asio/traits/equality_comparable.hpp

0001 //
0002 // traits/equality_comparable.hpp
0003 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0004 //
0005 // Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
0006 //
0007 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0008 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0009 //
0010
0011 #ifndef BOOST_ASIO_TRAITS_EQUALITY_COMPARABLE_HPP
0012 #define BOOST_ASIO_TRAITS_EQUALITY_COMPARABLE_HPP
0013
0014 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
0015 # pragma once
0016 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
0017
0018 #include <boost/asio/detail/config.hpp>
0019 #include <boost/asio/detail/type_traits.hpp>
0020
0021 #if defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
0022 # define BOOST_ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT 1
0023 #endif // defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
0024
0025 namespace boost {
0026 namespace asio {
0027 namespace traits {
0028
0029 template <typename T, typename = void>
0030 struct equality_comparable_default;
0031
0032 template <typename T, typename = void>
0033 struct equality_comparable;
0034
0035 } // namespace traits
0036 namespace detail {
0037
0038 struct no_equality_comparable
0039 {
0040   static constexpr bool is_valid = false;
0041   static constexpr bool is_noexcept = false;
0042 };
0043
0044 #if defined(BOOST_ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
0045
0046 template <typename T, typename = void>
0047 struct equality_comparable_trait : no_equality_comparable
0048 {
0049 };
0050
0051 template <typename T>
0052 struct equality_comparable_trait<T,
0053   void_t<
0054     decltype(
0055       static_cast<void>(
0056         static_cast<bool>(declval<const T>() == declval<const T>())
0057       ),
0058       static_cast<void>(
0059         static_cast<bool>(declval<const T>() != declval<const T>())
0060       )
0061     )
0062   >>
0063 {
0064   static constexpr bool is_valid = true;
0065
0066   static constexpr bool is_noexcept =
0067     noexcept(declval<const T>() == declval<const T>())
0068       && noexcept(declval<const T>() != declval<const T>());
0069 };
0070
0071 #else // defined(BOOST_ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
0072
0073 template <typename T, typename = void>
0074 struct equality_comparable_trait :
0075   conditional_t<
0076     is_same<T, decay_t<T>>::value,
0077     no_equality_comparable,
0078     traits::equality_comparable<decay_t<T>>
0079   >
0080 {
0081 };
0082
0083 #endif // defined(BOOST_ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
0084
0085 } // namespace detail
0086 namespace traits {
0087
0088 template <typename T, typename>
0089 struct equality_comparable_default : detail::equality_comparable_trait<T>
0090 {
0091 };
0092
0093 template <typename T, typename>
0094 struct equality_comparable : equality_comparable_default<T>
0095 {
0096 };
0097
0098 } // namespace traits
0099 } // namespace asio
0100 } // namespace boost
0101
0102 #endif // BOOST_ASIO_TRAITS_EQUALITY_COMPARABLE_HPP