variant.hpp

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/*
  Copyright (c) 2014, 2017, Randolph Voorhies, Shane Grant, Juan Pedro
  Bolivar Puente. All rights reserved.
 
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
      * Neither the name of the copyright holder nor the
        names of its contributors may be used to endorse or promote products
        derived from this software without specific prior written permission.
 
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
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  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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*/
#ifndef CEREAL_TYPES_STD_VARIANT_HPP_
#define CEREAL_TYPES_STD_VARIANT_HPP_
 
#include "cereal/cereal.hpp"
#include <variant>
#include <cstdint>
 
namespace cereal
{
  namespace variant_detail
  {
    template <class Archive>
    struct variant_save_visitor
    {
      variant_save_visitor(Archive & ar_) : ar(ar_) {}
 
      template<class T>
        void operator()(T const & value) const
        {
          ar( CEREAL_NVP_("data", value) );
        }
 
      Archive & ar;
    };
 
    template<int N, class Variant, class Archive>
    typename std::enable_if<N == std::variant_size_v<Variant>, void>::type
    load_variant(Archive & /*ar*/, int /*target*/, Variant & /*variant*/)
    {
      throw ::cereal::Exception("Error traversing variant during load");
    }
    template<int N, class Variant, class Archive>
    typename std::enable_if<N < std::variant_size_v<Variant>, void>::type
    load_variant(Archive & ar, int target, Variant & variant)
    {
      if(N == target)
      {
        variant.template emplace<N>();
        ar( CEREAL_NVP_("data", std::get<N>(variant)) );
      }
      else
        load_variant<N+1>(ar, target, variant);
    }
 
  } // namespace variant_detail
 
  template <class Archive, typename VariantType1, typename... VariantTypes> inline
  void CEREAL_SAVE_FUNCTION_NAME( Archive & ar, std::variant<VariantType1, VariantTypes...> const & variant )
  {
    std::int32_t index = static_cast<std::int32_t>(variant.index());
    ar( CEREAL_NVP_("index", index) );
    variant_detail::variant_save_visitor<Archive> visitor(ar);
    std::visit(visitor, variant);
  }
 
  template <class Archive, typename... VariantTypes> inline
  void CEREAL_LOAD_FUNCTION_NAME( Archive & ar, std::variant<VariantTypes...> & variant )
  {
    using variant_t = typename std::variant<VariantTypes...>;
 
    std::int32_t index;
    ar( CEREAL_NVP_("index", index) );
    if(index >= static_cast<std::int32_t>(std::variant_size_v<variant_t>))
      throw Exception("Invalid 'index' selector when deserializing std::variant");
 
    variant_detail::load_variant<0>(ar, index, variant);
  }
 
  template <class Archive>
  void CEREAL_SERIALIZE_FUNCTION_NAME( Archive &, std::monostate const & ) {}
} // namespace cereal
 
#endif // CEREAL_TYPES_STD_VARIANT_HPP_