| // |
| // awaitable.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 ASIO_AWAITABLE_HPP |
| #define ASIO_AWAITABLE_HPP |
| |
| #if defined(_MSC_VER) && (_MSC_VER >= 1200) |
| # pragma once |
| #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
| |
| #include "asio/detail/config.hpp" |
| |
| #if defined(ASIO_HAS_CO_AWAIT) || defined(GENERATING_DOCUMENTATION) |
| |
| #if defined(ASIO_HAS_STD_COROUTINE) |
| # include <coroutine> |
| #else // defined(ASIO_HAS_STD_COROUTINE) |
| # include <experimental/coroutine> |
| #endif // defined(ASIO_HAS_STD_COROUTINE) |
| |
| #include "asio/any_io_executor.hpp" |
| |
| #include "asio/detail/push_options.hpp" |
| |
| namespace asio { |
| namespace detail { |
| |
| #if defined(ASIO_HAS_STD_COROUTINE) |
| using std::coroutine_handle; |
| using std::suspend_always; |
| #else // defined(ASIO_HAS_STD_COROUTINE) |
| using std::experimental::coroutine_handle; |
| using std::experimental::suspend_always; |
| #endif // defined(ASIO_HAS_STD_COROUTINE) |
| |
| template <typename> class awaitable_thread; |
| template <typename, typename> class awaitable_frame; |
| |
| } // namespace detail |
| |
| /// The return type of a coroutine or asynchronous operation. |
| template <typename T, typename Executor = any_io_executor> |
| class awaitable |
| { |
| public: |
| /// The type of the awaited value. |
| typedef T value_type; |
| |
| /// The executor type that will be used for the coroutine. |
| typedef Executor executor_type; |
| |
| /// Default constructor. |
| constexpr awaitable() noexcept |
| : frame_(nullptr) |
| { |
| } |
| |
| /// Move constructor. |
| awaitable(awaitable&& other) noexcept |
| : frame_(std::exchange(other.frame_, nullptr)) |
| { |
| } |
| |
| /// Destructor |
| ~awaitable() |
| { |
| if (frame_) |
| frame_->destroy(); |
| } |
| |
| /// Checks if the awaitable refers to a future result. |
| bool valid() const noexcept |
| { |
| return !!frame_; |
| } |
| |
| #if !defined(GENERATING_DOCUMENTATION) |
| |
| // Support for co_await keyword. |
| bool await_ready() const noexcept |
| { |
| return false; |
| } |
| |
| // Support for co_await keyword. |
| template <class U> |
| void await_suspend( |
| detail::coroutine_handle<detail::awaitable_frame<U, Executor>> h) |
| { |
| frame_->push_frame(&h.promise()); |
| } |
| |
| // Support for co_await keyword. |
| T await_resume() |
| { |
| return awaitable(static_cast<awaitable&&>(*this)).frame_->get(); |
| } |
| |
| #endif // !defined(GENERATING_DOCUMENTATION) |
| |
| private: |
| template <typename> friend class detail::awaitable_thread; |
| template <typename, typename> friend class detail::awaitable_frame; |
| |
| // Not copy constructible or copy assignable. |
| awaitable(const awaitable&) = delete; |
| awaitable& operator=(const awaitable&) = delete; |
| |
| // Construct the awaitable from a coroutine's frame object. |
| explicit awaitable(detail::awaitable_frame<T, Executor>* a) |
| : frame_(a) |
| { |
| } |
| |
| detail::awaitable_frame<T, Executor>* frame_; |
| }; |
| |
| } // namespace asio |
| |
| #include "asio/detail/pop_options.hpp" |
| |
| #include "asio/impl/awaitable.hpp" |
| |
| #endif // defined(ASIO_HAS_CO_AWAIT) || defined(GENERATING_DOCUMENTATION) |
| |
| #endif // ASIO_AWAITABLE_HPP |