1 /* Weak references objects for Python. */
2 
3 #ifndef Py_WEAKREFOBJECT_H
4 #define Py_WEAKREFOBJECT_H
5 #ifdef __cplusplus
6 extern "C" {
7 #endif
8 
9 
10 typedef struct _PyWeakReference PyWeakReference;
11 
12 /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,
13  * and CallableProxyType.
14  */
15 struct _PyWeakReference {
16     PyObject_HEAD
17 
18     /* The object to which this is a weak reference, or Py_None if none.
19      * Note that this is a stealth reference:  wr_object's refcount is
20      * not incremented to reflect this pointer.
21      */
22     PyObject *wr_object;
23 
24     /* A callable to invoke when wr_object dies, or NULL if none. */
25     PyObject *wr_callback;
26 
27     /* A cache for wr_object's hash code.  As usual for hashes, this is -1
28      * if the hash code isn't known yet.
29      */
30     long hash;
31 
32     /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-
33      * terminated list of weak references to it.  These are the list pointers.
34      * If wr_object goes away, wr_object is set to Py_None, and these pointers
35      * have no meaning then.
36      */
37     PyWeakReference *wr_prev;
38     PyWeakReference *wr_next;
39 };
40 
41 PyAPI_DATA(PyTypeObject) _PyWeakref_RefType;
42 PyAPI_DATA(PyTypeObject) _PyWeakref_ProxyType;
43 PyAPI_DATA(PyTypeObject) _PyWeakref_CallableProxyType;
44 
45 #define PyWeakref_CheckRef(op) PyObject_TypeCheck(op, &_PyWeakref_RefType)
46 #define PyWeakref_CheckRefExact(op) \
47         (Py_TYPE(op) == &_PyWeakref_RefType)
48 #define PyWeakref_CheckProxy(op) \
49         ((Py_TYPE(op) == &_PyWeakref_ProxyType) || \
50          (Py_TYPE(op) == &_PyWeakref_CallableProxyType))
51 
52 /* This macro calls PyWeakref_CheckRef() last since that can involve a
53    function call; this makes it more likely that the function call
54    will be avoided. */
55 #define PyWeakref_Check(op) \
56         (PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op))
57 
58 
59 PyAPI_FUNC(PyObject *) PyWeakref_NewRef(PyObject *ob,
60                                               PyObject *callback);
61 PyAPI_FUNC(PyObject *) PyWeakref_NewProxy(PyObject *ob,
62                                                 PyObject *callback);
63 PyAPI_FUNC(PyObject *) PyWeakref_GetObject(PyObject *ref);
64 
65 PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head);
66 
67 PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);
68 
69 #define PyWeakref_GET_OBJECT(ref) (((PyWeakReference *)(ref))->wr_object)
70 
71 
72 #ifdef __cplusplus
73 }
74 #endif
75 #endif /* !Py_WEAKREFOBJECT_H */
76