//
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// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)
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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_DETAIL_VALUE_TRAITS_HPP
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#define BOOST_JSON_DETAIL_VALUE_TRAITS_HPP
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#include <boost/json/detail/config.hpp>
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#include <type_traits>
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#include <tuple>
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#include <utility>
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BOOST_JSON_NS_BEGIN
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namespace detail {
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template<std::size_t N>
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struct priority_tag
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: priority_tag<N - 1> { };
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template<>
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struct priority_tag<0> { };
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using std::begin;
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using std::end;
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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<typename T, typename = void>
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struct container_traits
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{
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static constexpr bool is_container = false;
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};
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template<typename T>
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struct container_traits<T, typename std::enable_if<
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std::is_same<decltype(begin(std::declval<T&>())),
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decltype(end(std::declval<T&>()))>::value>::type>
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{
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private:
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template<typename U, typename std::enable_if<
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std::is_convertible<decltype(std::declval<U&>().size()),
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std::size_t>::value>::type* = nullptr>
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static
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std::size_t
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size_impl(
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U&& cont,
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priority_tag<2>)
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{
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return cont.size();
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}
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template<typename U, typename std::enable_if<
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std::is_convertible<decltype(size(std::declval<U&>())),
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std::size_t>::value>::type* = nullptr>
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static
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std::size_t
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size_impl(
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U& cont,
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priority_tag<1>)
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{
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return size(cont);
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}
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template<typename U, std::size_t N>
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static
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std::size_t
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size_impl(
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U(&)[N],
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priority_tag<1>)
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{
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return N;
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}
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template<typename U>
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static
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std::size_t
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size_impl(U&, priority_tag<0>)
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{
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return 0;
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}
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template<typename U>
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static
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auto
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reserve_impl(
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U& cont,
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std::size_t size,
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priority_tag<1>) ->
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void_t<decltype(
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std::declval<U&>().reserve(0))>
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{
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cont.reserve(size);
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}
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template<typename U>
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static
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void
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reserve_impl(
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U&,
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std::size_t,
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priority_tag<0>) { }
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public:
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static constexpr bool is_container = true;
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using value_type = remove_cvref<
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decltype(*begin(std::declval<T&>()))>;
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template<typename U>
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static
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std::size_t
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try_size(U& cont)
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{
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return container_traits::size_impl(
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cont, priority_tag<2>());
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}
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template<typename U>
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static
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void
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try_reserve(
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U& cont,
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std::size_t size)
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{
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container_traits::reserve_impl(
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cont, size, priority_tag<1>());
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}
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};
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template<typename T, typename = void>
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struct map_traits
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{
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static constexpr bool is_map = false;
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static constexpr bool has_unique_keys = false;
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};
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template<typename T>
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struct map_traits<T, void_t<typename remove_cvref<T>::key_type,
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typename std::enable_if<container_traits<T>::is_container &&
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std::tuple_size<typename remove_cvref<T>::
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value_type>::value == 2>::type>>
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{
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private:
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template<typename U, typename = void>
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struct unique_keys : std::false_type { };
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template<typename U>
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struct unique_keys<U, typename std::enable_if<
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(std::tuple_size<remove_cvref<decltype(std::declval<
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remove_cvref<U>&>().emplace(std::declval<typename
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remove_cvref<U>::value_type>()))>>::value > 0)>::type>
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: std::true_type { };
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public:
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static constexpr bool is_map = true;
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static constexpr bool has_unique_keys = unique_keys<T>::value;
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using pair_key_type = typename std::tuple_element<
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0, typename remove_cvref<T>::value_type>::type;
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using pair_value_type = typename std::tuple_element<
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1, typename remove_cvref<T>::value_type>::type;
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static constexpr bool key_converts_to_string =
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std::is_convertible<pair_key_type, string_view>::value;
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};
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// does not include std::nullptr_t
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template<class T>
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using value_constructible = std::integral_constant<bool,
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std::is_same<detail::remove_cvref<T>, value>::value ||
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std::is_same<detail::remove_cvref<T>, object>::value ||
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std::is_same<detail::remove_cvref<T>, array>::value ||
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std::is_same<detail::remove_cvref<T>, string>::value ||
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std::is_same<detail::remove_cvref<T>, string_view>::value ||
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std::is_arithmetic<detail::remove_cvref<T>>::value ||
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std::is_same<detail::remove_cvref<T>,
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std::initializer_list<value_ref>>::value ||
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std::is_same<detail::remove_cvref<T>, value_ref>::value>;
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BOOST_STATIC_ASSERT(value_constructible<value>::value);
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} // detail
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BOOST_JSON_NS_END
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#endif
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