| 1 | /* Weak references objects for Python. */
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| 2 |
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| 3 | #ifndef Py_WEAKREFOBJECT_H
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| 4 | #define Py_WEAKREFOBJECT_H
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| 5 | #ifdef __cplusplus
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| 6 | extern "C" {
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| 7 | #endif
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| 8 |
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| 9 |
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| 10 | typedef struct _PyWeakReference PyWeakReference;
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| 11 |
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| 12 | /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,
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| 13 | * and CallableProxyType.
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| 14 | */
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| 15 | struct _PyWeakReference {
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| 16 | PyObject_HEAD
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| 17 |
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| 18 | /* The object to which this is a weak reference, or Py_None if none.
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| 19 | * Note that this is a stealth reference: wr_object's refcount is
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| 20 | * not incremented to reflect this pointer.
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| 21 | */
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| 22 | PyObject *wr_object;
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| 23 |
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| 24 | /* A callable to invoke when wr_object dies, or NULL if none. */
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| 25 | PyObject *wr_callback;
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| 26 |
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| 27 | /* A cache for wr_object's hash code. As usual for hashes, this is -1
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| 28 | * if the hash code isn't known yet.
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| 29 | */
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| 30 | long hash;
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| 31 |
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| 32 | /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-
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| 33 | * terminated list of weak references to it. These are the list pointers.
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| 34 | * If wr_object goes away, wr_object is set to Py_None, and these pointers
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| 35 | * have no meaning then.
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| 36 | */
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| 37 | PyWeakReference *wr_prev;
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| 38 | PyWeakReference *wr_next;
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| 39 | };
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| 40 |
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| 41 | PyAPI_DATA(PyTypeObject) _PyWeakref_RefType;
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| 42 | PyAPI_DATA(PyTypeObject) _PyWeakref_ProxyType;
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| 43 | PyAPI_DATA(PyTypeObject) _PyWeakref_CallableProxyType;
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| 44 |
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| 45 | #define PyWeakref_CheckRef(op) PyObject_TypeCheck(op, &_PyWeakref_RefType)
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| 46 | #define PyWeakref_CheckRefExact(op) \
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| 47 | (Py_TYPE(op) == &_PyWeakref_RefType)
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| 48 | #define PyWeakref_CheckProxy(op) \
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| 49 | ((Py_TYPE(op) == &_PyWeakref_ProxyType) || \
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| 50 | (Py_TYPE(op) == &_PyWeakref_CallableProxyType))
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| 51 |
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| 52 | #define PyWeakref_Check(op) \
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| 53 | (PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op))
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| 54 |
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| 55 |
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| 56 | PyAPI_FUNC(PyObject *) PyWeakref_NewRef(PyObject *ob,
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| 57 | PyObject *callback);
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| 58 | PyAPI_FUNC(PyObject *) PyWeakref_NewProxy(PyObject *ob,
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| 59 | PyObject *callback);
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| 60 | PyAPI_FUNC(PyObject *) PyWeakref_GetObject(PyObject *ref);
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| 61 |
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| 62 | PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head);
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| 63 |
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| 64 | PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);
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| 65 |
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| 66 | /* Explanation for the Py_REFCNT() check: when a weakref's target is part
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| 67 | of a long chain of deallocations which triggers the trashcan mechanism,
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| 68 | clearing the weakrefs can be delayed long after the target's refcount
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| 69 | has dropped to zero. In the meantime, code accessing the weakref will
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| 70 | be able to "see" the target object even though it is supposed to be
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| 71 | unreachable. See issue #16602. */
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| 72 |
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| 73 | #define PyWeakref_GET_OBJECT(ref) \
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| 74 | (Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \
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| 75 | ? ((PyWeakReference *)(ref))->wr_object \
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| 76 | : Py_None)
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| 77 |
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| 78 |
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| 79 | #ifdef __cplusplus
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| 80 | }
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| 81 | #endif
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| 82 | #endif /* !Py_WEAKREFOBJECT_H */
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