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File indexing completed on 2025-01-18 09:54:51
0001 /////////////////////////////////////////////////////////////////////////////// 0002 // Copyright (c) Lewis Baker 0003 // Licenced under MIT license. See LICENSE.txt for details. 0004 /////////////////////////////////////////////////////////////////////////////// 0005 #ifndef CPPCORO_ASYNC_MANUAL_RESET_EVENT_HPP_INCLUDED 0006 #define CPPCORO_ASYNC_MANUAL_RESET_EVENT_HPP_INCLUDED 0007 0008 #include <cppcoro/coroutine.hpp> 0009 #include <atomic> 0010 #include <cstdint> 0011 0012 namespace cppcoro 0013 { 0014 class async_manual_reset_event_operation; 0015 0016 /// An async manual-reset event is a coroutine synchronisation abstraction 0017 /// that allows one or more coroutines to wait until some thread calls 0018 /// set() on the event. 0019 /// 0020 /// When a coroutine awaits a 'set' event the coroutine continues without 0021 /// suspending. Otherwise, if it awaits a 'not set' event the coroutine is 0022 /// suspended and is later resumed inside the call to 'set()'. 0023 /// 0024 /// \seealso async_auto_reset_event 0025 class async_manual_reset_event 0026 { 0027 public: 0028 0029 /// Initialise the event to either 'set' or 'not set' state. 0030 /// 0031 /// \param initiallySet 0032 /// If 'true' then initialises the event to the 'set' state, otherwise 0033 /// initialises the event to the 'not set' state. 0034 async_manual_reset_event(bool initiallySet = false) noexcept; 0035 0036 ~async_manual_reset_event(); 0037 0038 /// Wait for the event to enter the 'set' state. 0039 /// 0040 /// If the event is already 'set' then the coroutine continues without 0041 /// suspending. 0042 /// 0043 /// Otherwise, the coroutine is suspended and later resumed when some 0044 /// thread calls 'set()'. The coroutine will be resumed inside the next 0045 /// call to 'set()'. 0046 async_manual_reset_event_operation operator co_await() const noexcept; 0047 0048 /// Query if the event is currently in the 'set' state. 0049 bool is_set() const noexcept; 0050 0051 /// Set the state of the event to 'set'. 0052 /// 0053 /// If there are pending coroutines awaiting the event then all 0054 /// pending coroutines are resumed within this call. 0055 /// Any coroutines that subsequently await the event will continue 0056 /// without suspending. 0057 /// 0058 /// This operation is a no-op if the event was already 'set'. 0059 void set() noexcept; 0060 0061 /// Set the state of the event to 'not-set'. 0062 /// 0063 /// Any coroutines that subsequently await the event will suspend 0064 /// until some thread calls 'set()'. 0065 /// 0066 /// This is a no-op if the state was already 'not set'. 0067 void reset() noexcept; 0068 0069 private: 0070 0071 friend class async_manual_reset_event_operation; 0072 0073 // This variable has 3 states: 0074 // - this - The state is 'set'. 0075 // - nullptr - The state is 'not set' with no waiters. 0076 // - other - The state is 'not set'. 0077 // Points to an 'async_manual_reset_event_operation' that is 0078 // the head of a linked-list of waiters. 0079 mutable std::atomic<void*> m_state; 0080 0081 }; 0082 0083 class async_manual_reset_event_operation 0084 { 0085 public: 0086 0087 explicit async_manual_reset_event_operation(const async_manual_reset_event& event) noexcept; 0088 0089 bool await_ready() const noexcept; 0090 bool await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept; 0091 void await_resume() const noexcept {} 0092 0093 private: 0094 0095 friend class async_manual_reset_event; 0096 0097 const async_manual_reset_event& m_event; 0098 async_manual_reset_event_operation* m_next; 0099 cppcoro::coroutine_handle<> m_awaiter; 0100 0101 }; 0102 } 0103 0104 #endif
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