RhodeCode

      }

    };

    template <typename _TypeMap>

    struct Memory<-1, _TypeMap> {

      static void destroy(int, char*) {

        LEMON_DEBUG(false, "Variant wrong index.");

      }

      static void copy(int, char*, const char*) {

        LEMON_DEBUG(false, "Variant wrong index.");

      }

    };

    template <int _idx, typename _TypeMap>

    struct Size {

      static const int value =

      CTMax<sizeof(typename _TypeMap::template Map<_idx>::Type),

            Size<_idx - 1, _TypeMap>::value>::value;

    };

    template <typename _TypeMap>

    struct Size<0, _TypeMap> {

      static const int value =

      sizeof(typename _TypeMap::template Map<0>::Type);

    };

  }

  /// \brief Variant type

  ///

  /// Simple Variant type. The Variant type is a type safe union. The

  /// C++ has strong limitations for using unions, for example we

  /// cannot store type with non default constructor or destructor in

  /// a union. This class always knowns the current state of the

  /// variant and it cares for the proper construction and

  /// destruction.

  ///

  /// \param _num The number of the types which can be stored in the

  /// variant type.

  /// \param _TypeMap This class describes the types of the Variant. The

  /// _TypeMap::Map<index>::Type should be a valid type for each index

  /// in the range {0, 1, ..., _num - 1}. The \c VariantTypeMap is helper

  /// class to define such type mappings up to 10 types.

  ///

  /// And the usage of the class:

  ///\code

  /// typedef Variant<3, VariantTypeMap<int, std::string, double> > MyVariant;

  /// MyVariant var;

  /// var.set<0>(12);

  /// std::cout << var.get<0>() << std::endl;

  /// var.set<1>("alpha");

  /// std::cout << var.get<1>() << std::endl;

  /// var.set<2>(0.75);

  /// std::cout << var.get<2>() << std::endl;

  ///\endcode

  ///

  /// The result of course:

  ///\code

  /// 12

  /// alpha

  /// 0.75

  ///\endcode

  template <int _num, typename _TypeMap>

  class Variant {

  public:

    static const int num = _num;

    typedef _TypeMap TypeMap;

    /// \brief Constructor

    ///

    /// This constructor initalizes to the default value of the \c type

    /// with 0 index.

    Variant() {

      flag = 0;

      new(reinterpret_cast<typename TypeMap::template Map<0>::Type*>(data))

        typename TypeMap::template Map<0>::Type();

    }

    /// \brief Copy constructor

    ///

    /// Copy constructor

    Variant(const Variant& variant) {

      flag = variant.flag;

      _variant_bits::Memory<num - 1, TypeMap>::copy(flag, data, variant.data);

    }

    /// \brief Assign operator

    ///

    /// Assign operator

    Variant& operator=(const Variant& variant) {

      if (this == &variant) return *this;

      _variant_bits::Memory<num - 1, TypeMap>::

        destroy(flag, data);

      flag = variant.flag;

      _variant_bits::Memory<num - 1, TypeMap>::

        copy(flag, data, variant.data);

      return *this;

    }

    /// \brief Destrcutor

    ///

    /// Destructor

    ~Variant() {

      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

    }

    /// \brief Set to the default value of the type with \c _idx index.

    ///

    /// This function sets the variant to the default value of the

    /// type with \c _idx index.

    template <int _idx>

    Variant& set() {

      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

      flag = _idx;

      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))

        typename TypeMap::template Map<_idx>::Type();

      return *this;

    }

    /// \brief Set to the given value of the type with \c _idx index.

    ///

    /// This function sets the variant to the given value of the type

    /// with \c _idx index.

    template <int _idx>

    Variant& set(const typename _TypeMap::template Map<_idx>::Type& init) {

      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);

      flag = _idx;

      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))

        typename TypeMap::template Map<_idx>::Type(init);

      return *this;

    }

    /// \brief Gets the current value of the type with \c _idx index.

    ///

    /// Gets the current value of the type with \c _idx index.

    template <int _idx>

    const typename TypeMap::template Map<_idx>::Type& get() const {

      LEMON_DEBUG(_idx == flag, "Variant wrong index");

      return *reinterpret_cast<const typename TypeMap::

        template Map<_idx>::Type*>(data);

    }

    /// \brief Gets the current value of the type with \c _idx index.

    ///

    /// Gets the current value of the type with \c _idx index.

    template <int _idx>

    typename _TypeMap::template Map<_idx>::Type& get() {

      LEMON_DEBUG(_idx == flag, "Variant wrong index");

      return *reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>

        (data);

    }

    /// \brief Returns the current state of the variant.

    ///

    /// Returns the current state of the variant.

    int state() const {

      return flag;

    }

  private:

    char data[_variant_bits::Size<num - 1, TypeMap>::value];

    int flag;

  };

  namespace _variant_bits {

    template <int _index, typename _List>

    struct Get {

      typedef typename Get<_index - 1, typename _List::Next>::Type Type;

    };

    template <typename _List>

    struct Get<0, _List> {

      typedef typename _List::Type Type;

    };

    struct List {};

    template <typename _Type, typename _List>

    struct Insert {

      typedef _List Next;

      typedef _Type Type;

    };

    template <int _idx, typename _T0, typename _T1, typename _T2,

              typename _T7, typename _T8, typename _T9>

    struct Mapper {

      typedef List L10;

      typedef Insert<_T9, L10> L9;

      typedef Insert<_T8, L9> L8;

      typedef Insert<_T7, L8> L7;

      typedef Insert<_T6, L7> L6;

      typedef Insert<_T5, L6> L5;

      typedef Insert<_T4, L5> L4;

      typedef Insert<_T3, L4> L3;

      typedef Insert<_T2, L3> L2;

      typedef Insert<_T1, L2> L1;

      typedef Insert<_T0, L1> L0;

      typedef typename Get<_idx, L0>::Type Type;

    };

  }

  /// \brief Helper class for Variant

  ///

  /// Helper class to define type mappings for Variant. This class

  /// converts the template parameters to be mappable by integer.

  /// \see Variant

  template <

    typename _T0,

    typename _T1 = void, typename _T2 = void, typename _T3 = void,

    typename _T7 = void, typename _T8 = void, typename _T9 = void>

  struct VariantTypeMap {

    template <int _idx>

    struct Map {

      typedef typename _variant_bits::

      Mapper<_idx, _T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9>::Type

      Type;

    };

  };

}

#endif