// Stopwatch.cpp: implementation of the CStopwatch class.
//
/////////////////////////////////////////////////////////////////////

#include "Stopwatch.h"
#include <mmsystem.h> // Multimedia timers

/////////////////////////////////////////////////////////////////////
// Construction/Destruction
/////////////////////////////////////////////////////////////////////

CStopwatch::CStopwatch()
{

  // Initialize the remaining member variables
  m_nStartTime.QuadPart = 0;

  // Save the frequency of the performance counters
  QueryPerformanceFrequency ((LARGE_INTEGER*) &m_nFrequency);

}

CStopwatch::~CStopwatch()
{

}

/////////////////////////////////////////////////////////////////////
// Utility Functions
/////////////////////////////////////////////////////////////////////

unsigned long __stdcall CStopwatch::Release()
{
  delete this;
  return 0;
}

/////////////////////////////////////////////////////////////////////
// Stopwatch Function Implementation
/////////////////////////////////////////////////////////////////////

HRESULT __stdcall CStopwatch::Start()
{
  if ( QueryPerformanceCounter( (LARGE_INTEGER*) &m_nStartTime) )
    return S_OK;
  else 
    return E_FAIL;
}

HRESULT __stdcall CStopwatch::ElapsedTime(float *Time)
{
  HRESULT hr;
  LARGE_INTEGER nStopTime;

  // Set the stop time immediately so that a minimum
  // amount of timer code is executed between the start
  // and stop times
  if ( !QueryPerformanceCounter( (LARGE_INTEGER*) &nStopTime )
      || (m_nStartTime.QuadPart == 0) 
     )
  {
    // Either QPC failed or
    // start was not called before stop
    hr = E_FAIL;
  }
  else
  {
    *Time = (float) (nStopTime.QuadPart - m_nStartTime.QuadPart);
    *Time = (*Time / m_nFrequency.QuadPart);
    hr = S_OK;
  }

  return hr;
}