include/boost/corosio/timer.hpp

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include/boost/corosio/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_TIMER_HPP
12		#define BOOST_COROSIO_TIMER_HPP
13
14		#include <boost/corosio/detail/config.hpp>
15		#include <boost/corosio/io/io_timer.hpp>
16		#include <boost/capy/ex/execution_context.hpp>
17		#include <boost/capy/concept/executor.hpp>
18
19		#include <chrono>
20		#include <cstddef>
21
22		namespace boost::corosio {
23
24		/** An asynchronous timer for coroutine I/O.
25
26		This class provides asynchronous timer operations that return
27		awaitable types. The timer can be used to schedule operations
28		to occur after a specified duration or at a specific time point.
29
30		Multiple coroutines may wait concurrently on the same timer.
31		When the timer expires, all waiters complete with success. When
32		the timer is cancelled, all waiters complete with an error that
33		compares equal to `capy::cond::canceled`.
34
35		Each timer operation participates in the affine awaitable protocol,
36		ensuring coroutines resume on the correct executor.
37
38		@par Thread Safety
39		Distinct objects: Safe.@n
40		Shared objects: Unsafe.
41
42		@par Semantics
43		Wraps platform timer facilities via the io_context reactor.
44		Operations dispatch to OS timer APIs (timerfd, IOCP timers,
45		kqueue EVFILT_TIMER).
46		*/
47		class BOOST_COROSIO_DECL timer : public io_timer
48		{
49		public:
50		/// Alias for backward compatibility.
51		using implementation = io_timer::implementation;
52
53		/** Destructor.
54
55		Cancels any pending operations and releases timer resources.
56		*/
57		~timer() override;
58
59		/** Construct a timer from an execution context.
60
61		@param ctx The execution context that will own this timer.
62		*/
63		explicit timer(capy::execution_context& ctx);
64
65		/** Construct a timer with an initial absolute expiry time.
66
67		@param ctx The execution context that will own this timer.
68		@param t The initial expiry time point.
69		*/
70		timer(capy::execution_context& ctx, time_point t);
71
72		/** Construct a timer with an initial relative expiry time.
73
74		@param ctx The execution context that will own this timer.
75		@param d The initial expiry duration relative to now.
76		*/
77		template<class Rep, class Period>
78	2	timer(capy::execution_context& ctx, std::chrono::duration<Rep, Period> d)
79	2	: timer(ctx)
80		{
81	2	expires_after(d);
82	2	}
83
84		/** Move constructor.
85
86		Transfers ownership of the timer resources.
87
88		@param other The timer to move from.
89		*/
90		timer(timer&& other) noexcept;
91
92		/** Move assignment operator.
93
94		Closes any existing timer and transfers ownership.
95
96		@param other The timer to move from.
97
98		@return Reference to this timer.
99		*/
100		timer& operator=(timer&& other) noexcept;
101
102		timer(timer const&) = delete;
103		timer& operator=(timer const&) = delete;
104
105		/** Cancel one pending asynchronous wait operation.
106
107		The oldest pending wait is cancelled (FIFO order). It
108		completes with an error code that compares equal to
109		`capy::cond::canceled`.
110
111		@return The number of operations that were cancelled (0 or 1).
112		*/
113	4	std::size_t cancel_one()
114		{
115	4	if (!get().might_have_pending_waits_)
116	2	return 0;
117	2	return do_cancel_one();
118		}
119
120		/** Set the timer's expiry time as an absolute time.
121
122		Any pending asynchronous wait operations will be cancelled.
123
124		@param t The expiry time to be used for the timer.
125
126		@return The number of pending operations that were cancelled.
127		*/
128	18	std::size_t expires_at(time_point t)
129		{
130	18	auto& impl = get();
131	18	impl.expiry_ = t;
132	18	if (impl.heap_index_ == implementation::npos &&
133	16	!impl.might_have_pending_waits_)
134	16	return 0;
135	2	return do_update_expiry();
136		}
137
138		/** Set the timer's expiry time relative to now.
139
140		Any pending asynchronous wait operations will be cancelled.
141
142		@param d The expiry time relative to now.
143
144		@return The number of pending operations that were cancelled.
145		*/
146	8466	std::size_t expires_after(duration d)
147		{
148	8466	auto& impl = get();
149	8466	if (d <= duration::zero())
150	6	impl.expiry_ = (time_point::min)();
151		else
152	8460	impl.expiry_ = clock_type::now() + d;
153	8466	if (impl.heap_index_ == implementation::npos &&
154	8462	!impl.might_have_pending_waits_)
155	8462	return 0;
156	4	return do_update_expiry();
157		}
158
159		/** Set the timer's expiry time relative to now.
160
161		This is a convenience overload that accepts any duration type
162		and converts it to the timer's native duration type. Any
163		pending asynchronous wait operations will be cancelled.
164
165		@param d The expiry time relative to now.
166
167		@return The number of pending operations that were cancelled.
168		*/
169		template<class Rep, class Period>
170	8466	std::size_t expires_after(std::chrono::duration<Rep, Period> d)
171		{
172	8466	return expires_after(std::chrono::duration_cast<duration>(d));
173		}
174
175		protected:
176		explicit timer(handle h) noexcept : io_timer(std::move(h)) {}
177
178		private:
179		std::size_t do_cancel() override;
180		std::size_t do_cancel_one();
181		std::size_t do_update_expiry();
182
183		/// Return the underlying implementation.
184	8504	implementation& get() const noexcept
185		{
186	8504	return *static_cast<implementation*>(h_.get());
187		}
188		};
189
190		} // namespace boost::corosio
191
192		#endif
193