227 lines
6.3 KiB
C++
227 lines
6.3 KiB
C++
//
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// execution/occupancy.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2021 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_EXECUTION_OCCUPANCY_HPP
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#define ASIO_EXECUTION_OCCUPANCY_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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#include "asio/execution/executor.hpp"
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#include "asio/execution/scheduler.hpp"
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#include "asio/execution/sender.hpp"
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#include "asio/is_applicable_property.hpp"
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#include "asio/traits/query_static_constexpr_member.hpp"
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#include "asio/traits/static_query.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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#if defined(GENERATING_DOCUMENTATION)
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namespace execution {
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/// A property that gives an estimate of the number of execution agents that
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/// should occupy the associated execution context.
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struct occupancy_t
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{
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/// The occupancy_t property applies to executors, senders, and schedulers.
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template <typename T>
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static constexpr bool is_applicable_property_v =
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is_executor_v<T> || is_sender_v<T> || is_scheduler_v<T>;
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/// The occupancy_t property cannot be required.
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static constexpr bool is_requirable = false;
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/// The occupancy_t property cannot be preferred.
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static constexpr bool is_preferable = false;
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/// The type returned by queries against an @c any_executor.
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typedef std::size_t polymorphic_query_result_type;
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};
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/// A special value used for accessing the occupancy_t property.
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constexpr occupancy_t occupancy;
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} // namespace execution
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#else // defined(GENERATING_DOCUMENTATION)
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namespace execution {
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namespace detail {
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template <int I = 0>
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struct occupancy_t
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{
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T>
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ASIO_STATIC_CONSTEXPR(bool,
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is_applicable_property_v = (
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is_executor<T>::value
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|| conditional<
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is_executor<T>::value,
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false_type,
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is_sender<T>
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>::type::value
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|| conditional<
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is_executor<T>::value,
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false_type,
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is_scheduler<T>
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>::type::value));
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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ASIO_STATIC_CONSTEXPR(bool, is_requirable = false);
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ASIO_STATIC_CONSTEXPR(bool, is_preferable = false);
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typedef std::size_t polymorphic_query_result_type;
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ASIO_CONSTEXPR occupancy_t()
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{
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}
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template <typename T>
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struct static_proxy
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{
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#if defined(ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT)
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struct type
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{
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template <typename P>
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static constexpr auto query(ASIO_MOVE_ARG(P) p)
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noexcept(
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noexcept(
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conditional<true, T, P>::type::query(ASIO_MOVE_CAST(P)(p))
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)
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)
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-> decltype(
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conditional<true, T, P>::type::query(ASIO_MOVE_CAST(P)(p))
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)
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{
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return T::query(ASIO_MOVE_CAST(P)(p));
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}
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};
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#else // defined(ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT)
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typedef T type;
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#endif // defined(ASIO_HAS_DEDUCED_QUERY_STATIC_CONSTEXPR_MEMBER_TRAIT)
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};
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template <typename T>
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struct query_static_constexpr_member :
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traits::query_static_constexpr_member<
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typename static_proxy<T>::type, occupancy_t> {};
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#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename T>
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static ASIO_CONSTEXPR
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typename query_static_constexpr_member<T>::result_type
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static_query()
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ASIO_NOEXCEPT_IF((
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query_static_constexpr_member<T>::is_noexcept))
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{
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return query_static_constexpr_member<T>::value();
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}
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template <typename E, typename T = decltype(occupancy_t::static_query<E>())>
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static ASIO_CONSTEXPR const T static_query_v
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= occupancy_t::static_query<E>();
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#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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#if !defined(ASIO_HAS_CONSTEXPR)
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static const occupancy_t instance;
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#endif // !defined(ASIO_HAS_CONSTEXPR)
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};
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#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <int I> template <typename E, typename T>
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const T occupancy_t<I>::static_query_v;
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#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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#if !defined(ASIO_HAS_CONSTEXPR)
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template <int I>
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const occupancy_t<I> occupancy_t<I>::instance;
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#endif
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} // namespace detail
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typedef detail::occupancy_t<> occupancy_t;
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#if defined(ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
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constexpr occupancy_t occupancy;
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#else // defined(ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
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namespace { static const occupancy_t& occupancy = occupancy_t::instance; }
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#endif
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} // namespace execution
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#if !defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T>
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struct is_applicable_property<T, execution::occupancy_t>
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: integral_constant<bool,
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execution::is_executor<T>::value
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|| conditional<
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execution::is_executor<T>::value,
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false_type,
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execution::is_sender<T>
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>::type::value
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|| conditional<
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execution::is_executor<T>::value,
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false_type,
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execution::is_scheduler<T>
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>::type::value>
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{
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};
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#endif // !defined(ASIO_HAS_VARIABLE_TEMPLATES)
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namespace traits {
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#if !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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|| !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename T>
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struct static_query<T, execution::occupancy_t,
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typename enable_if<
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execution::detail::occupancy_t<0>::
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query_static_constexpr_member<T>::is_valid
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
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typedef typename execution::detail::occupancy_t<0>::
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query_static_constexpr_member<T>::result_type result_type;
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static ASIO_CONSTEXPR result_type value()
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{
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return execution::detail::occupancy_t<0>::
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query_static_constexpr_member<T>::value();
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}
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};
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#endif // !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// || !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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} // namespace traits
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#endif // defined(GENERATING_DOCUMENTATION)
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_EXECUTION_OCCUPANCY_HPP
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