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// Copyright (c) 2006-2008 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.
#ifndef CHROME_COMMON_WORKER_THREAD_TICKER_H__
#define CHROME_COMMON_WORKER_THREAD_TICKER_H__
#include <windows.h>
#include <atlbase.h>
#include <vector>
#include "base/lock.h"
// This class provides the follwoing functionality:
// It invokes a set of registered handlers at periodic intervals in
// the context of an arbitrary worker thread.
// This functionality is similar to a waitable timer except that the
// timer in this case is a low-resolution timer (millisecond granularity)
// and it does not require the caller to be in an alertable wait state.
// The callbacks are invoked in the context of an arbitrary worker thread
// from the system thread pool
class WorkerThreadTicker {
public:
// This callback interface to be implemented by clients of this
// class
class Callback {
public:
// Gets invoked when the timer period is up
virtual void OnTick() = 0;
};
// tick_interval is the periodic interval in which to invoke the
// registered handlers
explicit WorkerThreadTicker(int tick_interval);
~WorkerThreadTicker();
// 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;
void set_tick_interval(int tick_interval) {
tick_interval_ = tick_interval;
}
int tick_interval() const {
return tick_interval_;
}
private:
// A list type that holds all registered callback interfaces
typedef std::vector<Callback*> TickHandlerListType;
// This is the callback function registered with the
// RegisterWaitForSingleObject API. It gets invoked in a system worker thread
// periodically at intervals of tick_interval_ miliiseconds
static void CALLBACK TickCallback(WorkerThreadTicker* this_ticker,
BOOLEAN timer_or_wait_fired);
// Helper that invokes all registered handlers
void InvokeHandlers();
// A dummy event to be used by the RegisterWaitForSingleObject API
CHandle dummy_event_;
// The wait handle returned by the RegisterWaitForSingleObject API
HANDLE wait_handle_;
// The interval at which the callbacks are to be invoked
int tick_interval_;
// Lock for the tick_handler_list_ list
Lock tick_handler_list_lock_;
// A list that holds all registered callback interfaces
TickHandlerListType tick_handler_list_;
DISALLOW_EVIL_CONSTRUCTORS(WorkerThreadTicker);
};
#endif // CHROME_COMMON_WORKER_THREAD_TICKER_H__
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