. /include/boost/corosio /timeout.hpp
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1   // 1   //
2   // Copyright (c) 2026 Steve Gerbino 2   // Copyright (c) 2026 Steve Gerbino
3   // Copyright (c) 2026 Michael Vandeberg 3   // Copyright (c) 2026 Michael Vandeberg
4   // 4   //
5   // Distributed under the Boost Software License, Version 1.0. (See accompanying 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) 6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7   // 7   //
8   // Official repository: https://github.com/cppalliance/corosio 8   // Official repository: https://github.com/cppalliance/corosio
9   // 9   //
10   10  
11   #ifndef BOOST_COROSIO_TIMEOUT_HPP 11   #ifndef BOOST_COROSIO_TIMEOUT_HPP
12   #define BOOST_COROSIO_TIMEOUT_HPP 12   #define BOOST_COROSIO_TIMEOUT_HPP
13   13  
14   #include <boost/corosio/detail/config.hpp> 14   #include <boost/corosio/detail/config.hpp>
15   #include <boost/corosio/detail/timeout_awaitable.hpp> 15   #include <boost/corosio/detail/timeout_awaitable.hpp>
16   #include <boost/capy/concept/io_awaitable.hpp> 16   #include <boost/capy/concept/io_awaitable.hpp>
17   17  
18   #include <chrono> 18   #include <chrono>
19   #include <type_traits> 19   #include <type_traits>
20   #include <utility> 20   #include <utility>
21   21  
22   namespace boost::corosio { 22   namespace boost::corosio {
23   23  
24   /** Race an io_result-returning awaitable against a deadline. 24   /** Race an io_result-returning awaitable against a deadline.
25   25  
26   Starts the awaitable with an interposed stop token and arms a 26   Starts the awaitable with an interposed stop token and arms a
27   timer. If the awaitable finishes first, its result is returned 27   timer. If the awaitable finishes first, its result is returned
28   as-is (success, error, or exception). If the deadline passes 28   as-is (success, error, or exception). If the deadline passes
29   first, the awaitable is cancelled and an `io_result` whose 29   first, the awaitable is cancelled and an `io_result` whose
30   `ec` compares equal to `capy::cond::timeout` (with a 30   `ec` compares equal to `capy::cond::timeout` (with a
31   default-initialized payload) is produced. 31   default-initialized payload) is produced.
32   32  
33 - Exceptions from the inner awaitable always propagate to the caller. 33 + Exceptions from the inner awaitable always propagate; they are
  34 + never swallowed by the timer.
34   35  
35 - @pre The awaiting coroutine's executor must belong to an 36 + @par Preconditions
36 - `io_context`. Any other execution context terminates with a 37 + The awaiting coroutine's executor must belong to an
37 - diagnostic, because silently running without a timer would 38 + `io_context`; any other execution context terminates with a
38 - drop the requested timeout. 39 + diagnostic.
39   40  
40   @par Cancellation 41   @par Cancellation
41   If the parent's stop token is activated, the inner awaitable 42   If the parent's stop token is activated, the inner awaitable
42   is cancelled and its cancellation result is returned. Requesting 43   is cancelled and its cancellation result is returned. Requesting
43   stop from another thread requires a multi-threaded-capable 44   stop from another thread requires a multi-threaded-capable
44 - `io_context`. A context running in `single_threaded` mode 45 + io_context; a context running in single_threaded mode
45 - (auto-enabled at `concurrency_hint` == 1) does not permit 46 + (auto-enabled at concurrency_hint == 1) does not permit
46   cross-thread cancellation. 47   cross-thread cancellation.
47   48  
48   @par Example 49   @par Example
49   @par !example timeout 50   @par !example timeout
50   51  
51   @param a The awaitable to race against the deadline. 52   @param a The awaitable to race against the deadline.
52   @param dur The maximum duration to wait, measured from 53   @param dur The maximum duration to wait, measured from
53   suspension. 54   suspension.
54   55  
55   @return An awaitable yielding `io_result` matching the inner 56   @return An awaitable yielding `io_result` matching the inner
56   awaitable's result type. 57   awaitable's result type.
57   58  
58   @see delay 59   @see delay
59   */ 60   */
60   template<capy::IoAwaitable A, typename Rep, typename Period> 61   template<capy::IoAwaitable A, typename Rep, typename Period>
61   requires detail::is_io_result_v< 62   requires detail::is_io_result_v<
62   std::remove_cvref_t<capy::awaitable_result_t<A>>> && 63   std::remove_cvref_t<capy::awaitable_result_t<A>>> &&
63   std::is_default_constructible_v< 64   std::is_default_constructible_v<
64   std::remove_cvref_t<capy::awaitable_result_t<A>>> 65   std::remove_cvref_t<capy::awaitable_result_t<A>>>
65   [[nodiscard]] auto 66   [[nodiscard]] auto
HITCBC 66   2055 timeout(A a, std::chrono::duration<Rep, Period> dur) 67   2055 timeout(A a, std::chrono::duration<Rep, Period> dur)
67   { 68   {
68   using namespace std::chrono; 69   using namespace std::chrono;
69   // Narrow reps wrap if nanoseconds::max() is converted into them; 70   // Narrow reps wrap if nanoseconds::max() is converted into them;
70   // a double comparison clamps safely in both directions. 71   // a double comparison clamps safely in both directions.
71   using dsec = duration<double>; 72   using dsec = duration<double>;
HITCBC 72   2055 auto ns = dsec(dur) >= dsec((nanoseconds::max)()) ? (nanoseconds::max)() 73   2055 auto ns = dsec(dur) >= dsec((nanoseconds::max)()) ? (nanoseconds::max)()
HITCBC 73   2053 : dsec(dur) <= dsec((nanoseconds::min)()) 74   2053 : dsec(dur) <= dsec((nanoseconds::min)())
HITCBC 74   2053 ? (nanoseconds::min)() 75   2053 ? (nanoseconds::min)()
HITCBC 75   2051 : duration_cast<nanoseconds>(dur); 76   2051 : duration_cast<nanoseconds>(dur);
HITCBC 76   4110 return detail::timeout_awaitable<A>(std::move(a), ns); 77   4110 return detail::timeout_awaitable<A>(std::move(a), ns);
77   } 78   }
78   79  
79   /** Race an io_result-returning awaitable against an absolute deadline. 80   /** Race an io_result-returning awaitable against an absolute deadline.
80   81  
81   Behaves as the duration overload with the deadline fixed at 82   Behaves as the duration overload with the deadline fixed at
82   `tp` instead of measured from suspension. 83   `tp` instead of measured from suspension.
83   84  
84   @param a The awaitable to race against the deadline. 85   @param a The awaitable to race against the deadline.
85   @param tp The steady-clock time point at which the awaitable 86   @param tp The steady-clock time point at which the awaitable
86   is cancelled. 87   is cancelled.
87   88  
88   @return An awaitable yielding `io_result` matching the inner 89   @return An awaitable yielding `io_result` matching the inner
89   awaitable's result type. 90   awaitable's result type.
90   91  
91   @see delay 92   @see delay
92   */ 93   */
93   template<capy::IoAwaitable A> 94   template<capy::IoAwaitable A>
94   requires detail::is_io_result_v< 95   requires detail::is_io_result_v<
95   std::remove_cvref_t<capy::awaitable_result_t<A>>> && 96   std::remove_cvref_t<capy::awaitable_result_t<A>>> &&
96   std::is_default_constructible_v< 97   std::is_default_constructible_v<
97   std::remove_cvref_t<capy::awaitable_result_t<A>>> 98   std::remove_cvref_t<capy::awaitable_result_t<A>>>
98   [[nodiscard]] auto 99   [[nodiscard]] auto
HITCBC 99   4 timeout(A a, std::chrono::steady_clock::time_point tp) 100   4 timeout(A a, std::chrono::steady_clock::time_point tp)
100   { 101   {
HITCBC 101   4 return detail::timeout_awaitable<A>(std::move(a), tp); 102   4 return detail::timeout_awaitable<A>(std::move(a), tp);
102   } 103   }
103   104  
104   } // namespace boost::corosio 105   } // namespace boost::corosio
105   106  
106   #endif 107   #endif