bpo-27575: port set intersection logic into dictview intersection (GH-7696)
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index f168ad5..fec3a87 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -4169,24 +4169,97 @@
return result;
}
-PyObject*
+static int
+dictitems_contains(_PyDictViewObject *dv, PyObject *obj);
+
+PyObject *
_PyDictView_Intersect(PyObject* self, PyObject *other)
{
- PyObject *result = PySet_New(self);
+ PyObject *result;
+ PyObject *it;
+ PyObject *key;
+ Py_ssize_t len_self;
+ int rv;
+ int (*dict_contains)(_PyDictViewObject *, PyObject *);
PyObject *tmp;
- _Py_IDENTIFIER(intersection_update);
+ /* Python interpreter swaps parameters when dict view
+ is on right side of & */
+ if (!PyDictViewSet_Check(self)) {
+ PyObject *tmp = other;
+ other = self;
+ self = tmp;
+ }
+
+ len_self = dictview_len((_PyDictViewObject *)self);
+
+ /* if other is a set and self is smaller than other,
+ reuse set intersection logic */
+ if (Py_TYPE(other) == &PySet_Type && len_self <= PyObject_Size(other)) {
+ _Py_IDENTIFIER(intersection);
+ return _PyObject_CallMethodIdObjArgs(other, &PyId_intersection, self, NULL);
+ }
+
+ /* if other is another dict view, and it is bigger than self,
+ swap them */
+ if (PyDictViewSet_Check(other)) {
+ Py_ssize_t len_other = dictview_len((_PyDictViewObject *)other);
+ if (len_other > len_self) {
+ PyObject *tmp = other;
+ other = self;
+ self = tmp;
+ }
+ }
+
+ /* at this point, two things should be true
+ 1. self is a dictview
+ 2. if other is a dictview then it is smaller than self */
+ result = PySet_New(NULL);
if (result == NULL)
return NULL;
+ it = PyObject_GetIter(other);
+
+ _Py_IDENTIFIER(intersection_update);
tmp = _PyObject_CallMethodIdOneArg(result, &PyId_intersection_update, other);
if (tmp == NULL) {
Py_DECREF(result);
return NULL;
}
-
Py_DECREF(tmp);
+
+ if (PyDictKeys_Check(self)) {
+ dict_contains = dictkeys_contains;
+ }
+ /* else PyDictItems_Check(self) */
+ else {
+ dict_contains = dictitems_contains;
+ }
+
+ while ((key = PyIter_Next(it)) != NULL) {
+ rv = dict_contains((_PyDictViewObject *)self, key);
+ if (rv < 0) {
+ goto error;
+ }
+ if (rv) {
+ if (PySet_Add(result, key)) {
+ goto error;
+ }
+ }
+ Py_DECREF(key);
+ }
+ Py_DECREF(it);
+ if (PyErr_Occurred()) {
+ Py_DECREF(result);
+ return NULL;
+ }
return result;
+
+error:
+ Py_DECREF(it);
+ Py_DECREF(result);
+ Py_DECREF(key);
+ return NULL;
}
static PyObject*