robot/include/rttr/detail/misc/iterator_wrapper.h

/************************************************************************************
*                                                                                   *
*   Copyright (c) 2014 - 2018 Axel Menzel <info@rttr.org>                           *
*                                                                                   *
*   This file is part of RTTR (Run Time Type Reflection)                            *
*   License: MIT License                                                            *
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#ifndef RTTR_ITERATOR_WRAPPER_H_
#define RTTR_ITERATOR_WRAPPER_H_

#include "rttr/detail/base/core_prerequisites.h"

#include "rttr/variant.h"

#include <memory>
#include <type_traits>

namespace rttr
{
namespace detail
{

using iterator_data = std::aligned_storage<sizeof(double)>::type;

template<typename T, bool Can_Place = (sizeof(T) <= sizeof(iterator_data)) &&
                                      (std::alignment_of<T>::value <= std::alignment_of<iterator_data>::value)>
using can_place_in_iterator_data = std::integral_constant<bool, Can_Place>;

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Itr>
struct iterator_wrapper_small
{
    using type = Itr;
    using iterator = Itr;

    static const Itr& get_iterator(const iterator_data& data)
    {
        return reinterpret_cast<const Itr&>(data);
    }

    static Itr& get_iterator(iterator_data& data)
    {
        return reinterpret_cast<Itr&>(data);
    }

    static void create(iterator_data& itr_tgt, const iterator& itr_src)
    {
        new (&itr_tgt) iterator(itr_src);
    }

    static void create(iterator_data& itr_tgt, const iterator_data& itr_src)
    {
        new (&itr_tgt) iterator(get_iterator(itr_src));
    }

    static void destroy(iterator_data& itr)
    {
        get_iterator(itr).~Itr();
    }
};

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Itr>
struct iterator_wrapper_big
{
    using type = Itr;
    using iterator = Itr;

    static const Itr& get_iterator(const iterator_data& data)
    {
        return *reinterpret_cast<Itr* const &>(data);
    }

    static Itr& get_iterator(iterator_data& data)
    {
        return *reinterpret_cast<Itr*&>(data);
    }

    static void create(iterator_data& itr_tgt, const iterator& itr_src)
    {
        reinterpret_cast<Itr*&>(itr_tgt) = new iterator(itr_src);
    }

    static void create(iterator_data& itr_tgt, const iterator_data& itr_src)
    {
        reinterpret_cast<Itr*&>(itr_tgt) = new iterator(*reinterpret_cast<Itr* const &>(itr_src));
    }

    static void destroy(iterator_data& itr)
    {
        auto& it = get_iterator(itr);
        delete &it;
    }
};

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Itr, typename Tp = conditional_t<can_place_in_iterator_data<Itr>::value,
                                                   iterator_wrapper_small<Itr>,
                                                   iterator_wrapper_big<Itr>>>
struct iterator_wrapper_base : Tp
{

    static void advance(iterator_data& itr, std::ptrdiff_t idx)
    {
        std::advance(Tp::get_iterator(itr), idx);
    }

    static bool equal(const iterator_data& lhs_itr, const iterator_data& rhs_itr) RTTR_NOEXCEPT
    {
        return (Tp::get_iterator(lhs_itr) == Tp::get_iterator(rhs_itr));
    }
};

/////////////////////////////////////////////////////////////////////////////////////////

template<typename Itr>
struct iterator_wrapper_associative_container : iterator_wrapper_base<Itr>
{
    static variant get_key(const iterator_data& itr)
    {
        auto& it = iterator_wrapper_base<Itr>::get_iterator(itr);
        return variant(std::ref(it->first));
    }

    static variant get_value(const iterator_data& itr)
    {
        auto& it = iterator_wrapper_base<Itr>::get_iterator(itr);
        return variant(std::ref(it->second));
    }
};

} // end namespace detail
} // end namespace rttr

#endif // RTTR_ITERATOR_WRAPPER_H_