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108 lines
2.6 KiB
C++
108 lines
2.6 KiB
C++
//
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// traits/query_member.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2022 Christopher M. Kohlhoff (chris at kohlhoff dot 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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#ifndef ASIO_TRAITS_QUERY_MEMBER_HPP
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#define ASIO_TRAITS_QUERY_MEMBER_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/type_traits.hpp"
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#if defined(ASIO_HAS_DECLTYPE) \
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&& defined(ASIO_HAS_NOEXCEPT) \
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&& defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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# define ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT 1
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#endif // defined(ASIO_HAS_DECLTYPE)
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// && defined(ASIO_HAS_NOEXCEPT)
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// && defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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#include "asio/detail/push_options.hpp"
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namespace asio {
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namespace traits {
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template <typename T, typename Property, typename = void>
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struct query_member_default;
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template <typename T, typename Property, typename = void>
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struct query_member;
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} // namespace traits
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namespace detail {
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struct no_query_member
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
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};
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#if defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT)
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template <typename T, typename Property, typename = void>
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struct query_member_trait : no_query_member
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{
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};
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template <typename T, typename Property>
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struct query_member_trait<T, Property,
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typename void_type<
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decltype(declval<T>().query(declval<Property>()))
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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using result_type = decltype(
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declval<T>().query(declval<Property>()));
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = noexcept(
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declval<T>().query(declval<Property>())));
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};
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#else // defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT)
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template <typename T, typename Property, typename = void>
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struct query_member_trait :
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conditional<
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is_same<T, typename decay<T>::type>::value
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&& is_same<Property, typename decay<Property>::type>::value,
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no_query_member,
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traits::query_member<
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typename decay<T>::type,
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typename decay<Property>::type>
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>::type
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{
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};
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#endif // defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT)
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} // namespace detail
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namespace traits {
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template <typename T, typename Property, typename>
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struct query_member_default :
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detail::query_member_trait<T, Property>
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{
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};
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template <typename T, typename Property, typename>
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struct query_member :
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query_member_default<T, Property>
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{
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};
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} // namespace traits
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_TRAITS_QUERY_MEMBER_HPP
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