import sys

    rustext.__name__  # trigger immediate actual import

else:

    # this would fail already without appropriate ancestor.__package__

    from mercurial.rustext.ancestor import AncestorsIterator

# picked from test-parse-index2, copied rather than imported

# so that it stays stable even if test-parse-index2 changes or disappears.

data_non_inlined = (

    b'\x00\x00\x00\x01\x00\x00\x00\x00\x00\x01D\x19'

    b'\x00\x07e\x12\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff'

    b'\xff\xff\xff\xff\xd1\xf4\xbb\xb0\xbe\xfc\x13\xbd\x8c\xd3\x9d'

    b'\x0f\xcd\xd9;\x8c\x07\x8cJ/\x00\x00\x00\x00\x00\x00\x00\x00\x00'

    b'\x00\x00\x00\x00\x00\x00\x01D\x19\x00\x00\x00\x00\x00\xdf\x00'

    b'\x00\x01q\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x00\xff'

    b'\xff\xff\xff\xc1\x12\xb9\x04\x96\xa4Z1t\x91\xdfsJ\x90\xf0\x9bh'

    b'\x07l&\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'

    b'\x00\x01D\xf8\x00\x00\x00\x00\x01\x1b\x00\x00\x01\xb8\x00\x00'

    b'\x00\x01\x00\x00\x00\x02\x00\x00\x00\x01\xff\xff\xff\xff\x02\n'

    b'\x0e\xc6&\xa1\x92\xae6\x0b\x02i\xfe-\xe5\xbao\x05\xd1\xe7\x00'

    b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01F'

    b'\x13\x00\x00\x00\x00\x01\xec\x00\x00\x03\x06\x00\x00\x00\x01'

    b'\x00\x00\x00\x03\x00\x00\x00\x02\xff\xff\xff\xff\x12\xcb\xeby1'

    b'\xb6\r\x98B\xcb\x07\xbd`\x8f\x92\xd9\xc4\x84\xbdK\x00\x00\x00'

    b'\x00\x00\x00\x00\x00\x00\x00\x00\x00'

    )

                 "rustext or the C Extension parsers module "

                 "ancestor relies on is not available")

    def parseindex(self):

        return cparsers.parse_index2(data_non_inlined, False)[0]

    def testiteratorrevlist(self):

        idx = self.parseindex()

        # checking test assumption about the index binary data:

        self.assertEqual({i: (r[5], r[6]) for i, r in enumerate(idx)},

                         {0: (-1, -1),

                          1: (0, -1),

                          2: (1, -1),

                          3: (2, -1)})

        ait = AncestorsIterator(idx, [3], 0, True)

        self.assertEqual([r for r in ait], [3, 2, 1, 0])

        ait = AncestorsIterator(idx, [3], 0, False)

        self.assertEqual([r for r in ait], [2, 1, 0])

    def testrefcount(self):

        idx = self.parseindex()

        start_count = sys.getrefcount(idx)

        # refcount increases upon iterator init...

        ait = AncestorsIterator(idx, [3], 0, True)

        self.assertEqual(sys.getrefcount(idx), start_count + 1)

        self.assertEqual(next(ait), 3)

        # and decreases once the iterator is removed

        del ait

        self.assertEqual(sys.getrefcount(idx), start_count)

        # and removing ref to the index after iterator init is no issue

        ait = AncestorsIterator(idx, [3], 0, True)

        del idx

        self.assertEqual([r for r in ait], [3, 2, 1, 0])

        data = (data_non_inlined[:64 + 27] +

                b'\xf2' +

                data_non_inlined[64 + 28:])

        idx = cparsers.parse_index2(data, False)[0]

        with self.assertRaises(rustext.GraphError) as arc:

            AncestorsIterator(idx, [1], -1, False)

        exc = arc.exception

        self.assertIsInstance(exc, ValueError)

        # rust-cpython issues appropriate str instances for Python 2 and 3

        self.assertEqual(exc.args, ('ParentOutOfRange', 1))