| // |
| // experimental/as_single.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_EXPERIMENTAL_AS_SINGLE_HPP |
| #define BOOST_ASIO_EXPERIMENTAL_AS_SINGLE_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/detail/push_options.hpp> |
| |
| namespace boost { |
| namespace asio { |
| namespace experimental { |
| |
| /// Completion token type used to specify that the completion handler |
| /// arguments should be combined into a single argument. |
| /** |
| * The as_single_t class is used to indicate that any arguments to the |
| * completion handler should be combined and passed as a single argument. |
| * If there is already one argument, that argument is passed as-is. If |
| * there is more than argument, the arguments are first moved into a |
| * @c std::tuple and that tuple is then passed to the completion handler. |
| */ |
| template <typename CompletionToken> |
| class as_single_t |
| { |
| public: |
| /// Tag type used to prevent the "default" constructor from being used for |
| /// conversions. |
| struct default_constructor_tag {}; |
| |
| /// Default constructor. |
| /** |
| * This constructor is only valid if the underlying completion token is |
| * default constructible and move constructible. The underlying completion |
| * token is itself defaulted as an argument to allow it to capture a source |
| * location. |
| */ |
| BOOST_ASIO_CONSTEXPR as_single_t( |
| default_constructor_tag = default_constructor_tag(), |
| CompletionToken token = CompletionToken()) |
| : token_(BOOST_ASIO_MOVE_CAST(CompletionToken)(token)) |
| { |
| } |
| |
| /// Constructor. |
| template <typename T> |
| BOOST_ASIO_CONSTEXPR explicit as_single_t( |
| BOOST_ASIO_MOVE_ARG(T) completion_token) |
| : token_(BOOST_ASIO_MOVE_CAST(T)(completion_token)) |
| { |
| } |
| |
| /// Adapts an executor to add the @c as_single_t completion token as the |
| /// default. |
| template <typename InnerExecutor> |
| struct executor_with_default : InnerExecutor |
| { |
| /// Specify @c as_single_t as the default completion token type. |
| typedef as_single_t default_completion_token_type; |
| |
| /// Construct the adapted executor from the inner executor type. |
| executor_with_default(const InnerExecutor& ex) BOOST_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 constraint< |
| is_convertible<OtherExecutor, InnerExecutor>::value |
| >::type = 0) BOOST_ASIO_NOEXCEPT |
| : InnerExecutor(ex) |
| { |
| } |
| }; |
| |
| /// Type alias to adapt an I/O object to use @c as_single_t as its |
| /// default completion token type. |
| #if defined(BOOST_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(BOOST_ASIO_HAS_ALIAS_TEMPLATES) |
| // || defined(GENERATING_DOCUMENTATION) |
| |
| /// Function helper to adapt an I/O object to use @c as_single_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(BOOST_ASIO_MOVE_ARG(T) object) |
| { |
| return typename decay<T>::type::template rebind_executor< |
| executor_with_default<typename decay<T>::type::executor_type> |
| >::other(BOOST_ASIO_MOVE_CAST(T)(object)); |
| } |
| |
| //private: |
| CompletionToken token_; |
| }; |
| |
| /// Create a completion token to specify that the completion handler arguments |
| /// should be combined into a single argument. |
| template <typename CompletionToken> |
| inline BOOST_ASIO_CONSTEXPR as_single_t<typename decay<CompletionToken>::type> |
| as_single(BOOST_ASIO_MOVE_ARG(CompletionToken) completion_token) |
| { |
| return as_single_t<typename decay<CompletionToken>::type>( |
| BOOST_ASIO_MOVE_CAST(CompletionToken)(completion_token)); |
| } |
| |
| } // namespace experimental |
| } // namespace asio |
| } // namespace boost |
| |
| #include <boost/asio/detail/pop_options.hpp> |
| |
| #include <boost/asio/experimental/impl/as_single.hpp> |
| |
| #endif // BOOST_ASIO_EXPERIMENTAL_AS_SINGLE_HPP |