mirror of
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252 lines
8.7 KiB
C++
252 lines
8.7 KiB
C++
#pragma once
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#include <ciso646> // not
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#include <limits> // numeric_limits
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#include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
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#include <utility> // declval
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#include <nlohmann/json_fwd.hpp>
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#include <nlohmann/detail/meta/cpp_future.hpp>
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#include <nlohmann/detail/meta/detected.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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namespace nlohmann
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{
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/*!
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@brief detail namespace with internal helper functions
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This namespace collects functions that should not be exposed,
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implementations of some @ref basic_json methods, and meta-programming helpers.
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@since version 2.1.0
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*/
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namespace detail
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{
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/////////////
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// helpers //
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/////////////
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template<typename> struct is_basic_json : std::false_type {};
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NLOHMANN_BASIC_JSON_TPL_DECLARATION
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struct is_basic_json<NLOHMANN_BASIC_JSON_TPL> : std::true_type {};
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//////////////////////////
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// aliases for detected //
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//////////////////////////
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template <typename T>
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using mapped_type_t = typename T::mapped_type;
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template <typename T>
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using key_type_t = typename T::key_type;
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template <typename T>
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using value_type_t = typename T::value_type;
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template <typename T>
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using difference_type_t = typename T::difference_type;
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template <typename T>
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using pointer_t = typename T::pointer;
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template <typename T>
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using reference_t = typename T::reference;
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template <typename T>
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using iterator_category_t = typename T::iterator_category;
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template <typename T>
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using iterator_t = typename T::iterator;
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template <typename T, typename... Args>
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using to_json_function = decltype(T::to_json(std::declval<Args>()...));
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template <typename T, typename... Args>
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using from_json_function = decltype(T::from_json(std::declval<Args>()...));
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template <typename T, typename U>
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using get_template_function = decltype(std::declval<T>().template get<U>());
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///////////////////
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// is_ functions //
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///////////////////
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template <typename T, typename = void>
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struct is_iterator_traits : std::false_type {};
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template <typename T>
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struct is_iterator_traits<std::iterator_traits<T>>
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{
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private:
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using traits = std::iterator_traits<T>;
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public:
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static constexpr auto value =
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is_detected<value_type_t, traits>::value &&
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is_detected<difference_type_t, traits>::value &&
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is_detected<pointer_t, traits>::value &&
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is_detected<iterator_category_t, traits>::value &&
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is_detected<reference_t, traits>::value;
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};
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// source: https://stackoverflow.com/a/37193089/4116453
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template <typename T, typename = void>
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struct is_complete_type : std::false_type {};
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template <typename T>
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struct is_complete_type<T, decltype(void(sizeof(T)))> : std::true_type {};
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template <typename BasicJsonType, typename CompatibleObjectType,
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typename = void>
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struct is_compatible_object_type_impl : std::false_type {};
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template <typename BasicJsonType, typename CompatibleObjectType>
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struct is_compatible_object_type_impl <
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BasicJsonType, CompatibleObjectType,
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enable_if_t<is_detected<mapped_type_t, CompatibleObjectType>::value and
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is_detected<key_type_t, CompatibleObjectType>::value >>
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{
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using object_t = typename BasicJsonType::object_t;
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// macOS's is_constructible does not play well with nonesuch...
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static constexpr bool value =
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std::is_constructible<typename object_t::key_type,
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typename CompatibleObjectType::key_type>::value and
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std::is_constructible<typename object_t::mapped_type,
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typename CompatibleObjectType::mapped_type>::value;
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};
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template <typename BasicJsonType, typename CompatibleObjectType>
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struct is_compatible_object_type
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: is_compatible_object_type_impl<BasicJsonType, CompatibleObjectType> {};
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template <typename BasicJsonType, typename CompatibleStringType,
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typename = void>
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struct is_compatible_string_type_impl : std::false_type {};
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template <typename BasicJsonType, typename CompatibleStringType>
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struct is_compatible_string_type_impl <
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BasicJsonType, CompatibleStringType,
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enable_if_t<is_detected_exact<typename BasicJsonType::string_t::value_type,
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value_type_t, CompatibleStringType>::value >>
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{
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static constexpr auto value =
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std::is_constructible<typename BasicJsonType::string_t, CompatibleStringType>::value;
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};
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template <typename BasicJsonType, typename CompatibleStringType>
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struct is_compatible_string_type
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: is_compatible_string_type_impl<BasicJsonType, CompatibleStringType> {};
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template <typename BasicJsonType, typename CompatibleArrayType, typename = void>
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struct is_compatible_array_type_impl : std::false_type {};
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template <typename BasicJsonType, typename CompatibleArrayType>
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struct is_compatible_array_type_impl <
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BasicJsonType, CompatibleArrayType,
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enable_if_t<is_detected<value_type_t, CompatibleArrayType>::value and
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is_detected<iterator_t, CompatibleArrayType>::value >>
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{
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// This is needed because json_reverse_iterator has a ::iterator type...
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// Therefore it is detected as a CompatibleArrayType.
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// The real fix would be to have an Iterable concept.
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static constexpr bool value = not is_iterator_traits<std::iterator_traits<CompatibleArrayType>>::value;
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};
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template <typename BasicJsonType, typename CompatibleArrayType>
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struct is_compatible_array_type
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: is_compatible_array_type_impl<BasicJsonType, CompatibleArrayType> {};
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template <typename RealIntegerType, typename CompatibleNumberIntegerType,
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typename = void>
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struct is_compatible_integer_type_impl : std::false_type {};
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template <typename RealIntegerType, typename CompatibleNumberIntegerType>
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struct is_compatible_integer_type_impl <
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RealIntegerType, CompatibleNumberIntegerType,
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enable_if_t<std::is_integral<RealIntegerType>::value and
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std::is_integral<CompatibleNumberIntegerType>::value and
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not std::is_same<bool, CompatibleNumberIntegerType>::value >>
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{
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// is there an assert somewhere on overflows?
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using RealLimits = std::numeric_limits<RealIntegerType>;
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using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;
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static constexpr auto value =
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std::is_constructible<RealIntegerType,
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CompatibleNumberIntegerType>::value and
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CompatibleLimits::is_integer and
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RealLimits::is_signed == CompatibleLimits::is_signed;
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};
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template <typename RealIntegerType, typename CompatibleNumberIntegerType>
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struct is_compatible_integer_type
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: is_compatible_integer_type_impl<RealIntegerType,
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CompatibleNumberIntegerType> {};
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// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
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template <typename BasicJsonType, typename T, typename = void>
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struct has_from_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_from_json<BasicJsonType, T,
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enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, from_json_function, serializer,
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const BasicJsonType&, T&>::value;
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};
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// This trait checks if JSONSerializer<T>::from_json(json const&) exists
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// this overload is used for non-default-constructible user-defined-types
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template <typename BasicJsonType, typename T, typename = void>
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struct has_non_default_from_json : std::false_type {};
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template<typename BasicJsonType, typename T>
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struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<T, from_json_function, serializer,
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const BasicJsonType&>::value;
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};
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// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
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// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
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template <typename BasicJsonType, typename T, typename = void>
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struct has_to_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, to_json_function, serializer, BasicJsonType&,
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T>::value;
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};
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template <typename BasicJsonType, typename CompatibleType, typename = void>
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struct is_compatible_type_impl: std::false_type {};
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template <typename BasicJsonType, typename CompatibleType>
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struct is_compatible_type_impl <
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BasicJsonType, CompatibleType,
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enable_if_t<is_complete_type<CompatibleType>::value >>
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{
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static constexpr bool value =
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has_to_json<BasicJsonType, CompatibleType>::value;
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};
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template <typename BasicJsonType, typename CompatibleType>
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struct is_compatible_type
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: is_compatible_type_impl<BasicJsonType, CompatibleType> {};
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} // namespace detail
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} // namespace nlohmann
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