What is the proper way to convert a FILETIME
structure into __int64
? Can you please tell me?
you can try the code follow. the code is from chromium project
template <class Dest, class Source>
inline Dest bit_cast(const Source& source) {
Dest dest;
memcpy(&dest, &source, sizeof(dest));
return dest;
}
//FILETIME to __int64
__int64 FileTimeToMicroseconds(const FILETIME& ft) {
return bit_cast<__int64, FILETIME>(ft) / 10;
}
void MicrosecondsToFileTime(__int64 us, FILETIME* ft) {
*ft = bit_cast<FILETIME, __int64>(us * 10);
}
int _tmain(int argc, _TCHAR* argv[])
{
__int64 nTmpUint64 = 13060762249644841;
time_t unixtime;
FILETIME nTmpFileTm;
MicrosecondsToFileTime(nTmpUint64,&nTmpFileTm);
return 0;
}
I don't think you're suppose to: "Do not cast a pointer to a FILETIME
structure to either a ULARGE_INTEGER*
or __int64*
value because it can cause alignment faults on 64-bit Windows."
Source.
If you really wanted it would be something like:
__int64 to_int64(FILETIME ft)
{
return static_cast<__int64>(ft.dwHighDateTime) << 32 | ft.dwLowDateTime;
}
FILETIME ft = // ...
__int64 t = to_int64(ft);
But something like:
FILETIME ft = // ...
__int64 t = *reinterpet_cast<__int64*>(&ft);
Is bad.
Try
(__int64(filetime.dwHighDateTime)<<32) | __int64(filetime.dwLowDateTime)
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:
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 );
Edit: I realise this merely confirms some of the other answers, but I thought it was worth adding for clarification.
Of course you could just pass in an __int64 casted to a filetime as follows *(FILETIME*)&int64Val. This will work fine under Visual C++.
ie
__int64 createTime = 0;
__int64 accessTime = 0;
__int64 writeTime = 0;
GetFileTime( hFile, *(FILETIME*)&createTime, *(FILETIME*)&accessTime, *(FILETIME*)&writeTime );
There is no need to revert to arcane constructs using bitwise OR's. The Windows API has got everything you need to do this.
unsigned __int64 convert( const FILETIME & ac_FileTime )
{
ULARGE_INTEGER lv_Large ;
lv_Large.LowPart = ac_FileTime.dwLowDateTime ;
lv_Large.HighPart = ac_FileTime.dwHighDateTime ;
return lv_Large.QuadPart ;
}
Or if you want to go to __int64 directly.
__int64 convert_to_int64( const FILETIME & ac_FileTime )
{
return static_cast< __int64 > ( convert( ac_FileTime ) ) ;
}