1 #include "Python.h"
2 #include "pycore_object.h" // _PyObject_GET_WEAKREFS_LISTPTR
3
4
5 #define GET_WEAKREFS_LISTPTR(o) \
6 ((PyWeakReference **) _PyObject_GET_WEAKREFS_LISTPTR(o))
7
8 /*[clinic input]
9 module _weakref
10 [clinic start generated code]*/
11 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=ffec73b85846596d]*/
12
13 #include "clinic/_weakref.c.h"
14
15 /*[clinic input]
16
17 _weakref.getweakrefcount -> Py_ssize_t
18
19 object: object
20 /
21
22 Return the number of weak references to 'object'.
23 [clinic start generated code]*/
24
25 static Py_ssize_t
_weakref_getweakrefcount_impl(PyObject * module,PyObject * object)26 _weakref_getweakrefcount_impl(PyObject *module, PyObject *object)
27 /*[clinic end generated code: output=301806d59558ff3e input=cedb69711b6a2507]*/
28 {
29 PyWeakReference **list;
30
31 if (!PyType_SUPPORTS_WEAKREFS(Py_TYPE(object)))
32 return 0;
33
34 list = GET_WEAKREFS_LISTPTR(object);
35 return _PyWeakref_GetWeakrefCount(*list);
36 }
37
38
39 static int
is_dead_weakref(PyObject * value)40 is_dead_weakref(PyObject *value)
41 {
42 if (!PyWeakref_Check(value)) {
43 PyErr_SetString(PyExc_TypeError, "not a weakref");
44 return -1;
45 }
46 return PyWeakref_GET_OBJECT(value) == Py_None;
47 }
48
49 /*[clinic input]
50
51 _weakref._remove_dead_weakref -> object
52
53 dct: object(subclass_of='&PyDict_Type')
54 key: object
55 /
56
57 Atomically remove key from dict if it points to a dead weakref.
58 [clinic start generated code]*/
59
60 static PyObject *
_weakref__remove_dead_weakref_impl(PyObject * module,PyObject * dct,PyObject * key)61 _weakref__remove_dead_weakref_impl(PyObject *module, PyObject *dct,
62 PyObject *key)
63 /*[clinic end generated code: output=d9ff53061fcb875c input=19fc91f257f96a1d]*/
64 {
65 if (_PyDict_DelItemIf(dct, key, is_dead_weakref) < 0) {
66 if (PyErr_ExceptionMatches(PyExc_KeyError))
67 /* This function is meant to allow safe weak-value dicts
68 with GC in another thread (see issue #28427), so it's
69 ok if the key doesn't exist anymore.
70 */
71 PyErr_Clear();
72 else
73 return NULL;
74 }
75 Py_RETURN_NONE;
76 }
77
78
79 PyDoc_STRVAR(weakref_getweakrefs__doc__,
80 "getweakrefs(object) -- return a list of all weak reference objects\n"
81 "that point to 'object'.");
82
83 static PyObject *
weakref_getweakrefs(PyObject * self,PyObject * object)84 weakref_getweakrefs(PyObject *self, PyObject *object)
85 {
86 PyObject *result = NULL;
87
88 if (PyType_SUPPORTS_WEAKREFS(Py_TYPE(object))) {
89 PyWeakReference **list = GET_WEAKREFS_LISTPTR(object);
90 Py_ssize_t count = _PyWeakref_GetWeakrefCount(*list);
91
92 result = PyList_New(count);
93 if (result != NULL) {
94 PyWeakReference *current = *list;
95 Py_ssize_t i;
96 for (i = 0; i < count; ++i) {
97 PyList_SET_ITEM(result, i, (PyObject *) current);
98 Py_INCREF(current);
99 current = current->wr_next;
100 }
101 }
102 }
103 else {
104 result = PyList_New(0);
105 }
106 return result;
107 }
108
109
110 PyDoc_STRVAR(weakref_proxy__doc__,
111 "proxy(object[, callback]) -- create a proxy object that weakly\n"
112 "references 'object'. 'callback', if given, is called with a\n"
113 "reference to the proxy when 'object' is about to be finalized.");
114
115 static PyObject *
weakref_proxy(PyObject * self,PyObject * args)116 weakref_proxy(PyObject *self, PyObject *args)
117 {
118 PyObject *object;
119 PyObject *callback = NULL;
120 PyObject *result = NULL;
121
122 if (PyArg_UnpackTuple(args, "proxy", 1, 2, &object, &callback)) {
123 result = PyWeakref_NewProxy(object, callback);
124 }
125 return result;
126 }
127
128
129 static PyMethodDef
130 weakref_functions[] = {
131 _WEAKREF_GETWEAKREFCOUNT_METHODDEF
132 _WEAKREF__REMOVE_DEAD_WEAKREF_METHODDEF
133 {"getweakrefs", weakref_getweakrefs, METH_O,
134 weakref_getweakrefs__doc__},
135 {"proxy", weakref_proxy, METH_VARARGS,
136 weakref_proxy__doc__},
137 {NULL, NULL, 0, NULL}
138 };
139
140 static int
weakref_exec(PyObject * module)141 weakref_exec(PyObject *module)
142 {
143 Py_INCREF(&_PyWeakref_RefType);
144 if (PyModule_AddObject(module, "ref", (PyObject *) &_PyWeakref_RefType) < 0) {
145 Py_DECREF(&_PyWeakref_RefType);
146 return -1;
147 }
148 Py_INCREF(&_PyWeakref_RefType);
149 if (PyModule_AddObject(module, "ReferenceType",
150 (PyObject *) &_PyWeakref_RefType) < 0) {
151 Py_DECREF(&_PyWeakref_RefType);
152 return -1;
153 }
154 Py_INCREF(&_PyWeakref_ProxyType);
155 if (PyModule_AddObject(module, "ProxyType",
156 (PyObject *) &_PyWeakref_ProxyType) < 0) {
157 Py_DECREF(&_PyWeakref_ProxyType);
158 return -1;
159 }
160 Py_INCREF(&_PyWeakref_CallableProxyType);
161 if (PyModule_AddObject(module, "CallableProxyType",
162 (PyObject *) &_PyWeakref_CallableProxyType) < 0) {
163 Py_DECREF(&_PyWeakref_CallableProxyType);
164 return -1;
165 }
166
167 return 0;
168 }
169
170 static struct PyModuleDef_Slot weakref_slots[] = {
171 {Py_mod_exec, weakref_exec},
172 {0, NULL}
173 };
174
175 static struct PyModuleDef weakrefmodule = {
176 PyModuleDef_HEAD_INIT,
177 "_weakref",
178 "Weak-reference support module.",
179 0,
180 weakref_functions,
181 weakref_slots,
182 NULL,
183 NULL,
184 NULL
185 };
186
187 PyMODINIT_FUNC
PyInit__weakref(void)188 PyInit__weakref(void)
189 {
190 return PyModuleDef_Init(&weakrefmodule);
191 }
192