Index/include / boost / corosio / io / io_timer.hpp

include/boost/corosio/io/io_timer.hpp

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include/boost/corosio/io/io_timer.hpp
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1 //
2 // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3 // Copyright (c) 2026 Steve Gerbino
4 //
5 // Distributed under the Boost Software License, Version 1.0. (See accompanying
6 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 //
8 // Official repository: https://github.com/cppalliance/corosio
9 //
10
11 #ifndef BOOST_COROSIO_IO_IO_TIMER_HPP
12 #define BOOST_COROSIO_IO_IO_TIMER_HPP
13
14 #include <boost/corosio/detail/config.hpp>
15 #include <boost/corosio/io/io_object.hpp>
16 #include <boost/capy/io_result.hpp>
17 #include <boost/capy/error.hpp>
18 #include <boost/capy/ex/executor_ref.hpp>
19 #include <boost/capy/ex/io_env.hpp>
20
21 #include <chrono>
22 #include <coroutine>
23 #include <cstddef>
24 #include <limits>
25 #include <stop_token>
26 #include <system_error>
27
28 namespace boost::corosio {
29
30 /** Abstract base for asynchronous timers.
31
32 Provides the common timer interface: `wait`, `cancel`, and
33 `expiry`. Concrete classes like @ref timer add the ability
34 to set expiry times and cancel individual waiters.
35
36 @par Thread Safety
37 Distinct objects: Safe.
38 Shared objects: Unsafe.
39
40 @see timer, io_object
41 */
42 class BOOST_COROSIO_DECL io_timer : public io_object
43 {
44 struct wait_awaitable
45 {
46 io_timer& t_;
47 std::stop_token token_;
48 mutable std::error_code ec_;
49
50 5396 explicit wait_awaitable(io_timer& t) noexcept : t_(t) {}
51
52 5396 bool await_ready() const noexcept
53 {
54 5396 return token_.stop_requested();
55 }
56
57 5396 capy::io_result<> await_resume() const noexcept
58 {
59 5396 if (token_.stop_requested())
60 ✗ return {capy::error::canceled};
61 5396 return {ec_};
62 }
63
64 5396 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
65 -> std::coroutine_handle<>
66 {
67 5396 token_ = env->stop_token;
68 5396 auto& impl = t_.get();
69 // Inline fast path: already expired and not in the heap
70 10770 if (impl.heap_index_ == implementation::npos &&
71 10744 (impl.expiry_ == (time_point::min)() ||
72 10766 impl.expiry_ <= clock_type::now()))
73 {
74 274 ec_ = {};
75 274 auto d = env->executor;
76 274 d.post(h);
77 274 return std::noop_coroutine();
78 }
79 5122 return impl.wait(h, env->executor, std::move(token_), &ec_);
80 }
81 };
82
83 public:
84 struct implementation : io_object::implementation
85 {
86 static constexpr std::size_t npos =
87 (std::numeric_limits<std::size_t>::max)();
88
89 std::chrono::steady_clock::time_point expiry_{};
90 std::size_t heap_index_ = npos;
91 bool might_have_pending_waits_ = false;
92
93 virtual std::coroutine_handle<> wait(
94 std::coroutine_handle<>,
95 capy::executor_ref,
96 std::stop_token,
97 std::error_code*) = 0;
98 };
99
100 /// The clock type used for time operations.
101 using clock_type = std::chrono::steady_clock;
102
103 /// The time point type for absolute expiry times.
104 using time_point = clock_type::time_point;
105
106 /// The duration type for relative expiry times.
107 using duration = clock_type::duration;
108
109 /** Cancel all pending asynchronous wait operations.
110
111 All outstanding operations complete with an error code that
112 compares equal to `capy::cond::canceled`.
113
114 @return The number of operations that were cancelled.
115 */
116 20 std::size_t cancel()
117 {
118 20 if (!get().might_have_pending_waits_)
119 12 return 0;
120 8 return do_cancel();
121 }
122
123 /** Return the timer's expiry time as an absolute time.
124
125 @return The expiry time point. If no expiry has been set,
126 returns a default-constructed time_point.
127 */
128 38 time_point expiry() const noexcept
129 {
130 38 return get().expiry_;
131 }
132
133 /** Wait for the timer to expire.
134
135 Multiple coroutines may wait on the same timer concurrently.
136 When the timer expires, all waiters complete with success.
137
138 The operation supports cancellation via `std::stop_token` through
139 the affine awaitable protocol. If the associated stop token is
140 triggered, only that waiter completes with an error that
141 compares equal to `capy::cond::canceled`; other waiters are
142 unaffected.
143
144 This timer must outlive the returned awaitable.
145
146 @return An awaitable that completes with `io_result<>`.
147 */
148 5396 auto wait()
149 {
150 5396 return wait_awaitable(*this);
151 }
152
153 protected:
154 /** Dispatch cancel to the concrete implementation.
155
156 @return The number of operations that were cancelled.
157 */
158 virtual std::size_t do_cancel() = 0;
159
160 5407 explicit io_timer(handle h) noexcept : io_object(std::move(h)) {}
161
162 /// Move construct.
163 2 io_timer(io_timer&& other) noexcept : io_object(std::move(other)) {}
164
165 /// Move assign.
166 io_timer& operator=(io_timer&& other) noexcept
167 {
168 if (this != &other)
169 h_ = std::move(other.h_);
170 return *this;
171 }
172
173 io_timer(io_timer const&) = delete;
174 io_timer& operator=(io_timer const&) = delete;
175
176 /// Return the underlying implementation.
177 5454 implementation& get() const noexcept
178 {
179 5454 return *static_cast<implementation*>(h_.get());
180 }
181 };
182
183 } // namespace boost::corosio
184
185 #endif
186