RhodeCode

    template <typename _Graph, bool _dir, typename _Map, 

	      typename _Converter = DefaultConverter<typename _Map::Value> >

    class GraphArcMapStorage : public MapStorageBase<typename _Graph::Edge> {

    public:

      typedef _Map Map;

      typedef _Converter Converter;

      typedef _Graph Graph;

      typedef typename Graph::Edge Item;

      static const bool dir = _dir;

    private:

      const Graph& _graph;

      Map& _map;

      Converter _converter;

    public:

      GraphArcMapStorage(const Graph& graph, Map& map, 

			 const Converter& converter = Converter()) 

	: _graph(graph), _map(map), _converter(converter) {}

      virtual ~GraphArcMapStorage() {}

      virtual void set(const Item& item ,const std::string& value) {

	_map.set(_graph.direct(item, dir), _converter(value));

      }

    };

    template <typename Graph>

    struct GraphArcLookUpConverter {

      const Graph& _graph;

      const std::map<std::string, typename Graph::Edge>& _map;

      GraphArcLookUpConverter(const Graph& graph, 

			      const std::map<std::string,

			                     typename Graph::Edge>& map) 

	: _graph(graph), _map(map) {}

      typename Graph::Arc operator()(const std::string& str) {

	if (str.empty() || (str[0] != '+' && str[0] != '-')) {

	  throw DataFormatError("Item must start with '+' or '-'");

	}

	typename std::map<std::string, typename Graph::Edge>

	  ::const_iterator it = _map.find(str.substr(1));

	if (it == _map.end()) {

	  throw DataFormatError("Item not found");

	}

	return _graph.direct(it->second, str[0] == '+');

      }

    };

  /// \ingroup lemon_io

  ///  

  /// \brief LGF reader for undirected graphs

  ///

  /// This utility reads an \ref lgf-format "LGF" file.

  template <typename _Graph>

  class GraphReader {

  public:

    typedef _Graph Graph;

    TEMPLATE_GRAPH_TYPEDEFS(Graph);

  private:

    std::istream* _is;

    bool local_is;

    Graph& _graph;

    std::string _nodes_caption;

    std::string _edges_caption;

    std::string _attributes_caption;

    typedef std::map<std::string, Node> NodeIndex;

    NodeIndex _node_index;

    typedef std::map<std::string, Edge> EdgeIndex;

    EdgeIndex _edge_index;

    typedef std::vector<std::pair<std::string, 

      _reader_bits::MapStorageBase<Node>*> > NodeMaps;    

    NodeMaps _node_maps; 

    typedef std::vector<std::pair<std::string,

      _reader_bits::MapStorageBase<Edge>*> > EdgeMaps;

    EdgeMaps _edge_maps;

    typedef std::multimap<std::string, _reader_bits::ValueStorageBase*> 

      Attributes;

    Attributes _attributes;

    typedef std::map<std::string, _reader_bits::Section*> Sections;

    Sections _sections;

    bool _use_nodes;

    bool _use_edges;

    int line_num;

    std::istringstream line;

  public:

    /// \brief Constructor

    ///

    /// Construct a undirected graph reader, which reads from the given

    /// input stream.

    GraphReader(std::istream& is, Graph& graph) 

      : _is(&is), local_is(false), _graph(graph),

	_use_nodes(false), _use_edges(false) {}

    /// \brief Constructor

    ///

    /// Construct a undirected graph reader, which reads from the given

    /// file.

    GraphReader(const std::string& fn, Graph& graph) 

      : _is(new std::ifstream(fn.c_str())), local_is(true), _graph(graph),

    	_use_nodes(false), _use_edges(false) {}

    /// \brief Constructor

    ///

    /// Construct a undirected graph reader, which reads from the given

    /// file.

    GraphReader(const char* fn, Graph& graph) 

      : _is(new std::ifstream(fn)), local_is(true), _graph(graph),

    	_use_nodes(false), _use_edges(false) {}

    /// \brief Copy constructor

    ///

    /// The copy constructor transfers all data from the other reader,

    /// therefore the copied reader will not be usable more. 

    GraphReader(GraphReader& other) 

      : _is(other._is), local_is(other.local_is), _graph(other._graph),

	_use_nodes(other._use_nodes), _use_edges(other._use_edges) {

      other._is = 0;

      other.local_is = false;

      _node_index.swap(other._node_index);

      _edge_index.swap(other._edge_index);

      _node_maps.swap(other._node_maps);

      _edge_maps.swap(other._edge_maps);

      _attributes.swap(other._attributes);

      _nodes_caption = other._nodes_caption;

      _edges_caption = other._edges_caption;

      _attributes_caption = other._attributes_caption;

      _sections.swap(other._sections);

    }

    /// \brief Destructor

    ~GraphReader() {

      for (typename NodeMaps::iterator it = _node_maps.begin(); 

	   it != _node_maps.end(); ++it) {

	delete it->second;

      }

      for (typename EdgeMaps::iterator it = _edge_maps.begin(); 

	   it != _edge_maps.end(); ++it) {

	delete it->second;

      }

      for (typename Attributes::iterator it = _attributes.begin(); 

	   it != _attributes.end(); ++it) {

	delete it->second;

      }

      for (typename Sections::iterator it = _sections.begin(); 

	   it != _sections.end(); ++it) {

	delete it->second;

      }

      if (local_is) {

	delete _is;

      }

    }

  private:

    GraphReader& operator=(const GraphReader&);

  public:

    /// \name Reading rules

    /// @{

    /// \brief Node map reading rule

    ///

    /// Add a node map reading rule to the reader.

    template <typename Map>

    GraphReader& nodeMap(const std::string& caption, Map& map) {

      checkConcept<concepts::WriteMap<Node, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Node>* storage = 

	new _reader_bits::MapStorage<Node, Map>(map);

      _node_maps.push_back(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Node map reading rule

    ///

    /// Add a node map reading rule with specialized converter to the

    /// reader.

    template <typename Map, typename Converter>

    GraphReader& nodeMap(const std::string& caption, Map& map, 

			   const Converter& converter = Converter()) {

      checkConcept<concepts::WriteMap<Node, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Node>* storage = 

	new _reader_bits::MapStorage<Node, Map, Converter>(map, converter);

      _node_maps.push_back(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Edge map reading rule

    ///

    /// Add an edge map reading rule to the reader.

    template <typename Map>

    GraphReader& edgeMap(const std::string& caption, Map& map) {

      checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Edge>* storage = 

	new _reader_bits::MapStorage<Edge, Map>(map);

      _edge_maps.push_back(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Edge map reading rule

    ///

    /// Add an edge map reading rule with specialized converter to the

    /// reader.

    template <typename Map, typename Converter>

    GraphReader& edgeMap(const std::string& caption, Map& map, 

			  const Converter& converter = Converter()) {

      checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Edge>* storage = 

	new _reader_bits::MapStorage<Edge, Map, Converter>(map, converter);

      _edge_maps.push_back(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Arc map reading rule

    ///

    /// Add an arc map reading rule to the reader.

    template <typename Map>

    GraphReader& arcMap(const std::string& caption, Map& map) {

      checkConcept<concepts::WriteMap<Arc, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Edge>* forward_storage = 

	new _reader_bits::GraphArcMapStorage<Graph, true, Map>(_graph, map);

      _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

      _reader_bits::MapStorageBase<Edge>* backward_storage = 

	new _reader_bits::GraphArcMapStorage<Graph, false, Map>(_graph, map);

      _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

      return *this;

    }

    /// \brief Arc map reading rule

    ///

    /// Add an arc map reading rule with specialized converter to the

    /// reader.

    template <typename Map, typename Converter>

    GraphReader& arcMap(const std::string& caption, Map& map, 

			  const Converter& converter = Converter()) {

      checkConcept<concepts::WriteMap<Arc, typename Map::Value>, Map>();

      _reader_bits::MapStorageBase<Edge>* forward_storage = 

	new _reader_bits::GraphArcMapStorage<Graph, true, Map, Converter>

	(_graph, map, converter);

      _edge_maps.push_back(std::make_pair('+' + caption, forward_storage));

      _reader_bits::MapStorageBase<Edge>* backward_storage = 

	new _reader_bits::GraphArcMapStorage<Graph, false, Map, Converter>

	(_graph, map, converter);

      _edge_maps.push_back(std::make_pair('-' + caption, backward_storage));

      return *this;

    }

    /// \brief Attribute reading rule

    ///

    /// Add an attribute reading rule to the reader.

    template <typename Value>

    GraphReader& attribute(const std::string& caption, Value& value) {

      _reader_bits::ValueStorageBase* storage = 

	new _reader_bits::ValueStorage<Value>(value);

      _attributes.insert(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Attribute reading rule

    ///

    /// Add an attribute reading rule with specialized converter to the

    /// reader.

    template <typename Value, typename Converter>

    GraphReader& attribute(const std::string& caption, Value& value, 

			     const Converter& converter = Converter()) {

      _reader_bits::ValueStorageBase* storage = 

	new _reader_bits::ValueStorage<Value, Converter>(value, converter);

      _attributes.insert(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Node reading rule

    ///

    /// Add a node reading rule to reader.

    GraphReader& node(const std::string& caption, Node& node) {

      typedef _reader_bits::MapLookUpConverter<Node> Converter;

      Converter converter(_node_index);

      _reader_bits::ValueStorageBase* storage = 

	new _reader_bits::ValueStorage<Node, Converter>(node, converter);

      _attributes.insert(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Edge reading rule

    ///

    /// Add an edge reading rule to reader.

    GraphReader& edge(const std::string& caption, Edge& edge) {

      typedef _reader_bits::MapLookUpConverter<Edge> Converter;

      Converter converter(_edge_index);

      _reader_bits::ValueStorageBase* storage = 

	new _reader_bits::ValueStorage<Edge, Converter>(edge, converter);

      _attributes.insert(std::make_pair(caption, storage));

      return *this;

    }

    /// \brief Arc reading rule

    ///

    /// Add an arc reading rule to reader.

    GraphReader& arc(const std::string& caption, Arc& arc) {

      typedef _reader_bits::GraphArcLookUpConverter<Graph> Converter;

      Converter converter(_graph, _edge_index);

      _reader_bits::ValueStorageBase* storage = 

	new _reader_bits::ValueStorage<Arc, Converter>(arc, converter);

      _attributes.insert(std::make_pair(caption, storage));

      return *this;

    }

    /// @}

    /// \name Select section by name

    /// @{

    /// \brief Set \c \@nodes section to be read

    ///

    /// Set \c \@nodes section to be read

    GraphReader& nodes(const std::string& caption) {

      _nodes_caption = caption;

      return *this;

    }

    /// \brief Set \c \@edges section to be read

    ///

    /// Set \c \@edges section to be read

    GraphReader& edges(const std::string& caption) {

      _edges_caption = caption;

      return *this;

    }

    /// \brief Set \c \@attributes section to be read

    ///

    /// Set \c \@attributes section to be read

    GraphReader& attributes(const std::string& caption) {

      _attributes_caption = caption;

      return *this;

    }

    /// @}

    /// \name Section readers

    /// @{

    /// \brief Add a section processor with line oriented reading

    ///

    /// In the \e LGF file extra sections can be placed, which contain

    /// any data in arbitrary format. These sections can be read with

    /// this function line by line. The first parameter is the type

    /// descriptor of the section, the second is a functor, which

    /// takes just one \c std::string parameter. At the reading

    /// process, each line of the section will be given to the functor

    /// object. However, the empty lines and the comment lines are

    /// filtered out, and the leading whitespaces are stipped from

    /// each processed string.

    ///

    /// For example let's see a section, which contain several

    /// integers, which should be inserted into a vector.

    ///\code

    ///  @numbers

    ///  12 45 23

    ///  4

    ///  23 6

    ///\endcode

    ///

    /// The functor is implemented as an struct:

    ///\code

    ///  struct NumberSection {

    ///    std::vector<int>& _data;

    ///    NumberSection(std::vector<int>& data) : _data(data) {}

    ///    void operator()(const std::string& line) {

    ///      std::istringstream ls(line);

    ///      int value;

    ///      while (ls >> value) _data.push_back(value);

    ///    }

    ///  };

    ///

    ///  // ...

    ///

    ///  reader.sectionLines("numbers", NumberSection(vec));  

    ///\endcode

    template <typename Functor>

    GraphReader& sectionLines(const std::string& type, Functor functor) {

      LEMON_ASSERT(!type.empty(), "Type is not empty.");

      LEMON_ASSERT(_sections.find(type) == _sections.end(), 

		   "Multiple reading of section.");

      LEMON_ASSERT(type != "nodes" && type != "arcs" && type != "edges" &&

		   type != "attributes", "Multiple reading of section.");

      _sections.insert(std::make_pair(type, 

        new _reader_bits::LineSection<Functor>(functor)));

      return *this;

    }

    /// \brief Add a section processor with stream oriented reading

    ///

    /// In the \e LGF file extra sections can be placed, which contain

    /// any data in arbitrary format. These sections can be read

    /// directly with this function. The first parameter is the type

    /// of the section, the second is a functor, which takes an \c

    /// std::istream& and an int& parameter, the latter regard to the

    /// line number of stream. The functor can read the input while

    /// the section go on, and the line number should be modified

    /// accordingly.

    template <typename Functor>

    GraphReader& sectionStream(const std::string& type, Functor functor) {

      LEMON_ASSERT(!type.empty(), "Type is not empty.");

      LEMON_ASSERT(_sections.find(type) == _sections.end(), 

		   "Multiple reading of section.");

      LEMON_ASSERT(type != "nodes" && type != "arcs" && type != "edges" &&

		   type != "attributes", "Multiple reading of section.");

      _sections.insert(std::make_pair(type, 

	 new _reader_bits::StreamSection<Functor>(functor)));

      return *this;

    }    

    /// @}

    /// \name Using previously constructed node or edge set

    /// @{

    /// \brief Use previously constructed node set

    ///

    /// Use previously constructed node set, and specify the node

    /// label map.

    template <typename Map>

    GraphReader& useNodes(const Map& map) {

      checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

      LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

      _use_nodes = true;

      _writer_bits::DefaultConverter<typename Map::Value> converter;

      for (NodeIt n(_graph); n != INVALID; ++n) {

	_node_index.insert(std::make_pair(converter(map[n]), n));

      }

      return *this;

    }

    /// \brief Use previously constructed node set

    ///

    /// Use previously constructed node set, and specify the node

    /// label map and a functor which converts the label map values to

    /// std::string.

    template <typename Map, typename Converter>

    GraphReader& useNodes(const Map& map, 

			    const Converter& converter = Converter()) {

      checkConcept<concepts::ReadMap<Node, typename Map::Value>, Map>();

      LEMON_ASSERT(!_use_nodes, "Multiple usage of useNodes() member"); 

      _use_nodes = true;

      for (NodeIt n(_graph); n != INVALID; ++n) {

	_node_index.insert(std::make_pair(converter(map[n]), n));

      }

      return *this;

    }

    /// \brief Use previously constructed edge set

    ///

    /// Use previously constructed edge set, and specify the edge

    /// label map.

    template <typename Map>

    GraphReader& useEdges(const Map& map) {

      checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

      LEMON_ASSERT(!_use_edges, "Multiple usage of useEdges() member");

      _use_edges = true;

      _writer_bits::DefaultConverter<typename Map::Value> converter;

      for (EdgeIt a(_graph); a != INVALID; ++a) {

	_edge_index.insert(std::make_pair(converter(map[a]), a));

      }

      return *this;

    }

    /// \brief Use previously constructed edge set

    ///

    /// Use previously constructed edge set, and specify the edge

    /// label map and a functor which converts the label map values to

    /// std::string.

    template <typename Map, typename Converter>

    GraphReader& useEdges(const Map& map, 

			    const Converter& converter = Converter()) {

      checkConcept<concepts::ReadMap<Edge, typename Map::Value>, Map>();

      LEMON_ASSERT(!_use_edges, "Multiple usage of useEdges() member"); 

      _use_edges = true;

      for (EdgeIt a(_graph); a != INVALID; ++a) {

	_edge_index.insert(std::make_pair(converter(map[a]), a));

      }

      return *this;

    }

    /// @}

  private:

    bool readLine() {

      std::string str;

      while(++line_num, std::getline(*_is, str)) {

	line.clear(); line.str(str);

	char c;

	if (line >> std::ws >> c && c != '#') {

	  line.putback(c);

	  return true;

	}

      }

      return false;

    }

    bool readSuccess() {

      return static_cast<bool>(*_is);

    }

    void skipSection() {

      char c;

      while (readSuccess() && line >> c && c != '@') {

	readLine();

      }

      line.putback(c);

    }

    void readNodes() {

      std::vector<int> map_index(_node_maps.size());

      int map_num, label_index;

      if (!readLine()) 

	throw DataFormatError("Cannot find map captions");

      {

	std::map<std::string, int> maps;

	std::string map;

	int index = 0;

	while (_reader_bits::readToken(line, map)) {

	  if (maps.find(map) != maps.end()) {

	    std::ostringstream msg;

	    msg << "Multiple occurence of node map: " << map;

	    throw DataFormatError(msg.str().c_str());

	  }

	  maps.insert(std::make_pair(map, index));

	  ++index;

	}

	for (int i = 0; i < static_cast<int>(_node_maps.size()); ++i) {

	  std::map<std::string, int>::iterator jt = 

	    maps.find(_node_maps[i].first);

	  if (jt == maps.end()) {

	    std::ostringstream msg;

	    msg << "Map not found in file: " << _node_maps[i].first;

	    throw DataFormatError(msg.str().c_str());

	  }

	  map_index[i] = jt->second;

	}

	{

	  std::map<std::string, int>::iterator jt = maps.find("label");

	  if (jt == maps.end())

	    throw DataFormatError("Label map not found in file");

	  label_index = jt->second;

	}

	map_num = maps.size();

      }

      char c;

      while (readLine() && line >> c && c != '@') {

	line.putback(c);

	std::vector<std::string> tokens(map_num);

	for (int i = 0; i < map_num; ++i) {

	  if (!_reader_bits::readToken(line, tokens[i])) {

	    std::ostringstream msg;

	    msg << "Column not found (" << i + 1 << ")";

	    throw DataFormatError(msg.str().c_str());

	  }

	}

	if (line >> std::ws >> c)

	  throw DataFormatError("Extra character on the end of line");

	Node n;

	if (!_use_nodes) {

	  n = _graph.addNode();

	  _node_index.insert(std::make_pair(tokens[label_index], n));

	} else {

	  typename std::map<std::string, Node>::iterator it =

	    _node_index.find(tokens[label_index]);

	  if (it == _node_index.end()) {

	    std::ostringstream msg;

	    msg << "Node with label not found: " << tokens[label_index];

	    throw DataFormatError(msg.str().c_str());	    

	  }

	  n = it->second;

	}

	for (int i = 0; i < static_cast<int>(_node_maps.size()); ++i) {

	  _node_maps[i].second->set(n, tokens[map_index[i]]);

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

    }

    void readEdges() {

      std::vector<int> map_index(_edge_maps.size());

      int map_num, label_index;

      if (!readLine()) 

	throw DataFormatError("Cannot find map captions");

      {

	std::map<std::string, int> maps;

	std::string map;

	int index = 0;

	while (_reader_bits::readToken(line, map)) {

	  if (maps.find(map) != maps.end()) {

	    std::ostringstream msg;

	    msg << "Multiple occurence of edge map: " << map;

	    throw DataFormatError(msg.str().c_str());

	  }

	  maps.insert(std::make_pair(map, index));

	  ++index;

	}

	for (int i = 0; i < static_cast<int>(_edge_maps.size()); ++i) {

	  std::map<std::string, int>::iterator jt = 

	    maps.find(_edge_maps[i].first);

	  if (jt == maps.end()) {

	    std::ostringstream msg;

	    msg << "Map not found in file: " << _edge_maps[i].first;

	    throw DataFormatError(msg.str().c_str());

	  }

	  map_index[i] = jt->second;

	}

	{

	  std::map<std::string, int>::iterator jt = maps.find("label");

	  if (jt == maps.end())

	    throw DataFormatError("Label map not found in file");

	  label_index = jt->second;

	}

	map_num = maps.size();

      }

      char c;

      while (readLine() && line >> c && c != '@') {

	line.putback(c);

	std::string source_token;

	std::string target_token;

	if (!_reader_bits::readToken(line, source_token))

	  throw DataFormatError("Source not found");

	if (!_reader_bits::readToken(line, target_token))

	  throw DataFormatError("Source not found");

	std::vector<std::string> tokens(map_num);

	for (int i = 0; i < map_num; ++i) {

	  if (!_reader_bits::readToken(line, tokens[i])) {

	    std::ostringstream msg;

	    msg << "Column not found (" << i + 1 << ")";

	    throw DataFormatError(msg.str().c_str());

	  }

	}

	if (line >> std::ws >> c)

	  throw DataFormatError("Extra character on the end of line");

	Edge e;

	if (!_use_edges) {

          typename NodeIndex::iterator it;

          it = _node_index.find(source_token);

          if (it == _node_index.end()) {

            std::ostringstream msg;

            msg << "Item not found: " << source_token;

            throw DataFormatError(msg.str().c_str());

          }

          Node source = it->second;

          it = _node_index.find(target_token);

          if (it == _node_index.end()) {       

            std::ostringstream msg;            

            msg << "Item not found: " << target_token;

            throw DataFormatError(msg.str().c_str());

          }                                          

          Node target = it->second;                            

	  e = _graph.addEdge(source, target);

	  _edge_index.insert(std::make_pair(tokens[label_index], e));

	} else {

	  typename std::map<std::string, Edge>::iterator it =

	    _edge_index.find(tokens[label_index]);

	  if (it == _edge_index.end()) {

	    std::ostringstream msg;

	    msg << "Edge with label not found: " << tokens[label_index];

	    throw DataFormatError(msg.str().c_str());	    

	  }

	  e = it->second;

	}

	for (int i = 0; i < static_cast<int>(_edge_maps.size()); ++i) {

	  _edge_maps[i].second->set(e, tokens[map_index[i]]);

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

    }

    void readAttributes() {

      std::set<std::string> read_attr;

      char c;

      while (readLine() && line >> c && c != '@') {

	line.putback(c);

	std::string attr, token;

	if (!_reader_bits::readToken(line, attr))

	  throw DataFormatError("Attribute name not found");

	if (!_reader_bits::readToken(line, token))

	  throw DataFormatError("Attribute value not found");

	if (line >> c)

	  throw DataFormatError("Extra character on the end of line");	  

	{

	  std::set<std::string>::iterator it = read_attr.find(attr);

	  if (it != read_attr.end()) {

	    std::ostringstream msg;

	    msg << "Multiple occurence of attribute " << attr;

	    throw DataFormatError(msg.str().c_str());

	  }

	  read_attr.insert(attr);

	}

	{

	  typename Attributes::iterator it = _attributes.lower_bound(attr);

	  while (it != _attributes.end() && it->first == attr) {

	    it->second->set(token);

	    ++it;

	  }

	}

      }

      if (readSuccess()) {

	line.putback(c);

      }

      for (typename Attributes::iterator it = _attributes.begin();

	   it != _attributes.end(); ++it) {

	if (read_attr.find(it->first) == read_attr.end()) {

	  std::ostringstream msg;

	  msg << "Attribute not found in file: " << it->first;

	  throw DataFormatError(msg.str().c_str());

	}	

      }

    }

  public:

    /// \name Execution of the reader    

    /// @{

    /// \brief Start the batch processing

    ///

    /// This function starts the batch processing

    void run() {

      LEMON_ASSERT(_is != 0, "This reader assigned to an other reader");

      bool nodes_done = false;

      bool edges_done = false;

      bool attributes_done = false;

      std::set<std::string> extra_sections;

      line_num = 0;      

      readLine();

      while (readSuccess()) {

	skipSection();

	try {

	  char c;

	  std::string section, caption;

	  line >> c;

	  _reader_bits::readToken(line, section);

	  _reader_bits::readToken(line, caption);

	  if (line >> c) 

	    throw DataFormatError("Extra character on the end of line");

	  if (section == "nodes" && !nodes_done) {

	    if (_nodes_caption.empty() || _nodes_caption == caption) {

	      readNodes();

	      nodes_done = true;

	    }

	  } else if ((section == "edges" || section == "arcs") && 

		     !edges_done) {

	    if (_edges_caption.empty() || _edges_caption == caption) {

	      readEdges();

	      edges_done = true;

	    }

	  } else if (section == "attributes" && !attributes_done) {

	    if (_attributes_caption.empty() || _attributes_caption == caption) {

	      readAttributes();

	      attributes_done = true;

	    }

	  } else {

	    if (extra_sections.find(section) != extra_sections.end()) {

	      std::ostringstream msg;

	      msg << "Multiple occurence of section " << section;

	      throw DataFormatError(msg.str().c_str());

	    }

	    Sections::iterator it = _sections.find(section);

	    if (it != _sections.end()) {

	      extra_sections.insert(section);

	      it->second->process(*_is, line_num);

	      readLine();

	    } else {

	      readLine();

	      skipSection();

	    }

	  }

	} catch (DataFormatError& error) {

	  error.line(line_num);

	  throw;

	}	

      }

      if (!nodes_done) {

	throw DataFormatError("Section @nodes not found");

      }

      if (!edges_done) {

	throw DataFormatError("Section @edges not found");

      }

      if (!attributes_done && !_attributes.empty()) {

	throw DataFormatError("Section @attributes not found");

      }

    }

    /// @}

  };

  /// \relates GraphReader

  template <typename Graph>

  GraphReader<Graph> graphReader(std::istream& is, Graph& graph) {

    GraphReader<Graph> tmp(is, graph);

    return tmp;

  }

  /// \relates GraphReader

  template <typename Graph>

  GraphReader<Graph> graphReader(const std::string& fn, 

				       Graph& graph) {

    GraphReader<Graph> tmp(fn, graph);

    return tmp;

  }

  /// \relates GraphReader

  template <typename Graph>

  GraphReader<Graph> graphReader(const char* fn, Graph& graph) {

    GraphReader<Graph> tmp(fn, graph);

    return tmp;

  }

    template <typename _Graph, bool _dir, typename _Map>

    class GraphArcMapLess {

    public:

      typedef _Map Map;

      typedef _Graph Graph;

      typedef typename Graph::Edge Item;

    private:

      const Graph& _graph;

      const Map& _map;

    public:

      GraphArcMapLess(const Graph& graph, const Map& map) 

	: _graph(graph), _map(map) {}

      bool operator()(const Item& left, const Item& right) {

	return _map[_graph.direct(left, _dir)] < 

	  _map[_graph.direct(right, _dir)];

      }

    };

    template <typename _Graph, bool _dir, typename _Map, 

	      typename _Converter = DefaultConverter<typename _Map::Value> >

    class GraphArcMapStorage : public MapStorageBase<typename _Graph::Edge> {

    public:

      typedef _Map Map;

      typedef _Converter Converter;

      typedef _Graph Graph;

      typedef typename Graph::Edge Item;

      static const bool dir = _dir;

    private:

      const Graph& _graph;

      const Map& _map;

      Converter _converter;

    public:

      GraphArcMapStorage(const Graph& graph, const Map& map,  

			 const Converter& converter = Converter()) 

	: _graph(graph), _map(map), _converter(converter) {}

      virtual ~GraphArcMapStorage() {}

      virtual std::string get(const Item& item) {

	return _converter(_map[_graph.direct(item, dir)]);

      }

      virtual void sort(std::vector<Item>& items) {

	GraphArcMapLess<Graph, dir, Map> less(_graph, _map);

	std::sort(items.begin(), items.end(), less);

      }

    };

    template <typename Graph>

    struct GraphArcLookUpConverter {

      const Graph& _graph;

      const std::map<typename Graph::Edge, std::string>& _map;

      GraphArcLookUpConverter(const Graph& graph, 

			      const std::map<typename Graph::Edge, 

			                     std::string>& map) 

	: _graph(graph), _map(map) {}

      std::string operator()(const typename Graph::Arc& val) {

	typename std::map<typename Graph::Edge, std::string>

	  ::const_iterator it = _map.find(val);

	if (it == _map.end()) {

	  throw DataFormatError("Item not found");

	}

	return (_graph.direction(val) ? '+' : '-') + it->second;

      }

    };

  /// \ingroup lemon_io

  ///  

  /// \brief LGF writer for directed graphs

  ///

  /// This utility writes an \ref lgf-format "LGF" file.

  template <typename _Graph>

  class GraphWriter {

  public:

    typedef _Graph Graph;

    TEMPLATE_GRAPH_TYPEDEFS(Graph);

  private:

    std::ostream* _os;

    bool local_os;

    Graph& _graph;

    std::string _nodes_caption;

    std::string _edges_caption;

    std::string _attributes_caption;

    typedef std::map<Node, std::string> NodeIndex;

    NodeIndex _node_index;

    typedef std::map<Edge, std::string> EdgeIndex;

    EdgeIndex _edge_index;

    typedef std::vector<std::pair<std::string, 

      _writer_bits::MapStorageBase<Node>* > > NodeMaps;    

    NodeMaps _node_maps; 

    typedef std::vector<std::pair<std::string, 

      _writer_bits::MapStorageBase<Edge>* > >EdgeMaps;

    EdgeMaps _edge_maps;

    typedef std::vector<std::pair<std::string, 

      _writer_bits::ValueStorageBase*> > Attributes;

    Attributes _attributes;

    bool _skip_nodes;

    bool _skip_edges;

  public:

    /// \brief Constructor

    ///

    /// Construct a directed graph writer, which writes to the given

    /// output stream.

    GraphWriter(std::ostream& is, Graph& graph) 

      : _os(&is), local_os(false), _graph(graph),

	_skip_nodes(false), _skip_edges(false) {}

    /// \brief Constructor

    ///

    /// Construct a directed graph writer, which writes to the given

    /// output file.

    GraphWriter(const std::string& fn, Graph& graph) 

      : _os(new std::ofstream(fn.c_str())), local_os(true), _graph(graph),

	_skip_nodes(false), _skip_edges(false) {}

    /// \brief Constructor

    ///

    /// Construct a directed graph writer, which writes to the given

    /// output file.

    GraphWriter(const char* fn, Graph& graph) 

      : _os(new std::ofstream(fn)), local_os(true), _graph(graph),

	_skip_nodes(false), _skip_edges(false) {}