Use a PyDictObject again for the array type cache; retrieving items

from the WeakValueDictionary was slower by nearly a factor of 3.

To avoid leaks, weakref proxies for the array types are put into the
cache dict, with weakref callbacks that removes the entries when the
type goes away.

Modules/_ctypes/_ctypes.c

@@ -127,12 +127,134 @@ bytes(cdata)
 
 PyObject *PyExc_ArgError;
 static PyTypeObject Simple_Type;
-PyObject *array_types_cache;
 
 char *conversion_mode_encoding = NULL;
 char *conversion_mode_errors = NULL;
 
 
+/****************************************************************/
+
+typedef struct {
+	PyObject_HEAD
+	PyObject *key;
+	PyObject *dict;
+} DictRemoverObject;
+
+static void
+_DictRemover_dealloc(PyObject *_self)
+{
+	DictRemoverObject *self = (DictRemoverObject *)_self;
+	Py_XDECREF(self->key);
+	Py_XDECREF(self->dict);
+	Py_TYPE(self)->tp_free(_self);
+}
+
+static PyObject *
+_DictRemover_call(PyObject *_self, PyObject *args, PyObject *kw)
+{
+	DictRemoverObject *self = (DictRemoverObject *)_self;
+	if (self->key && self->dict) {
+		if (-1 == PyDict_DelItem(self->dict, self->key))
+			/* XXX Error context */
+			PyErr_WriteUnraisable(Py_None);
+		Py_DECREF(self->key);
+		self->key = NULL;
+		Py_DECREF(self->dict);
+		self->dict = NULL;
+	}
+	Py_INCREF(Py_None);
+	return Py_None;
+}
+
+static PyTypeObject DictRemover_Type = {
+	PyVarObject_HEAD_INIT(NULL, 0)
+	"_ctypes.DictRemover",			/* tp_name */
+	sizeof(DictRemoverObject),		/* tp_basicsize */
+	0,					/* tp_itemsize */
+	_DictRemover_dealloc,			/* tp_dealloc */
+	0,					/* tp_print */
+	0,					/* tp_getattr */
+	0,					/* tp_setattr */
+	0,					/* tp_compare */
+	0,			       		/* tp_repr */
+	0,					/* tp_as_number */
+	0,					/* tp_as_sequence */
+	0,					/* tp_as_mapping */
+	0,					/* tp_hash */
+	_DictRemover_call,			/* tp_call */
+	0,					/* tp_str */
+	0,					/* tp_getattro */
+	0,					/* tp_setattro */
+	0,					/* tp_as_buffer */
+/* XXX should participate in GC? */
+	Py_TPFLAGS_DEFAULT,			/* tp_flags */
+	"deletes a key from a dictionary",	/* tp_doc */
+	0,					/* tp_traverse */
+	0,					/* tp_clear */
+	0,					/* tp_richcompare */
+	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 */
+	0,					/* tp_init */
+	0,					/* tp_alloc */
+	PyType_GenericNew,			/* tp_new */
+	0,					/* tp_free */
+};
+
+int
+PyDict_SetItemProxy(PyObject *dict, PyObject *key, PyObject *item)
+{
+	PyObject *obj;
+	DictRemoverObject *remover;
+	PyObject *proxy;
+	int result;
+
+	obj = PyObject_CallObject((PyObject *)&DictRemover_Type, NULL);
+	if (obj == NULL)
+		return -1;
+
+	remover = (DictRemoverObject *)obj;
+	assert(remover->key == NULL);
+	assert(remover->dict == NULL);
+	Py_INCREF(key);
+	remover->key = key;
+	Py_INCREF(dict);
+	remover->dict = dict;
+
+	proxy = PyWeakref_NewProxy(item, obj);
+	Py_DECREF(obj);
+	if (proxy == NULL)
+		return -1;
+
+	result = PyDict_SetItem(dict, key, proxy);
+	Py_DECREF(proxy);
+	return result;
+}
+
+PyObject *
+PyDict_GetItemProxy(PyObject *dict, PyObject *key)
+{
+	PyObject *result;
+	PyObject *item = PyDict_GetItem(dict, key);
+
+	if (item == NULL)
+		return NULL;
+	if (!PyWeakref_CheckProxy(item))
+		return item;
+	result = PyWeakref_GET_OBJECT(item);
+	if (result == Py_None)
+		return NULL;
+	return result;
+}
+
 /******************************************************************/
 /*
   StructType_Type - a meta type/class.  Creating a new class using this one as
@@ -4102,10 +4224,16 @@ PyTypeObject Array_Type = {
 PyObject *
 CreateArrayType(PyObject *itemtype, Py_ssize_t length)
 {
+	static PyObject *cache;
 	PyObject *key;
 	PyObject *result;
 	char name[256];
 
+	if (cache == NULL) {
+		cache = PyDict_New();
+		if (cache == NULL)
+			return NULL;
+	}
 #if (PY_VERSION_HEX < 0x02050000)
 	key = Py_BuildValue("(Oi)", itemtype, length);
 #else
@@ -4113,12 +4241,12 @@ CreateArrayType(PyObject *itemtype, Py_ssize_t length)
 #endif
 	if (!key)
 		return NULL;
-	result = PyObject_GetItem(array_types_cache, key);
+	result = PyDict_GetItemProxy(cache, key);
 	if (result) {
+		Py_INCREF(result);
 		Py_DECREF(key);
 		return result;
-	} else
+	}
-		PyErr_Clear();
 
 	if (!PyType_Check(itemtype)) {
 		PyErr_SetString(PyExc_TypeError,
@@ -4148,7 +4276,7 @@ CreateArrayType(PyObject *itemtype, Py_ssize_t length)
 		);
 	if (!result)
 		return NULL;
-	if (-1 == PyObject_SetItem(array_types_cache, key, result)) {
+	if (-1 == PyDict_SetItemProxy(cache, key, result)) {
 		Py_DECREF(key);
 		Py_DECREF(result);
 		return NULL;
@@ -4965,7 +5093,6 @@ PyMODINIT_FUNC
 init_ctypes(void)
 {
 	PyObject *m;
-	PyObject *weakref;
 
 /* Note:
    ob_type is the metatype (the 'type'), defaults to PyType_Type,
@@ -4978,16 +5105,6 @@ init_ctypes(void)
 	if (!m)
 		return;
 
-	weakref = PyImport_ImportModule("weakref");
-	if (weakref == NULL)
-		return;
-	array_types_cache = PyObject_CallMethod(weakref,
-						"WeakValueDictionary",
-						NULL);
-	if (array_types_cache == NULL)
-		return;
-	Py_DECREF(weakref);
-
 	if (PyType_Ready(&PyCArg_Type) < 0)
 		return;
 
@@ -5083,6 +5200,10 @@ init_ctypes(void)
 	 * Other stuff
 	 */
 
+	DictRemover_Type.tp_new = PyType_GenericNew;
+	if (PyType_Ready(&DictRemover_Type) < 0)
+		return;
+
 #ifdef MS_WIN32
 	if (create_comerror() < 0)
 		return;