include/nlohmann/detail/iterators/iterator_traits.hpp

#pragma once

#include <iterator> // random_access_iterator_tag

#include <nlohmann/detail/meta/void_t.hpp>
#include <nlohmann/detail/meta/cpp_future.hpp>

namespace nlohmann
{
namespace detail
{
template<typename It, typename = void>
struct iterator_types {};

template<typename It>
struct iterator_types <
    It,
    void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
    typename It::reference, typename It::iterator_category >>
{
    using difference_type = typename It::difference_type;
    using value_type = typename It::value_type;
    using pointer = typename It::pointer;
    using reference = typename It::reference;
    using iterator_category = typename It::iterator_category;
};

// This is required as some compilers implement std::iterator_traits in a way that
// doesn't work with SFINAE. See https://github.com/nlohmann/json/issues/1341.
template<typename T, typename = void>
struct iterator_traits
{
};

template<typename T>
struct iterator_traits < T, enable_if_t < !std::is_pointer<T>::value >>
            : iterator_types<T>
{
};

template<typename T>
struct iterator_traits<T*, enable_if_t<std::is_object<T>::value>>
{
    using iterator_category = std::random_access_iterator_tag;
    using value_type = T;
    using difference_type = ptrdiff_t;
    using pointer = T*;
    using reference = T&;
};
} // namespace detail
} // namespace nlohmann