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1 | // |
2 | // impl/use_future.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 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_IMPL_USE_FUTURE_HPP | |
12 | #define BOOST_ASIO_IMPL_USE_FUTURE_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 <future> | |
20 | #include <boost/asio/async_result.hpp> | |
21 | #include <boost/system/error_code.hpp> | |
22 | #include <boost/asio/handler_type.hpp> | |
23 | #include <boost/system/system_error.hpp> | |
24 | ||
25 | #include <boost/asio/detail/push_options.hpp> | |
26 | ||
27 | namespace boost { | |
28 | namespace asio { | |
29 | namespace detail { | |
30 | ||
31 | // Completion handler to adapt a promise as a completion handler. | |
32 | template <typename T> | |
33 | class promise_handler | |
34 | { | |
35 | public: | |
36 | // Construct from use_future special value. | |
37 | template <typename Alloc> | |
38 | promise_handler(use_future_t<Alloc> uf) | |
39 | : promise_(std::allocate_shared<std::promise<T> >( | |
40 | typename Alloc::template rebind<char>::other(uf.get_allocator()), | |
41 | std::allocator_arg, | |
42 | typename Alloc::template rebind<char>::other(uf.get_allocator()))) | |
43 | { | |
44 | } | |
45 | ||
46 | void operator()(T t) | |
47 | { | |
48 | promise_->set_value(t); | |
49 | } | |
50 | ||
51 | void operator()(const boost::system::error_code& ec, T t) | |
52 | { | |
53 | if (ec) | |
54 | promise_->set_exception( | |
55 | std::make_exception_ptr( | |
56 | boost::system::system_error(ec))); | |
57 | else | |
58 | promise_->set_value(t); | |
59 | } | |
60 | ||
61 | //private: | |
62 | std::shared_ptr<std::promise<T> > promise_; | |
63 | }; | |
64 | ||
65 | // Completion handler to adapt a void promise as a completion handler. | |
66 | template <> | |
67 | class promise_handler<void> | |
68 | { | |
69 | public: | |
70 | // Construct from use_future special value. Used during rebinding. | |
71 | template <typename Alloc> | |
72 | promise_handler(use_future_t<Alloc> uf) | |
73 | : promise_(std::allocate_shared<std::promise<void> >( | |
74 | typename Alloc::template rebind<char>::other(uf.get_allocator()), | |
75 | std::allocator_arg, | |
76 | typename Alloc::template rebind<char>::other(uf.get_allocator()))) | |
77 | { | |
78 | } | |
79 | ||
80 | void operator()() | |
81 | { | |
82 | promise_->set_value(); | |
83 | } | |
84 | ||
85 | void operator()(const boost::system::error_code& ec) | |
86 | { | |
87 | if (ec) | |
88 | promise_->set_exception( | |
89 | std::make_exception_ptr( | |
90 | boost::system::system_error(ec))); | |
91 | else | |
92 | promise_->set_value(); | |
93 | } | |
94 | ||
95 | //private: | |
96 | std::shared_ptr<std::promise<void> > promise_; | |
97 | }; | |
98 | ||
99 | // Ensure any exceptions thrown from the handler are propagated back to the | |
100 | // caller via the future. | |
101 | template <typename Function, typename T> | |
102 | void asio_handler_invoke(Function f, promise_handler<T>* h) | |
103 | { | |
104 | std::shared_ptr<std::promise<T> > p(h->promise_); | |
105 | try | |
106 | { | |
107 | f(); | |
108 | } | |
109 | catch (...) | |
110 | { | |
111 | p->set_exception(std::current_exception()); | |
112 | } | |
113 | } | |
114 | ||
115 | } // namespace detail | |
116 | ||
117 | #if !defined(GENERATING_DOCUMENTATION) | |
118 | ||
119 | // Handler traits specialisation for promise_handler. | |
120 | template <typename T> | |
121 | class async_result<detail::promise_handler<T> > | |
122 | { | |
123 | public: | |
124 | // The initiating function will return a future. | |
125 | typedef std::future<T> type; | |
126 | ||
127 | // Constructor creates a new promise for the async operation, and obtains the | |
128 | // corresponding future. | |
129 | explicit async_result(detail::promise_handler<T>& h) | |
130 | { | |
131 | value_ = h.promise_->get_future(); | |
132 | } | |
133 | ||
134 | // Obtain the future to be returned from the initiating function. | |
135 | type get() { return std::move(value_); } | |
136 | ||
137 | private: | |
138 | type value_; | |
139 | }; | |
140 | ||
141 | // Handler type specialisation for use_future. | |
142 | template <typename Allocator, typename ReturnType> | |
143 | struct handler_type<use_future_t<Allocator>, ReturnType()> | |
144 | { | |
145 | typedef detail::promise_handler<void> type; | |
146 | }; | |
147 | ||
148 | // Handler type specialisation for use_future. | |
149 | template <typename Allocator, typename ReturnType, typename Arg1> | |
150 | struct handler_type<use_future_t<Allocator>, ReturnType(Arg1)> | |
151 | { | |
152 | typedef detail::promise_handler<Arg1> type; | |
153 | }; | |
154 | ||
155 | // Handler type specialisation for use_future. | |
156 | template <typename Allocator, typename ReturnType> | |
157 | struct handler_type<use_future_t<Allocator>, | |
158 | ReturnType(boost::system::error_code)> | |
159 | { | |
160 | typedef detail::promise_handler<void> type; | |
161 | }; | |
162 | ||
163 | // Handler type specialisation for use_future. | |
164 | template <typename Allocator, typename ReturnType, typename Arg2> | |
165 | struct handler_type<use_future_t<Allocator>, | |
166 | ReturnType(boost::system::error_code, Arg2)> | |
167 | { | |
168 | typedef detail::promise_handler<Arg2> type; | |
169 | }; | |
170 | ||
171 | #endif // !defined(GENERATING_DOCUMENTATION) | |
172 | ||
173 | } // namespace asio | |
174 | } // namespace boost | |
175 | ||
176 | #include <boost/asio/detail/pop_options.hpp> | |
177 | ||
178 | #endif // BOOST_ASIO_IMPL_USE_FUTURE_HPP |