source: lemon-0.x/lemon/bits/variant.h @ 2204:5617107d27e9

/* -*- 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.
 *
 */

#ifndef LEMON_BITS_VARIANT_H
#define LEMON_BITS_VARIANT_H

#include <lemon/error.h>

namespace lemon {

  template <bool left, bool right>
  struct CTOr {
    static const bool value = true;
  };

  template <>
  struct CTOr<false, false> {
    static const bool value = false;
  };

  template <bool left, bool right>
  struct CTAnd {
    static const bool value = false;
  };

  template <>
  struct CTAnd<true, true> {
    static const bool value = true;
  };

  template <int left, int right>
  struct CTEqual {
    static const bool value = false;
  };

  template <int val>
  struct CTEqual<val, val> {
    static const bool value = true;
  };


  template <int left, int right>
  struct CTLess {
    static const bool value = left < right;
  };

  template <int left>
  struct CTLess<left, 0> {
    static const bool value = false;
  };

  template <int right>
  struct CTLess<0, right> {
    static const bool value = true;
  };

  template <>
  struct CTLess<0, 0> {
    static const bool value = false;
  };

  template <>
  struct CTLess<1, 1> {
    static const bool value = false;
  };

  template <bool less, int left, int right>
  struct CTMaxImpl {
    static const int value = left;    
  };

  template <int left, int right>
  struct CTMaxImpl<true, left, right> {
    static const int value = right;
  };
  
  template <int left, int right>
  struct CTMax {
    static const int value = 
    CTMaxImpl<CTLess<left, right>::value, left, right>::value;
  };


  /// \brief Simple Variant type with two type
  ///
  /// Simple Variant type with two type
  template <typename _First, typename _Second>
  class BiVariant {
  public:

    typedef _First First;
    typedef _Second Second;

    struct WrongStateError : public lemon::LogicError {
    public:
      virtual const char* what() const throw() {
        return "lemon::BiVariant::WrongStateError";
      }
    };

    BiVariant() {
      flag = true;
      new(reinterpret_cast<First*>(data)) First();
    }

    BiVariant(const First& first) {
      flag = true;
      new(reinterpret_cast<First*>(data)) First(first);
    }

    BiVariant(const Second& second) {
      flag = false;
      new(reinterpret_cast<Second*>(data)) Second(second);
    }

    BiVariant(const BiVariant& bivariant) {
      flag = bivariant.flag;
      if (flag) {
        new(reinterpret_cast<First*>(data)) First(bivariant.first());      
      } else {
        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      
      }
    }

    ~BiVariant() {
      destroy();
    }

    BiVariant& setFirst() {
      destroy();
      flag = true;
      new(reinterpret_cast<First*>(data)) First();   
      return *this;
    }

    BiVariant& setFirst(const First& first) {
      destroy();
      flag = true;
      new(reinterpret_cast<First*>(data)) First(first);   
      return *this;
    }

    BiVariant& setSecond() {
      destroy();
      flag = false;
      new(reinterpret_cast<Second*>(data)) Second();   
      return *this;
    }

    BiVariant& setSecond(const Second& second) {
      destroy();
      flag = false;
      new(reinterpret_cast<Second*>(data)) Second(second);   
      return *this;
    }

    BiVariant& operator=(const First& first) {
      return setFirst(first);
    }

    BiVariant& operator=(const Second& second) {
      return setSecond(second);
    }


    BiVariant& operator=(const BiVariant& bivariant) {
      if (this == &bivariant) return *this;
      destroy();
      flag = bivariant.flag;
      if (flag) {
        new(reinterpret_cast<First*>(data)) First(bivariant.first());      
      } else {
        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      
      }
      return *this;
    }

    First& first() {
      LEMON_ASSERT(flag, WrongStateError());
      return *reinterpret_cast<First*>(data); 
    }

    const First& first() const { 
      LEMON_ASSERT(flag, WrongStateError());
      return *reinterpret_cast<const First*>(data); 
    }

    operator First&() { return first(); }
    operator const First&() const { return first(); }

    Second& second() { 
      LEMON_ASSERT(!flag, WrongStateError());
      return *reinterpret_cast<Second*>(data); 
    }

    const Second& second() const { 
      LEMON_ASSERT(!flag, WrongStateError());
      return *reinterpret_cast<const Second*>(data); 
    }

    operator Second&() { return second(); }
    operator const Second&() const { return second(); }

    bool firstState() const { return flag; }
    bool secondState() const { return !flag; }

  private:

    void destroy() {
      if (flag) {
        reinterpret_cast<First*>(data)->~First();
      } else {
        reinterpret_cast<Second*>(data)->~Second();
      }
    }
    
    char data[CTMax<sizeof(First), sizeof(Second)>::value];
    bool flag;
  };

}


#endif