time_t和SYSTEMTIME 与TDateTime的转换 (转)

 在vc中实现time_t和SYSTEMTIME 与delphi中的TDateTime的转换。

delphi中的TDateTime其实就是一个double型。

TDateTime TimetToDateTime(time_t t)
{
 double result=(double)t / 86400.0 + 25569;
 return TDateTime(result);
}

time_t DateTimeToTimet(TDateTime dt)
{
 return time_t((dt-25569) * 86400.0);
}

void DateTimeToSystemTime(TDateTime dt, LPSYSTEMTIME pst)
{
 double t= (dt-25569) * 86400.0;
 FILETIME ft;

 LONGLONG ll = LONGLONG((t* 10000000) + 116444736000000000);
 ft.dwLowDateTime = (DWORD) ll;
 ft.dwHighDateTime = (DWORD)(ll >> 32);

 FileTimeToSystemTime( &ft, pst );
}

TDateTime SystemTimeToDateTime(SYSTEMTIME st)
{
 FILETIME ft;
 SystemTimeToFileTime( &st, &ft );

 LONGLONG ll;

 ULARGE_INTEGER ui;
 ui.LowPart = ft.dwLowDateTime;
 ui.HighPart = ft.dwHighDateTime;

 ll = ft.dwHighDateTime;
 ll = (ll<<32) + ft.dwLowDateTime;

 TDateTime result =25569+(LONGLONG)(ui.QuadPart - 116444736000000000) / 864000000000.0;
 return result;
}

原文: 

http://blog.csdn.net/constantine/archive/2008/12/25/3607513.aspx