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include/boost/corosio/io/io_timer.hpp

96.7% Lines (29/30) 100.0% Functions (10/10)
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 8464 explicit wait_awaitable(io_timer& t) noexcept : t_(t) {}
51
52 8464 bool await_ready() const noexcept
53 {
54 8464 return token_.stop_requested();
55 }
56
57 8464 capy::io_result<> await_resume() const noexcept
58 {
59 8464 if (token_.stop_requested())
60 ✗ return {capy::error::canceled};
61 8464 return {ec_};
62 }
63
64 8464 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
65 -> std::coroutine_handle<>
66 {
67 8464 token_ = env->stop_token;
68 8464 auto& impl = t_.get();
69 // Inline fast path: already expired and not in the heap
70 16906 if (impl.heap_index_ == implementation::npos &&
71 16880 (impl.expiry_ == (time_point::min)() ||
72 16902 impl.expiry_ <= clock_type::now()))
73 {
74 279 ec_ = {};
75 279 auto d = env->executor;
76 279 d.post(h);
77 279 return std::noop_coroutine();
78 }
79 8185 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 @return An awaitable that completes with `io_result<>`.
145 */
146 8464 auto wait()
147 {
148 8464 return wait_awaitable(*this);
149 }
150
151 protected:
152 /** Dispatch cancel to the concrete implementation.
153
154 @return The number of operations that were cancelled.
155 */
156 virtual std::size_t do_cancel() = 0;
157
158 8475 explicit io_timer(handle h) noexcept : io_object(std::move(h)) {}
159
160 /// Move construct.
161 2 io_timer(io_timer&& other) noexcept : io_object(std::move(other)) {}
162
163 /// Move assign.
164 io_timer& operator=(io_timer&& other) noexcept
165 {
166 if (this != &other)
167 h_ = std::move(other.h_);
168 return *this;
169 }
170
171 io_timer(io_timer const&) = delete;
172 io_timer& operator=(io_timer const&) = delete;
173
174 /// Return the underlying implementation.
175 8522 implementation& get() const noexcept
176 {
177 8522 return *static_cast<implementation*>(h_.get());
178 }
179 };
180
181 } // namespace boost::corosio
182
183 #endif
184