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

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


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

CStopwatch::CStopwatch()
{

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

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

}

CStopwatch::~CStopwatch()
{

}

/////////////////////////////////////////////////////////////////////
// IUnknown Functions
/////////////////////////////////////////////////////////////////////

HRESULT __stdcall CStopwatch::QueryInterface(
  REFIID riid,
  void **ppvObject)
{
  HRESULT hr = S_OK;

  if (riid == IID_IUnknown) 
    *ppvObject = static_cast<IUnknown*>(
      static_cast<IStopwatch*>(this));
  else if (riid == IID_IStopwatch) 
    *ppvObject = static_cast<IStopwatch*>(this);
  else 
  {
    ppvObject = NULL;
    hr = E_NOINTERFACE;
  }

  
  if (SUCCEEDED(hr))
    (static_cast<IUnknown*>(*ppvObject))->AddRef();

  return hr;

}

unsigned long __stdcall CStopwatch::AddRef()
{
  return InterlockedIncrement( &m_nReferenceCount );
}

unsigned long __stdcall CStopwatch::Release()
{
  if (InterlockedDecrement( &m_nReferenceCount ) == 0)
  {
    delete this;
    return 0;
  }
  return m_nReferenceCount;
}


/////////////////////////////////////////////////////////////////////
// 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;
}