143 lines
3.8 KiB
C++
143 lines
3.8 KiB
C++
//
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// Copyright (c) 2022 Klemens Morgenstern (klemens.morgenstern@gmx.net)
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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 BOOST_COBALT_TASK_HPP
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#define BOOST_COBALT_TASK_HPP
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#include <boost/cobalt/detail/handler.hpp>
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#include <boost/cobalt/detail/task.hpp>
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#include <boost/cobalt/op.hpp>
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#include <boost/asio/append.hpp>
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#include <boost/asio/deferred.hpp>
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namespace boost::cobalt
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{
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// tag::outline[]
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template<typename Return>
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struct [[nodiscard]] task
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{
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task(task &&lhs) noexcept = default;
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task& operator=(task &&) noexcept = default;
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// enable `co_await`
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auto operator co_await ();
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// end::outline[]
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task(const task &) = delete;
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task& operator=(const task &) = delete;
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using promise_type = detail::task_promise<Return>;
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constexpr task(noop<Return> n) : receiver_(std::move(n)){}
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private:
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template<typename>
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friend struct detail::task_promise;
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task(detail::task_promise<Return> * task) : receiver_(task)
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{
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}
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detail::task_receiver<Return> receiver_;
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friend struct detail::async_initiate_spawn;
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// tag::outline[]
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};
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// end::outline[]
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struct use_task_t
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{
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/// Default constructor.
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constexpr use_task_t()
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{
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}
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/// Adapts an executor to add the @c use_task_t completion token as the
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/// default.
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template <typename InnerExecutor>
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struct executor_with_default : InnerExecutor
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{
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/// Specify @c use_task_t as the default completion token type.
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typedef use_task_t default_completion_token_type;
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executor_with_default(const InnerExecutor& ex) noexcept
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: InnerExecutor(ex)
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{
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}
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/// Construct the adapted executor from the inner executor type.
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template <typename InnerExecutor1>
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executor_with_default(const InnerExecutor1& ex,
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typename std::enable_if<
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std::conditional<
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!std::is_same<InnerExecutor1, executor_with_default>::value,
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std::is_convertible<InnerExecutor1, InnerExecutor>,
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std::false_type
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>::type::value>::type = 0) noexcept
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: InnerExecutor(ex)
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{
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}
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};
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/// Type alias to adapt an I/O object to use @c use_task_t as its
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/// default completion token type.
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template <typename T>
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using as_default_on_t = typename T::template rebind_executor<
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executor_with_default<typename T::executor_type> >::other;
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/// Function helper to adapt an I/O object to use @c use_task_t as its
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/// default completion token type.
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template <typename T>
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static typename std::decay_t<T>::template rebind_executor<
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executor_with_default<typename std::decay_t<T>::executor_type>
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>::other
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as_default_on(T && object)
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{
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return typename std::decay_t<T>::template rebind_executor<
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executor_with_default<typename std::decay_t<T>::executor_type>
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>::other(std::forward<T>(object));
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}
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};
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constexpr use_task_t use_task{};
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template<typename T>
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inline auto task<T>::operator co_await () {return receiver_.get_awaitable();}
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}
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namespace boost::asio
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{
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template<typename ... Args>
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struct async_result<boost::cobalt::use_task_t, void(Args...)>
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{
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using return_type = cobalt::task<
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typename decltype(cobalt::interpret_as_result(std::declval<std::tuple<Args...>>()))::value_type>;
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template <typename Initiation, typename... InitArgs>
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static auto initiate(Initiation initiation,
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boost::cobalt::use_task_t,
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InitArgs ... args) -> return_type
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{
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co_return co_await async_initiate<
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const cobalt::use_op_t&, void(Args...)>(
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std::move(initiation),
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cobalt::use_op, std::move(args)...);
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}
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};
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}
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#endif //BOOST_COBALT_COBALT_HPP
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