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