Demonstrate problem from getting 64-bit timestamp to nanosec in Windows

gettimestamp_cpp_windows.cpp

// Demonstrate problem in GetSystemTimeAsFileTime(..) call
// The time returned is not very precised
//
ULARGE_INTEGER prev_timestamp, timestamp;
prev_timestamp.QuadPart = 0;

for(int i = 0 ; i < 100 ; ++i, prev_timestamp = timestamp){

	FILETIME now;
	GetSystemTimeAsFileTime(&now);

	timestamp.HighPart = now.dwHighDateTime;
	timestamp.LowPart = now.dwLowDateTime;

	ULONGLONG diff = timestamp.QuadPart - prev_timestamp.QuadPart;

	// The unit for timestamp's diff is 10 nanosecond or 0.1 microsecond
	// Divide this number by 10 to convert unit to microsecond
	//
	if(diff != 0)
		printf("TIMESTAMP DIFF = %I64u\n\n", diff);
}