| // |
| // execution/context.hpp |
| // ~~~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
| // |
| // Distributed under the Boost Software License, Version 1.0. (See accompanying |
| // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| // |
| |
| #ifndef BOOST_ASIO_EXECUTION_CONTEXT2_HPP |
| #define BOOST_ASIO_EXECUTION_CONTEXT2_HPP |
| |
| #if defined(_MSC_VER) && (_MSC_VER >= 1200) |
| # pragma once |
| #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
| |
| #include <boost/asio/detail/config.hpp> |
| #include <boost/asio/detail/type_traits.hpp> |
| #include <boost/asio/execution/executor.hpp> |
| #include <boost/asio/execution/scheduler.hpp> |
| #include <boost/asio/execution/sender.hpp> |
| #include <boost/asio/is_applicable_property.hpp> |
| #include <boost/asio/traits/query_static_constexpr_member.hpp> |
| #include <boost/asio/traits/static_query.hpp> |
| |
| #if defined(BOOST_ASIO_HAS_STD_ANY) |
| # include <any> |
| #endif // defined(BOOST_ASIO_HAS_STD_ANY) |
| |
| #include <boost/asio/detail/push_options.hpp> |
| |
| namespace boost { |
| namespace asio { |
| |
| #if defined(GENERATING_DOCUMENTATION) |
| |
| namespace execution { |
| |
| /// A property that is used to obtain the execution context that is associated |
| /// with an executor. |
| struct context_t |
| { |
| /// The context_t property applies to executors, senders, and schedulers. |
| template <typename T> |
| static constexpr bool is_applicable_property_v = |
| is_executor_v<T> || is_sender_v<T> || is_scheduler_v<T>; |
| |
| /// The context_t property cannot be required. |
| static constexpr bool is_requirable = false; |
| |
| /// The context_t property cannot be preferred. |
| static constexpr bool is_preferable = false; |
| |
| /// The type returned by queries against an @c any_executor. |
| typedef std::any polymorphic_query_result_type; |
| }; |
| |
| /// A special value used for accessing the context_t property. |
| constexpr context_t context; |
| |
| } // namespace execution |
| |
| #else // defined(GENERATING_DOCUMENTATION) |
| |
| namespace execution { |
| namespace detail { |
| |
| template <int I = 0> |
| struct context_t |
| { |
| #if defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) |
| template <typename T> |
| BOOST_ASIO_STATIC_CONSTEXPR(bool, |
| is_applicable_property_v = ( |
| is_executor<T>::value |
| || conditional< |
| is_executor<T>::value, |
| false_type, |
| is_sender<T> |
| >::type::value |
| || conditional< |
| is_executor<T>::value, |
| false_type, |
| is_scheduler<T> |
| >::type::value)); |
| #endif // defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) |
| |
| BOOST_ASIO_STATIC_CONSTEXPR(bool, is_requirable = false); |
| BOOST_ASIO_STATIC_CONSTEXPR(bool, is_preferable = false); |
| |
| #if defined(BOOST_ASIO_HAS_STD_ANY) |
| typedef std::any polymorphic_query_result_type; |
| #endif // defined(BOOST_ASIO_HAS_STD_ANY) |
| |
| BOOST_ASIO_CONSTEXPR context_t() |
| { |
| } |
| |
| template <typename T> |
| struct static_proxy |
| { |
| #if defined(BOOST_ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT) |
| struct type |
| { |
| template <typename P> |
| static constexpr auto query(BOOST_ASIO_MOVE_ARG(P) p) |
| noexcept( |
| noexcept( |
| conditional<true, T, P>::type::query(BOOST_ASIO_MOVE_CAST(P)(p)) |
| ) |
| ) |
| -> decltype( |
| conditional<true, T, P>::type::query(BOOST_ASIO_MOVE_CAST(P)(p)) |
| ) |
| { |
| return T::query(BOOST_ASIO_MOVE_CAST(P)(p)); |
| } |
| }; |
| #else // defined(BOOST_ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT) |
| typedef T type; |
| #endif // defined(BOOST_ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT) |
| }; |
| |
| template <typename T> |
| struct query_static_constexpr_member : |
| traits::query_static_constexpr_member< |
| typename static_proxy<T>::type, context_t> {}; |
| |
| #if defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \ |
| && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| template <typename T> |
| static BOOST_ASIO_CONSTEXPR |
| typename query_static_constexpr_member<T>::result_type |
| static_query() |
| BOOST_ASIO_NOEXCEPT_IF(( |
| query_static_constexpr_member<T>::is_noexcept)) |
| { |
| return query_static_constexpr_member<T>::value(); |
| } |
| |
| template <typename E, typename T = decltype(context_t::static_query<E>())> |
| static BOOST_ASIO_CONSTEXPR const T static_query_v |
| = context_t::static_query<E>(); |
| #endif // defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) |
| // && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| |
| #if !defined(BOOST_ASIO_HAS_CONSTEXPR) |
| static const context_t instance; |
| #endif // !defined(BOOST_ASIO_HAS_CONSTEXPR) |
| }; |
| |
| #if defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \ |
| && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| template <int I> template <typename E, typename T> |
| const T context_t<I>::static_query_v; |
| #endif // defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) |
| // && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| |
| #if !defined(BOOST_ASIO_HAS_CONSTEXPR) |
| template <int I> |
| const context_t<I> context_t<I>::instance; |
| #endif |
| |
| } // namespace detail |
| |
| typedef detail::context_t<> context_t; |
| |
| #if defined(BOOST_ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION) |
| constexpr context_t context; |
| #else // defined(BOOST_ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION) |
| namespace { static const context_t& context = context_t::instance; } |
| #endif |
| |
| } // namespace execution |
| |
| #if !defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) |
| |
| template <typename T> |
| struct is_applicable_property<T, execution::context_t> |
| : integral_constant<bool, |
| execution::is_executor<T>::value |
| || conditional< |
| execution::is_executor<T>::value, |
| false_type, |
| execution::is_sender<T> |
| >::type::value |
| || conditional< |
| execution::is_executor<T>::value, |
| false_type, |
| execution::is_scheduler<T> |
| >::type::value> |
| { |
| }; |
| |
| #endif // !defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) |
| |
| namespace traits { |
| |
| #if !defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \ |
| || !defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| |
| template <typename T> |
| struct static_query<T, execution::context_t, |
| typename enable_if< |
| execution::detail::context_t<0>:: |
| query_static_constexpr_member<T>::is_valid |
| >::type> |
| { |
| BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true); |
| |
| typedef typename execution::detail::context_t<0>:: |
| query_static_constexpr_member<T>::result_type result_type; |
| |
| static BOOST_ASIO_CONSTEXPR result_type value() |
| { |
| return execution::detail::context_t<0>:: |
| query_static_constexpr_member<T>::value(); |
| } |
| }; |
| |
| #endif // !defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) |
| // || !defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) |
| |
| } // namespace traits |
| |
| #endif // defined(GENERATING_DOCUMENTATION) |
| |
| } // namespace asio |
| } // namespace boost |
| |
| #include <boost/asio/detail/pop_options.hpp> |
| |
| #endif // BOOST_ASIO_EXECUTION_CONTEXT2_HPP |