timer.h

Go to the documentation of this file.

/******************************************************************************
 *   Copyright (C) 2013-2014 by Alexander Rykovanov                        *
 *   rykovanov.as@gmail.com                                                   *
 *                                                                            *
 *   This library is free software; you can redistribute it and/or modify     *
 *   it under the terms of the GNU Lesser General Public License as           *
 *   published by the Free Software Foundation; version 3 of the License.     *
 *                                                                            *
 *   This library is distributed in the hope that it will be useful,          *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of           *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            *
 *   GNU Lesser General Public License for more details.                      *
 *                                                                            *
 *   You should have received a copy of the GNU Lesser General Public License *
 *   along with this library; if not, write to the                            *
 *   Free Software Foundation, Inc.,                                          *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.                *
 ******************************************************************************/

#pragma once

#include <atomic>
#include <boost/asio/deadline_timer.hpp>
#include <boost/chrono.hpp>
#include <mutex>
#include <condition_variable>

namespace OpcUa
{
  class PeriodicTimer
  {
  public:
    PeriodicTimer(boost::asio::io_service& io)
      : Timer(io)
      , IsCanceled(true)
      , Stopped(true)
    {
    }

    ~PeriodicTimer()
    {
      Cancel();
    }

    void Start(const boost::asio::deadline_timer::duration_type& t, std::function<void()> handler)
    {
      std::unique_lock<std::mutex> lock(Mutex);
      if (!Stopped)
        return;

      Stopped = false;
      IsCanceled = false;
      Timer.expires_from_now(t);
      Timer.async_wait([this, handler, t](const boost::system::error_code& error){
        OnTimer(error, handler, t);
      });
    }

    void Cancel()
    {
      std::unique_lock<std::mutex> lock(Mutex);
      if (Stopped)
        return;

      IsCanceled = true;
      Timer.cancel();
      StopEvent.wait(lock, [this](){
        return static_cast<bool>(Stopped);
      });
    }

  private:
    void OnTimer(const boost::system::error_code& error, std::function<void()> handler, boost::asio::deadline_timer::duration_type t)
    {
      std::unique_lock<std::mutex> lock(Mutex);
      if (IsCanceled || error)
      {
        Stopped = true;
        IsCanceled = true;
        StopEvent.notify_all();
        return;
      }

      handler();

      Timer.expires_from_now(t);
      Timer.async_wait([this, handler, t](const boost::system::error_code& error){
        OnTimer(error, handler, t);
      });
    }

  private:
    std::mutex Mutex;
    std::condition_variable StopEvent;
    boost::asio::deadline_timer Timer;
    std::atomic<bool> IsCanceled;
    std::atomic<bool> Stopped;
  };
}