1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CHROME_COMMON_WORKER_THREAD_TICKER_H_ 6 #define CHROME_COMMON_WORKER_THREAD_TICKER_H_ 7 8 #include <vector> 9 10 #include "base/synchronization/lock.h" 11 #include "base/threading/thread.h" 12 13 // This class provides the following functionality: 14 // It invokes a set of registered handlers at periodic intervals in 15 // the context of an arbitrary worker thread. 16 // The timer runs on a separate thread, so it will run even if the current 17 // thread is hung. Similarly, the callbacks will be called on a separate 18 // thread so they won't block the main thread. 19 class WorkerThreadTicker { 20 public: 21 // This callback interface to be implemented by clients of this 22 // class 23 class Callback { 24 public: 25 // Gets invoked when the timer period is up 26 virtual void OnTick() = 0; 27 28 protected: ~Callback()29 virtual ~Callback() {} 30 }; 31 32 // tick_interval is the periodic interval in which to invoke the 33 // registered handlers (in milliseconds) 34 explicit WorkerThreadTicker(int tick_interval); 35 36 ~WorkerThreadTicker(); 37 38 // Registers a callback handler interface 39 // tick_handler is the handler interface to register. The ownership of this 40 // object is not transferred to this class. 41 bool RegisterTickHandler(Callback *tick_handler); 42 43 // Unregisters a callback handler interface 44 // tick_handler is the handler interface to unregister 45 bool UnregisterTickHandler(Callback *tick_handler); 46 47 // Starts the ticker. Returns false if the ticker is already running 48 // or if the Start fails. 49 bool Start(); 50 // Stops the ticker and waits for all callbacks. to be done. This method 51 // does not provide a way to stop without waiting for the callbacks to be 52 // done because this is inherently risky. 53 // Returns false is the ticker is not running 54 bool Stop(); IsRunning()55 bool IsRunning() const { 56 return is_running_; 57 } 58 set_tick_interval(int tick_interval)59 void set_tick_interval(int tick_interval) { 60 tick_interval_ = base::TimeDelta::FromMilliseconds(tick_interval); 61 } 62 tick_interval()63 int tick_interval() const { 64 return tick_interval_.InMilliseconds(); 65 } 66 67 private: 68 void ScheduleTimerTask(); 69 70 void TimerTask(); 71 72 // A list type that holds all registered callback interfaces 73 typedef std::vector<Callback*> TickHandlerListType; 74 75 // Lock to protect is_running_ and tick_handler_list_ 76 base::Lock lock_; 77 78 base::Thread timer_thread_; 79 bool is_running_; 80 81 // The interval at which the callbacks are to be invoked 82 base::TimeDelta tick_interval_; 83 84 // A list that holds all registered callback interfaces 85 TickHandlerListType tick_handler_list_; 86 87 DISALLOW_COPY_AND_ASSIGN(WorkerThreadTicker); 88 }; 89 90 #endif // CHROME_COMMON_WORKER_THREAD_TICKER_H_ 91