在C ++中为FILETIME结构分配数据和时间

Question

In windows and in C++. I have following code.

typedef struct _FILETIME {
    DWORD dwLowDateTime;
    DWORD dwHighDateTime;
} FILETIME, *PFILETIME, *LPFILETIME;

struct DateTime
{
    unsigned int dwLowDateTime;
    unsigned int dwHighDateTime;
};

FILETIME ftTime;
GetSystemTimeAsFileTime(&ftTime);

DateTime myTime;
myTime.dwHighDateTime = (unsigned int)ftTime.dwHighDateTime;
myTime.dwLowDateTime  = (unsigned int)ftTime.dwLowDateTime;

Now I have requirement to assign values like

2012-06-25 12:00:10.123

to "myTime" or ftTime.

How can I achive this?

Another question is how can I get number of seconds elapsed like 64-bit integer for date "2012-06-25 12:00:10.123" ? How do I convert this to __int64 so that I assign to FILETIME?

I have seen in another question post

__int64 t;
FILETIME ft;
ft.dwLowDateTime = (DWORD)t;
ft.dwHighDateTime = (DWORD)(t >> 32);

I am not supposed to use Boost in my project.

Thanks!

Answer 1

Assign the value "2012-06-25 12:00:10.123" to the SystemTime structure and convert it into FileTime using the function SystemTimeToFileTime.

SYSTEMTIME st,st1;
st.wDay = 25;
st.wMonth = 06;
st.wYear = 2012;
st.wHour = 12;
st.wMinute = 10;
st.wSecond = 10;
st.wMilliseconds = 10;

FILETIME ft;
SystemTimeToFileTime(&st,&ft);
FileTimeToSystemTime(&ft,&st1);

Answer 2

Use SystemTimeToFileTime .

Assign the datetime data to the SYSTEMTIME structure.

typedef struct _SYSTEMTIME {
  WORD wYear;
  WORD wMonth;
  WORD wDayOfWeek;
  WORD wDay;
  WORD wHour;
  WORD wMinute;
  WORD wSecond;
  WORD wMilliseconds;
} SYSTEMTIME, *PSYSTEMTIME;

And use

BOOL WINAPI SystemTimeToFileTime(
  __in   const SYSTEMTIME *lpSystemTime,
  __out  LPFILETIME lpFileTime
);

for the conversion.

Update: For converting from the string to date,time components, you can use DateTime::Parse Method(String) method. Then assign the values to the SYSTEMTIME structure and then convert that to FileTime .

Answer 3

There are multiple ways and functions that can get you there.

You can use DosDateTimeToFileTime() to convert year/month/day h:m:s into FILETIME . You'll need to take additional care of the odd seconds and second fractions.

You also have C(++)'s mktime() to first get time in seconds since 1970. Then you'd need to convert it to seconds since January 1st 1601 by adding 11644473600 to it, scale it to 100-nanoseconds and add the seconds fraction.

But SystemTimeToFileTime() is a better choice because it handles milliseconds as well.

It's not clear what you mean by how can I get number of seconds elapsed like 64-bit integer for date "2012-06-25 12:00:10.123"?

Seconds elapsed since then until now? If so, you get the current time in seconds and convert the given date/time to seconds (described above) and subtract one from the other.

Seconds elapsed since an earlier time until then? Do the same, get seconds for both date/time pairs and subtract.