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1import unittest
2from ctypes import *
3
4class StructFieldsTestCase(unittest.TestCase):
5    # Structure/Union classes must get 'finalized' sooner or
6    # later, when one of these things happen:
7    #
8    # 1. _fields_ is set.
9    # 2. An instance is created.
10    # 3. The type is used as field of another Structure/Union.
11    # 4. The type is subclassed
12    #
13    # When they are finalized, assigning _fields_ is no longer allowed.
14
15    def test_1_A(self):
16        class X(Structure):
17            pass
18        self.assertEqual(sizeof(X), 0) # not finalized
19        X._fields_ = [] # finalized
20        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
21
22    def test_1_B(self):
23        class X(Structure):
24            _fields_ = [] # finalized
25        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
26
27    def test_2(self):
28        class X(Structure):
29            pass
30        X()
31        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
32
33    def test_3(self):
34        class X(Structure):
35            pass
36        class Y(Structure):
37            _fields_ = [("x", X)] # finalizes X
38        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
39
40    def test_4(self):
41        class X(Structure):
42            pass
43        class Y(X):
44            pass
45        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
46        Y._fields_ = []
47        self.assertRaises(AttributeError, setattr, X, "_fields_", [])
48
49    def test_5(self):
50        class X(Structure):
51            _fields_ = (("char", c_char * 5),)
52
53        x = X(b'#' * 5)
54        x.char = b'a\0b\0'
55        self.assertEqual(bytes(x), b'a\x00###')
56
57    # __set__ and __get__ should raise a TypeError in case their self
58    # argument is not a ctype instance.
59    def test___set__(self):
60        class MyCStruct(Structure):
61            _fields_ = (("field", c_int),)
62        self.assertRaises(TypeError,
63                          MyCStruct.field.__set__, 'wrong type self', 42)
64
65        class MyCUnion(Union):
66            _fields_ = (("field", c_int),)
67        self.assertRaises(TypeError,
68                          MyCUnion.field.__set__, 'wrong type self', 42)
69
70    def test___get__(self):
71        class MyCStruct(Structure):
72            _fields_ = (("field", c_int),)
73        self.assertRaises(TypeError,
74                          MyCStruct.field.__get__, 'wrong type self', 42)
75
76        class MyCUnion(Union):
77            _fields_ = (("field", c_int),)
78        self.assertRaises(TypeError,
79                          MyCUnion.field.__get__, 'wrong type self', 42)
80
81if __name__ == "__main__":
82    unittest.main()
83