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- //
- // 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
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