SF 560736. Optimize list iteration by filling the tp_iter slot.

Lib/test/test_descrtut.py

@@ -202,6 +202,7 @@ Instead, you can get the same information from the list type:
      '__iadd__',
      '__imul__',
      '__init__',
+     '__iter__',
      '__le__',
      '__len__',
      '__lt__',

Objects/iterobject.c

@@ -68,25 +68,15 @@ iter_iternext(PyObject *iterator)
 	it = (seqiterobject *)iterator;
 	seq = it->it_seq;
 
-	if (PyList_CheckExact(seq)) {
-		PyObject *item;
-		if (it->it_index >= PyList_GET_SIZE(seq)) {
-			return NULL;
-		}
-		item = PyList_GET_ITEM(seq, it->it_index);
-		it->it_index++;
-		Py_INCREF(item);
-		return item;
-	}
 	if (PyTuple_CheckExact(seq)) {
-		PyObject *item;
-		if (it->it_index >= PyTuple_GET_SIZE(seq)) {
-			return NULL;
+		if (it->it_index < PyTuple_GET_SIZE(seq)) {
+			PyObject *item;
+			item = PyTuple_GET_ITEM(seq, it->it_index);
+			it->it_index++;
+			Py_INCREF(item);
+			return item;
 		}
-		item = PyTuple_GET_ITEM(seq, it->it_index);
-		it->it_index++;
-		Py_INCREF(item);
-		return item;
+		return NULL;
 	}
 	else {
 		PyObject *result = PySequence_ITEM(seq, it->it_index);

Objects/listobject.c

@@ -1682,6 +1682,8 @@ static char list_doc[] =
 "list() -> new list\n"
 "list(sequence) -> new list initialized from sequence's items";
 
+staticforward PyObject * list_iter(PyObject *seq);
+
 PyTypeObject PyList_Type = {
 	PyObject_HEAD_INIT(&PyType_Type)
 	0,
@@ -1710,7 +1712,7 @@ PyTypeObject PyList_Type = {
  	(inquiry)list_clear,			/* tp_clear */
 	list_richcompare,			/* tp_richcompare */
 	0,					/* tp_weaklistoffset */
-	0,					/* tp_iter */
+	list_iter,				/* tp_iter */
 	0,					/* tp_iternext */
 	list_methods,				/* tp_methods */
 	0,					/* tp_members */
@@ -1811,3 +1813,118 @@ static PyTypeObject immutable_list_type = {
 	0,					/* tp_init */
 	/* NOTE: This is *not* the standard list_type struct! */
 };
+
+
+/*********************** List Iterator **************************/
+
+typedef struct {
+        PyObject_HEAD
+        long      it_index;
+        PyObject *it_seq;
+} listiterobject;
+
+PyTypeObject PyListIter_Type;
+
+PyObject *
+list_iter(PyObject *seq)
+{
+        listiterobject *it;
+
+        if (!PyList_Check(seq)) {
+                PyErr_BadInternalCall();
+                return NULL;
+        }
+        it = PyObject_GC_New(listiterobject, &PyListIter_Type);
+        if (it == NULL)
+                return NULL;
+        it->it_index = 0;
+        Py_INCREF(seq);
+        it->it_seq = seq;
+        _PyObject_GC_TRACK(it);
+        return (PyObject *)it;
+}
+
+static void
+listiter_dealloc(listiterobject *it)
+{
+        _PyObject_GC_UNTRACK(it);
+        Py_DECREF(it->it_seq);
+        PyObject_GC_Del(it);
+}
+
+static int
+listiter_traverse(listiterobject *it, visitproc visit, void *arg)
+{
+        return visit(it->it_seq, arg);
+}
+
+
+static PyObject *
+listiter_getiter(PyObject *it)
+{
+        Py_INCREF(it);
+        return it;
+}
+
+static PyObject *
+listiter_next(PyObject *it)
+{
+        PyObject *seq;
+        PyObject *item;
+
+        assert(PyList_Check(it));
+        seq = ((listiterobject *)it)->it_seq;
+
+        if (((listiterobject *)it)->it_index < PyList_GET_SIZE(seq)) {
+		item = ((PyListObject *)(seq))->ob_item[((listiterobject *)it)->it_index++];
+                Py_INCREF(item);
+                return item;
+        }
+        return NULL;
+}
+
+static PyMethodDef listiter_methods[] = {
+        {"next",        (PyCFunction)listiter_next,     METH_NOARGS,
+         "it.next() -- get the next value, or raise StopIteration"},
+        {NULL,          NULL}           /* sentinel */
+};
+
+PyTypeObject PyListIter_Type = {
+        PyObject_HEAD_INIT(&PyType_Type)
+        0,                                      /* ob_size */
+        "listiterator",                         /* tp_name */
+        sizeof(listiterobject),                 /* tp_basicsize */
+        0,                                      /* tp_itemsize */
+        /* methods */
+        (destructor)listiter_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 */
+        0,                                      /* tp_call */
+        0,                                      /* tp_str */
+        PyObject_GenericGetAttr,                /* tp_getattro */
+        0,                                      /* tp_setattro */
+        0,                                      /* tp_as_buffer */
+        Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
+        0,                                      /* tp_doc */
+        (traverseproc)listiter_traverse,        /* tp_traverse */
+        0,                                      /* tp_clear */
+        0,                                      /* tp_richcompare */
+        0,                                      /* tp_weaklistoffset */
+        (getiterfunc)listiter_getiter,          /* tp_iter */
+        (iternextfunc)listiter_next,            /* tp_iternext */
+        listiter_methods,			/* tp_methods */
+        0,                                      /* tp_members */
+        0,                                      /* tp_getset */
+        0,                                      /* tp_base */
+        0,                                      /* tp_dict */
+        0,                                      /* tp_descr_get */
+        0,                                      /* tp_descr_set */
+};
+