573 lines
17 KiB
C++
573 lines
17 KiB
C++
//
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// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)
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// Copyright (c) 2022 Dmitry Arkhipov (grisumbras@yandex.ru)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/json
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//
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#ifndef BOOST_JSON_IMPL_CONVERSION_HPP
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#define BOOST_JSON_IMPL_CONVERSION_HPP
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#include <boost/json/fwd.hpp>
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#include <boost/json/value.hpp>
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#include <boost/json/string_view.hpp>
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#include <boost/describe/enumerators.hpp>
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#include <boost/describe/members.hpp>
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#include <boost/describe/bases.hpp>
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#include <boost/mp11/algorithm.hpp>
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#include <boost/mp11/utility.hpp>
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#include <boost/system/result.hpp>
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#include <iterator>
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#include <tuple>
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#include <utility>
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#ifndef BOOST_NO_CXX17_HDR_VARIANT
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# include <variant>
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#endif // BOOST_NO_CXX17_HDR_VARIANT
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namespace boost {
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namespace json {
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namespace detail {
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#ifdef __cpp_lib_nonmember_container_access
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using std::size;
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#endif
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template<std::size_t I, class T>
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using tuple_element_t = typename std::tuple_element<I, T>::type;
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template<class T>
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using iterator_type = decltype(std::begin(std::declval<T&>()));
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template<class T>
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using iterator_traits = std::iterator_traits< iterator_type<T> >;
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template<class T>
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using value_type = typename iterator_traits<T>::value_type;
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template<class T>
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using mapped_type = tuple_element_t< 1, value_type<T> >;
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// had to make the metafunction always succeeding in order to make it work
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// with msvc 14.0
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template<class T>
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using key_type_helper = tuple_element_t< 0, value_type<T> >;
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template<class T>
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using key_type = mp11::mp_eval_or<
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void,
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key_type_helper,
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T>;
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template<class T>
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using are_begin_and_end_same = std::is_same<
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iterator_type<T>,
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decltype(std::end(std::declval<T&>()))>;
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// msvc 14.0 gets confused when std::is_same is used directly
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template<class A, class B>
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using is_same_msvc_140 = std::is_same<A, B>;
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template<class T>
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using is_its_own_value = is_same_msvc_140<value_type<T>, T>;
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template<class T>
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using not_its_own_value = mp11::mp_not< is_its_own_value<T> >;
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template<class T>
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using begin_iterator_category = typename std::iterator_traits<
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iterator_type<T>>::iterator_category;
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template<class T>
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using has_positive_tuple_size = mp11::mp_bool<
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(std::tuple_size<T>::value > 0) >;
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template<class T>
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using has_unique_keys = has_positive_tuple_size<decltype(
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std::declval<T&>().emplace(
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std::declval<value_type<T>>()))>;
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template<class T>
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using has_string_type = std::is_same<
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typename T::string_type, std::basic_string<typename T::value_type> >;
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template<class T>
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struct is_value_type_pair_helper : std::false_type
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{ };
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template<class T1, class T2>
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struct is_value_type_pair_helper<std::pair<T1, T2>> : std::true_type
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{ };
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template<class T>
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using is_value_type_pair = is_value_type_pair_helper<value_type<T>>;
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template<class T>
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using has_size_member_helper
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= std::is_convertible<decltype(std::declval<T&>().size()), std::size_t>;
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template<class T>
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using has_size_member = mp11::mp_valid_and_true<has_size_member_helper, T>;
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template<class T>
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using has_free_size_helper
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= std::is_convertible<
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decltype(size(std::declval<T const&>())),
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std::size_t>;
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template<class T>
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using has_free_size = mp11::mp_valid_and_true<has_free_size_helper, T>;
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template<class T>
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using size_implementation = mp11::mp_cond<
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has_size_member<T>, mp11::mp_int<3>,
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has_free_size<T>, mp11::mp_int<2>,
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std::is_array<T>, mp11::mp_int<1>,
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mp11::mp_true, mp11::mp_int<0>>;
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template<class T>
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std::size_t
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try_size(T&& cont, mp11::mp_int<3>)
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{
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return cont.size();
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}
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template<class T>
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std::size_t
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try_size(T& cont, mp11::mp_int<2>)
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{
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return size(cont);
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}
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template<class T, std::size_t N>
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std::size_t
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try_size(T(&)[N], mp11::mp_int<1>)
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{
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return N;
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}
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template<class T>
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std::size_t
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try_size(T&, mp11::mp_int<0>)
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{
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return 0;
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}
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template<class T>
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using has_push_back_helper
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= decltype(std::declval<T&>().push_back(std::declval<value_type<T>>()));
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template<class T>
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using has_push_back = mp11::mp_valid<has_push_back_helper, T>;
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template<class T>
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using inserter_implementation = mp11::mp_cond<
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is_tuple_like<T>, mp11::mp_int<2>,
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has_push_back<T>, mp11::mp_int<1>,
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mp11::mp_true, mp11::mp_int<0>>;
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template<class T>
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iterator_type<T>
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inserter(
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T& target,
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mp11::mp_int<2>)
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{
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return target.begin();
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}
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template<class T>
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std::back_insert_iterator<T>
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inserter(
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T& target,
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mp11::mp_int<1>)
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{
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return std::back_inserter(target);
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}
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template<class T>
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std::insert_iterator<T>
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inserter(
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T& target,
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mp11::mp_int<0>)
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{
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return std::inserter( target, target.end() );
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}
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using value_from_conversion = mp11::mp_true;
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using value_to_conversion = mp11::mp_false;
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struct user_conversion_tag { };
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struct context_conversion_tag : user_conversion_tag { };
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struct full_context_conversion_tag : context_conversion_tag { };
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struct native_conversion_tag { };
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struct value_conversion_tag : native_conversion_tag { };
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struct object_conversion_tag : native_conversion_tag { };
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struct array_conversion_tag : native_conversion_tag { };
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struct string_conversion_tag : native_conversion_tag { };
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struct bool_conversion_tag : native_conversion_tag { };
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struct number_conversion_tag : native_conversion_tag { };
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struct integral_conversion_tag : number_conversion_tag { };
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struct floating_point_conversion_tag : number_conversion_tag { };
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struct null_like_conversion_tag { };
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struct string_like_conversion_tag { };
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struct map_like_conversion_tag { };
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struct path_conversion_tag { };
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struct sequence_conversion_tag { };
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struct tuple_conversion_tag { };
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struct described_class_conversion_tag { };
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struct described_enum_conversion_tag { };
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struct variant_conversion_tag { };
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struct optional_conversion_tag { };
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struct no_conversion_tag { };
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template<class... Args>
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using supports_tag_invoke = decltype(tag_invoke( std::declval<Args>()... ));
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template<class T>
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using has_user_conversion_from_impl = supports_tag_invoke<
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value_from_tag, value&, T&& >;
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template<class T>
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using has_user_conversion_to_impl = supports_tag_invoke<
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value_to_tag<T>, value const& >;
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template<class T>
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using has_nonthrowing_user_conversion_to_impl = supports_tag_invoke<
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try_value_to_tag<T>, value const& >;
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template< class T, class Dir >
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using has_user_conversion1 = mp11::mp_if<
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std::is_same<Dir, value_from_conversion>,
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mp11::mp_valid<has_user_conversion_from_impl, T>,
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mp11::mp_or<
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mp11::mp_valid<has_user_conversion_to_impl, T>,
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mp11::mp_valid<has_nonthrowing_user_conversion_to_impl, T>>>;
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template< class Ctx, class T >
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using has_context_conversion_from_impl = supports_tag_invoke<
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value_from_tag, value&, T&&, Ctx const& >;
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template< class Ctx, class T >
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using has_context_conversion_to_impl = supports_tag_invoke<
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value_to_tag<T>, value const&, Ctx const& >;
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template< class Ctx, class T >
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using has_nonthrowing_context_conversion_to_impl = supports_tag_invoke<
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try_value_to_tag<T>, value const&, Ctx const& >;
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template< class Ctx, class T, class Dir >
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using has_user_conversion2 = mp11::mp_if<
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std::is_same<Dir, value_from_conversion>,
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mp11::mp_valid<has_context_conversion_from_impl, Ctx, T>,
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mp11::mp_or<
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mp11::mp_valid<has_context_conversion_to_impl, Ctx, T>,
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mp11::mp_valid<has_nonthrowing_context_conversion_to_impl, Ctx, T>>>;
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template< class Ctx, class T >
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using has_full_context_conversion_from_impl = supports_tag_invoke<
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value_from_tag, value&, T&&, Ctx const&, Ctx const& >;
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template< class Ctx, class T >
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using has_full_context_conversion_to_impl = supports_tag_invoke<
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value_to_tag<T>, value const&, Ctx const&, Ctx const& >;
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template< class Ctx, class T >
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using has_nonthrowing_full_context_conversion_to_impl = supports_tag_invoke<
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try_value_to_tag<T>, value const&, Ctx const&, Ctx const& >;
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template< class Ctx, class T, class Dir >
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using has_user_conversion3 = mp11::mp_if<
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std::is_same<Dir, value_from_conversion>,
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mp11::mp_valid<has_full_context_conversion_from_impl, Ctx, T>,
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mp11::mp_or<
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mp11::mp_valid<has_full_context_conversion_to_impl, Ctx, T>,
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mp11::mp_valid<
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has_nonthrowing_full_context_conversion_to_impl, Ctx, T>>>;
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template< class T >
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using described_non_public_members = describe::describe_members<
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T, describe::mod_private | describe::mod_protected>;
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template< class T >
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using described_bases = describe::describe_bases<
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T, describe::mod_any_access>;
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#if defined(BOOST_MSVC) && BOOST_MSVC < 1920
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template< class T >
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struct described_member_t_impl;
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template< class T, class C >
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struct described_member_t_impl<T C::*>
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{
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using type = T;
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};
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template< class T, class D >
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using described_member_t = remove_cvref<
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typename described_member_t_impl<
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remove_cvref<decltype(D::pointer)> >::type>;
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#else
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template< class T, class D >
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using described_member_t = remove_cvref<decltype(
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std::declval<T&>().* D::pointer )>;
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#endif
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template< class T >
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using described_members = describe::describe_members<
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T, describe::mod_any_access | describe::mod_inherited>;
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// user conversion (via tag_invoke)
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template< class Ctx, class T, class Dir >
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using user_conversion_category = mp11::mp_cond<
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has_user_conversion3<Ctx, T, Dir>, full_context_conversion_tag,
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has_user_conversion2<Ctx, T, Dir>, context_conversion_tag,
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has_user_conversion1<T, Dir>, user_conversion_tag>;
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// native conversions (constructors and member functions of value)
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template< class T >
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using native_conversion_category = mp11::mp_cond<
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std::is_same<T, value>, value_conversion_tag,
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std::is_same<T, array>, array_conversion_tag,
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std::is_same<T, object>, object_conversion_tag,
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std::is_same<T, string>, string_conversion_tag>;
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// generic conversions
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template< class T >
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using generic_conversion_category = mp11::mp_cond<
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std::is_same<T, bool>, bool_conversion_tag,
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std::is_integral<T>, integral_conversion_tag,
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std::is_floating_point<T>, floating_point_conversion_tag,
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is_null_like<T>, null_like_conversion_tag,
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is_string_like<T>, string_like_conversion_tag,
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is_map_like<T>, map_like_conversion_tag,
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is_sequence_like<T>, sequence_conversion_tag,
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is_tuple_like<T>, tuple_conversion_tag,
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is_described_class<T>, described_class_conversion_tag,
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is_described_enum<T>, described_enum_conversion_tag,
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is_variant_like<T>, variant_conversion_tag,
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is_optional_like<T>, optional_conversion_tag,
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is_path_like<T>, path_conversion_tag,
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// failed to find a suitable implementation
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mp11::mp_true, no_conversion_tag>;
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template< class T >
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using nested_type = typename T::type;
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template< class T1, class T2 >
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using conversion_category_impl_helper = mp11::mp_eval_if_not<
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std::is_same<detail::no_conversion_tag, T1>,
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T1,
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mp11::mp_eval_or_q, T1, mp11::mp_quote<nested_type>, T2>;
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template< class Ctx, class T, class Dir >
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struct conversion_category_impl
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{
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using type = mp11::mp_fold<
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mp11::mp_list<
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mp11::mp_defer<user_conversion_category, Ctx, T, Dir>,
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mp11::mp_defer<native_conversion_category, T>,
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mp11::mp_defer<generic_conversion_category, T>>,
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no_conversion_tag,
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conversion_category_impl_helper>;
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};
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template< class Ctx, class T, class Dir >
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using conversion_category =
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typename conversion_category_impl< Ctx, T, Dir >::type;
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template< class T >
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using any_conversion_tag = mp11::mp_not<
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std::is_same< T, no_conversion_tag > >;
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template< class T, class Dir, class... Ctxs >
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struct conversion_category_impl< std::tuple<Ctxs...>, T, Dir >
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{
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using ctxs = mp11::mp_list< remove_cvref<Ctxs>... >;
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using cats = mp11::mp_list<
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conversion_category<remove_cvref<Ctxs>, T, Dir>... >;
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template< class I >
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using exists = mp11::mp_less< I, mp11::mp_size<cats> >;
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using context2 = mp11::mp_find< cats, full_context_conversion_tag >;
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using context1 = mp11::mp_find< cats, context_conversion_tag >;
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using context0 = mp11::mp_find< cats, user_conversion_tag >;
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using index = mp11::mp_cond<
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exists<context2>, context2,
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exists<context1>, context1,
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exists<context0>, context0,
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mp11::mp_true, mp11::mp_find_if< cats, any_conversion_tag > >;
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using type = mp11::mp_eval_or<
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no_conversion_tag,
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mp11::mp_at, cats, index >;
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};
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struct no_context
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{};
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struct allow_exceptions
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{};
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template <class T, class Dir>
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using can_convert = mp11::mp_not<
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std::is_same<
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detail::conversion_category<no_context, T, Dir>,
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detail::no_conversion_tag>>;
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template<class Impl1, class Impl2>
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using conversion_round_trips_helper = mp11::mp_or<
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std::is_same<Impl1, Impl2>,
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std::is_base_of<user_conversion_tag, Impl1>,
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std::is_base_of<user_conversion_tag, Impl2>>;
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template< class Ctx, class T, class Dir >
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using conversion_round_trips = conversion_round_trips_helper<
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conversion_category<Ctx, T, Dir>,
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conversion_category<Ctx, T, mp11::mp_not<Dir>>>;
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template< class T1, class T2 >
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struct copy_cref_helper
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{
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using type = remove_cvref<T2>;
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};
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template< class T1, class T2 >
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using copy_cref = typename copy_cref_helper< T1, T2 >::type;
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template< class T1, class T2 >
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struct copy_cref_helper<T1 const, T2>
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{
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using type = remove_cvref<T2> const;
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};
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template< class T1, class T2 >
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struct copy_cref_helper<T1&, T2>
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{
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using type = copy_cref<T1, T2>&;
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};
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template< class T1, class T2 >
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struct copy_cref_helper<T1&&, T2>
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{
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using type = copy_cref<T1, T2>&&;
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};
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template< class Rng, class Traits >
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using forwarded_value_helper = mp11::mp_if<
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std::is_convertible<
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typename Traits::reference,
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copy_cref<Rng, typename Traits::value_type> >,
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copy_cref<Rng, typename Traits::value_type>,
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typename Traits::value_type >;
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template< class Rng >
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using forwarded_value = forwarded_value_helper<
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Rng, iterator_traits< Rng > >;
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template< class Ctx, class T, class Dir >
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struct supported_context
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{
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using type = Ctx;
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static
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type const&
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get( Ctx const& ctx ) noexcept
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{
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return ctx;
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}
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};
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template< class T, class Dir, class... Ctxs >
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struct supported_context< std::tuple<Ctxs...>, T, Dir >
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{
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using Ctx = std::tuple<Ctxs...>;
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using impl = conversion_category_impl<Ctx, T, Dir>;
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using index = typename impl::index;
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using next_supported = supported_context<
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mp11::mp_at< typename impl::ctxs, index >, T, Dir >;
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using type = typename next_supported::type;
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static
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type const&
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get( Ctx const& ctx ) noexcept
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{
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return next_supported::get( std::get<index::value>( ctx ) );
|
|
}
|
|
};
|
|
|
|
template< class T >
|
|
using value_result_type = typename std::decay<
|
|
decltype( std::declval<T&>().value() )>::type;
|
|
|
|
template< class T >
|
|
using can_reset = decltype( std::declval<T&>().reset() );
|
|
|
|
template< class T >
|
|
using has_valueless_by_exception =
|
|
decltype( std::declval<T const&>().valueless_by_exception() );
|
|
|
|
} // namespace detail
|
|
|
|
template <class T>
|
|
struct result_for<T, value>
|
|
{
|
|
using type = system::result< detail::remove_cvref<T> >;
|
|
};
|
|
|
|
template<class T>
|
|
struct is_string_like
|
|
: std::is_convertible<T, string_view>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_path_like
|
|
: mp11::mp_all<
|
|
mp11::mp_valid_and_true<detail::is_its_own_value, T>,
|
|
mp11::mp_valid_and_true<detail::has_string_type, T>>
|
|
{ };
|
|
template<class T>
|
|
struct is_sequence_like
|
|
: mp11::mp_all<
|
|
mp11::mp_valid_and_true<detail::are_begin_and_end_same, T>,
|
|
mp11::mp_valid_and_true<detail::not_its_own_value, T>,
|
|
mp11::mp_valid<detail::begin_iterator_category, T>>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_map_like
|
|
: mp11::mp_all<
|
|
is_sequence_like<T>,
|
|
mp11::mp_valid_and_true<detail::is_value_type_pair, T>,
|
|
is_string_like<detail::key_type<T>>,
|
|
mp11::mp_valid_and_true<detail::has_unique_keys, T>>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_tuple_like
|
|
: mp11::mp_valid_and_true<detail::has_positive_tuple_size, T>
|
|
{ };
|
|
|
|
template<>
|
|
struct is_null_like<std::nullptr_t>
|
|
: std::true_type
|
|
{ };
|
|
|
|
#ifndef BOOST_NO_CXX17_HDR_VARIANT
|
|
template<>
|
|
struct is_null_like<std::monostate>
|
|
: std::true_type
|
|
{ };
|
|
#endif // BOOST_NO_CXX17_HDR_VARIANT
|
|
|
|
template<class T>
|
|
struct is_described_class
|
|
: mp11::mp_and<
|
|
describe::has_describe_members<T>,
|
|
mp11::mp_not< std::is_union<T> >,
|
|
mp11::mp_empty<
|
|
mp11::mp_eval_or<
|
|
mp11::mp_list<>, detail::described_non_public_members, T>>,
|
|
mp11::mp_empty<
|
|
mp11::mp_eval_or<mp11::mp_list<>, detail::described_bases, T>>>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_described_enum
|
|
: describe::has_describe_enumerators<T>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_variant_like : mp11::mp_valid<detail::has_valueless_by_exception, T>
|
|
{ };
|
|
|
|
template<class T>
|
|
struct is_optional_like
|
|
: mp11::mp_and<
|
|
mp11::mp_not<std::is_void<
|
|
mp11::mp_eval_or<void, detail::value_result_type, T>>>,
|
|
mp11::mp_valid<detail::can_reset, T>>
|
|
{ };
|
|
|
|
} // namespace json
|
|
} // namespace boost
|
|
|
|
#endif // BOOST_JSON_IMPL_CONVERSION_HPP
|