FILETIME to __int64

Question

What is the proper way to convert a FILETIME structure into __int64? Can you please tell me?

Answer 1

I had exactly the same issue, googled for it, and came here. But I also found a useful Microsoft support page at
https://support.microsoft.com/en-gb/help/188768/info-working-with-the-filetime-structure

It says:

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Performing Arithmetic with File Times

It is often necessary to perform a simple arithmetic on file times. For example, you might need to know when a file is 30 days old. To perform an arithmetic on a file time, you need to convert the FILETIME to a quadword (a 64-bit integer), perform the arithmetic, and then convert the result back to a FILETIME.

Assuming ft is a FILETIME structure containing the creation time of a file, the following sample code adds 30 days to the time:

   ULONGLONG qwResult;

   // Copy the time into a quadword.
   qwResult = (((ULONGLONG) ft.dwHighDateTime) << 32) + ft.dwLowDateTime;

   // Add 30 days.
   qwResult += 30 * _DAY;

   // Copy the result back into the FILETIME structure.
   ft.dwLowDateTime  = (DWORD) (qwResult & 0xFFFFFFFF );
   ft.dwHighDateTime = (DWORD) (qwResult >> 32 );

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Edit: I realise this merely confirms some of the other answers, but I thought it was worth adding for clarification.