[pywin32-bugs] [ pywin32-Bugs-3454662 ] GetFileAttributesEx, GetFileTime yield wrong time

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Bugs item #3454662, was opened at 2011-12-08 13:06
Message generated for change (Tracker Item Submitted) made by kxroberto
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: kxroberto (kxroberto)
Assigned to: Nobody/Anonymous (nobody)
Summary: GetFileAttributesEx, GetFileTime yield wrong time

Initial Comment:
>  >>> os.path.getmtime('x.txt')
> 1193160881
>  >>> int(win32file.GetFileAttributesExW('x.txt')[-2])
> 1193153681
>  >>> int(win32file.GetFileAttributesExW('x.txt')[-2]) - 
> os.path.getmtime('x.txt')
> -7200
> 
> (Win XP)
> is this a bug, or is there a issue with timezones/summer time? 
> aren't time.time() values absolute?
> 

had this issue again.

py_GetFileAttributesEx creates <PyTime> objects from (linear) FILETIME).

PyTime stores linear time as well (Windows VariantTime "DATE"), but the conversion is done via SYSTEMTIME - with hour,minute,... :-)

py_GetFileAttributesEx  > PyObject_FromFILEX_INFO > PyWinObject_FromFILETIME > FileTimeToSystemTime > PyTime


Upon int(<PyTime>)  the conversion from PyTime back to linear time is again done via SYSTEMTIME. 

These conversions via SYSTEMTIME are somehow buggy and principally bogus (during daylight-saving transition hours) overall.


=> the bug should perhaps be fixed by computing Pytime.m_time directly from FILETIME via  y = a*x + b

perhaps even better: GetFileAttributesEx  should simply return Pythonic time.time() style linear time stamps, not PyTime.
(but not backwards compatible; possibly by a flag parameter)


Python example for linear time conversion:

    def FILETIME2time(ft):
        "returns time.time() style seconds from FILETIME"
        tutc = ft.dwHighDateTime * 4294967296L + ft.dwLowDateTime
        tt = tutc * 100e-9 - 11644473600
        return tt


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