Add a fast path (no iterator creation) for a common case for repeating deques of size 1
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index dbe44e1..3e2c69f 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -1211,6 +1211,7 @@
static PyObject *
deque_copy(PyObject *deque)
{
+ dequeobject *old_deque = (dequeobject *)deque;
if (Py_TYPE(deque) == &deque_type) {
dequeobject *new_deque;
PyObject *rv;
@@ -1218,8 +1219,14 @@
new_deque = (dequeobject *)deque_new(&deque_type, (PyObject *)NULL, (PyObject *)NULL);
if (new_deque == NULL)
return NULL;
- new_deque->maxlen = ((dequeobject *)deque)->maxlen;
- rv = deque_extend(new_deque, deque);
+ new_deque->maxlen = old_deque->maxlen;
+ /* Fast path for the deque_repeat() common case where len(deque) == 1 */
+ if (Py_SIZE(deque) == 1 && new_deque->maxlen != 0) {
+ PyObject *item = old_deque->leftblock->data[old_deque->leftindex];
+ rv = deque_append(new_deque, item);
+ } else {
+ rv = deque_extend(new_deque, deque);
+ }
if (rv != NULL) {
Py_DECREF(rv);
return (PyObject *)new_deque;
@@ -1227,11 +1234,11 @@
Py_DECREF(new_deque);
return NULL;
}
- if (((dequeobject *)deque)->maxlen == -1)
+ if (old_deque->maxlen == -1)
return PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "O", deque, NULL);
else
return PyObject_CallFunction((PyObject *)(Py_TYPE(deque)), "Oi",
- deque, ((dequeobject *)deque)->maxlen, NULL);
+ deque, old_deque->maxlen, NULL);
}
PyDoc_STRVAR(copy_doc, "Return a shallow copy of a deque.");