// // execution/context_as.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_CONTEXT_AS_HPP #define BOOST_ASIO_EXECUTION_CONTEXT_AS_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/context.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/query.hpp> #include <boost/asio/traits/query_static_constexpr_member.hpp> #include <boost/asio/traits/static_query.hpp> #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. template <typename U> struct context_as_t { /// The context_as_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 T polymorphic_query_result_type; }; /// A special value used for accessing the context_as_t property. template <typename U> constexpr context_as_t context_as; } // namespace execution #else // defined(GENERATING_DOCUMENTATION) namespace execution { template <typename T> struct context_as_t { #if defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) template <typename U> BOOST_ASIO_STATIC_CONSTEXPR(bool, is_applicable_property_v = ( is_executor<U>::value || conditional< is_executor<U>::value, false_type, is_sender<U> >::type::value || conditional< is_executor<U>::value, false_type, is_scheduler<U> >::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); typedef T polymorphic_query_result_type; BOOST_ASIO_CONSTEXPR context_as_t() { } BOOST_ASIO_CONSTEXPR context_as_t(context_t) { } #if defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \ && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) template <typename E> static BOOST_ASIO_CONSTEXPR typename context_t::query_static_constexpr_member<E>::result_type static_query() BOOST_ASIO_NOEXCEPT_IF(( context_t::query_static_constexpr_member<E>::is_noexcept)) { return context_t::query_static_constexpr_member<E>::value(); } template <typename E, typename U = decltype(context_as_t::static_query<E>())> static BOOST_ASIO_CONSTEXPR const U static_query_v = context_as_t::static_query<E>(); #endif // defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) // && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) template <typename Executor, typename U> friend BOOST_ASIO_CONSTEXPR U query( const Executor& ex, const context_as_t<U>&, typename enable_if< is_same<T, U>::value >::type* = 0, typename enable_if< can_query<const Executor&, const context_t&>::value >::type* = 0) #if !defined(__clang__) // Clang crashes if noexcept is used here. #if defined(BOOST_ASIO_MSVC) // Visual C++ wants the type to be qualified. BOOST_ASIO_NOEXCEPT_IF(( is_nothrow_query<const Executor&, const context_t&>::value)) #else // defined(BOOST_ASIO_MSVC) BOOST_ASIO_NOEXCEPT_IF(( is_nothrow_query<const Executor&, const context_t&>::value)) #endif // defined(BOOST_ASIO_MSVC) #endif // !defined(__clang__) { return boost::asio::query(ex, context); } }; #if defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \ && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) template <typename T> template <typename E, typename U> const U context_as_t<T>::static_query_v; #endif // defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) // && defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) #if (defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) \ && defined(BOOST_ASIO_HAS_CONSTEXPR)) \ || defined(GENERATING_DOCUMENTATION) template <typename T> constexpr context_as_t<T> context_as{}; #endif // (defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) // && defined(BOOST_ASIO_HAS_CONSTEXPR)) // || defined(GENERATING_DOCUMENTATION) } // namespace execution #if !defined(BOOST_ASIO_HAS_VARIABLE_TEMPLATES) template <typename T, typename U> struct is_applicable_property<T, execution::context_as_t<U> > : 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, typename U> struct static_query<T, execution::context_as_t<U>, typename enable_if< static_query<T, execution::context_t>::is_valid >::type> : static_query<T, execution::context_t> { }; #endif // !defined(BOOST_ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) // || !defined(BOOST_ASIO_HAS_SFINAE_VARIABLE_TEMPLATES) #if !defined(BOOST_ASIO_HAS_DEDUCED_QUERY_FREE_TRAIT) template <typename T, typename U> struct query_free<T, execution::context_as_t<U>, typename enable_if< can_query<const T&, const execution::context_t&>::value >::type> { BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = true); BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = (is_nothrow_query<const T&, const execution::context_t&>::value)); typedef U result_type; }; #endif // !defined(BOOST_ASIO_HAS_DEDUCED_QUERY_FREE_TRAIT) } // namespace traits #endif // defined(GENERATING_DOCUMENTATION) } // namespace asio } // namespace boost #include <boost/asio/detail/pop_options.hpp> #endif // BOOST_ASIO_EXECUTION_CONTEXT_AS_HPP