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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <vector>
#include "base/synchronization/lock.h"
#include "base/threading/thread.h"
// This class provides the following functionality:
// It invokes a set of registered handlers at periodic intervals in
// the context of an arbitrary worker thread.
// The timer runs on a separate thread, so it will run even if the current
// thread is hung. Similarly, the callbacks will be called on a separate
// thread so they won't block the main thread.
class WorkerThreadTicker {
// This callback interface to be implemented by clients of this
// class
class Callback {
// Gets invoked when the timer period is up
virtual void OnTick() = 0;
virtual ~Callback() {}
// tick_interval is the periodic interval in which to invoke the
// registered handlers (in milliseconds)
explicit WorkerThreadTicker(int tick_interval);
// Registers a callback handler interface
// tick_handler is the handler interface to register. The ownership of this
// object is not transferred to this class.
bool RegisterTickHandler(Callback *tick_handler);
// Unregisters a callback handler interface
// tick_handler is the handler interface to unregister
bool UnregisterTickHandler(Callback *tick_handler);
// Starts the ticker. Returns false if the ticker is already running
// or if the Start fails.
bool Start();
// Stops the ticker and waits for all callbacks. to be done. This method
// does not provide a way to stop without waiting for the callbacks to be
// done because this is inherently risky.
// Returns false is the ticker is not running
bool Stop();
bool IsRunning() const {
return is_running_;
void set_tick_interval(int tick_interval) {
tick_interval_ = base::TimeDelta::FromMilliseconds(tick_interval);
int tick_interval() const {
return tick_interval_.InMilliseconds();
void ScheduleTimerTask();
void TimerTask();
// A list type that holds all registered callback interfaces
typedef std::vector<Callback*> TickHandlerListType;
// Lock to protect is_running_ and tick_handler_list_
base::Lock lock_;
base::Thread timer_thread_;
bool is_running_;
// The interval at which the callbacks are to be invoked
base::TimeDelta tick_interval_;
// A list that holds all registered callback interfaces
TickHandlerListType tick_handler_list_;