Andrew Hsieh | 83760d2 | 2013-06-18 12:24:28 -0700 | [diff] [blame] | 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 | /* Explanation for the Py_REFCNT() check: when a weakref's target is part |
| 70 | of a long chain of deallocations which triggers the trashcan mechanism, |
| 71 | clearing the weakrefs can be delayed long after the target's refcount |
| 72 | has dropped to zero. In the meantime, code accessing the weakref will |
| 73 | be able to "see" the target object even though it is supposed to be |
| 74 | unreachable. See issue #16602. */ |
| 75 | |
| 76 | #define PyWeakref_GET_OBJECT(ref) \ |
| 77 | (Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \ |
| 78 | ? ((PyWeakReference *)(ref))->wr_object \ |
| 79 | : Py_None) |
| 80 | |
| 81 | |
| 82 | #ifdef __cplusplus |
| 83 | } |
| 84 | #endif |
| 85 | #endif /* !Py_WEAKREFOBJECT_H */ |