Class WindowsFileLock

src/filelock/_windows.py:175–213

Uses ``LockFileEx`` to hard lock a byte range of the lock file on Windows systems. Lock file cleanup: Windows attempts to delete the lock file after release, but deletion is not guaranteed in multi-threaded scenarios where another thread holds an open handle. The lock

            raise ctypes.WinError(ctypes.get_last_error())

    class WindowsFileLock(BaseFileLock):
        """
        Uses ``LockFileEx`` to hard lock a byte range of the lock file on Windows systems.

        Lock file cleanup: Windows attempts to delete the lock file after release, but deletion is
        not guaranteed in multi-threaded scenarios where another thread holds an open handle. The lock
        file may persist on disk, which does not affect lock correctness.
        """

        def _acquire(self) -> None:
            raise_on_not_writable_file(self.lock_file)
            ensure_directory_exists(self.lock_file)

            # The reparse test is bound to the opened handle, so a symlink or junction swapped in cannot defeat it
            # through a check-then-open TOCTOU race.
            fd = _open_non_reparse_fd(self.lock_file, self._open_mode())
            if fd is None:
                return  # open contention (share conflict or a name pending deletion); let the retry loop try again
            try:
                locked = _lock_fd_nonblocking(fd)
                if locked:
                    self._mark_descriptor_owned(fd)
            except BaseException:  # pragma: no cover  # cleanup only if the lock attempt itself raises
                os.close(fd)
                raise
            if not locked:
                os.close(fd)  # another holder owns the byte-range lock; let the retry loop try again

        def _release(self) -> None:
            fd = cast("int", self._context.lock_file_fd)
            # Retain the descriptor until the OS unlock succeeds: if UnlockFileEx raises, the byte-range lock is still
            # held, so is_locked must keep reporting held rather than losing the fd. Only after the unlock commits do
            # close and unlink run as post-unlock cleanup; their failure cannot make the lock held again.
            _unlock_fd(fd)
            self._mark_descriptor_released()
            self._close_released_fd(fd, default_suppresses=False)
            if not self._preserve_lock_file:  # preserve_lock_file keeps a stable file identity for the caller (#605)
                with suppress(OSError):
                    Path(self.lock_file).unlink()

    def _open_non_reparse_fd(path: str, mode: int) -> int | None:
        """