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