detail {
  /** @internal
   * Extracts the type of a bundled vertex property from a vertex
   * property. The primary template matches when we have hit the end
   * of the @c property<> list.
   */
  template<typename VertexProperty>
  struct extract_bundled_vertex
  {
    typedef VertexProperty type;
  };

  /** @internal
   * Recursively extract the bundled vertex property from a vertex
   * property.
   */
  template<typename Tag, typename T, typename Base>
  struct extract_bundled_vertex<property<Tag, T, Base> >
    : extract_bundled_vertex<Base>
  { };

  /**
   * We have found the bundled vertex property type, marked with
   * vertex_bundle_t.
   */
  template<typename T, typename Base>
  struct extract_bundled_vertex<property<vertex_bundle_t, T, Base> >
  {
    typedef T type;
  };

  /**
   * Translate @c no_property into @c error_property_not_found when we
   * have failed to extract a bundled vertex property type.
   */
  template<>
  struct extract_bundled_vertex<no_property>
  {
    typedef boost::detail::error_property_not_found type;
  };
}

/*******************************************************************
 * Named graph mixin                                               *
 *******************************************************************/

/**
 * named_graph is a mixin that provides names for the vertices of a
 * graph, including a mapping from names to vertices. Graph types that
 * may or may not be have vertex names (depending on the properties
 * supplied by the user) should use maybe_named_graph.
 *
 * Template parameters:
 *
 *   Graph: the graph type that derives from named_graph
 *
 *   Vertex: the type of a vertex descriptor in Graph. Note: we cannot
 *   use graph_traits here, because the Graph is not yet defined.
 *
 *   VertexProperty: the type stored with each vertex in the Graph.
 */
template<typename Graph, typename Vertex, typename VertexProperty>
class named_graph
{
public:
  /// The type of the function object that extracts names from vertex
  /// properties.
  typedef typename internal_vertex_name<VertexProperty>::type extract_name_type;
  /// The type of the "bundled" property, from which the name can be
  /// extracted.
  typedef typename detail::extract_bundled_vertex<VertexProperty>::type
    bundled_vertex_property_type;

  /// The type of the function object that generates vertex properties
  /// from names, for the implicit addition of vertices.
  typedef typename internal_vertex_constructor<VertexProperty>::type
    vertex_constructor_type;

  /// The type used to name vertices in the graph
  typedef typename remove_cv<
            typename remove_reference<
              typename extract_name_type::result_type>::type>::type
    vertex_name_type;

  /// The type of vertex descriptors in the graph
  typedef Vertex vertex_descriptor;

private:
  /// Key extractor for use with the multi_index_container
  struct extract_name_from_vertex
  {
    typedef vertex_name_type result_type;

    extract_name_from_vertex(Graph& graph, const extract_name_type& extract)
      : graph(graph), extract(extract) { }

    const result_type& operator()(Vertex vertex) const
    {
      return extract(graph[vertex]);
    }

    Graph& graph;
    extract_name_type extract;
  };

public:
  /// The type that maps names to vertices
  typedef multi_index::multi_index_container<
            Vertex,
            multi_index::indexed_by<
              multi_index::hashed_unique<multi_index::tag<vertex_name_t>,
                                         extract_name_from_vertex> >
          > named_vertices_type;

  /// The set of vertices, indexed by name
  typedef typename named_vertices_type::template index<vertex_name_t>::type
    vertices_by_name_type;

  /// Construct an instance of the named graph mixin, using the given
  /// function object to extract a name from the bundled property
  /// associated with a vertex.
  named_graph(const extract_name_type& extract = extract_name_type(),
              const vertex_constructor_type& vertex_constructor
                = vertex_constructor_type());

  /// Notify the named_graph that we have added the given vertex. The
  /// name of the vertex will be added to the mapping.
  void added_vertex(Vertex vertex);

  /// Notify the named_graph that we are removing the given
  /// vertex. The name of the vertex will be removed from the mapping.
  void removing_vertex(Vertex vertex);

  /// Notify the named_graph that we are clearing the graph.
  /// This will clear out all of the name->vertex mappings
  void clearing_graph();

  /// Retrieve the derived instance
  Graph&       derived()       { return static_cast<Graph&>(*this); }
  const Graph& derived() const { return static_cast<const Graph&>(*this); }

  /// Extract the name from a vertex property instance
  typename extract_name_type::result_type
  extract_name(const bundled_vertex_property_type& property);

  /// Search for a vertex that has the given property (based on its
  /// name)
  optional<vertex_descriptor>
  vertex_by_property(const bundled_vertex_property_type& property);

  /// Mapping from names to vertices
  named_vertices_type named_vertices;

  /// Constructs a vertex from the name of that vertex
  vertex_constructor_type vertex_constructor;
};

/// Helper macro containing the template parameters of named_graph
#define BGL_NAMED_GRAPH_PARAMS \
  typename Graph, typename Vertex, typename VertexProperty
/// Helper macro containing the named_graph<...> instantiation
#define BGL_NAMED_GRAPH \
  named_graph<Graph, Vertex, VertexProperty>

template<BGL_NAMED_GRAPH_PARAMS>
BGL_NAMED_GRAPH::named_graph(const extract_name_type& extract,
                             const vertex_constructor_type& vertex_constructor)
  : named_vertices(
      typename named_vertices_type::ctor_args_list(
        boost::make_tuple(
          boost::make_tuple(
            0, // initial number of buckets
            extract_name_from_vertex(derived(), extract),
            boost::hash<vertex_name_type>(),
            std::equal_to<vertex_name_type>())))),
    vertex_constructor(vertex_constructor)
{
}

template<BGL_NAMED_GRAPH_PARAMS>
inline void BGL_NAMED_GRAPH::added_vertex(Vertex vertex)
{
  named_vertices.insert(vertex);
}

template<BGL_NAMED_GRAPH_PARAMS>
inline void BGL_NAMED_GRAPH::removing_vertex(Vertex vertex)
{
  typedef typename BGL_NAMED_GRAPH::vertex_name_type vertex_name_type;
  const vertex_name_type& vertex_name = extract_name(derived()[vertex]);
  named_vertices.erase(vertex_name);
}

template<BGL_NAMED_GRAPH_PARAMS>
inline void BGL_NAMED_GRAPH::clearing_graph()
{
  named_vertices.clear();
}

template<BGL_NAMED_GRAPH_PARAMS>
typename BGL_NAMED_GRAPH::extract_name_type::result_type
BGL_NAMED_GRAPH::extract_name(const bundled_vertex_property_type& property)
{
  return named_vertices.key_extractor().extract(property);
}

template<BGL_NAMED_GRAPH_PARAMS>
optional<typename BGL_NAMED_GRAPH::vertex_descriptor>
BGL_NAMED_GRAPH::
vertex_by_property(const bundled_vertex_property_type& property)
{
  return find_vertex(extract_name(property), *this);
}

/// Retrieve the vertex associated with the given name
template<BGL_NAMED_GRAPH_PARAMS>
optional<Vertex>
find_vertex(typename BGL_NAMED_GRAPH::vertex_name_type const& name,
            const BGL_NAMED_GRAPH& g)
{
  typedef typename BGL_NAMED_GRAPH::vertices_by_name_type
    vertices_by_name_type;

  // Retrieve the set of vertices indexed by name
  vertices_by_name_type const& vertices_by_name
    = g.named_vertices.template get<vertex_name_t>();

  /// Look for a vertex with the given name
  typename vertices_by_name_type::const_iterator iter
    = vertices_by_name.find(name);

  if (iter == vertices_by_name.end())
    return optional<Vertex>(); // vertex not found
  else
    return *iter;
}

/// Retrieve the vertex associated with the given name, or add a new
/// vertex with that name if no such vertex is available.
template<BGL_NAMED_GRAPH_PARAMS>
Vertex
add_vertex(typename BGL_NAMED_GRAPH::vertex_name_type const& name,
           BGL_NAMED_GRAPH& g)
{
  if (optional<Vertex> vertex = find_vertex(name, g))
    /// We found the vertex, so return it
    return *vertex;
  else
    /// There is no vertex with the given name, so create one
    return add_vertex(g.vertex_constructor(name), g.derived());
}

/// Add an edge using vertex names to refer to the vertices
template<BGL_NAMED_GRAPH_PARAMS>
std::pair<typename graph_traits<Graph>::edge_descriptor, bool>
add_edge(typename BGL_NAMED_GRAPH::vertex_name_type const& u_name,
         typename BGL_NAMED_GRAPH::vertex_name_type const& v_name,
         BGL_NAMED_GRAPH& g)
{
  return add_edge(add_vertex(u_name, g.derived()),
                  add_vertex(v_name, g.derived()),
                  g.derived());
}

/// Add an edge using vertex descriptors or names to refer to the vertices
template<BGL_NAMED_GRAPH_PARAMS>
std::pair<typename graph_traits<Graph>::edge_descriptor, bool>
add_edge(typename BGL_NAMED_GRAPH::vertex_descriptor const& u,
         typename BGL_NAMED_GRAPH::vertex_name_type const& v_name,
         BGL_NAMED_GRAPH& g)
{
  return add_edge(u,
                  add_vertex(v_name, g.derived()),
                  g.derived());
}

/// Add an edge using vertex descriptors or names to refer to the vertices
template<BGL_NAMED_GRAPH_PARAMS>
std::pair<typename graph_traits<Graph>::edge_descriptor, bool>
add_edge(typename BGL_NAMED_GRAPH::vertex_name_type const& u_name,
         typename BGL_NAMED_GRAPH::vertex_descriptor const& v,
         BGL_NAMED_GRAPH& g)
{
  return add_edge(add_vertex(u_name, g.derived()),
                  v,
                  g.derived());
}

#undef BGL_NAMED_GRAPH
#undef BGL_NAMED_GRAPH_PARAMS

/*******************************************************************
 * Maybe named graph mixin                                         *
 *******************************************************************/

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
/**
 * A graph mixin that can provide a mapping from names to vertices,
 * and use that mapping to simplify creation and manipulation of
 * graphs.
 */
template<typename Graph, typename Vertex, typename VertexProperty,
         typename ExtractName
           = typename internal_vertex_name<VertexProperty>::type>
struct maybe_named_graph : public named_graph<Graph, Vertex, VertexProperty>
{
};

/**
 * A graph mixin that can provide a mapping from names to vertices,
 * and use that mapping to simplify creation and manipulation of
 * graphs. This partial specialization turns off this functionality
 * when the @c VertexProperty does not have an internal vertex name.
 */
template<typename Graph, typename Vertex, typename VertexProperty>
struct maybe_named_graph<Graph, Vertex, VertexProperty, void>
{
  /// The type of the "bundled" property, from which the name can be
  /// extracted.
  typedef typename detail::extract_bundled_vertex<VertexProperty>::type
    bundled_vertex_property_type;

  /// Notify the named_graph that we have added the given vertex. This
  /// is a no-op.
  void added_vertex(Vertex) { }

  /// Notify the named_graph that we are removing the given
  /// vertex. This is a no-op.
  void removing_vertex(Vertex) { }

  /// Notify the named_graph that we are clearing the graph. This is a
  /// no-op.
  void clearing_graph() { }

  /// Search for a vertex that has the given property (based on its
  /// name). This always returns an empty optional<>
  optional<Vertex>
  vertex_by_property(const bundled_vertex_property_type&)
  {
    return optional<Vertex>();
  }
};
#else
template<typename Graph, typename Vertex, typename VertexProperty,
         typename ExtractName
           = typename internal_vertex_name<VertexProperty>::type>
struct maybe_named_graph
{
  /// The type of the "bundled" property, from which the name can be
  /// extracted.
  typedef typename detail::extract_bundled_vertex<VertexProperty>::type
    bundled_vertex_property_type;

  /// Notify the named_graph that we have added the given vertex. This
  /// is a no-op.
  void added_vertex(Vertex) { }

  /// Notify the named_graph that we are removing the given
  /// vertex. This is a no-op.
  void removing_vertex(Vertex) { }

  /// Notify the named_graph that we are clearing the graph. This is a
  /// no-op.
  void clearing_graph() { }

  /// Search for a vertex that has the given property (based on its
  /// name). This always returns an empty optional<>
  template<typename Property>
  optional<Vertex>
  vertex_by_property(const bundled_vertex_property_type&)
  {
    return optional<Vertex>();
  }
};
#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

} } // end namespace boost::graph

#endif // BOOST_GRAPH_NAMED_GRAPH_HPP