windows下C++高精度计时

class CTimeCost
    {
    public:
        CTimeCost(const string &str)
            : m_str(str)
        {
            QueryPerformanceFrequency(&m_freg);
            QueryPerformanceCounter(&m_begin);
        }

        ~CTimeCost()
        {
            LARGE_INTEGER end;
            QueryPerformanceCounter(&end);
            __int64 nTick = (end.QuadPart - m_begin.QuadPart) * 1000 * 1000 / m_freg.QuadPart;

            int len = 2048;
            char *buf = new char[len + 1];
            memset(buf, 0, len + 1);
            sprintf_s(buf, len, "\n%s cost %ld微秒\n", m_str.c_str(), nTick);

            OutputDebugStringA(buf);
            cout << buf << endl;

            delete[]buf;
            buf = NULL;
        }

    private:
        string m_str;
        LARGE_INTEGER m_begin;
        LARGE_INTEGER m_freg;
    };

　　//使用方法
    void TestTimeCost()
    {
        {
            CTimeCost once("this block cost");
            Sleep(1);
        }

        cout << "other code run" << endl;
    }