import unittest
import ctypes
from ctypes import POINTER, c_void_p
from ._support import PyCSimpleType
class PyCSimpleTypeAsMetaclassTest(unittest.TestCase):
def tearDown(self):
# to not leak references, we must clean _pointer_type_cache
ctypes._reset_cache()
def test_creating_pointer_in_dunder_new_1(self):
# Test metaclass whose instances are C types; when the type is
# created it automatically creates a pointer type for itself.
# The pointer type is also an instance of the metaclass.
# Such an implementation is used in `IUnknown` of the `comtypes`
# project. See gh-124520.
class ct_meta(type):
def __new__(cls, name, bases, namespace):
self = super().__new__(cls, name, bases, namespace)
# Avoid recursion: don't set up a pointer to
# a pointer (to a pointer...)
if bases == (c_void_p,):
# When creating PtrBase itself, the name
# is not yet available
return self
if issubclass(self, PtrBase):
return self
if bases == (object,):
ptr_bases = (self, PtrBase)
else:
ptr_bases = (self, POINTER(bases[0]))
p = p_meta(f"POINTER({self.__name__})", ptr_bases, {})
ctypes._pointer_type_cache[self] = p
return self
class p_meta(PyCSimpleType, ct_meta):
pass
class PtrBase(c_void_p, metaclass=p_meta):
pass
class CtBase(object, metaclass=ct_meta):
pass
class Sub(CtBase):
pass
class Sub2(Sub):
pass
self.assertIsInstance(POINTER(Sub2), p_meta)
self.assertTrue(issubclass(POINTER(Sub2), Sub2))
self.assertTrue(issubclass(POINTER(Sub2), POINTER(Sub)))
self.assertTrue(issubclass(POINTER(Sub), POINTER(CtBase)))
def test_creating_pointer_in_dunder_new_2(self):
# A simpler variant of the above, used in `CoClass` of the `comtypes`
# project.
class ct_meta(type):
def __new__(cls, name, bases, namespace):
self = super().__new__(cls, name, bases, namespace)
if isinstance(self, p_meta):
return self
p = p_meta(f"POINTER({self.__name__})", (self, c_void_p), {})
ctypes._pointer_type_cache[self] = p
return self
class p_meta(PyCSimpleType, ct_meta):
pass
class Core(object):
pass
class CtBase(Core, metaclass=ct_meta):
pass
class Sub(CtBase):
pass
self.assertIsInstance(POINTER(Sub), p_meta)
self.assertTrue(issubclass(POINTER(Sub), Sub))
def test_creating_pointer_in_dunder_init_1(self):
class ct_meta(type):
def __init__(self, name, bases, namespace):
super().__init__(name, bases, namespace)
# Avoid recursion.
# (See test_creating_pointer_in_dunder_new_1)
if bases == (c_void_p,):
return
if issubclass(self, PtrBase):
return
if bases == (object,):
ptr_bases = (self, PtrBase)
else:
ptr_bases = (self, POINTER(bases[0]))
p = p_meta(f"POINTER({self.__name__})", ptr_bases, {})
ctypes._pointer_type_cache[self] = p
class p_meta(PyCSimpleType, ct_meta):
pass
class PtrBase(c_void_p, metaclass=p_meta):
pass
class CtBase(object, metaclass=ct_meta):
pass
class Sub(CtBase):
pass
class Sub2(Sub):
pass
self.assertIsInstance(POINTER(Sub2), p_meta)
self.assertTrue(issubclass(POINTER(Sub2), Sub2))
self.assertTrue(issubclass(POINTER(Sub2), POINTER(Sub)))
self.assertTrue(issubclass(POINTER(Sub), POINTER(CtBase)))
def test_creating_pointer_in_dunder_init_2(self):
class ct_meta(type):
def __init__(self, name, bases, namespace):
super().__init__(name, bases, namespace)
# Avoid recursion.
# (See test_creating_pointer_in_dunder_new_2)
if isinstance(self, p_meta):
return
p = p_meta(f"POINTER({self.__name__})", (self, c_void_p), {})
ctypes._pointer_type_cache[self] = p
class p_meta(PyCSimpleType, ct_meta):
pass
class Core(object):
pass
class CtBase(Core, metaclass=ct_meta):
pass
class Sub(CtBase):
pass
self.assertIsInstance(POINTER(Sub), p_meta)
self.assertTrue(issubclass(POINTER(Sub), Sub))
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