C++ 微秒级统计程序运行时间

 class timer
 {
 public:
     timer();
     ~timer();

     void start(void);

     void end(void);

     DWORD getTime(void) const;

 private:
     LARGE_INTEGER m_i64CPUFreq;
     LARGE_INTEGER m_i64Begin;
     LARGE_INTEGER m_i64End;
     void reset(void);
 };

 //测试例子
 void CTest1Dlg::OnOK()
 {
     timer t;
     t.start();
     {
         for(int i = 0; i < 1000000; i++)
         {
             int n = i;
         }
     }
     t.end();

     CString s;
     s.Format("%u", t.getTime());
     AfxMessageBox(s);
 }


 timer::timer()
 {
     QueryPerformanceFrequency(&m_i64CPUFreq);
 }

 timer::~timer()
 {

 }

 void timer::start(void)
 {
     reset();
     QueryPerformanceCounter(&m_i64Begin);
 }

 void timer::end(void)
 {
     QueryPerformanceCounter(&m_i64End);
 }

 DWORD timer::getTime(void) const
 {
     DWORD dwTotalMicrosecond = 0;
     LARGE_INTEGER i64TickCount;
     i64TickCount.QuadPart = m_i64End.QuadPart - m_i64Begin.QuadPart;
     dwTotalMicrosecond = (DWORD) (i64TickCount.QuadPart * 1000000 / m_i64CPUFreq.QuadPart);

     return dwTotalMicrosecond;
 }

 void timer::reset(void)
 {
     m_i64Begin = m_i64End;
 }