293 lines
7.1 KiB
C++
293 lines
7.1 KiB
C++
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//
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// execution/schedule.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2023 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_SCHEDULE_HPP
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#define ASIO_EXECUTION_SCHEDULE_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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#if !defined(ASIO_NO_DEPRECATED)
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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/traits/schedule_member.hpp"
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#include "asio/traits/schedule_free.hpp"
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#include "asio/detail/push_options.hpp"
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#if defined(GENERATING_DOCUMENTATION)
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namespace asio {
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namespace execution {
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/// A customisation point that is used to obtain a sender from a scheduler.
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/**
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* The name <tt>execution::schedule</tt> denotes a customisation point object.
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* For some subexpression <tt>s</tt>, let <tt>S</tt> be a type such that
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* <tt>decltype((s))</tt> is <tt>S</tt>. The expression
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* <tt>execution::schedule(s)</tt> is expression-equivalent to:
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*
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* @li <tt>s.schedule()</tt>, if that expression is valid and its type models
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* <tt>sender</tt>.
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*
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* @li Otherwise, <tt>schedule(s)</tt>, if that expression is valid and its
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* type models <tt>sender</tt> with overload resolution performed in a context
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* that includes the declaration <tt>void schedule();</tt> and that does not
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* include a declaration of <tt>execution::schedule</tt>.
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*
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* @li Otherwise, <tt>S</tt> if <tt>S</tt> satisfies <tt>executor</tt>.
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*
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* @li Otherwise, <tt>execution::schedule(s)</tt> is ill-formed.
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*/
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inline constexpr unspecified schedule = unspecified;
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/// A type trait that determines whether a @c schedule expression is
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/// well-formed.
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/**
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* Class template @c can_schedule is a trait that is derived from @c true_type
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* if the expression <tt>execution::schedule(std::declval<S>())</tt> is well
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* formed; otherwise @c false_type.
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*/
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template <typename S>
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struct can_schedule :
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integral_constant<bool, automatically_determined>
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{
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};
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} // namespace execution
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} // namespace asio
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#else // defined(GENERATING_DOCUMENTATION)
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namespace asio_execution_schedule_fn {
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using asio::decay;
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using asio::declval;
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using asio::enable_if;
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using asio::execution::is_executor;
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using asio::traits::schedule_free;
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using asio::traits::schedule_member;
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void schedule();
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enum overload_type
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{
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identity,
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call_member,
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call_free,
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ill_formed
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};
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template <typename S, typename = void, typename = void, typename = void>
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struct call_traits
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = ill_formed);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
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typedef void result_type;
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};
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template <typename S>
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struct call_traits<S,
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typename enable_if<
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schedule_member<S>::is_valid
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>::type> :
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schedule_member<S>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = call_member);
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};
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template <typename S>
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struct call_traits<S,
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typename enable_if<
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!schedule_member<S>::is_valid
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>::type,
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typename enable_if<
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schedule_free<S>::is_valid
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>::type> :
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schedule_free<S>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = call_free);
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};
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template <typename S>
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struct call_traits<S,
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typename enable_if<
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!schedule_member<S>::is_valid
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>::type,
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typename enable_if<
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!schedule_free<S>::is_valid
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>::type,
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typename enable_if<
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is_executor<typename decay<S>::type>::value
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = identity);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
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#if defined(ASIO_HAS_MOVE)
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typedef ASIO_MOVE_ARG(S) result_type;
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#else // defined(ASIO_HAS_MOVE)
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typedef ASIO_MOVE_ARG(typename decay<S>::type) result_type;
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#endif // defined(ASIO_HAS_MOVE)
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};
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struct impl
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{
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<S>::overload == identity,
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typename call_traits<S>::result_type
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>::type
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operator()(ASIO_MOVE_ARG(S) s) const
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ASIO_NOEXCEPT_IF((
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call_traits<S>::is_noexcept))
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{
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return ASIO_MOVE_CAST(S)(s);
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}
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#if defined(ASIO_HAS_MOVE)
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<S>::overload == call_member,
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typename call_traits<S>::result_type
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>::type
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operator()(S&& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<S>::is_noexcept))
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{
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return ASIO_MOVE_CAST(S)(s).schedule();
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}
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<S>::overload == call_free,
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typename call_traits<S>::result_type
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>::type
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operator()(S&& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<S>::is_noexcept))
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{
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return schedule(ASIO_MOVE_CAST(S)(s));
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}
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#else // defined(ASIO_HAS_MOVE)
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<S&>::overload == call_member,
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typename call_traits<S&>::result_type
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>::type
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operator()(S& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<S&>::is_noexcept))
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{
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return s.schedule();
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}
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<const S&>::overload == call_member,
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typename call_traits<const S&>::result_type
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>::type
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operator()(const S& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<const S&>::is_noexcept))
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{
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return s.schedule();
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}
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<S&>::overload == call_free,
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typename call_traits<S&>::result_type
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>::type
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operator()(S& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<S&>::is_noexcept))
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{
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return schedule(s);
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}
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template <typename S>
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ASIO_CONSTEXPR typename enable_if<
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call_traits<const S&>::overload == call_free,
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typename call_traits<const S&>::result_type
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>::type
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operator()(const S& s) const
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ASIO_NOEXCEPT_IF((
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call_traits<const S&>::is_noexcept))
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{
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return schedule(s);
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}
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#endif // defined(ASIO_HAS_MOVE)
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};
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template <typename T = impl>
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struct static_instance
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{
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static const T instance;
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};
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template <typename T>
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const T static_instance<T>::instance = {};
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} // namespace asio_execution_schedule_fn
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namespace asio {
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namespace execution {
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namespace {
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static ASIO_CONSTEXPR const asio_execution_schedule_fn::impl&
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schedule = asio_execution_schedule_fn::static_instance<>::instance;
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} // namespace
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template <typename S>
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struct can_schedule :
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integral_constant<bool,
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asio_execution_schedule_fn::call_traits<S>::overload !=
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asio_execution_schedule_fn::ill_formed>
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{
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};
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename S>
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constexpr bool can_schedule_v = can_schedule<S>::value;
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename S>
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struct is_nothrow_schedule :
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integral_constant<bool,
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asio_execution_schedule_fn::call_traits<S>::is_noexcept>
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{
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};
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename S>
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constexpr bool is_nothrow_schedule_v
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= is_nothrow_schedule<S>::value;
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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} // namespace execution
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} // namespace asio
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#endif // defined(GENERATING_DOCUMENTATION)
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#include "asio/detail/pop_options.hpp"
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#endif // !defined(ASIO_NO_DEPRECATED)
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#endif // ASIO_EXECUTION_SCHEDULE_HPP
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