c++ - 通过 SYSTEMTIME 检查文件的 LastWriteTime 是昨天

Question

我想检查很多文件的 LastWriteTimes 是否与系统昨天的日期相同。我的问题是如何以 SYSTEMTIME 格式设置昨天的日期时间。以下是我的代码。

    bool checkLastWriteTime(FILETIME ftLastWriteTime)
    {
        SYSTEMTIME stUTC, stLocal;
        // Convert the last-write time to local time.
        FileTimeToSystemTime(&ftLastWriteTime, &stUTC);
        SystemTimeToTzSpecificLocalTime(NULL, &stUTC, &stLocal);

        // Build a string showing the date and time.
        _tprintf(TEXT("%02d/%02d/%d  %02d:%02d\n"),
            stLocal.wMonth, stLocal.wDay, stLocal.wYear,
            stLocal.wHour, stLocal.wMinute);

        SYSTEMTIME localTime;
        GetLocalTime(&localTime);

      //
      //How to get the date of yesterday from localTime?
      //

        if (stLocal.wYear == localTime.wYear && stLocal.wMonth == localTime.wMonth && stLocal.wDay == localTime.wDay)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

Answer 1

“昨天”是一个范围。结束时间很容易计算，发生在今天早上 12 点:

SYSTEMTIME now;
GetLocalTime(&now);
SYSTEMTIME stYesterdayEnd = { now.wYear, now.wMonth, now.wDayOfWeek, now.wDay };
FILETIME ftYesterdayEnd;
SystemTimeToFileTime(&stYesterdayEnd, &ftYesterdayEnd);

它在那之前 24 小时开始。因此，您需要从 ftYesterdayEnd 中减去 100 纳秒单位。 FILETIME 有点棘手，我们将使用 LARGE_INTEGER 来简化它:

LARGE_INTEGER liYesterdayBeg = { ftYesterdayEnd.dwLowDateTime, ftYesterdayEnd.dwHighDateTime };
ULONGLONG oneday = 24ULL * 60 * 60 * 1000 * 1000 * 10;
liYesterdayBeg.QuadPart -= oneday;
FILETIME ftYesterdayBeg = { liYesterdayBeg.LowPart, liYesterdayBeg.HighPart };

现在您可以编写函数了:

bool wasWrittenYesterday(FILETIME ftLastWriteTime)
{
    // As above
    //...
    return ftLastWriteTime >= ftYesterdayBeg && ftLastWriteTime < ftYesterdayEnd
}