1 // Copyright (c) 2009 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 #pragma once 8 9 #include <vector> 10 11 #include "base/synchronization/lock.h" 12 #include "base/threading/thread.h" 13 14 // This class provides the following functionality: 15 // It invokes a set of registered handlers at periodic intervals in 16 // the context of an arbitrary worker thread. 17 // The timer runs on a separate thread, so it will run even if the current 18 // thread is hung. Similarly, the callbacks will be called on a separate 19 // thread so they won't block the main thread. 20 class WorkerThreadTicker { 21 public: 22 // This callback interface to be implemented by clients of this 23 // class 24 class Callback { 25 public: 26 // Gets invoked when the timer period is up 27 virtual void OnTick() = 0; 28 29 protected: ~Callback()30 virtual ~Callback() {} 31 }; 32 33 // tick_interval is the periodic interval in which to invoke the 34 // registered handlers (in milliseconds) 35 explicit WorkerThreadTicker(int tick_interval); 36 37 ~WorkerThreadTicker(); 38 39 // Registers a callback handler interface 40 // tick_handler is the handler interface to register. The ownership of this 41 // object is not transferred to this class. 42 bool RegisterTickHandler(Callback *tick_handler); 43 44 // Unregisters a callback handler interface 45 // tick_handler is the handler interface to unregister 46 bool UnregisterTickHandler(Callback *tick_handler); 47 48 // Starts the ticker. Returns false if the ticker is already running 49 // or if the Start fails. 50 bool Start(); 51 // Stops the ticker and waits for all callbacks. to be done. This method 52 // does not provide a way to stop without waiting for the callbacks to be 53 // done because this is inherently risky. 54 // Returns false is the ticker is not running 55 bool Stop(); IsRunning()56 bool IsRunning() const { 57 return is_running_; 58 } 59 set_tick_interval(int tick_interval)60 void set_tick_interval(int tick_interval) { 61 tick_interval_ = tick_interval; 62 } 63 tick_interval()64 int tick_interval() const { 65 return tick_interval_; 66 } 67 68 private: 69 class TimerTask; 70 71 void ScheduleTimerTask(); 72 73 // A list type that holds all registered callback interfaces 74 typedef std::vector<Callback*> TickHandlerListType; 75 76 // Lock to protect is_running_ and tick_handler_list_ 77 base::Lock lock_; 78 79 base::Thread timer_thread_; 80 bool is_running_; 81 82 // The interval at which the callbacks are to be invoked 83 int tick_interval_; 84 85 // A list that holds all registered callback interfaces 86 TickHandlerListType tick_handler_list_; 87 88 DISALLOW_COPY_AND_ASSIGN(WorkerThreadTicker); 89 }; 90 91 #endif // CHROME_COMMON_WORKER_THREAD_TICKER_H_ 92