1 - 
//
 
2 - 
// Copyright (c) 2026 Michael Vandeberg
 
3 - 
//
 
4 - 
// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
5 - 
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
6 - 
//
 
7 - 
// Official repository: https://github.com/cppalliance/capy
 
8 - 
//
 
9 -
 
10 - 
#ifndef BOOST_CAPY_EX_TIMER_SERVICE_HPP
 
11 - 
#define BOOST_CAPY_EX_TIMER_SERVICE_HPP
 
12 -
 
13 - 
#include <boost/capy/detail/config.hpp>
 
14 - 
#include <boost/capy/ex/execution_context.hpp>
 
15 -
 
16 - 
#include <chrono>
 
17 - 
#include <cstdint>
 
18 - 
#include <functional>
 
19 - 
#include <mutex>
 
20 - 
#include <condition_variable>
 
21 - 
#include <queue>
 
22 - 
#include <thread>
 
23 - 
#include <unordered_set>
 
24 - 
#include <vector>
 
25 -
 
26 - 
namespace boost {
 
27 - 
namespace capy {
 
28 - 
namespace detail {
 
29 -
 
30 - 
/* Shared timer thread for an execution_context.
 
31 -
 
32 - 
   One background std::thread per execution_context. All timeouts
 
33 - 
   scheduled through this context share the same thread, which sleeps
 
34 - 
   on a condition variable until the next deadline.
 
35 -
 
36 - 
   The timer thread never touches coroutine frames or executors
 
37 - 
   directly — callbacks are responsible for posting work through
 
38 - 
   the appropriate executor.
 
39 - 
*/
 
40 -
 
41 - 
class BOOST_CAPY_DECL
 
42 - 
    timer_service
 
43 - 
    : public execution_context::service
 
44 - 
{
 
45 - 
public:
 
46 - 
    using timer_id = std::uint64_t;
 
47 -
 
48 - 
    explicit timer_service(execution_context& ctx);
 
49 -
 
50 - 
    /** Schedule a callback to fire after a duration.
 
51 -
 
52 - 
        The callback is invoked on the timer service's background
 
53 - 
        thread. It must not block for extended periods.
 
54 -
 
55 - 
        @return An id that can be passed to cancel().
 
56 - 
    */
 
57 - 
    template<typename Rep, typename Period>
 
58 - 
    timer_id schedule_after(
 
59 - 
        std::chrono::duration<Rep, Period> dur,
 
60 - 
        std::function<void()> cb)
 
61 - 
    {
 
62 - 
        auto deadline = std::chrono::steady_clock::now() + dur;
 
63 - 
        return schedule_at(deadline, std::move(cb));
 
64 - 
    }
 
65 -
 
66 - 
    /** Cancel a pending timer.
 
67 -
 
68 - 
        After this function returns, the callback is guaranteed
 
69 - 
        not to be running and will never be invoked. If the
 
70 - 
        callback is currently executing on the timer thread,
 
71 - 
        this call blocks until it completes.
 
72 -
 
73 - 
        Safe to call with any id, including ids that have
 
74 - 
        already fired, been cancelled, or were never issued.
 
75 - 
    */
 
76 - 
    void cancel(timer_id id);
 
77 -
 
78 - 
protected:
 
79 - 
    void shutdown() override;
 
80 -
 
81 - 
private:
 
82 - 
    struct entry
 
83 - 
    {
 
84 - 
        std::chrono::steady_clock::time_point deadline;
 
85 - 
        timer_id id;
 
86 - 
        std::function<void()> callback;
 
87 -
 
88 - 
        bool operator>(entry const& o) const noexcept
 
89 - 
        {
 
90 - 
            return deadline > o.deadline;
 
91 - 
        }
 
92 - 
    };
 
93 -
 
94 - 
    timer_id schedule_at(
 
95 - 
        std::chrono::steady_clock::time_point deadline,
 
96 - 
        std::function<void()> cb);
 
97 -
 
98 - 
    void run();
 
99 -
 
100 - 
// warning C4251: std types need to have dll-interface
 
101 - 
#ifdef _MSC_VER
 
102 - 
# pragma warning(push)
 
103 - 
# pragma warning(disable: 4251)
 
104 - 
#endif
 
105 - 
    std::mutex mutex_;
 
106 - 
    std::condition_variable cv_;
 
107 - 
    std::condition_variable cancel_cv_;
 
108 - 
    std::priority_queue<
 
109 - 
        entry,
 
110 - 
        std::vector<entry>,
 
111 - 
        std::greater<>> queue_;
 
112 - 
    std::unordered_set<timer_id> active_ids_;
 
113 - 
    timer_id next_id_ = 0;
 
114 - 
    timer_id executing_id_ = 0;
 
115 - 
    bool stopped_ = false;
 
116 - 
    std::thread thread_;
 
117 - 
#ifdef _MSC_VER
 
118 - 
# pragma warning(pop)
 
119 - 
#endif
 
120 - 
};
 
121 -
 
122 - 
} // detail
 
123 - 
} // capy
 
124 - 
} // boost
 
125 -
 
126 - 
#endif