| // |
| // use_awaitable.hpp |
| // ~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2020 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_USE_AWAITABLE_HPP |
| #define ASIO_USE_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) |
| |
| #include "asio/awaitable.hpp" |
| #include "asio/detail/handler_tracking.hpp" |
| |
| #if defined(ASIO_ENABLE_HANDLER_TRACKING) |
| # if defined(ASIO_HAS_SOURCE_LOCATION) |
| # include "asio/detail/source_location.hpp" |
| # endif // defined(ASIO_HAS_SOURCE_LOCATION) |
| #endif // defined(ASIO_ENABLE_HANDLER_TRACKING) |
| |
| #include "asio/detail/push_options.hpp" |
| |
| namespace asio { |
| |
| /// A completion token that represents the currently executing coroutine. |
| /** |
| * The @c use_awaitable_t class, with its value @c use_awaitable, is used to |
| * represent the currently executing coroutine. This completion token may be |
| * passed as a handler to an asynchronous operation. For example: |
| * |
| * @code awaitable<void> my_coroutine() |
| * { |
| * std::size_t n = co_await my_socket.async_read_some(buffer, use_awaitable); |
| * ... |
| * } @endcode |
| * |
| * When used with co_await, the initiating function (@c async_read_some in the |
| * above example) suspends the current coroutine. The coroutine is resumed when |
| * the asynchronous operation completes, and the result of the operation is |
| * returned. |
| */ |
| template <typename Executor = any_io_executor> |
| struct use_awaitable_t |
| { |
| /// Default constructor. |
| ASIO_CONSTEXPR use_awaitable_t( |
| #if defined(ASIO_ENABLE_HANDLER_TRACKING) |
| # if defined(ASIO_HAS_SOURCE_LOCATION) |
| detail::source_location location = detail::source_location::current() |
| # endif // defined(ASIO_HAS_SOURCE_LOCATION) |
| #endif // defined(ASIO_ENABLE_HANDLER_TRACKING) |
| ) |
| #if defined(ASIO_ENABLE_HANDLER_TRACKING) |
| # if defined(ASIO_HAS_SOURCE_LOCATION) |
| : file_name_(location.file_name()), |
| line_(location.line()), |
| function_name_(location.function_name()) |
| # else // defined(ASIO_HAS_SOURCE_LOCATION) |
| : file_name_(0), |
| line_(0), |
| function_name_(0) |
| # endif // defined(ASIO_HAS_SOURCE_LOCATION) |
| #endif // defined(ASIO_ENABLE_HANDLER_TRACKING) |
| { |
| } |
| |
| /// Constructor used to specify file name, line, and function name. |
| ASIO_CONSTEXPR use_awaitable_t(const char* file_name, |
| int line, const char* function_name) |
| #if defined(ASIO_ENABLE_HANDLER_TRACKING) |
| : file_name_(file_name), |
| line_(line), |
| function_name_(function_name) |
| #endif // defined(ASIO_ENABLE_HANDLER_TRACKING) |
| { |
| #if !defined(ASIO_ENABLE_HANDLER_TRACKING) |
| (void)file_name; |
| (void)line; |
| (void)function_name; |
| #endif // !defined(ASIO_ENABLE_HANDLER_TRACKING) |
| } |
| |
| /// Adapts an executor to add the @c use_awaitable_t completion token as the |
| /// default. |
| template <typename InnerExecutor> |
| struct executor_with_default : InnerExecutor |
| { |
| /// Specify @c use_awaitable_t as the default completion token type. |
| typedef use_awaitable_t default_completion_token_type; |
| |
| /// Construct the adapted executor from the inner executor type. |
| executor_with_default(const InnerExecutor& ex) ASIO_NOEXCEPT |
| : InnerExecutor(ex) |
| { |
| } |
| |
| /// Convert the specified executor to the inner executor type, then use |
| /// that to construct the adapted executor. |
| template <typename OtherExecutor> |
| executor_with_default(const OtherExecutor& ex, |
| typename enable_if< |
| is_convertible<OtherExecutor, InnerExecutor>::value |
| >::type* = 0) ASIO_NOEXCEPT |
| : InnerExecutor(ex) |
| { |
| } |
| }; |
| |
| /// Type alias to adapt an I/O object to use @c use_awaitable_t as its |
| /// default completion token type. |
| #if defined(ASIO_HAS_ALIAS_TEMPLATES) \ |
| || defined(GENERATING_DOCUMENTATION) |
| template <typename T> |
| using as_default_on_t = typename T::template rebind_executor< |
| executor_with_default<typename T::executor_type> >::other; |
| #endif // defined(ASIO_HAS_ALIAS_TEMPLATES) |
| // || defined(GENERATING_DOCUMENTATION) |
| |
| /// Function helper to adapt an I/O object to use @c use_awaitable_t as its |
| /// default completion token type. |
| template <typename T> |
| static typename decay<T>::type::template rebind_executor< |
| executor_with_default<typename decay<T>::type::executor_type> |
| >::other |
| as_default_on(ASIO_MOVE_ARG(T) object) |
| { |
| return typename decay<T>::type::template rebind_executor< |
| executor_with_default<typename decay<T>::type::executor_type> |
| >::other(ASIO_MOVE_CAST(T)(object)); |
| } |
| |
| #if defined(ASIO_ENABLE_HANDLER_TRACKING) |
| const char* file_name_; |
| int line_; |
| const char* function_name_; |
| #endif // defined(ASIO_ENABLE_HANDLER_TRACKING) |
| }; |
| |
| /// A completion token object that represents the currently executing coroutine. |
| /** |
| * See the documentation for asio::use_awaitable_t for a usage example. |
| */ |
| #if defined(GENERATING_DOCUMENTATION) |
| constexpr use_awaitable_t<> use_awaitable; |
| #elif defined(ASIO_HAS_CONSTEXPR) |
| constexpr use_awaitable_t<> use_awaitable(0, 0, 0); |
| #elif defined(ASIO_MSVC) |
| __declspec(selectany) use_awaitable_t<> use_awaitable(0, 0, 0); |
| #endif |
| |
| } // namespace asio |
| |
| #include "asio/detail/pop_options.hpp" |
| |
| #include "asio/impl/use_awaitable.hpp" |
| |
| #endif // defined(ASIO_HAS_CO_AWAIT) || defined(GENERATING_DOCUMENTATION) |
| |
| #endif // ASIO_USE_AWAITABLE_HPP |