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//
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//
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// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
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// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
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// Copyright (c) 2026 Steve Gerbino
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// Copyright (c) 2026 Steve Gerbino
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//
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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//
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// Official repository: https://github.com/cppalliance/corosio
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// Official repository: https://github.com/cppalliance/corosio
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//
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//
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#ifndef BOOST_COROSIO_IO_IO_TIMER_HPP
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#ifndef BOOST_COROSIO_IO_IO_TIMER_HPP
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#define BOOST_COROSIO_IO_IO_TIMER_HPP
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#define BOOST_COROSIO_IO_IO_TIMER_HPP
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#include <boost/corosio/detail/config.hpp>
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#include <boost/corosio/detail/config.hpp>
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#include <boost/corosio/io/io_object.hpp>
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#include <boost/corosio/io/io_object.hpp>
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#include <boost/capy/io_result.hpp>
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#include <boost/capy/io_result.hpp>
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#include <boost/capy/error.hpp>
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#include <boost/capy/error.hpp>
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#include <boost/capy/ex/executor_ref.hpp>
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#include <boost/capy/ex/executor_ref.hpp>
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#include <boost/capy/ex/io_env.hpp>
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#include <boost/capy/ex/io_env.hpp>
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20  
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#include <chrono>
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#include <chrono>
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#include <coroutine>
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#include <coroutine>
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#include <cstddef>
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#include <cstddef>
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#include <limits>
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#include <limits>
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#include <stop_token>
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#include <stop_token>
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#include <system_error>
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#include <system_error>
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27  
28   
namespace boost::corosio {
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namespace boost::corosio {
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29  
30   
/** Abstract base for asynchronous timers.
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/** Abstract base for asynchronous timers.
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31  
32   
    Provides the common timer interface: `wait`, `cancel`, and
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    Provides the common timer interface: `wait`, `cancel`, and
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    `expiry`. Concrete classes like @ref timer add the ability
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    `expiry`. Concrete classes like @ref timer add the ability
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    to set expiry times and cancel individual waiters.
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    to set expiry times and cancel individual waiters.
35  
35  
36   
    @par Thread Safety
36   
    @par Thread Safety
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    Distinct objects: Safe.
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    Distinct objects: Safe.
38   
    Shared objects: Unsafe.
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    Shared objects: Unsafe.
39  
39  
40   
    @see timer, io_object
40   
    @see timer, io_object
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*/
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*/
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class BOOST_COROSIO_DECL io_timer : public io_object
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class BOOST_COROSIO_DECL io_timer : public io_object
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{
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{
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    struct wait_awaitable
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    struct wait_awaitable
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    {
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    {
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        io_timer& t_;
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        io_timer& t_;
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        std::stop_token token_;
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        std::stop_token token_;
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        mutable std::error_code ec_;
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        mutable std::error_code ec_;
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49  
50   
        explicit wait_awaitable(io_timer& t) noexcept : t_(t) {}
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        explicit wait_awaitable(io_timer& t) noexcept : t_(t) {}
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51  
52   
        bool await_ready() const noexcept
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        bool await_ready() const noexcept
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        {
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        {
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            return token_.stop_requested();
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            return token_.stop_requested();
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        }
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        }
56  
56  
57   
        capy::io_result<> await_resume() const noexcept
57   
        capy::io_result<> await_resume() const noexcept
58   
        {
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        {
59   
            if (token_.stop_requested())
59   
            if (token_.stop_requested())
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                return {capy::error::canceled};
60   
                return {capy::error::canceled};
61   
            return {ec_};
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            return {ec_};
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        }
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        }
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64   
        auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
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        auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
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            -> std::coroutine_handle<>
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            -> std::coroutine_handle<>
66   
        {
66   
        {
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            token_     = env->stop_token;
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            token_     = env->stop_token;
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            auto& impl = t_.get();
68   
            auto& impl = t_.get();
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            // Inline fast path: already expired and not in the heap
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            // Inline fast path: already expired and not in the heap
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            if (impl.heap_index_ == implementation::npos &&
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            if (impl.heap_index_ == implementation::npos &&
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                (impl.expiry_ == (time_point::min)() ||
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                (impl.expiry_ == (time_point::min)() ||
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                 impl.expiry_ <= clock_type::now()))
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                 impl.expiry_ <= clock_type::now()))
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            {
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            {
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                ec_    = {};
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                ec_    = {};
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                token_ = {};  // match normal path so await_resume
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                token_ = {};  // match normal path so await_resume
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                              // returns ec_, not a stale stop check
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                              // returns ec_, not a stale stop check
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                auto d = env->executor;
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                auto d = env->executor;
78   
                d.post(h);
78   
                d.post(h);
79   
                return std::noop_coroutine();
79   
                return std::noop_coroutine();
80   
            }
80   
            }
81   
            return impl.wait(h, env->executor, std::move(token_), &ec_);
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            return impl.wait(h, env->executor, std::move(token_), &ec_);
82   
        }
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        }
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    };
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    };
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public:
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public:
 
86 + 
    /** Backend interface for timer wait operations.
 
87 +
 
88 + 
        Holds per-timer state (expiry, heap position) and provides
 
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        the virtual `wait` entry point that concrete timer services
 
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        override.
 
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    */
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    struct implementation : io_object::implementation
92   
    struct implementation : io_object::implementation
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    {
93   
    {
 
94 + 
        /// Sentinel value indicating the timer is not in the heap.
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        static constexpr std::size_t npos =
95   
        static constexpr std::size_t npos =
89   
            (std::numeric_limits<std::size_t>::max)();
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            (std::numeric_limits<std::size_t>::max)();
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98 + 
        /// The absolute expiry time point.
91   
        std::chrono::steady_clock::time_point expiry_{};
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        std::chrono::steady_clock::time_point expiry_{};
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        std::size_t heap_index_        = npos;
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        /// Index in the timer service's min-heap, or `npos`.
 
102 + 
        std::size_t heap_index_ = npos;
 
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104 + 
        /// True if `wait()` has been called since last cancel.
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        bool might_have_pending_waits_ = false;
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        bool might_have_pending_waits_ = false;
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        /// Initiate an asynchronous wait for the timer to expire.
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        virtual std::coroutine_handle<> wait(
108   
        virtual std::coroutine_handle<> wait(
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            std::coroutine_handle<>,
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            std::coroutine_handle<>,
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            capy::executor_ref,
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            capy::executor_ref,
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            std::stop_token,
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            std::stop_token,
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            std::error_code*) = 0;
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            std::error_code*) = 0;
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    };
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    };
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102   
    /// The clock type used for time operations.
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    /// The clock type used for time operations.
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    using clock_type = std::chrono::steady_clock;
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    using clock_type = std::chrono::steady_clock;
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105   
    /// The time point type for absolute expiry times.
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    /// The time point type for absolute expiry times.
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    using time_point = clock_type::time_point;
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    using time_point = clock_type::time_point;
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108   
    /// The duration type for relative expiry times.
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    /// The duration type for relative expiry times.
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    using duration = clock_type::duration;
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    using duration = clock_type::duration;
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123  
111   
    /** Cancel all pending asynchronous wait operations.
124   
    /** Cancel all pending asynchronous wait operations.
112  
125  
113   
        All outstanding operations complete with an error code that
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        All outstanding operations complete with an error code that
114   
        compares equal to `capy::cond::canceled`.
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        compares equal to `capy::cond::canceled`.
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128  
116   
        @return The number of operations that were cancelled.
129   
        @return The number of operations that were cancelled.
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    */
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    */
118   
    std::size_t cancel()
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    std::size_t cancel()
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    {
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    {
120   
        if (!get().might_have_pending_waits_)
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        if (!get().might_have_pending_waits_)
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            return 0;
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            return 0;
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        return do_cancel();
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        return do_cancel();
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    }
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    }
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125   
    /** Return the timer's expiry time as an absolute time.
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    /** Return the timer's expiry time as an absolute time.
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127   
        @return The expiry time point. If no expiry has been set,
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        @return The expiry time point. If no expiry has been set,
128   
            returns a default-constructed time_point.
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            returns a default-constructed time_point.
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    */
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    */
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    time_point expiry() const noexcept
143   
    time_point expiry() const noexcept
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    {
144   
    {
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        return get().expiry_;
145   
        return get().expiry_;
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    }
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    }
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135   
    /** Wait for the timer to expire.
148   
    /** Wait for the timer to expire.
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137   
        Multiple coroutines may wait on the same timer concurrently.
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        Multiple coroutines may wait on the same timer concurrently.
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        When the timer expires, all waiters complete with success.
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        When the timer expires, all waiters complete with success.
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        The operation supports cancellation via `std::stop_token` through
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        The operation supports cancellation via `std::stop_token` through
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        the affine awaitable protocol. If the associated stop token is
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        the affine awaitable protocol. If the associated stop token is
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        triggered, only that waiter completes with an error that
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        triggered, only that waiter completes with an error that
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        compares equal to `capy::cond::canceled`; other waiters are
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        compares equal to `capy::cond::canceled`; other waiters are
144   
        unaffected.
157   
        unaffected.
145  
158  
146   
        This timer must outlive the returned awaitable.
159   
        This timer must outlive the returned awaitable.
147  
160  
148   
        @return An awaitable that completes with `io_result<>`.
161   
        @return An awaitable that completes with `io_result<>`.
149   
    */
162   
    */
150   
    auto wait()
163   
    auto wait()
151   
    {
164   
    {
152   
        return wait_awaitable(*this);
165   
        return wait_awaitable(*this);
153   
    }
166   
    }
154  
167  
155   
protected:
168   
protected:
156   
    /** Dispatch cancel to the concrete implementation.
169   
    /** Dispatch cancel to the concrete implementation.
157  
170  
158   
        @return The number of operations that were cancelled.
171   
        @return The number of operations that were cancelled.
159   
    */
172   
    */
160   
    virtual std::size_t do_cancel() = 0;
173   
    virtual std::size_t do_cancel() = 0;
161  
174  
162   
    explicit io_timer(handle h) noexcept : io_object(std::move(h)) {}
175   
    explicit io_timer(handle h) noexcept : io_object(std::move(h)) {}
163  
176  
164   
    /// Move construct.
177   
    /// Move construct.
165   
    io_timer(io_timer&& other) noexcept : io_object(std::move(other)) {}
178   
    io_timer(io_timer&& other) noexcept : io_object(std::move(other)) {}
166  
179  
167   
    /// Move assign.
180   
    /// Move assign.
168   
    io_timer& operator=(io_timer&& other) noexcept
181   
    io_timer& operator=(io_timer&& other) noexcept
169   
    {
182   
    {
170   
        if (this != &other)
183   
        if (this != &other)
171   
            h_ = std::move(other.h_);
184   
            h_ = std::move(other.h_);
172   
        return *this;
185   
        return *this;
173   
    }
186   
    }
174  
187  
175   
    io_timer(io_timer const&)            = delete;
188   
    io_timer(io_timer const&)            = delete;
176   
    io_timer& operator=(io_timer const&) = delete;
189   
    io_timer& operator=(io_timer const&) = delete;
177  
190  
178   
    /// Return the underlying implementation.
191   
    /// Return the underlying implementation.
179   
    implementation& get() const noexcept
192   
    implementation& get() const noexcept
180   
    {
193   
    {
181   
        return *static_cast<implementation*>(h_.get());
194   
        return *static_cast<implementation*>(h_.get());
182   
    }
195   
    }
183   
};
196   
};
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197  
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} // namespace boost::corosio
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} // namespace boost::corosio
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#endif
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#endif