. /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   // 4   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 5   // 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   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 7   //
7   // Official repository: https://github.com/cppalliance/corosio 8   // Official repository: https://github.com/cppalliance/corosio
8   // 9   //
9   10  
10   #ifndef BOOST_COROSIO_TIMEOUT_HPP 11   #ifndef BOOST_COROSIO_TIMEOUT_HPP
11   #define BOOST_COROSIO_TIMEOUT_HPP 12   #define BOOST_COROSIO_TIMEOUT_HPP
12   13  
13   #include <boost/corosio/detail/config.hpp> 14   #include <boost/corosio/detail/config.hpp>
14   #include <boost/corosio/detail/timeout_awaitable.hpp> 15   #include <boost/corosio/detail/timeout_awaitable.hpp>
15   #include <boost/capy/concept/io_awaitable.hpp> 16   #include <boost/capy/concept/io_awaitable.hpp>
16   17  
17   #include <chrono> 18   #include <chrono>
18   #include <type_traits> 19   #include <type_traits>
19   #include <utility> 20   #include <utility>
20   21  
21   namespace boost::corosio { 22   namespace boost::corosio {
22   23  
23   /** Race an io_result-returning awaitable against a deadline. 24   /** Race an io_result-returning awaitable against a deadline.
24   25  
25   Starts the awaitable with an interposed stop token and arms a 26   Starts the awaitable with an interposed stop token and arms a
26   timer. If the awaitable finishes first, its result is returned 27   timer. If the awaitable finishes first, its result is returned
27   as-is (success, error, or exception). If the deadline passes 28   as-is (success, error, or exception). If the deadline passes
28   first, the awaitable is cancelled and an `io_result` whose 29   first, the awaitable is cancelled and an `io_result` whose
29   `ec` compares equal to `capy::cond::timeout` (with a 30   `ec` compares equal to `capy::cond::timeout` (with a
30   default-initialized payload) is produced. 31   default-initialized payload) is produced.
31   32  
32   Exceptions from the inner awaitable always propagate; they are 33   Exceptions from the inner awaitable always propagate; they are
33   never swallowed by the timer. 34   never swallowed by the timer.
34   35  
35   @par Preconditions 36   @par Preconditions
36   The awaiting coroutine's executor must belong to an 37   The awaiting coroutine's executor must belong to an
37   `io_context`; any other execution context terminates with a 38   `io_context`; any other execution context terminates with a
38   diagnostic. 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 - @code 50 + @par !example timeout
50 - auto [ec, n] = co_await timeout(sock.read_some(buf), 50ms);  
51 - if (ec == capy::cond::timeout)  
52 - co_return;  
53 - @endcode  
54   51  
55   @param a The awaitable to race against the deadline. 52   @param a The awaitable to race against the deadline.
56   @param dur The maximum duration to wait, measured from 53   @param dur The maximum duration to wait, measured from
57   suspension. 54   suspension.
58   55  
59   @return An awaitable yielding `io_result` matching the inner 56   @return An awaitable yielding `io_result` matching the inner
60   awaitable's result type. 57   awaitable's result type.
61   58  
62   @see delay 59   @see delay
63   */ 60   */
64   template<capy::IoAwaitable A, typename Rep, typename Period> 61   template<capy::IoAwaitable A, typename Rep, typename Period>
65   requires detail::is_io_result_v< 62   requires detail::is_io_result_v<
66   std::remove_cvref_t<capy::awaitable_result_t<A>>> && 63   std::remove_cvref_t<capy::awaitable_result_t<A>>> &&
67   std::is_default_constructible_v< 64   std::is_default_constructible_v<
68   std::remove_cvref_t<capy::awaitable_result_t<A>>> 65   std::remove_cvref_t<capy::awaitable_result_t<A>>>
HITCBC 69   2055 [[nodiscard]] auto timeout(A a, std::chrono::duration<Rep, Period> dur) 66   2055 [[nodiscard]] auto timeout(A a, std::chrono::duration<Rep, Period> dur)
70   { 67   {
71   using namespace std::chrono; 68   using namespace std::chrono;
72   // Narrow reps wrap if nanoseconds::max() is converted into them; 69   // Narrow reps wrap if nanoseconds::max() is converted into them;
73   // a double comparison clamps safely in both directions. 70   // a double comparison clamps safely in both directions.
74   using dsec = duration<double>; 71   using dsec = duration<double>;
HITCBC 75   4082 auto ns = dsec(dur) >= dsec((nanoseconds::max)()) 72   4082 auto ns = dsec(dur) >= dsec((nanoseconds::max)())
HITCBC 76   4082 ? (nanoseconds::max)() 73   4082 ? (nanoseconds::max)()
HITCBC 77   2053 : dsec(dur) <= dsec((nanoseconds::min)()) 74   2053 : dsec(dur) <= dsec((nanoseconds::min)())
HITCBC 78   2053 ? (nanoseconds::min)() 75   2053 ? (nanoseconds::min)()
HITCBC 79   2051 : duration_cast<nanoseconds>(dur); 76   2051 : duration_cast<nanoseconds>(dur);
HITCBC 80   4110 return detail::timeout_awaitable<A>(std::move(a), ns); 77   4110 return detail::timeout_awaitable<A>(std::move(a), ns);
81   } 78   }
82   79  
83   /** Race an io_result-returning awaitable against an absolute deadline. 80   /** Race an io_result-returning awaitable against an absolute deadline.
84   81  
85   Behaves as the duration overload with the deadline fixed at 82   Behaves as the duration overload with the deadline fixed at
86   `tp` instead of measured from suspension. 83   `tp` instead of measured from suspension.
87   84  
88   @param a The awaitable to race against the deadline. 85   @param a The awaitable to race against the deadline.
89   @param tp The steady-clock time point at which the awaitable 86   @param tp The steady-clock time point at which the awaitable
90   is cancelled. 87   is cancelled.
91   88  
92   @return An awaitable yielding `io_result` matching the inner 89   @return An awaitable yielding `io_result` matching the inner
93   awaitable's result type. 90   awaitable's result type.
94   91  
95   @see delay 92   @see delay
96   */ 93   */
97   template<capy::IoAwaitable A> 94   template<capy::IoAwaitable A>
98   requires detail::is_io_result_v< 95   requires detail::is_io_result_v<
99   std::remove_cvref_t<capy::awaitable_result_t<A>>> && 96   std::remove_cvref_t<capy::awaitable_result_t<A>>> &&
100   std::is_default_constructible_v< 97   std::is_default_constructible_v<
101   std::remove_cvref_t<capy::awaitable_result_t<A>>> 98   std::remove_cvref_t<capy::awaitable_result_t<A>>>
HITCBC 102   4 [[nodiscard]] auto timeout(A a, std::chrono::steady_clock::time_point tp) 99   4 [[nodiscard]] auto timeout(A a, std::chrono::steady_clock::time_point tp)
103   { 100   {
HITCBC 104   4 return detail::timeout_awaitable<A>(std::move(a), tp); 101   4 return detail::timeout_awaitable<A>(std::move(a), tp);
105   } 102   }
106   103  
107   } // namespace boost::corosio 104   } // namespace boost::corosio
108   105  
109   #endif 106   #endif