source: lemon-0.x/lemon/lemon_reader.h @ 2334:c1e936e6a46b

/* -*- C++ -*-
 *
 * This file is a part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2003-2006
 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
 * (Egervary Research Group on Combinatorial Optimization, EGRES).
 *
 * Permission to use, modify and distribute this software is granted
 * provided that this copyright notice appears in all copies. For
 * precise terms see the accompanying LICENSE file.
 *
 * This software is provided "AS IS" with no warranty of any kind,
 * express or implied, and with no claim as to its suitability for any
 * purpose.
 *
 */

///\ingroup lemon_io
///\file
///\brief Lemon Format reader.


#ifndef LEMON_LEMON_READER_H
#define LEMON_LEMON_READER_H


#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
#include <map>
#include <memory>

#include <lemon/error.h>
#include <lemon/graph_utils.h>
#include <lemon/bits/utility.h>
#include <lemon/bits/item_reader.h>

#include <lemon/dim2.h>

#include <lemon/concept_check.h>
#include <lemon/concepts/maps.h>

namespace lemon {

  namespace _reader_bits {

    template <typename T>
    bool operator<(T, T) {
      throw DataFormatError("Label is not comparable");
    }

    template <typename T>
    struct Less {
      bool operator()(const T& p, const T& q) const {
        return p < q;
      }
    };

    template <typename Item>
    class ItemLabelReader {
    public:

      bool isLabelReader() { return true; }

      void readLabel(std::istream&, Item&) {}
      
      template <class _ItemLabelReader>
      struct Constraints {
        void constraints() {
          bool b = reader.isLabelReader();
          ignore_unused_variable_warning(b);
          Item item;
          reader.readLabel(is, item);
        }
        _ItemLabelReader& reader;
        std::istream& is;
      };

    };

    template <typename Item>
    class ItemReader {
    public:
      void read(std::istream&, Item&) {}
      
      template <class _ItemReader>
      struct Constraints {
        void constraints() {
          Item item;
          reader.read(is, item);
        }
        _ItemReader& reader;
        std::istream& is;
      };

    };

    template <typename Map>
    struct Ref { typedef Map& Type; };
    template <typename Map>
    struct Arg { typedef Map& Type; };

    template <typename Graph, typename Map>
    class ForwardComposeMap {
    public:
      typedef typename Graph::UEdge Key;
      typedef typename Map::Value Value;

      ForwardComposeMap(const Graph& _graph, typename Arg<Map>::Type _map) 
        : graph(_graph), map(_map) {}
      
      void set(const Key& key, const Value& val) {
        map.set(graph.direct(key, true), val);
      }

    private:
      const Graph& graph;
      typename Ref<Map>::Type map;
    };

    template <typename Graph, typename Map>
    ForwardComposeMap<Graph, Map>
    forwardComposeMap(const Graph& graph, const Map& map) {
      return ForwardComposeMap<Graph, Map>(graph, map);
    }

    template <typename Graph, typename Map>
    ForwardComposeMap<Graph, Map>
    forwardComposeMap(const Graph& graph, Map& map) {
      return ForwardComposeMap<Graph, Map>(graph, map);
    }

    template <typename Graph, typename Map>
    class BackwardComposeMap {
    public:
      typedef typename Graph::UEdge Key;
      typedef typename Map::Value Value;

      BackwardComposeMap(const Graph& _graph, typename Arg<Map>::Type _map) 
        : graph(_graph), map(_map) {}
      
      void set(const Key& key, const Value& val) {
        map.set(graph.direct(key, false), val);
      }

    private:
      const Graph& graph;
      typename Ref<Map>::Type map;
    };


    template <typename Graph, typename Map>
    BackwardComposeMap<Graph, Map>
    backwardComposeMap(const Graph& graph, const Map& map) {
      return BackwardComposeMap<Graph, Map>(graph, map);
    }

    template <typename Graph, typename Map>
    BackwardComposeMap<Graph, Map>
    backwardComposeMap(const Graph& graph, Map& map) {
      return BackwardComposeMap<Graph, Map>(graph, map);
    }

    template <typename Graph, typename Map>
    struct Ref<ForwardComposeMap<Graph, Map> > { 
      typedef ForwardComposeMap<Graph, Map> Type;
    };
    template <typename Graph, typename Map>
    struct Arg<ForwardComposeMap<Graph, Map> > { 
      typedef const ForwardComposeMap<Graph, Map>& Type;
    };

    template <typename Graph, typename Map>
    struct Ref<BackwardComposeMap<Graph, Map> > { 
      typedef BackwardComposeMap<Graph, Map> Type; 
    };
    template <typename Graph, typename Map>
    struct Arg<BackwardComposeMap<Graph, Map> > { 
      typedef const BackwardComposeMap<Graph, Map>& Type; 
    };

    template <typename Map>
    struct Ref<dim2::XMap<Map> > { 
      typedef dim2::XMap<Map> Type;
    };
    template <typename Map>
    struct Arg<dim2::XMap<Map> > { 
      typedef const dim2::XMap<Map>& Type;
    };

    template <typename Map>
    struct Ref<dim2::YMap<Map> > { 
      typedef dim2::YMap<Map> Type;
    };
    template <typename Map>
    struct Arg<dim2::YMap<Map> > { 
      typedef const dim2::YMap<Map>& Type;
    };


    template <typename _Item>
    class MapReaderBase;
    
    template <typename _Item>
    class MapInverterBase : public MapReaderBase<_Item> {
    public:
      typedef _Item Item;
      virtual void read(std::istream&, const Item&) = 0;
      virtual Item read(std::istream&) const = 0;

      virtual MapInverterBase<_Item>* getInverter() {
        return this;
      }
    };

    template <typename _Item, typename _Map, typename _Reader>
    class MapReaderInverter : public MapInverterBase<_Item> {
    public:
      typedef _Item Item;
      typedef _Reader Reader;
      typedef typename Reader::Value Value;
      typedef _Map Map;
      typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

      typename _reader_bits::Ref<Map>::Type map;
      Reader reader;
      Inverse inverse;

      MapReaderInverter(typename _reader_bits::Arg<Map>::Type _map,
                        const Reader& _reader) 
        : map(_map), reader(_reader) {}

      virtual ~MapReaderInverter() {}

      virtual void read(std::istream& is, const Item& item) {
        Value value;
        reader.read(is, value);
        map.set(item, value);
        typename Inverse::iterator it = inverse.find(value);
        if (it == inverse.end()) {
          inverse.insert(std::make_pair(value, item));
        } else {
          throw DataFormatError("Multiple label occurence");
        }
      }

      virtual Item read(std::istream& is) const {
        Value value;
        reader.read(is, value); 
        typename Inverse::const_iterator it = inverse.find(value);
        if (it != inverse.end()) {
          return it->second;
        } else {
          throw DataFormatError("Invalid label error");
        }
      }      
    };

    template <typename _Item, typename _Reader>
    class SkipReaderInverter : public MapInverterBase<_Item> {
    public:
      typedef _Item Item;
      typedef _Reader Reader;
      typedef typename Reader::Value Value;
      typedef std::map<Value, Item, _reader_bits::Less<Value> > Inverse;

      Reader reader;

      SkipReaderInverter(const Reader& _reader) 
        : reader(_reader) {}

      virtual ~SkipReaderInverter() {}

      virtual void read(std::istream& is, const Item& item) {
        Value value;
        reader.read(is, value);
        typename Inverse::iterator it = inverse.find(value);
        if (it == inverse.end()) {
          inverse.insert(std::make_pair(value, item));
        } else {
          throw DataFormatError("Multiple label occurence error");
        }
      }

      virtual Item read(std::istream& is) const {
        Value value;
        reader.read(is, value); 
        typename Inverse::const_iterator it = inverse.find(value);
        if (it != inverse.end()) {
          return it->second;
        } else {
          throw DataFormatError("Invalid label error");
        }
      }

    private:
      Inverse inverse;
    };

    template <typename _Item>    
    class MapReaderBase {
    public:
      typedef _Item Item;

      MapReaderBase() { _touched = false; }
      
      void touch() { _touched = true; }
      bool touched() const { return _touched; }

      virtual ~MapReaderBase() {}

      virtual void read(std::istream& is, const Item& item) = 0;
      virtual MapInverterBase<_Item>* getInverter() = 0;

    private:      
      bool _touched;

    };

    template <typename _Item, typename _Map, typename _Reader>
    class MapReader : public MapReaderBase<_Item> {
    public:
      typedef _Map Map;
      typedef _Reader Reader;
      typedef typename Reader::Value Value;
      typedef _Item Item;
      
      typename _reader_bits::Ref<Map>::Type map;
      Reader reader;

      MapReader(typename _reader_bits::Arg<Map>::Type _map, 
                const Reader& _reader) 
        : map(_map), reader(_reader) {}

      virtual ~MapReader() {}

      virtual void read(std::istream& is, const Item& item) {
        Value value;
        reader.read(is, value);
        map.set(item, value);
      }

      virtual MapInverterBase<_Item>* getInverter() {
        return new MapReaderInverter<Item, Map, Reader>(map, reader);
      }
    };


    template <typename _Item, typename _Reader>
    class SkipReader : public MapReaderBase<_Item> {
    public:
      typedef _Reader Reader;
      typedef typename Reader::Value Value;
      typedef _Item Item;

      Reader reader;
      SkipReader(const Reader& _reader) : reader(_reader) {}

      virtual ~SkipReader() {}

      virtual void read(std::istream& is, const Item&) {
        Value value;
        reader.read(is, value);
      }      

      virtual MapInverterBase<Item>* getInverter() {
        return new SkipReaderInverter<Item, Reader>(reader);
      }
    };

    template <typename _Item>
    class LabelReaderBase {
    public:
      typedef _Item Item;
      virtual ~LabelReaderBase() {}
      virtual Item read(std::istream& is) const = 0;
      virtual bool isLabelReader() const = 0;
    };

    template <typename _Item, typename _BoxedLabelReader>
    class LabelReader : public LabelReaderBase<_Item> {
    public:
      typedef _Item Item;
      typedef _BoxedLabelReader BoxedLabelReader;
      
      const BoxedLabelReader& boxedLabelReader;

      LabelReader(const BoxedLabelReader& _boxedLabelReader) 
        : boxedLabelReader(_boxedLabelReader) {}

      virtual Item read(std::istream& is) const {
        Item item;
        boxedLabelReader.readLabel(is, item);
        return item;
      }

      virtual bool isLabelReader() const {
        return boxedLabelReader.isLabelReader();
      }
    };

    template <typename _Item>
    class ItemStore {
    public:

      typedef _Item Item;

      ItemStore(Item& _item) : item(&_item) { 
        _touched = false; 
      }
      
      void touch() { _touched = true; }
      bool touched() const { return _touched; }

      void read(const Item& _item) {
        *item = _item;
      }
      
    private:
      Item* item;
      bool _touched;
    };

    class ValueReaderBase {
    public:
      virtual void read(std::istream&) {};
      ValueReaderBase() { _touched = false; }

      void touch() { _touched = true; }
      bool touched() const { return _touched; }

      virtual ~ValueReaderBase() {}
    private:
      bool _touched;
    };

    template <typename _Value, typename _Reader>
    class ValueReader : public ValueReaderBase {
    public:
      typedef _Value Value;
      typedef _Reader Reader;

      ValueReader(Value& _value, const Reader& _reader)
        : value(_value), reader(_reader) {}

      virtual void read(std::istream& is) {
        reader.read(is, value);
      }
    private:
      Value& value;
      Reader reader;
    };

  }

  /// \ingroup lemon_io
  /// \brief Lemon Format reader class.
  /// 
  /// The Lemon Format contains several sections. We do not want to
  /// determine what sections are in a lemon file we give only a framework
  /// to read a section oriented format.
  ///
  /// In the Lemon Format each section starts with a line containing a
  /// \c \@ character on the first not white space position. This line
  /// is the header line of the section. Each of the next lines belong
  /// to this section until a line starting with \c \@ character is
  /// found. This line can start a new section or it can close the
  /// file with the \c \@end line.  The file format ignores the empty
  /// and comment lines. The line is comment line if it starts with a
  /// \c # character.
  ///
  /// The framework provides an abstract LemonReader::SectionReader class
  /// that defines the interface of a SectionReader. The SectionReader
  /// has the \c header() member function that gets a header line string and
  /// decides if it wants to process the next section. Several SectionReaders
  /// can be attached to a LemonReader and the first attached that can
  /// process the section will be used. Its \c read() member will be called
  /// with a stream containing the section. From this stream the empty and
  /// comment lines are filtered out.
  ///
  /// \relates GraphReader
  /// \relates NodeSetReader
  /// \relates EdgeSetReader
  /// \relates NodesReader
  /// \relates EdgesReader
  /// \relates AttributeReader
  class LemonReader {
  private:
    
    class FilterStreamBuf : public std::streambuf {
    public:

      typedef std::streambuf Parent;
      typedef Parent::char_type char_type;
      FilterStreamBuf(std::istream& is, int& num) 
        : _is(is), _base(0), _eptr(0), 
          _num(num), skip_state(after_endl) {}

    protected:

      enum skip_state_type {
        no_skip,
        after_endl,
        comment_line
      };

      char_type small_buf[1];


      std::istream& _is;

      char_type* _base;
      char_type* _eptr;

      int& _num;

      skip_state_type skip_state;


      char_type* base() { return _base; }

      char_type* eptr() { return _eptr; }

      int_type blen() { return _eptr - _base; }

      void setb(char_type* buf, int_type len) {
        _base = buf;
        _eptr = buf + len;
      }
  
      virtual std::streambuf* setbuf(char *buf, std::streamsize len) {
        if (base()) return 0;
        if (buf != 0 && len >= (int)sizeof(small_buf)) {
          setb(buf, len);
        } else {
          setb(small_buf, sizeof(small_buf));
        }
        setg(0, 0, 0);
        return this;
      }

      bool put_char(char c) {
        switch (skip_state) {
        case no_skip:
          switch (c) {
          case '\n': 
            skip_state = after_endl;
            return true;
          default:
            return true;
          }
        case after_endl:
          switch (c) {
          case '@':
            return false;
          case '\n': 
            return false;
          case '#':
            skip_state = comment_line;
            return false;
          default:
            if (!isspace(c)) {
              skip_state = no_skip;
              return true;
            } else {
              return false;
            }
          }
          break;
        case comment_line:
          switch (c) {
          case '\n': 
            skip_state = after_endl;
            return false;
          default:
            return false;
          }
        }
        return false;
      }

      virtual int_type underflow() {
        char c;
        if (_is.read(&c, 1)) {
          _is.putback(c);
          if (c == '@') {
            return EOF;
          }
        } else {
          return EOF;
        }
        char_type *ptr;
        for (ptr = base(); ptr != eptr(); ++ptr) {
          if (_is.read(&c, 1)) {
            if (c == '\n') ++_num;
            if (put_char(c)) {
              *ptr = c;
            } else {
              if (skip_state == after_endl && c == '@') {
                _is.putback('@');
                break;
              }
              --ptr;
            }
          } else {
            break;
          }
        }
        setg(base(), base(), ptr);
        return *base();
      }

      virtual int_type sync() {
        return EOF;
      }
    };

  public:

    /// \brief Abstract base class for reading a section.
    ///
    /// This class has an \c header() member function what get a 
    /// header line string and decides if it want to process the next 
    /// section. Several SectionReaders can be attached to an LemonReader 
    /// and the first attached what can process the section will be used. 
    /// Its \c read() member will called with a stream contains the section. 
    /// From this stream the empty lines and comments are filtered out.
    class SectionReader {
      friend class LemonReader;
    protected:
      /// \brief Constructor for SectionReader.
      ///
      /// Constructor for SectionReader. It attach this reader to
      /// the given LemonReader.
      SectionReader(LemonReader& reader) {
        reader.attach(*this);
      }

      virtual ~SectionReader() {}

      /// \brief Gives back true when the SectionReader can process 
      /// the section with the given header line.
      ///
      /// It gives back true when the SectionReader can process
      /// the section with the given header line.
      virtual bool header(const std::string& line) = 0;

      /// \brief Reader function of the section.
      ///
      /// It reads the content of the section.
      virtual void read(std::istream& is) = 0;

      /// \brief The given section missing in the file.
      ///
      /// The given section missing in the file.
      virtual void missing() {};
    };

    /// \brief Constructor for LemonReader.
    ///
    /// Constructor for LemonReader which reads from the given stream.
    LemonReader(std::istream& _is) 
      : is(&_is), own_is(false) {}

    /// \brief Constructor for LemonReader.
    ///
    /// Constructor for LemonReader which reads from the given file.
    LemonReader(const std::string& filename) 
      : is(0), own_is(true) {
      is = new std::ifstream(filename.c_str());
      if (is->fail()) {
        throw FileOpenError(filename);
      }
    }

    /// \brief Desctructor for LemonReader.
    ///
    /// Desctructor for LemonReader.
    ~LemonReader() {
      if (own_is) {
        delete is;
      }
    }

  private:
    LemonReader(const LemonReader&);
    void operator=(const LemonReader&);

    void attach(SectionReader& reader) {
      readers.push_back(std::make_pair(&reader, false));
    }

  public:
    /// \brief Executes the LemonReader.
    /// 
    /// It executes the LemonReader.
    void run() {
      int line_num = 0;
      std::string line;
      try {
        SectionReaders::iterator it;
        while ((++line_num, getline(*is, line)) && line.find("@end") != 0) {
          for (it = readers.begin(); it != readers.end(); ++it) {
            if (it->first->header(line)) {
              it->second = true;
              char buf[2048];
              FilterStreamBuf buffer(*is, line_num);
              buffer.pubsetbuf(buf, sizeof(buf));
              std::istream is(&buffer);
              it->first->read(is);
              break;
            }
          }
        }
        for (it = readers.begin(); it != readers.end(); ++it) {
          if (!it->second) {
            it->first->missing();
          }
        }
      } catch (DataFormatError& error) {
        error.line(line_num);
        throw;
      } 
    }


  private:

    std::istream* is;
    bool own_is;

    typedef std::vector<std::pair<SectionReader*, bool> > SectionReaders;
    SectionReaders readers;

  };

  /// \ingroup section_io
  /// \brief SectionReader for reading a graph's nodeset.
  ///
  /// The lemon format can store multiple graph nodesets with several maps.
  /// The nodeset section's header line is \c \@nodeset \c nodeset_name, but the
  /// \c nodeset_name may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes a node in the nodeset, and
  /// contains the mapped values for each map.
  ///
  /// If the nodeset contains an \c "label" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c readLabel() member will read a value from the given stream it will
  /// give back that node which is mapped to this value.
  ///
  /// \relates LemonReader
  template <typename _Graph, typename _Traits = DefaultReaderTraits>
  class NodeSetReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;
    typedef typename Traits::Skipper DefaultSkipper;

    /// \brief Constructor.
    ///
    /// Constructor for NodeSetReader. It creates the NodeSetReader and
    /// attach it into the given LemonReader. The nodeset reader will
    /// add the read nodes to the given Graph. The reader will read
    /// the section when the \c section_name and the \c _name are the same. 
    NodeSetReader(LemonReader& _reader, 
                  Graph& _graph, 
                  const std::string& _name = std::string(),
                  const DefaultSkipper& _skipper = DefaultSkipper()) 
      : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {} 


    /// \brief Destructor.
    ///
    /// Destructor for NodeSetReader.
    virtual ~NodeSetReader() {
      for (typename MapReaders::iterator it = readers.begin(); 
           it != readers.end(); ++it) {
        delete it->second;
      }
    }

  private:
    NodeSetReader(const NodeSetReader&);
    void operator=(const NodeSetReader&);
  
  public:

    /// \brief Add a new node map reader command for the reader.
    ///
    /// Add a new node map reader command for the reader.
    template <typename Map>
    NodeSetReader& readNodeMap(std::string name, Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    template <typename Map>
    NodeSetReader& readNodeMap(std::string name, const Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    /// \brief Add a new node map reader command for the reader.
    ///
    /// Add a new node map reader command for the reader.
    template <typename Reader, typename Map>
    NodeSetReader& readNodeMap(std::string name, Map& map, 
                               const Reader& reader = Reader()) {
      return _readMap<Reader, Map, typename _reader_bits::Arg<Map>::Type>
        (name, map, reader);
    }

    template <typename Reader, typename Map>
    NodeSetReader& readNodeMap(std::string name, const Map& map, 
                               const Reader& reader = Reader()) {
      return _readMap<Reader, Map, typename _reader_bits::Arg<Map>::Type>
        (name, map, reader);
    }

  private:

    template <typename Reader, typename Map, typename MapParameter>
    NodeSetReader& _readMap(std::string name, MapParameter map, 
                            const Reader& reader = Reader()) {
      checkConcept<concepts::WriteMap<Node, typename Map::Value>, Map>();
      checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for node map: " << name;
        throw IoParameterError(msg.message());
      }      
      readers.insert(
        make_pair(name, new _reader_bits::
                  MapReader<Node, Map, Reader>(map, reader)));
      return *this;
    }

  public:

    /// \brief Add a new node map skipper command for the reader.
    ///
    /// Add a new node map skipper command for the reader.
    template <typename Reader>
    NodeSetReader& skipNodeMap(std::string name, 
                           const Reader& reader = Reader()) {
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for node map: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, new _reader_bits::
                               SkipReader<Node, Reader>(reader)));
      return *this;
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line starts with \c \@nodeset,
    /// and the header line's name and the nodeset's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@nodeset" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      std::vector<_reader_bits::MapReaderBase<Node>* > index;
      std::string line;

      getline(is, line);
      std::istringstream ls(line);
      std::string id;
      while (ls >> id) {
        typename MapReaders::iterator it = readers.find(id);
        if (it != readers.end()) {
          it->second->touch();
          index.push_back(it->second);
        } else {
          index.push_back(&skipper);
        }
        if (id == "label") {
          inverter.reset(index.back()->getInverter());
          index.back() = inverter.get();
        }
      }
      for (typename MapReaders::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second->touched()) {
          ErrorMessage msg;
          msg << "Map not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
      while (getline(is, line)) {       
        Node node = graph.addNode();
        std::istringstream ls(line);
        for (int i = 0; i < (int)index.size(); ++i) {
          index[i]->read(ls, node);
        }
      }
    }

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "NodeSet section not found in file: @nodeset " << name;
      throw IoParameterError(msg.message());
    }

  public:

    /// \brief Returns true if the nodeset can give back the node by its label.
    ///
    /// Returns true if the nodeset can give back the node by its label.
    /// It is possible only if an "label" named map was read.
    bool isLabelReader() const {
      return inverter.get() != 0;
    }

    /// \brief Gives back the node by its label.
    ///
    /// It reads an id from the stream and gives back which node belongs to
    /// it. It is possible only if there was read an "label" named map.
    void readLabel(std::istream& is, Node& node) const {
      node = inverter->read(is);
    } 

  private:

    typedef std::map<std::string, _reader_bits::MapReaderBase<Node>*> MapReaders;
    MapReaders readers;
   
    Graph& graph;   
    std::string name;
    _reader_bits::SkipReader<Node, DefaultSkipper> skipper;

    std::auto_ptr<_reader_bits::MapInverterBase<Node> > inverter;
  };

  /// \ingroup section_io
  /// \brief SectionReader for reading a graph's edgeset.
  ///
  /// The lemon format can store multiple graph edgesets with several maps.
  /// The edgeset section's header line is \c \@edgeset \c edgeset_name, but the
  /// \c edgeset_name may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes an edge in the edgeset. The
  /// line contains the source and the target nodes' id and the mapped 
  /// values for each map.
  ///
  /// If the edgeset contains an \c "label" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c readLabel() member will read a value from the given stream it will
  /// give back that edge which is mapped to this value.
  ///
  /// The edgeset reader needs a node id reader to identify which nodes
  /// have to be connected. If a NodeSetReader reads an "label" named map,
  /// it will be able to resolve the nodes by ids.
  ///
  /// \relates LemonReader
  template <typename _Graph, typename _Traits = DefaultReaderTraits>
  class EdgeSetReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;
    typedef typename Traits::Skipper DefaultSkipper;

    /// \brief Constructor.
    ///
    /// Constructor for EdgeSetReader. It creates the EdgeSetReader and
    /// attach it into the given LemonReader. The edgeset reader will
    /// add the read edges to the given Graph. It will use the given
    /// node id reader to read the source and target nodes of the edges.
    /// The reader will read the section only if the \c _name and the 
    /// \c edgset_name are the same. 
    template <typename NodeLabelReader>
    EdgeSetReader(LemonReader& _reader, 
                  Graph& _graph, 
                  const NodeLabelReader& _nodeLabelReader, 
                  const std::string& _name = std::string(),
                  const DefaultSkipper& _skipper = DefaultSkipper()) 
      : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {
      checkConcept<_reader_bits::ItemLabelReader<Node>, NodeLabelReader>();
      nodeLabelReader.reset(new _reader_bits::
                         LabelReader<Node, NodeLabelReader>(_nodeLabelReader));
    }
    /// \brief Destructor.
    ///
    /// Destructor for EdgeSetReader.
    virtual ~EdgeSetReader() {
      for (typename MapReaders::iterator it = readers.begin(); 
           it != readers.end(); ++it) {
        delete it->second;
      }
    }

  private:
    EdgeSetReader(const EdgeSetReader&);
    void operator=(const EdgeSetReader&);

  public:

    /// \brief Add a new edge map reader command for the reader.
    ///
    /// Add a new edge map reader command for the reader.
    template <typename Map>
    EdgeSetReader& readEdgeMap(std::string name, Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    template <typename Map>
    EdgeSetReader& readEdgeMap(std::string name, const Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    /// \brief Add a new edge map reader command for the reader.
    ///
    /// Add a new edge map reader command for the reader.
    template <typename Reader, typename Map>
    EdgeSetReader& readEdgeMap(std::string name, Map& map, 
                           const Reader& reader = Reader()) {
      return _readMap<Reader, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map, reader);
    }

    template <typename Reader, typename Map>
    EdgeSetReader& readEdgeMap(std::string name, const Map& map, 
                               const Reader& reader = Reader()) {
      return _readMap<Reader, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map, reader);
    }

  private:

    template <typename Reader, typename Map, typename MapParameter>
    EdgeSetReader& _readMap(std::string name, MapParameter map, 
                            const Reader& reader = Reader()) {
      checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();
      checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for edge map: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(
        make_pair(name, new _reader_bits::
                  MapReader<Edge, Map, Reader>(map, reader)));
      return *this;
    }

  public:

    /// \brief Add a new edge map skipper command for the reader.
    ///
    /// Add a new edge map skipper command for the reader.
    template <typename Reader>
    EdgeSetReader& skipEdgeMap(std::string name, 
                               const Reader& reader = Reader()) {
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for edge map: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, new _reader_bits::
                               SkipReader<Edge, Reader>(reader)));
      return *this;
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line starts with \c \@edgeset,
    /// and the header line's name and the edgeset's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@edgeset" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      if (!nodeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find nodeset or label map");
      }
      std::vector<_reader_bits::MapReaderBase<Edge>* > index;
      std::string line;

      getline(is, line);
      std::istringstream ls(line);      
      std::string id;
      while (ls >> id) {
        typename MapReaders::iterator it = readers.find(id);
        if (it != readers.end()) {
          index.push_back(it->second);
          it->second->touch();
        } else {
          index.push_back(&skipper);
        }
        if (id == "label") {
          inverter.reset(index.back()->getInverter());
          index.back() = inverter.get();
        }
      }
      for (typename MapReaders::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second->touched()) {
          ErrorMessage msg;
          msg << "Map not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
      while (getline(is, line)) {       
        std::istringstream ls(line);
        Node from = nodeLabelReader->read(ls);
        Node to = nodeLabelReader->read(ls);
        Edge edge = graph.addEdge(from, to);
        for (int i = 0; i < (int)index.size(); ++i) {
          index[i]->read(ls, edge);
        }
      }
    }

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "EdgeSet section not found in file: @edgeset " << name;
      throw IoParameterError(msg.message());
    }

  public:

    /// \brief Returns true if the edgeset can give back the edge by its label.
    ///
    /// Returns true if the edgeset can give back the edge by its label.
    /// It is possible only if an "label" named map was read.
    bool isLabelReader() const {
      return inverter.get() != 0;
    }

    /// \brief Gives back the edge by its label.
    ///
    /// It reads an id from the stream and gives back which edge belongs to
    /// it. It is possible only if there was read an "label" named map.
    void readLabel(std::istream& is, Edge& edge) const {
      edge = inverter->read(is);
    } 

  private:

    typedef std::map<std::string, _reader_bits::MapReaderBase<Edge>*> 
    MapReaders;
    
    MapReaders readers;
   
    Graph& graph;   
    std::string name;
    _reader_bits::SkipReader<Edge, DefaultSkipper> skipper;

    std::auto_ptr<_reader_bits::MapInverterBase<Edge> > inverter;
    std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;
  };

  /// \ingroup section_io
  /// \brief SectionReader for reading a undirected graph's edgeset.
  ///
  /// The lemon format can store multiple undirected edgesets with several 
  /// maps. The undirected edgeset section's header line is \c \@uedgeset 
  /// \c uedgeset_name, but the \c uedgeset_name may be empty.
  ///
  /// The first line of the section contains the names of the maps separated
  /// with white spaces. Each next lines describes an edge in the edgeset. The
  /// line contains the connected nodes' id and the mapped values for each map.
  ///
  /// The section can handle the directed as a syntactical sugar. Two
  /// undirected edge map describes one directed edge map. This two maps
  /// are the forward map and the backward map and the names of this map
  /// is near the same just with a prefix \c '+' or \c '-' character 
  /// difference.
  ///
  /// If the edgeset contains an \c "label" named map then it will be regarded
  /// as id map. This map should contain only unique values and when the 
  /// \c readLabel() member will read a value from the given stream it will
  /// give back that uicted edge which is mapped to this value.
  ///
  /// The undirected edgeset reader needs a node id reader to identify which 
  /// nodes have to be connected. If a NodeSetReader reads an "label" named 
  /// map, it will be able to resolve the nodes by ids.
  ///
  /// \relates LemonReader
  template <typename _Graph, typename _Traits = DefaultReaderTraits>
  class UEdgeSetReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
  public:

    typedef _Graph Graph;
    typedef _Traits Traits;
    typedef typename Graph::Node Node;
    typedef typename Graph::Edge Edge;
    typedef typename Graph::UEdge UEdge;
    typedef typename Traits::Skipper DefaultSkipper;

    /// \brief Constructor.
    ///
    /// Constructor for UEdgeSetReader. It creates the UEdgeSetReader 
    /// and attach it into the given LemonReader. The undirected edgeset 
    /// reader will add the read undirected edges to the given Graph. It 
    /// will use the given node id reader to read the source and target 
    /// nodes of the edges. The reader will read the section only if the 
    /// \c _name and the \c uedgset_name are the same. 
    template <typename NodeLabelReader>
    UEdgeSetReader(LemonReader& _reader, 
                       Graph& _graph, 
                       const NodeLabelReader& _nodeLabelReader, 
                       const std::string& _name = std::string(),
                       const DefaultSkipper& _skipper = DefaultSkipper()) 
      : Parent(_reader), graph(_graph), name(_name), skipper(_skipper) {
      checkConcept<_reader_bits::ItemLabelReader<Node>, NodeLabelReader>();
      nodeLabelReader.reset(new _reader_bits::
                         LabelReader<Node, NodeLabelReader>(_nodeLabelReader));
    }
    /// \brief Destructor.
    ///
    /// Destructor for UEdgeSetReader.
    virtual ~UEdgeSetReader() {
      for (typename MapReaders::iterator it = readers.begin(); 
           it != readers.end(); ++it) {
        delete it->second;
      }
    }

  private:
    UEdgeSetReader(const UEdgeSetReader&);
    void operator=(const UEdgeSetReader&);

  public:

    /// \brief Add a new undirected edge map reader command for the reader.
    ///
    /// Add a new edge undirected map reader command for the reader.
    template <typename Map>
    UEdgeSetReader& readUEdgeMap(std::string name, Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map, 
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    template <typename Map>
    UEdgeSetReader& readUEdgeMap(std::string name, const Map& map) {
      return _readMap<
        typename Traits::template Reader<typename Map::Value>, Map, 
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    /// \brief Add a new undirected edge map reader command for the reader.
    ///
    /// Add a new edge undirected map reader command for the reader.
    template <typename Reader, typename Map>
    UEdgeSetReader& readUEdgeMap(std::string name, Map& map, 
                                         const Reader& reader = Reader()) {
      return _readMap<Reader, Map, typename _reader_bits::Arg<Map>::Type>
        (name, map, reader);
    }

    template <typename Reader, typename Map>
    UEdgeSetReader& readUEdgeMap(std::string name, const Map& map, 
                                         const Reader& reader = Reader()) {
      return _readMap<Reader, Map, typename _reader_bits::Arg<Map>::Type >
        (name, map, reader);
    }

  private:

    template <typename Reader, typename Map, typename MapParameter>
    UEdgeSetReader& _readMap(std::string name, MapParameter map,
                                 const Reader& reader = Reader()) {
      checkConcept<concepts::WriteMap<UEdge, typename Map::Value>, Map>();
      checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for edge map: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(
        make_pair(name, new _reader_bits::
                  MapReader<UEdge, Map, Reader>(map, reader)));
      return *this;
    }

  public:

    /// \brief Add a new undirected edge map skipper command for the reader.
    ///
    /// Add a new undirected edge map skipper command for the reader.
    template <typename Reader>
    UEdgeSetReader& skipUEdgeMap(std::string name, 
                                         const Reader& reader = Reader()) {
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for node map: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, new _reader_bits::
                               SkipReader<UEdge, Reader>(reader)));
      return *this;
    }

    /// \brief Add a new directed edge map reader command for the reader.
    ///
    /// Add a new directed edge map reader command for the reader.
    template <typename Map>
    UEdgeSetReader& readEdgeMap(std::string name, Map& map) {
      return _readDirMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    template <typename Map>
    UEdgeSetReader& readEdgeMap(std::string name, const Map& map) {
      return _readDirMap<
        typename Traits::template Reader<typename Map::Value>, Map,
        typename _reader_bits::Arg<Map>::Type>(name, map);
    }

    /// \brief Add a new directed edge map reader command for the reader.
    ///
    /// Add a new directed edge map reader command for the reader.
    template <typename Reader, typename Map>
    UEdgeSetReader& readEdgeMap(std::string name, Map& map, 
                                    const Reader& reader = Reader()) {
      return _readDirMap<Reader, Map, typename _reader_bits::Arg<Map>::Type>
        (name, map, reader);
    }

    template <typename Reader, typename Map>
    UEdgeSetReader& readEdgeMap(std::string name, const Map& map, 
                                    const Reader& reader = Reader()) {
      return _readDirMap<Reader, Map, typename _reader_bits::Arg<Map>::Type>
        (name, map, reader);
    }

  private:

    template <typename Reader, typename Map, typename MapParameter>
    UEdgeSetReader& _readDirMap(std::string name, MapParameter map,
                                    const Reader& reader = Reader()) { 
      checkConcept<_reader_bits::ItemReader<typename Map::Value>, Reader>();
      checkConcept<concepts::WriteMap<Edge, typename Map::Value>, Map>();
      readUEdgeMap("+" + name, 
                   _reader_bits::forwardComposeMap(graph, map), reader);
      readUEdgeMap("-" + name, 
                   _reader_bits::backwardComposeMap(graph, map), reader);
      return *this;      
    }

  public:

    /// \brief Add a new directed edge map skipper command for the reader.
    ///
    /// Add a new directed edge map skipper command for the reader.
    template <typename Reader>
    UEdgeSetReader& skipEdgeMap(std::string name, 
                                const Reader& reader = Reader()) {
      skipUEdgeMap("+" + name, reader);
      skipUEdgeMap("-" + name, reader);
      return *this;
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line starts with \c \@uedgeset,
    /// and the header line's name and the edgeset's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@uedgeset" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      if (!nodeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find nodeset or label map");
      }
      std::vector<_reader_bits::MapReaderBase<UEdge>* > index;
      std::string line;

      getline(is, line);
      std::istringstream ls(line);      
      std::string id;
      while (ls >> id) {
        typename MapReaders::iterator it = readers.find(id);
        if (it != readers.end()) {
          index.push_back(it->second);
          it->second->touch();
        } else {
          index.push_back(&skipper);
        }
        if (id == "label") {
          inverter.reset(index.back()->getInverter());
          index.back() = inverter.get();
        }
      }
      for (typename MapReaders::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second->touched()) {
          ErrorMessage msg;
          msg << "Map not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
      while (getline(is, line)) {       
        std::istringstream ls(line);
        Node from = nodeLabelReader->read(ls);
        Node to = nodeLabelReader->read(ls);
        UEdge edge = graph.addEdge(from, to);
        for (int i = 0; i < (int)index.size(); ++i) {
          index[i]->read(ls, edge);
        }
      }
    }

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "UEdgeSet section not found in file: @uedgeset " << name;
      throw IoParameterError(msg.message());
    }

  public:

    /// \brief Returns true if the edgeset can give back the edge by its label.
    ///
    /// Returns true if the edgeset can give back the undirected edge by its 
    /// id. It is possible only if an "label" named map was read.
    bool isLabelReader() const {
      return inverter.get() != 0;
    }

    /// \brief Gives back the undirected edge by its label.
    ///
    /// It reads an id from the stream and gives back which undirected edge 
    /// belongs to it. It is possible only if there was read an "label" named map.
    void readLabel(std::istream& is, UEdge& uEdge) const {
      uEdge = inverter->read(is);
    } 

    /// \brief Gives back the directed edge by its label.
    ///
    /// It reads an id from the stream and gives back which directed edge 
    /// belongs to it. The directed edge id is the \c '+' or \c '-' character
    /// and the undirected edge id. It is possible only if there was read 
    /// an "label" named map.
    void readLabel(std::istream& is, Edge& edge) const {
      char c;
      is >> c;
      UEdge uEdge = inverter->read(is);
      if (c == '+') {
        edge = graph.direct(uEdge, true);
      } else if (c == '-') {
        edge = graph.direct(uEdge, false);
      } else {
        throw DataFormatError("Wrong id format for edge "
                              "in undirected edgeset");
      }
    } 

  private:

    typedef std::map<std::string, 
                     _reader_bits::MapReaderBase<UEdge>*> MapReaders;
    MapReaders readers;
   
    Graph& graph;   
    std::string name;
    _reader_bits::SkipReader<UEdge, DefaultSkipper> skipper;

    std::auto_ptr<_reader_bits::MapInverterBase<UEdge> > inverter;
    std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;
  };

  /// \ingroup section_io
  /// \brief SectionReader for reading labeled nodes.
  ///
  /// The nodes section's header line is \c \@nodes \c nodes_name, but the
  /// \c nodes_name may be empty.
  ///
  /// Each line in the section contains the name of the node 
  /// and then the node id. 
  ///
  /// \relates LemonReader
  template <typename _Graph>
  class NodeReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
    typedef _Graph Graph;
    typedef typename Graph::Node Node;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for NodeReader. It creates the NodeReader and
    /// attach it into the given LemonReader. It will use the given
    /// node id reader to give back the nodes. The reader will read the 
    /// section only if the \c _name and the \c nodes_name are the same. 
    template <typename _LabelReader>
    NodeReader(LemonReader& _reader, const _LabelReader& _labelReader, 
               const std::string& _name = std::string()) 
      : Parent(_reader), name(_name) {
      checkConcept<_reader_bits::ItemLabelReader<Node>, _LabelReader>();
      nodeLabelReader.reset(new _reader_bits::
                         LabelReader<Node, _LabelReader>(_labelReader));
    }

    /// \brief Destructor.
    ///
    /// Destructor for NodeReader.
    virtual ~NodeReader() {}

  private:
    NodeReader(const NodeReader&);
    void operator=(const NodeReader&);

  public:

    /// \brief Add a node reader command for the NodeReader.
    ///
    /// Add a node reader command for the NodeReader.
    void readNode(const std::string& name, Node& item) {
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for node: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, _reader_bits::ItemStore<Node>(item)));
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line start with \c \@nodes,
    /// and the header line's name and the reader's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@nodes" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      if (!nodeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find nodeset or label map");
      }
      std::string line;
      while (getline(is, line)) {
        std::istringstream ls(line);
        std::string id;
        ls >> id;
        typename NodeReaders::iterator it = readers.find(id);
        if (it != readers.end()) {
          it->second.read(nodeLabelReader->read(ls));
          it->second.touch();
        }       
      }
      for (typename NodeReaders::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second.touched()) {
          ErrorMessage msg;
          msg << "Node not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
    }

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "Nodes section not found in file: @nodes " << name;
      throw IoParameterError(msg.message());
    }
    
  private:

    std::string name;

    typedef std::map<std::string, _reader_bits::ItemStore<Node> > NodeReaders;
    NodeReaders readers;
    std::auto_ptr<_reader_bits::LabelReaderBase<Node> > nodeLabelReader;
  };

  /// \ingroup section_io
  /// \brief SectionReader for reading labeled edges.
  ///
  /// The edges section's header line is \c \@edges \c edges_name, but the
  /// \c edges_name may be empty.
  ///
  /// Each line in the section contains the name of the edge 
  /// and then the edge id. 
  ///
  /// \relates LemonReader
  template <typename _Graph>
  class EdgeReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
    typedef _Graph Graph;
    typedef typename Graph::Edge Edge;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for EdgeReader. It creates the EdgeReader and
    /// attach it into the given LemonReader. It will use the given
    /// edge id reader to give back the edges. The reader will read the 
    /// section only if the \c _name and the \c edges_name are the same. 
    template <typename _LabelReader>
    EdgeReader(LemonReader& _reader, const _LabelReader& _labelReader, 
               const std::string& _name = std::string()) 
      : Parent(_reader), name(_name) {
      checkConcept<_reader_bits::ItemLabelReader<Edge>, _LabelReader>();
      edgeLabelReader.reset(new _reader_bits::
                         LabelReader<Edge, _LabelReader>(_labelReader));
    }

    /// \brief Destructor.
    ///
    /// Destructor for EdgeReader.
    virtual ~EdgeReader() {}
  private:
    EdgeReader(const EdgeReader&);
    void operator=(const EdgeReader&);

  public:

    /// \brief Add an edge reader command for the EdgeReader.
    ///
    /// Add an edge reader command for the EdgeReader.
    void readEdge(const std::string& name, Edge& item) {
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for edge: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, _reader_bits::ItemStore<Edge>(item)));
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line start with \c \@edges,
    /// and the header line's name and the reader's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@edges" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      if (!edgeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find edgeset or label map");
      }
      std::string line;
      while (getline(is, line)) {
        std::istringstream ls(line);
        std::string id;
        ls >> id;
        typename EdgeReaders::iterator it = readers.find(id);
        if (it != readers.end()) {
          it->second.read(edgeLabelReader->read(ls));
          it->second.touch();
        }       
      }
      for (typename EdgeReaders::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second.touched()) {
          ErrorMessage msg;
          msg << "Edge not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
    }

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "Edges section not found in file: @edges " << name;
      throw IoParameterError(msg.message());
    }
    
  private:

    std::string name;

    typedef std::map<std::string, _reader_bits::ItemStore<Edge> > EdgeReaders;
    EdgeReaders readers;
    std::auto_ptr<_reader_bits::LabelReaderBase<Edge> > edgeLabelReader;
  };

  /// \ingroup section_io
  /// \brief SectionReader for reading labeled undirected edges.
  ///
  /// The undirected edges section's header line is \c \@uedges 
  /// \c uedges_name, but the \c uedges_name may be empty.
  ///
  /// Each line in the section contains the name of the undirected edge 
  /// and then the undirected edge id. 
  ///
  /// \relates LemonReader
  template <typename _Graph>
  class UEdgeReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
    typedef _Graph Graph;
    typedef typename Graph::Edge Edge;
    typedef typename Graph::UEdge UEdge;
  public:
    
    /// \brief Constructor.
    ///
    /// Constructor for UEdgeReader. It creates the UEdgeReader and
    /// attach it into the given LemonReader. It will use the given
    /// undirected edge id reader to give back the edges. The reader will 
    /// read the section only if the \c _name and the \c uedges_name are 
    /// the same. 
    template <typename _LabelReader>
    UEdgeReader(LemonReader& _reader, const _LabelReader& _labelReader, 
               const std::string& _name = std::string()) 
      : Parent(_reader), name(_name) {
      checkConcept<_reader_bits::ItemLabelReader<UEdge>, _LabelReader>();
      checkConcept<_reader_bits::ItemLabelReader<Edge>, _LabelReader>();
      uEdgeLabelReader.reset(new _reader_bits::
                              LabelReader<UEdge, _LabelReader>(_labelReader));
      edgeLabelReader.reset(new _reader_bits::
                         LabelReader<Edge, _LabelReader>(_labelReader));
    }

    /// \brief Destructor.
    ///
    /// Destructor for UEdgeReader.
    virtual ~UEdgeReader() {}
  private:
    UEdgeReader(const UEdgeReader&);
    void operator=(const UEdgeReader&);

  public:

    /// \brief Add an undirected edge reader command for the UEdgeReader.
    ///
    /// Add an undirected edge reader command for the UEdgeReader.
    void readUEdge(const std::string& name, UEdge& item) {
      if (uEdgeReaders.find(name) != uEdgeReaders.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for undirected edge: " << name;
        throw IoParameterError(msg.message());
      }
      uEdgeReaders.insert(make_pair(name, _reader_bits::
                                        ItemStore<UEdge>(item)));
    }

    /// \brief Add an edge reader command for the UEdgeReader.
    ///
    /// Add an edge reader command for the UEdgeReader.
    void readEdge(const std::string& name, Edge& item) {
      if (edgeReaders.find(name) != edgeReaders.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for edge: " << name;
        throw IoParameterError(msg.message());
      }
      edgeReaders.insert(make_pair(name, _reader_bits::ItemStore<Edge>(item)));
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line start with \c \@edges,
    /// and the header line's name and the reader's name are the same.
    virtual bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@uedges" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    virtual void read(std::istream& is) {
      if (!edgeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find undirected edgeset or label map");
      }
      if (!uEdgeLabelReader->isLabelReader()) {
        throw DataFormatError("Cannot find undirected edgeset or label map");
      }
      std::string line;
      while (getline(is, line)) {
        std::istringstream ls(line);
        std::string id;
        ls >> id;
        {
          typename UEdgeReaders::iterator it = uEdgeReaders.find(id);
          if (it != uEdgeReaders.end()) {
            it->second.read(uEdgeLabelReader->read(ls));
            it->second.touch();
            continue;
          }     
        } {
          typename EdgeReaders::iterator it = edgeReaders.find(id);
          if (it != edgeReaders.end()) {
            it->second.read(edgeLabelReader->read(ls));
            it->second.touch();
            continue;
          }     
        }
      }
      for (typename EdgeReaders::iterator it = edgeReaders.begin();
           it != edgeReaders.end(); ++it) {
        if (!it->second.touched()) {
          ErrorMessage msg;
          msg << "Edge not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
      for (typename UEdgeReaders::iterator it = uEdgeReaders.begin();
           it != uEdgeReaders.end(); ++it) {
        if (!it->second.touched()) {
          ErrorMessage msg;
          msg << "UEdge not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }
      }
    }

    virtual void missing() {
      if (edgeReaders.empty() && uEdgeReaders.empty()) return;
      ErrorMessage msg;
      msg << "UEdges section not found in file: @uedges " << name;
      throw IoParameterError(msg.message());
    }
    
  private:

    std::string name;

    typedef std::map<std::string, 
                     _reader_bits::ItemStore<UEdge> > UEdgeReaders;
    UEdgeReaders uEdgeReaders;
    std::auto_ptr<_reader_bits::LabelReaderBase<UEdge> > uEdgeLabelReader;

    typedef std::map<std::string, _reader_bits::ItemStore<Edge> > EdgeReaders;
    EdgeReaders edgeReaders;
    std::auto_ptr<_reader_bits::LabelReaderBase<Edge> > edgeLabelReader;
  };

  /// \ingroup section_io
  /// \brief SectionReader for attributes.
  ///
  /// The lemon format can store multiple attribute set. Each set has
  /// the header line \c \@attributes \c attributeset_name, but the 
  /// attributeset_name may be empty.
  ///
  /// The attributeset section contains several lines. Each of them starts
  /// with an attribute and then a the value for the id.
  ///
  /// \relates LemonReader
  template <typename _Traits = DefaultReaderTraits>
  class AttributeReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
    typedef _Traits Traits; 
  public:
    /// \brief Constructor.
    ///
    /// Constructor for AttributeReader. It creates the AttributeReader and
    /// attach it into the given LemonReader. The reader process a section
    /// only if the \c section_name and the \c _name are the same.
    AttributeReader(LemonReader& _reader, 
                    const std::string& _name = std::string()) 
      : Parent(_reader), name(_name) {}

    /// \brief Destructor.
    ///
    /// Destructor for AttributeReader.
    virtual ~AttributeReader() {
      for (typename Readers::iterator it = readers.begin(); 
           it != readers.end(); ++it) {
        delete it->second;
      }
    }

  private:
    AttributeReader(const AttributeReader&);
    void operator=(AttributeReader&);

  public:
    /// \brief Add an attribute reader command for the reader.
    ///
    /// Add an attribute reader command for the reader.
    template <typename Value>
    AttributeReader& readAttribute(const std::string& id, Value& value) {
      return readAttribute<typename Traits::template Reader<Value> >
        (id, value);
    }

    /// \brief Add an attribute reader command for the reader.
    ///
    /// Add an attribute reader command for the reader.
    template <typename Reader, typename Value>
    AttributeReader& readAttribute(const std::string& name, Value& value,
                                   const Reader& reader = Reader()) {
      checkConcept<_reader_bits::ItemReader<Value>, Reader>();
      if (readers.find(name) != readers.end()) {
        ErrorMessage msg;
        msg << "Multiple read rule for attribute: " << name;
        throw IoParameterError(msg.message());
      }
      readers.insert(make_pair(name, new _reader_bits::
                               ValueReader<Value, Reader>(value, reader)));
      return *this;
    }

  protected:

    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the header line start with \c \@attributes,
    /// and the header line's id and the attributeset's id are the same.
    bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command;
      std::string id;
      ls >> command >> id;
      return command == "@attributes" && name == id;
    }

    /// \brief Reader function of the section.
    ///
    /// It reads the content of the section.
    void read(std::istream& is) {
      std::string line;
      while (getline(is, line)) {
        std::istringstream ls(line);
        std::string id;
        ls >> id;
        typename Readers::iterator it = readers.find(id);
        if (it != readers.end()) {
          it->second->read(ls);
          it->second->touch();
        }
      }
      for (typename Readers::iterator it = readers.begin();
           it != readers.end(); ++it) {
        if (!it->second->touched()) {
          ErrorMessage msg;
          msg << "Attribute not found in file: " << it->first;
          throw IoParameterError(msg.message());
        }       
      }
    }    

    virtual void missing() {
      if (readers.empty()) return;
      ErrorMessage msg;
      msg << "Attribute section not found in file: @attributes " << name;
      throw IoParameterError(msg.message());
    }

  private:
    std::string name;

    typedef std::map<std::string, _reader_bits::ValueReaderBase*> Readers;
    Readers readers;  
  };

  /// \ingroup section_io
  /// \brief SectionReader for retrieve what is in the file.
  ///
  /// SectionReader for retrieve what is in the file. If you want
  /// to know which sections, maps and items are in the file
  /// use the next code:
  ///\code
  /// LemonReader reader("input.lgf");
  /// ContentReader content(reader);
  /// reader.run();
  ///\endcode
  class ContentReader : public LemonReader::SectionReader {
    typedef LemonReader::SectionReader Parent;
  public:
    /// \brief Constructor.
    ///
    /// Constructor for
    ContentReader(LemonReader& _reader) : Parent(_reader) {}

    /// \brief Desctructor.
    ///
    /// Desctructor.
    virtual ~ContentReader() {}

    /// \brief Gives back how many nodesets are in the file.
    ///
    /// Gives back how many nodesets are in the file.
    int nodeSetNum() const {
      return nodesets.size();
    }

    /// \brief Gives back the name of nodeset on the indiced position.
    ///
    /// Gives back the name of nodeset on the indiced position.
    std::string nodeSetName(int index) const {
      return nodesets[index].name;
    }

    /// \brief Gives back the map names of nodeset on the indiced position.
    ///
    /// Gives back the map names of nodeset on the indiced position.
    const std::vector<std::string>& nodeSetMaps(int index) const {
      return nodesets[index].items;
    }

    /// \brief Gives back how many edgesets are in the file.
    ///
    /// Gives back how many edgesets are in the file.
    int edgeSetNum() const {
      return edgesets.size();
    }

    /// \brief Gives back the name of edgeset on the indiced position.
    ///
    /// Gives back the name of edgeset on the indiced position.
    std::string edgeSetName(int index) const {
      return edgesets[index].name;
    }

    /// \brief Gives back the map names of edgeset on the indiced position.
    ///
    /// Gives back the map names of edgeset on the indiced position.
    const std::vector<std::string>& edgeSetMaps(int index) const {
      return edgesets[index].items;
    }

    /// \brief Gives back how many undirected edgesets are in the file.
    ///
    /// Gives back how many undirected edgesets are in the file.
    int uEdgeSetNum() const {
      return uedgesets.size();
    }

    /// \brief Gives back the name of undirected edgeset on the indiced 
    /// position.
    ///
    /// Gives back the name of undirected edgeset on the indiced position.
    std::string uEdgeSetName(int index) const {
      return uedgesets[index].name;
    }

    /// \brief Gives back the map names of undirected edgeset on the indiced 
    /// position.
    ///
    /// Gives back the map names of undirected edgeset on the indiced position.
    const std::vector<std::string>& uEdgeSetMaps(int index) const {
      return uedgesets[index].items;
    }

    /// \brief Gives back how many labeled nodes section are in the file.
    ///
    /// Gives back how many labeled nodes section are in the file.
    int nodesNum() const {
      return nodes.size();
    }

    /// \brief Gives back the name of labeled nodes section on the indiced 
    /// position.
    ///
    /// Gives back the name of labeled nodes section on the indiced position.
    std::string nodesName(int index) const {
      return nodes[index].name;
    }

    /// \brief Gives back the names of the labeled nodes in the indiced 
    /// section.
    ///
    /// Gives back the names of the labeled nodes in the indiced section.
    const std::vector<std::string>& nodesItems(int index) const {
      return nodes[index].items;
    }

    /// \brief Gives back how many labeled edges section are in the file.
    ///
    /// Gives back how many labeled edges section are in the file.
    int edgesNum() const {
      return edges.size();
    }

    /// \brief Gives back the name of labeled edges section on the indiced 
    /// position.
    ///
    /// Gives back the name of labeled edges section on the indiced position.
    std::string edgesName(int index) const {
      return edges[index].name;
    }

    /// \brief Gives back the names of the labeled edges in the indiced 
    /// section.
    ///
    /// Gives back the names of the labeled edges in the indiced section.
    const std::vector<std::string>& edgesItems(int index) const {
      return edges[index].items;
    }
 
    /// \brief Gives back how many labeled undirected edges section are 
    /// in the file.
    ///
    /// Gives back how many labeled undirected edges section are in the file.
    int uEdgesNum() const {
      return uedges.size();
    }

    /// \brief Gives back the name of labeled undirected edges section 
    /// on the indiced position.
    ///
    /// Gives back the name of labeled undirected edges section on the 
    /// indiced position.
    std::string uEdgesName(int index) const {
      return uedges[index].name;
    }

    /// \brief Gives back the names of the labeled undirected edges in 
    /// the indiced section.
    ///
    /// Gives back the names of the labeled undirected edges in the 
    /// indiced section.
    const std::vector<std::string>& uEdgesItems(int index) const {
      return uedges[index].items;
    }

 
    /// \brief Gives back how many attributes section are in the file.
    ///
    /// Gives back how many attributes section are in the file.
    int attributesNum() const {
      return attributes.size();
    }

    /// \brief Gives back the name of attributes section on the indiced 
    /// position.
    ///
    /// Gives back the name of attributes section on the indiced position.
    std::string attributesName(int index) const {
      return attributes[index].name;
    }

    /// \brief Gives back the names of the attributes in the indiced section.
    ///
    /// Gives back the names of the attributes in the indiced section.
    const std::vector<std::string>& attributesItems(int index) const {
      return attributes[index].items;
    }

    const std::vector<std::string>& otherSections() const {
      return sections;
    }

  protected:
    
    /// \brief Gives back true when the SectionReader can process 
    /// the section with the given header line.
    ///
    /// It gives back true when the section is common section.
    bool header(const std::string& line) {
      std::istringstream ls(line);
      std::string command, name;
      ls >> command >> name;
      if (command == "@nodeset") {
        current = command;
        nodesets.push_back(SectionInfo(name));
      } else if (command == "@edgeset") {
        current = command;
        edgesets.push_back(SectionInfo(name));
      } else if (command == "@uedgeset") {
        current = command;
        uedgesets.push_back(SectionInfo(name));
      } else if (command == "@nodes") {
        current = command;
        nodes.push_back(SectionInfo(name));
      } else if (command == "@edges") {
        current = command;
        edges.push_back(SectionInfo(name));
      } else if (command == "@uedges") {
        current = command;
        uedges.push_back(SectionInfo(name));
      } else if (command == "@attributes") {
        current = command;
        attributes.push_back(SectionInfo(name));
      } else {
        sections.push_back(line);
        return false;
      }
      return true;
    }

    /// \brief Retrieve the items from various sections.
    ///
    /// Retrieve the items from various sections.
    void read(std::istream& is) {
      if (current == "@nodeset") {
        readMapNames(is, nodesets.back().items);
      } else if (current == "@edgeset") {
        readMapNames(is, edgesets.back().items);
      } else if (current == "@uedgeset") {
        readMapNames(is, uedgesets.back().items);
      } else if (current == "@nodes") {
        readItemNames(is, nodes.back().items);
      } else if (current == "@edges") {
        readItemNames(is, edges.back().items);
      } else if (current == "@uedges") {
        readItemNames(is, uedges.back().items);
      } else if (current == "@attributes") {
        readItemNames(is, attributes.back().items);
      }
    }    

  private:

    void readMapNames(std::istream& is, std::vector<std::string>& maps) {
      std::string line, name;
      std::getline(is, line);
      std::istringstream ls(line);
      while (ls >> name) {
        maps.push_back(name);
      }
      while (getline(is, line));
    }

    void readItemNames(std::istream& is, std::vector<std::string>& maps) {
      std::string line, name;
      while (std::getline(is, line)) {
        std::istringstream ls(line);
        ls >> name;
        maps.push_back(name);
      }
    }

    struct SectionInfo {
      std::string name;
      std::vector<std::string> items;

      SectionInfo(const std::string& _name) : name(_name) {}
    };

    std::vector<SectionInfo> nodesets;
    std::vector<SectionInfo> edgesets;
    std::vector<SectionInfo> uedgesets;

    std::vector<SectionInfo> nodes;
    std::vector<SectionInfo> edges;
    std::vector<SectionInfo> uedges;

    std::vector<SectionInfo> attributes;

    std::vector<std::string> sections;

    std::string current;

  };

}
#endif