def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def test_struct_alignment(self):
        class X(Structure):
            _fields_ = [("x", c_char * 3)]
        self.assertEqual(alignment(X), calcsize("s"))
        self.assertEqual(sizeof(X), calcsize("3s"))

        class Y(Structure):
            _fields_ = [("x", c_char * 3),
                        ("y", c_int)]
        self.assertEqual(alignment(Y), calcsize("i"))
        self.assertEqual(sizeof(Y), calcsize("3si"))

        class SI(Structure):
            _fields_ = [("a", X),
                        ("b", Y)]
        self.assertEqual(alignment(SI), max(alignment(Y), alignment(X)))
        self.assertEqual(sizeof(SI), calcsize("3s0i 3si 0i"))

        class IS(Structure):
            _fields_ = [("b", Y),
                        ("a", X)]

        self.assertEqual(alignment(SI), max(alignment(X), alignment(Y)))
        self.assertEqual(sizeof(IS), calcsize("3si 3s 0i"))

        class XX(Structure):
            _fields_ = [("a", X),
                        ("b", X)]
        self.assertEqual(alignment(XX), alignment(X))
        self.assertEqual(sizeof(XX), calcsize("3s 3s 0s"))