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1 | // |
2 | // experimental/coro.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2021-2022 Klemens D. Morgenstern | |
6 | // (klemens dot morgenstern at gmx dot net) | |
7 | // | |
8 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
9 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
10 | // | |
11 | ||
12 | #ifndef BOOST_ASIO_EXPERIMENTAL_CORO_HPP | |
13 | #define BOOST_ASIO_EXPERIMENTAL_CORO_HPP | |
14 | ||
15 | #if defined(_MSC_VER) && (_MSC_VER >= 1200) | |
16 | # pragma once | |
17 | #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) | |
18 | ||
19 | #include <boost/asio/detail/config.hpp> | |
20 | #include <boost/asio/dispatch.hpp> | |
21 | #include <boost/asio/error.hpp> | |
22 | #include <boost/system/error_code.hpp> | |
23 | #include <boost/asio/experimental/coro_traits.hpp> | |
24 | #include <boost/asio/experimental/detail/coro_promise_allocator.hpp> | |
25 | #include <boost/asio/experimental/detail/partial_promise.hpp> | |
26 | #include <boost/asio/experimental/use_coro.hpp> | |
27 | #include <boost/asio/post.hpp> | |
28 | ||
29 | #include <boost/asio/detail/push_options.hpp> | |
30 | ||
31 | namespace boost { | |
32 | namespace asio { | |
33 | namespace experimental { | |
34 | namespace detail { | |
35 | ||
36 | template <typename T, typename Coroutine> | |
37 | struct coro_with_arg; | |
38 | ||
39 | } // namespace detail | |
40 | ||
41 | /// The main type of a resumable coroutine. | |
42 | /** | |
43 | * Template parameter @c Yield specifies type or signature used by co_yield, | |
44 | * @c Return specifies the type used for co_return, and @c Executor specifies | |
45 | * the underlying executor type. | |
46 | */ | |
47 | template <typename Yield = void, typename Return = void, | |
48 | typename Executor = any_io_executor> | |
49 | struct coro | |
50 | { | |
51 | /// The traits of the coroutine. See boost::asio::experimental::coro_traits | |
52 | /// for details. | |
53 | using traits = coro_traits<Yield, Return, Executor>; | |
54 | ||
55 | /// The value that can be passed into a symmetrical cororoutine. @c void if | |
56 | /// asymmetrical. | |
57 | using input_type = typename traits::input_type; | |
58 | ||
59 | /// The type that can be passed out through a co_yield. | |
60 | using yield_type = typename traits::yield_type; | |
61 | ||
62 | /// The type that can be passed out through a co_return. | |
63 | using return_type = typename traits::return_type; | |
64 | ||
65 | /// The type received by a co_await or async_resume. Its a combination of | |
66 | /// yield and return. | |
67 | using result_type = typename traits::result_type; | |
68 | ||
69 | /// The signature used by the async_resume. | |
70 | using signature_type = typename traits::signature_type; | |
71 | ||
72 | /// Whether or not the coroutine is noexcept. | |
73 | constexpr static bool is_noexcept = traits::is_noexcept; | |
74 | ||
75 | /// The error type of the coroutine. Void for noexcept | |
76 | using error_type = typename traits::error_type; | |
77 | ||
78 | /// Completion handler type used by async_resume. | |
79 | using completion_handler = typename traits::completion_handler; | |
80 | ||
81 | /// The internal promise-type of the coroutine. | |
82 | using promise_type = detail::coro_promise<Yield, Return, Executor>; | |
83 | ||
84 | #if !defined(GENERATING_DOCUMENTATION) | |
85 | template <typename T, typename Coroutine> | |
86 | friend struct detail::coro_with_arg; | |
87 | #endif // !defined(GENERATING_DOCUMENTATION) | |
88 | ||
89 | /// The executor type. | |
90 | using executor_type = Executor; | |
91 | ||
92 | #if !defined(GENERATING_DOCUMENTATION) | |
93 | friend struct detail::coro_promise<Yield, Return, Executor>; | |
94 | #endif // !defined(GENERATING_DOCUMENTATION) | |
95 | ||
96 | /// The default constructor, gives an invalid coroutine. | |
97 | coro() = default; | |
98 | ||
99 | /// Move constructor. | |
100 | coro(coro&& lhs) noexcept | |
101 | : coro_(std::exchange(lhs.coro_, nullptr)) | |
102 | { | |
103 | } | |
104 | ||
105 | coro(const coro &) = delete; | |
106 | ||
107 | /// Move assignment. | |
108 | coro& operator=(coro&& lhs) noexcept | |
109 | { | |
110 | std::swap(coro_, lhs.coro_); | |
111 | return *this; | |
112 | } | |
113 | ||
114 | coro& operator=(const coro&) = delete; | |
115 | ||
116 | /// Destructor. Destroys the coroutine, if it holds a valid one. | |
117 | /** | |
118 | * @note This does not cancel an active coroutine. Destructing a resumable | |
119 | * coroutine, i.e. one with a call to async_resume that has not completed, is | |
120 | * undefined behaviour. | |
121 | */ | |
122 | ~coro() | |
123 | { | |
124 | if (coro_ != nullptr) | |
125 | { | |
126 | struct destroyer | |
127 | { | |
128 | detail::coroutine_handle<promise_type> handle; | |
129 | ||
130 | destroyer(const detail::coroutine_handle<promise_type>& handle) | |
131 | : handle(handle) | |
132 | { } | |
133 | ||
134 | destroyer(destroyer&& lhs) | |
135 | : handle(std::exchange(lhs.handle, nullptr)) | |
136 | { | |
137 | } | |
138 | ||
139 | destroyer(const destroyer&) = delete; | |
140 | ||
141 | void operator()() {} | |
142 | ||
143 | ~destroyer() | |
144 | { | |
145 | if (handle) | |
146 | handle.destroy(); | |
147 | } | |
148 | }; | |
149 | ||
150 | auto handle = | |
151 | detail::coroutine_handle<promise_type>::from_promise(*coro_); | |
152 | if (handle) | |
153 | boost::asio::dispatch(coro_->get_executor(), destroyer{handle}); | |
154 | } | |
155 | } | |
156 | ||
157 | /// Get the used executor. | |
158 | executor_type get_executor() const | |
159 | { | |
160 | if (coro_) | |
161 | return coro_->get_executor(); | |
162 | ||
163 | if constexpr (std::is_default_constructible_v<Executor>) | |
164 | return Executor{}; | |
165 | else | |
166 | throw std::logic_error("Coroutine has no executor"); | |
167 | } | |
168 | ||
169 | /// Resume the coroutine. | |
170 | /** | |
171 | * @param token The completion token of the async resume. | |
172 | * | |
173 | * @attention Calling an invalid coroutine with a noexcept signature is | |
174 | * undefined behaviour. | |
175 | * | |
176 | * @note This overload is only available for coroutines without an input | |
177 | * value. | |
178 | */ | |
179 | template <typename CompletionToken> | |
180 | requires std::is_void_v<input_type> | |
181 | auto async_resume(CompletionToken&& token) & | |
182 | { | |
183 | return async_initiate<CompletionToken, | |
184 | typename traits::completion_handler>( | |
185 | initiate_async_resume(this), token); | |
186 | } | |
187 | ||
188 | /// Resume the coroutine. | |
189 | /** | |
190 | * @param token The completion token of the async resume. | |
191 | * | |
192 | * @attention Calling an invalid coroutine with a noexcept signature is | |
193 | * undefined behaviour. | |
194 | * | |
195 | * @note This overload is only available for coroutines with an input value. | |
196 | */ | |
197 | template <typename CompletionToken, detail::convertible_to<input_type> T> | |
198 | auto async_resume(T&& ip, CompletionToken&& token) & | |
199 | { | |
200 | return async_initiate<CompletionToken, | |
201 | typename traits::completion_handler>( | |
202 | initiate_async_resume(this), token, std::forward<T>(ip)); | |
203 | } | |
204 | ||
205 | /// Operator used for coroutines without input value. | |
206 | auto operator co_await() requires (std::is_void_v<input_type>) | |
207 | { | |
208 | return awaitable_t{*this}; | |
209 | } | |
210 | ||
211 | /// Operator used for coroutines with input value. | |
212 | /** | |
213 | * @param ip The input value | |
214 | * | |
215 | * @returns An awaitable handle. | |
216 | * | |
217 | * @code | |
218 | * coro<void> push_values(coro<double(int)> c) | |
219 | * { | |
220 | * std::optional<double> res = co_await c(42); | |
221 | * } | |
222 | * @endcode | |
223 | */ | |
224 | template <detail::convertible_to<input_type> T> | |
225 | auto operator()(T&& ip) | |
226 | { | |
227 | return detail::coro_with_arg<std::decay_t<T>, coro>{ | |
228 | std::forward<T>(ip), *this}; | |
229 | } | |
230 | ||
231 | /// Check whether the coroutine is open, i.e. can be resumed. | |
232 | bool is_open() const | |
233 | { | |
234 | if (coro_) | |
235 | { | |
236 | auto handle = | |
237 | detail::coroutine_handle<promise_type>::from_promise(*coro_); | |
238 | return handle && !handle.done(); | |
239 | } | |
240 | else | |
241 | return false; | |
242 | } | |
243 | ||
244 | /// Check whether the coroutine is open, i.e. can be resumed. | |
245 | explicit operator bool() const { return is_open(); } | |
246 | ||
247 | private: | |
248 | struct awaitable_t; | |
249 | ||
250 | struct initiate_async_resume; | |
251 | ||
252 | explicit coro(promise_type* const cr) : coro_(cr) {} | |
253 | ||
254 | promise_type* coro_{nullptr}; | |
255 | }; | |
256 | ||
257 | } // namespace experimental | |
258 | } // namespace asio | |
259 | } // namespace boost | |
260 | ||
261 | #include <boost/asio/detail/pop_options.hpp> | |
262 | ||
263 | #include <boost/asio/experimental/impl/coro.hpp> | |
264 | ||
265 | #endif // BOOST_ASIO_EXPERIMENTAL_CORO_HPP |