两个SYSTEMTIME变量之间的差异

Question

我想区分两个SYSTEMTIME变量.我之前看到有人问过这个问题,但他被告知要将两个SYSTEMTIME结构转换为FILETIME ..还有另一种方法可以解决这个问题吗？

SYSTEMTIME st;
GetSystemTime(&st);

---这里的一些代码---

  SYSTEMTIME st2;
  GetSystemTime(&st2);

ST-ST2？

Answer 1

SYSTEMTIME operator-(const SYSTEMTIME& pSr,const SYSTEMTIME& pSl)
{
    SYSTEMTIME t_res;
    FILETIME v_ftime;
    ULARGE_INTEGER v_ui;
    __int64 v_right,v_left,v_res;
    SystemTimeToFileTime(&pSr,&v_ftime);
    v_ui.LowPart=v_ftime.dwLowDateTime;
    v_ui.HighPart=v_ftime.dwHighDateTime;
    v_right=v_ui.QuadPart;

    SystemTimeToFileTime(&pSl,&v_ftime);
    v_ui.LowPart=v_ftime.dwLowDateTime;
    v_ui.HighPart=v_ftime.dwHighDateTime;
    v_left=v_ui.QuadPart;

    v_res=v_right-v_left;

    v_ui.QuadPart=v_res;
    v_ftime.dwLowDateTime=v_ui.LowPart;
    v_ftime.dwHighDateTime=v_ui.HighPart;
    FileTimeToSystemTime(&v_ftime,&t_res);
    return t_res;
}

Answer 2

它在MSDN文档中非常清楚地说:

建议您不要在SYSTEMTIME结构中添加和减去值以获取相对时间.相反,你应该

• 将SYSTEMTIME结构转换为FILETIME结构.
• 将生成的FILETIME结构复制到ULARGE_INTEGER结构.
• 对ULARGE_INTEGER值使用普通的64位算术运算.

为什么不这样做呢？

Answer 3

ft1和ft2是文件时间结构

ULARGE_INTEGER ul1;
    ul1.LowPart = ft1.dwLowDateTime;
    ul1.HighPart = ft1.dwHighDateTime;

ULARGE_INTEGER ul2;
    ul2.LowPart = ft2.dwLowDateTime;
    ul2.HighPart = ft2.dwHighDateTime;


ul2.QuadPart -= ul1.QuadPart;

毫秒差异......

ULARGE_INTEGER uliRetValue;
    uliRetValue.QuadPart = 0;


    uliRetValue = ul2;
    uliRetValue.QuadPart /= 10;
    uliRetValue.QuadPart /= 1000; // To Milliseconds