Thread: Writing FILETIME or SYSTEMTIME to File?

Hi all,

I am very new to VC++, (VB Convert), and am only writing my second C++ program.

I am looking to write either a FILETIME struct or a SYSTEMTIME struct to a file for later usage. I am using the CreateFile, WriteFile, CloseHandle APIs to handle writing to file.

But I'm not sure how to handle the data if I want to retrieve it later.

• Is it possible to write the FILETIME to a file in binary using the WriteFile API?
• or... is there a way to write the 2 DWORD values of the FILETIME struct as binary that can easily be retrieved as 2 separate values later?
• Or should I leave it as system time and then put it into the file as a string value that I can tokenize during retrieval?

Code I have thus far is

Code:

SYSTEMTIME stCurrent;
FILETIME ftCurrent;
HANDLE hWriteFile;
LPDWORD lpBytesWritten = 0;
long lRetVal;

GetSystemTime(&stCurrent);
SystemTimeToFileTime(&stCurrent, &ftCurrent);

hWriteFile = CreateFile("C:\\Temp\\file.dat", 
     GENERIC_WRITE,
     0, 
     NULL, 
     CREATE_ALWAYS, 
     FILE_ATTRIBUTE_NORMAL, 
     NULL);

lRetVal = WriteFile(hWriteFile,
     &ftCurrent,
     sizeof(ftCurrent),
     lpBytesWritten,
     NULL);

CloseHandle(hWriteFile);

if(lRetVal == ERROR_SUCCESS){return true;]
     else{return false;}

Thanks one and all for any advice you can lend!

PS...
The purpose of the class I'm working on is to catch the current system time. Then, following an application installation, compare the lastwritetime of the CLASSES_ROOT and LOCAL_MACHINE reg keys to see what was changed by the installation.
I am calling the GetSystemTime API and then, potentially, using the SystemTimeToFileTime API to convert to FILETIME.

Alternatively you could use the free store, and continue going the way you were:

Code:

LPDWORD lpBytesWritten = new DWORD;
.
.
.
lRetVal = WriteFile(hWriteFile,
     &ftCurrent,
     sizeof(ftCurrent),
     lpBytesWritten,
     NULL);
.
.
.
delete lpBytesWritten;

If you don't know yet, the "new" operator allocates space for the following data type and returns a pointer to that space. So, lpBytesWritten now contains the address of a DWORD. The "delete" operator ensures that the allocated memory is released.

In this case, it isn't really necessary to use new and delete, but it's handy to know about them.