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149 lines
4.3 KiB
149 lines
4.3 KiB
// |
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// associated_executor.hpp |
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// ~~~~~~~~~~~~~~~~~~~~~~~ |
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// |
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// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
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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 ASIO_ASSOCIATED_EXECUTOR_HPP |
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#define ASIO_ASSOCIATED_EXECUTOR_HPP |
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#if defined(_MSC_VER) && (_MSC_VER >= 1200) |
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# pragma once |
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
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#include "asio/detail/config.hpp" |
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#include "asio/detail/type_traits.hpp" |
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#include "asio/is_executor.hpp" |
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#include "asio/system_executor.hpp" |
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#include "asio/detail/push_options.hpp" |
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namespace asio { |
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namespace detail { |
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template <typename> |
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struct associated_executor_check |
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{ |
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typedef void type; |
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}; |
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template <typename T, typename E, typename = void> |
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struct associated_executor_impl |
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{ |
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typedef E type; |
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static type get(const T&, const E& e) ASIO_NOEXCEPT |
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{ |
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return e; |
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} |
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}; |
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template <typename T, typename E> |
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struct associated_executor_impl<T, E, |
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typename associated_executor_check<typename T::executor_type>::type> |
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{ |
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typedef typename T::executor_type type; |
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static type get(const T& t, const E&) ASIO_NOEXCEPT |
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{ |
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return t.get_executor(); |
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} |
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}; |
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} // namespace detail |
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/// Traits type used to obtain the executor associated with an object. |
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/** |
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* A program may specialise this traits type if the @c T template parameter in |
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* the specialisation is a user-defined type. The template parameter @c |
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* Executor shall be a type meeting the Executor requirements. |
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* |
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* Specialisations shall meet the following requirements, where @c t is a const |
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* reference to an object of type @c T, and @c e is an object of type @c |
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* Executor. |
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* |
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* @li Provide a nested typedef @c type that identifies a type meeting the |
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* Executor requirements. |
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* |
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* @li Provide a noexcept static member function named @c get, callable as @c |
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* get(t) and with return type @c type. |
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* |
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* @li Provide a noexcept static member function named @c get, callable as @c |
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* get(t,e) and with return type @c type. |
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*/ |
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template <typename T, typename Executor = system_executor> |
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struct associated_executor |
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{ |
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/// If @c T has a nested type @c executor_type, <tt>T::executor_type</tt>. |
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/// Otherwise @c Executor. |
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#if defined(GENERATING_DOCUMENTATION) |
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typedef see_below type; |
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#else // defined(GENERATING_DOCUMENTATION) |
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typedef typename detail::associated_executor_impl<T, Executor>::type type; |
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#endif // defined(GENERATING_DOCUMENTATION) |
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/// If @c T has a nested type @c executor_type, returns |
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/// <tt>t.get_executor()</tt>. Otherwise returns @c ex. |
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static type get(const T& t, |
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const Executor& ex = Executor()) ASIO_NOEXCEPT |
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{ |
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return detail::associated_executor_impl<T, Executor>::get(t, ex); |
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} |
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}; |
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/// Helper function to obtain an object's associated executor. |
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/** |
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* @returns <tt>associated_executor<T>::get(t)</tt> |
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*/ |
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template <typename T> |
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inline typename associated_executor<T>::type |
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get_associated_executor(const T& t) ASIO_NOEXCEPT |
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{ |
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return associated_executor<T>::get(t); |
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} |
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/// Helper function to obtain an object's associated executor. |
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/** |
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* @returns <tt>associated_executor<T, Executor>::get(t, ex)</tt> |
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*/ |
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template <typename T, typename Executor> |
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inline typename associated_executor<T, Executor>::type |
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get_associated_executor(const T& t, const Executor& ex, |
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typename enable_if<is_executor< |
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Executor>::value>::type* = 0) ASIO_NOEXCEPT |
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{ |
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return associated_executor<T, Executor>::get(t, ex); |
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} |
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/// Helper function to obtain an object's associated executor. |
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/** |
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* @returns <tt>associated_executor<T, typename |
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* ExecutionContext::executor_type>::get(t, ctx.get_executor())</tt> |
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*/ |
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template <typename T, typename ExecutionContext> |
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inline typename associated_executor<T, |
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typename ExecutionContext::executor_type>::type |
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get_associated_executor(const T& t, ExecutionContext& ctx, |
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typename enable_if<is_convertible<ExecutionContext&, |
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execution_context&>::value>::type* = 0) ASIO_NOEXCEPT |
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{ |
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return associated_executor<T, |
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typename ExecutionContext::executor_type>::get(t, ctx.get_executor()); |
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} |
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#if defined(ASIO_HAS_ALIAS_TEMPLATES) |
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template <typename T, typename Executor = system_executor> |
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using associated_executor_t = typename associated_executor<T, Executor>::type; |
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#endif // defined(ASIO_HAS_ALIAS_TEMPLATES) |
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} // namespace asio |
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#include "asio/detail/pop_options.hpp" |
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#endif // ASIO_ASSOCIATED_EXECUTOR_HPP
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