Eryk Sun <eryk...@gmail.com> added the comment:
> As far as I know os.stat() resets d.stat() maybe should be added > some option to d.stat() to force update(). d.stat(nt_force_update=True). It depends on the filesystem. NTFS will update the directory entry as soon as the link is accessed by CreateFileW. But that's relatively expensive, and actually one of the more expensive steps in an os.stat call. > I am not sure if os.path.getmtime() can reset d.stat(). genericpath.getmtime calls os.stat: https://github.com/python/cpython/blob/d0981e61a5869c48e0a70a512967558391272a93/Lib/genericpath.py#L53 lexists, exists, getctime, getatime, getmtime, getsize, isdir, and isfile could be modified to call WinAPI GetFileAttributesExW [1], which is implemented via NtQueryFullAttributesFile [2], an optimized system call to get a file's network-open information. This can be significantly faster than the sequence of system calls that are required by os.stat. Note that this does not update the NTFS directory entry for the accessed link, unlike CreateFileW, but it does return updated information. The GetFileAttributesExW result would be used if the call succeeds and the file isn't a reparse point. Otherwise fall back on os.stat (win32_xstat_impl). If passed an fd, try GetFileInformationByHandleEx to get the FileBasicInfo and FileStandardInfo, or use a single system call via NTAPI NtQueryInformationFile: FileNetworkOpenInformation, which is the same info that GetFileAttributesExW returns. This could be implemented in C as nt._basic_stat(filename, follow_symlinks=True), where follow_symlinks means the expanded set of Windows name-surrogate reparse points. The C implementation would fall back on win32_xstat_impl. Note that a basic stat would not guarantee to return the following fields: st_ino, st_dev, and st_nlink. Alternatively, it could be implemented as a keyword-only basic=True option for os.stat, which would be ignored by POSIX. This way the high-level functions could continue to have a common implementation in genericpath.py. [1] https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfileattributesexw [2] https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-zwqueryfullattributesfile ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue41106> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
