A Class To Encapsulate MultiMedia Timers

This simple class encapsulates the multimedia timers. To use the class include mmTimers.cpp and mmTimers.h in your project. Link with winmm.lib. To use a timer derive a class from CMMTimers and override member timerProc. timerProc will be called when the timer goes off. Instantiate a variable of the new class. The parameter to the constructor is the timer resolution in ms. To start a timer call startTimer. The first parameter specifies the period of the timer in ms. The second parameter specifies whether the timer is a one shot or periodic timer. To stop a periodic timer call stopTimer.

This code was developed with Visual C++ 5.0 and has been tested on NT 4.0.

The source follows:

The header file, mmTimers.h

#ifndef ___multimedia_timers___
#define ___multimedia_timers___

#include 

 

class CMMTimers
{
public:
 CMMTimers(UINT resolution);
 virtual ~CMMTimers();

 UINT getTimerRes() { return timerRes; };

 bool startTimer(UINT period,bool oneShot);
 bool stopTimer();

 virtual void timerProc() {};

protected:
 UINT timerRes;
 UINT timerId;
};

#endif 

The source file, mmTimers.cpp

#include "StdAfx.h"
#include "mmTimers.h"

CMMTimers::CMMTimers(UINT resolution) : timerRes(0), timerId(0)
{
 TIMECAPS tc;

 if (TIMERR_NOERROR == timeGetDevCaps(&tc,sizeof(TIMECAPS)))
 {
  timerRes = min(max(tc.wPeriodMin,resolution),tc.wPeriodMax);
  timeBeginPeriod(timerRes);
 }
}

CMMTimers::~CMMTimers()
{
 stopTimer();
 if (0 != timerRes)
 {
  timeEndPeriod(timerRes);
  timerRes = 0;
 }
}

extern "C"
void CALLBACK internalTimerProc(UINT id, UINT msg,
DWORD dwUser, DWORD dw1, DWORD dw2)
{
 CMMTimers * timer = (CMMTimers *)dwUser;

 timer->timerProc();
}

bool CMMTimers::startTimer(UINT period,bool oneShot)
{
 bool  res = false;
 MMRESULT result;

 result = timeSetEvent(period, timerRes, internalTimerProc,
 (DWORD)this,oneShot ? TIME_ONESHOT : TIME_PERIODIC);
 if (NULL != result)
 {
  timerId = (UINT)result;
  res = true;
 }

 return res;
}

bool CMMTimers::stopTimer()
{
 MMRESULT result;

 result = timeKillEvent(timerId);
 if (TIMERR_NOERROR == result)
  timerId = 0;

 return TIMERR_NOERROR == result;
} 

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