Make weak references subclassable:
- weakref.ref and weakref.ReferenceType will become aliases for each
other
- weakref.ref will be a modern, new-style class with proper __new__
and __init__ methods
- weakref.WeakValueDictionary will have a lighter memory footprint,
using a new weakref.ref subclass to associate the key with the
value, allowing us to have only a single object of overhead for each
dictionary entry (currently, there are 3 objects of overhead per
entry: a weakref to the value, a weakref to the dictionary, and a
function object used as a weakref callback; the weakref to the
dictionary could be avoided without this change)
- a new macro, PyWeakref_CheckRefExact(), will be added
- PyWeakref_CheckRef() will check for subclasses of weakref.ref
This closes SF patch #983019.
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 575a928..572c224 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -19,6 +19,15 @@
}
+static void
+init_weakref(PyWeakReference *self, PyObject *ob, PyObject *callback)
+{
+ self->hash = -1;
+ self->wr_object = ob;
+ Py_XINCREF(callback);
+ self->wr_callback = callback;
+}
+
static PyWeakReference *
new_weakref(PyObject *ob, PyObject *callback)
{
@@ -26,10 +35,7 @@
result = PyObject_GC_New(PyWeakReference, &_PyWeakref_RefType);
if (result) {
- result->hash = -1;
- result->wr_object = ob;
- Py_XINCREF(callback);
- result->wr_callback = callback;
+ init_weakref(result, ob, callback);
PyObject_GC_Track(result);
}
return result;
@@ -92,11 +98,11 @@
}
static void
-weakref_dealloc(PyWeakReference *self)
+weakref_dealloc(PyObject *self)
{
- PyObject_GC_UnTrack((PyObject *)self);
- clear_weakref(self);
- PyObject_GC_Del(self);
+ PyObject_GC_UnTrack(self);
+ clear_weakref((PyWeakReference *) self);
+ self->ob_type->tp_free(self);
}
@@ -193,6 +199,134 @@
PyWeakref_GET_OBJECT(other), op);
}
+/* Given the head of an object's list of weak references, extract the
+ * two callback-less refs (ref and proxy). Used to determine if the
+ * shared references exist and to determine the back link for newly
+ * inserted references.
+ */
+static void
+get_basic_refs(PyWeakReference *head,
+ PyWeakReference **refp, PyWeakReference **proxyp)
+{
+ *refp = NULL;
+ *proxyp = NULL;
+
+ if (head != NULL && head->wr_callback == NULL) {
+ /* We need to be careful that the "basic refs" aren't
+ subclasses of the main types. That complicates this a
+ little. */
+ if (PyWeakref_CheckRefExact(head)) {
+ *refp = head;
+ head = head->wr_next;
+ }
+ if (head != NULL
+ && head->wr_callback == NULL
+ && PyWeakref_CheckProxy(head)) {
+ *proxyp = head;
+ /* head = head->wr_next; */
+ }
+ }
+}
+
+/* Insert 'newref' in the list after 'prev'. Both must be non-NULL. */
+static void
+insert_after(PyWeakReference *newref, PyWeakReference *prev)
+{
+ newref->wr_prev = prev;
+ newref->wr_next = prev->wr_next;
+ if (prev->wr_next != NULL)
+ prev->wr_next->wr_prev = newref;
+ prev->wr_next = newref;
+}
+
+/* Insert 'newref' at the head of the list; 'list' points to the variable
+ * that stores the head.
+ */
+static void
+insert_head(PyWeakReference *newref, PyWeakReference **list)
+{
+ PyWeakReference *next = *list;
+
+ newref->wr_prev = NULL;
+ newref->wr_next = next;
+ if (next != NULL)
+ next->wr_prev = newref;
+ *list = newref;
+}
+
+static int
+parse_weakref_init_args(char *funcname, PyObject *args, PyObject *kwargs,
+ PyObject **obp, PyObject **callbackp)
+{
+ /* XXX Should check that kwargs == NULL or is empty. */
+ return PyArg_UnpackTuple(args, funcname, 1, 2, obp, callbackp);
+}
+
+static PyObject *
+weakref___new__(PyTypeObject *type, PyObject *args, PyObject *kwargs)
+{
+ PyWeakReference *self = NULL;
+ PyObject *ob, *callback = NULL;
+
+ if (parse_weakref_init_args("__new__", args, kwargs, &ob, &callback)) {
+ PyWeakReference *ref, *proxy;
+ PyWeakReference **list;
+
+ if (!PyType_SUPPORTS_WEAKREFS(ob->ob_type)) {
+ PyErr_Format(PyExc_TypeError,
+ "cannot create weak reference to '%s' object",
+ ob->ob_type->tp_name);
+ return NULL;
+ }
+ if (callback == Py_None)
+ callback = NULL;
+ list = GET_WEAKREFS_LISTPTR(ob);
+ get_basic_refs(*list, &ref, &proxy);
+ if (callback == NULL && type == &_PyWeakref_RefType) {
+ if (ref != NULL) {
+ /* We can re-use an existing reference. */
+ Py_INCREF(ref);
+ return (PyObject *)ref;
+ }
+ }
+ /* We have to create a new reference. */
+ /* Note: the tp_alloc() can trigger cyclic GC, so the weakref
+ list on ob can be mutated. This means that the ref and
+ proxy pointers we got back earlier may have been collected,
+ so we need to compute these values again before we use
+ them. */
+ self = (PyWeakReference *) (type->tp_alloc(type, 0));
+ if (self != NULL) {
+ init_weakref(self, ob, callback);
+ if (callback == NULL && type == &_PyWeakref_RefType) {
+ insert_head(self, list);
+ }
+ else {
+ PyWeakReference *prev;
+
+ get_basic_refs(*list, &ref, &proxy);
+ prev = (proxy == NULL) ? ref : proxy;
+ if (prev == NULL)
+ insert_head(self, list);
+ else
+ insert_after(self, prev);
+ }
+ }
+ }
+ return (PyObject *)self;
+}
+
+static int
+weakref___init__(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+ PyObject *tmp;
+
+ if (parse_weakref_init_args("__init__", args, kwargs, &tmp, &tmp))
+ return 0;
+ else
+ return 1;
+}
+
PyTypeObject
_PyWeakref_RefType = {
@@ -201,7 +335,7 @@
"weakref",
sizeof(PyWeakReference),
0,
- (destructor)weakref_dealloc,/*tp_dealloc*/
+ weakref_dealloc, /*tp_dealloc*/
0, /*tp_print*/
0, /*tp_getattr*/
0, /*tp_setattr*/
@@ -210,18 +344,33 @@
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
- (hashfunc)weakref_hash, /*tp_hash*/
+ (hashfunc)weakref_hash, /*tp_hash*/
(ternaryfunc)weakref_call, /*tp_call*/
0, /*tp_str*/
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
- Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_RICHCOMPARE,
+ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_RICHCOMPARE
+ | Py_TPFLAGS_BASETYPE, /*tp_flags*/
0, /*tp_doc*/
(traverseproc)gc_traverse, /*tp_traverse*/
(inquiry)gc_clear, /*tp_clear*/
(richcmpfunc)weakref_richcompare, /*tp_richcompare*/
- 0, /*tp_weaklistoffset*/
+ 0, /*tp_weaklistoffset*/
+ 0, /*tp_iter*/
+ 0, /*tp_iternext*/
+ 0, /*tp_methods*/
+ 0, /*tp_members*/
+ 0, /*tp_getset*/
+ 0, /*tp_base*/
+ 0, /*tp_dict*/
+ 0, /*tp_descr_get*/
+ 0, /*tp_descr_set*/
+ 0, /*tp_dictoffset*/
+ (initproc)weakref___init__, /*tp_init*/
+ PyType_GenericAlloc, /*tp_alloc*/
+ weakref___new__, /*tp_new*/
+ PyObject_GC_Del, /*tp_free*/
};
@@ -363,6 +512,15 @@
return 1;
}
+static void
+proxy_dealloc(PyWeakReference *self)
+{
+ if (self->wr_callback != NULL)
+ PyObject_GC_UnTrack((PyObject *)self);
+ clear_weakref(self);
+ PyObject_GC_Del(self);
+}
+
/* sequence slots */
static PyObject *
@@ -496,7 +654,7 @@
sizeof(PyWeakReference),
0,
/* methods */
- (destructor)weakref_dealloc, /* tp_dealloc */
+ (destructor)proxy_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
@@ -531,7 +689,7 @@
sizeof(PyWeakReference),
0,
/* methods */
- (destructor)weakref_dealloc, /* tp_dealloc */
+ (destructor)proxy_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
@@ -558,56 +716,6 @@
};
-/* Given the head of an object's list of weak references, extract the
- * two callback-less refs (ref and proxy). Used to determine if the
- * shared references exist and to determine the back link for newly
- * inserted references.
- */
-static void
-get_basic_refs(PyWeakReference *head,
- PyWeakReference **refp, PyWeakReference **proxyp)
-{
- *refp = NULL;
- *proxyp = NULL;
-
- if (head != NULL && head->wr_callback == NULL) {
- if (head->ob_type == &_PyWeakref_RefType) {
- *refp = head;
- head = head->wr_next;
- }
- if (head != NULL && head->wr_callback == NULL) {
- *proxyp = head;
- head = head->wr_next;
- }
- }
-}
-
-/* Insert 'newref' in the list after 'prev'. Both must be non-NULL. */
-static void
-insert_after(PyWeakReference *newref, PyWeakReference *prev)
-{
- newref->wr_prev = prev;
- newref->wr_next = prev->wr_next;
- if (prev->wr_next != NULL)
- prev->wr_next->wr_prev = newref;
- prev->wr_next = newref;
-}
-
-/* Insert 'newref' at the head of the list; 'list' points to the variable
- * that stores the head.
- */
-static void
-insert_head(PyWeakReference *newref, PyWeakReference **list)
-{
- PyWeakReference *next = *list;
-
- newref->wr_prev = NULL;
- newref->wr_next = next;
- if (next != NULL)
- next->wr_prev = newref;
- *list = newref;
-}
-
PyObject *
PyWeakref_NewRef(PyObject *ob, PyObject *callback)
@@ -769,8 +877,10 @@
current->wr_callback = NULL;
clear_weakref(current);
- handle_callback(current, callback);
- Py_DECREF(callback);
+ if (callback != NULL) {
+ handle_callback(current, callback);
+ Py_DECREF(callback);
+ }
}
else {
PyObject *tuple = PyTuple_New(count * 2);
@@ -787,10 +897,12 @@
current = next;
}
for (i = 0; i < count; ++i) {
- PyObject *current = PyTuple_GET_ITEM(tuple, i * 2);
PyObject *callback = PyTuple_GET_ITEM(tuple, i * 2 + 1);
- handle_callback((PyWeakReference *)current, callback);
+ if (callback != NULL) {
+ PyObject *current = PyTuple_GET_ITEM(tuple, i * 2);
+ handle_callback((PyWeakReference *)current, callback);
+ }
}
Py_DECREF(tuple);
}