1 // 2 // packaged_task.hpp 3 // ~~~~~~~~~~~~~~~~~ 4 // 5 // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com) 6 // 7 // Distributed under the Boost Software License, Version 1.0. (See accompanying 8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 9 // 10 11 #ifndef BOOST_ASIO_PACKAGED_TASK_HPP 12 #define BOOST_ASIO_PACKAGED_TASK_HPP 13 14 #if defined(_MSC_VER) && (_MSC_VER >= 1200) 15 # pragma once 16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) 17 18 #include <boost/asio/detail/config.hpp> 19 #include <boost/asio/detail/future.hpp> 20 21 #if defined(BOOST_ASIO_HAS_STD_FUTURE_CLASS) \ 22 || defined(GENERATING_DOCUMENTATION) 23 24 #include <boost/asio/async_result.hpp> 25 #include <boost/asio/detail/type_traits.hpp> 26 #include <boost/asio/detail/variadic_templates.hpp> 27 28 #include <boost/asio/detail/push_options.hpp> 29 30 namespace boost { 31 namespace asio { 32 33 #if defined(BOOST_ASIO_HAS_VARIADIC_TEMPLATES) \ 34 || defined(GENERATING_DOCUMENTATION) 35 36 /// Partial specialisation of @c async_result for @c std::packaged_task. 37 template <typename Result, typename... Args, typename Signature> 38 class async_result<std::packaged_task<Result(Args...)>, Signature> 39 { 40 public: 41 /// The packaged task is the concrete completion handler type. 42 typedef std::packaged_task<Result(Args...)> completion_handler_type; 43 44 /// The return type of the initiating function is the future obtained from 45 /// the packaged task. 46 typedef std::future<Result> return_type; 47 48 /// The constructor extracts the future from the packaged task. async_result(completion_handler_type & h)49 explicit async_result(completion_handler_type& h) 50 : future_(h.get_future()) 51 { 52 } 53 54 /// Returns the packaged task's future. get()55 return_type get() 56 { 57 return std::move(future_); 58 } 59 60 private: 61 return_type future_; 62 }; 63 64 #else // defined(BOOST_ASIO_HAS_VARIADIC_TEMPLATES) 65 // || defined(GENERATING_DOCUMENTATION) 66 67 template <typename Result, typename Signature> 68 struct async_result<std::packaged_task<Result()>, Signature> 69 { 70 typedef std::packaged_task<Result()> completion_handler_type; 71 typedef std::future<Result> return_type; 72 73 explicit async_result(completion_handler_type& h) 74 : future_(h.get_future()) 75 { 76 } 77 78 return_type get() 79 { 80 return std::move(future_); 81 } 82 83 private: 84 return_type future_; 85 }; 86 87 #define BOOST_ASIO_PRIVATE_ASYNC_RESULT_DEF(n) \ 88 template <typename Result, \ 89 BOOST_ASIO_VARIADIC_TPARAMS(n), typename Signature> \ 90 class async_result< \ 91 std::packaged_task<Result(BOOST_ASIO_VARIADIC_TARGS(n))>, Signature> \ 92 { \ 93 public: \ 94 typedef std::packaged_task< \ 95 Result(BOOST_ASIO_VARIADIC_TARGS(n))> \ 96 completion_handler_type; \ 97 \ 98 typedef std::future<Result> return_type; \ 99 \ 100 explicit async_result(completion_handler_type& h) \ 101 : future_(h.get_future()) \ 102 { \ 103 } \ 104 \ 105 return_type get() \ 106 { \ 107 return std::move(future_); \ 108 } \ 109 \ 110 private: \ 111 return_type future_; \ 112 }; \ 113 /**/ 114 BOOST_ASIO_VARIADIC_GENERATE(BOOST_ASIO_PRIVATE_ASYNC_RESULT_DEF) 115 #undef BOOST_ASIO_PRIVATE_ASYNC_RESULT_DEF 116 117 #endif // defined(BOOST_ASIO_HAS_VARIADIC_TEMPLATES) 118 // || defined(GENERATING_DOCUMENTATION) 119 120 } // namespace asio 121 } // namespace boost 122 123 #include <boost/asio/detail/pop_options.hpp> 124 125 #endif // defined(BOOST_ASIO_HAS_STD_FUTURE_CLASS) 126 // || defined(GENERATING_DOCUMENTATION) 127 128 #endif // BOOST_ASIO_PACKAGED_TASK_HPP 129