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Add a fast path (no iterator creation) for a common case for repeating deques of size 1

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Raymond Hettinger 2015-09-19 09:05:42 -07:00
parent 026977717e
commit aed8830af3
2 changed files with 20 additions and 4 deletions
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15
Modules/_collectionsmodule.c
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@ -1211,6 +1211,7 @@ deque_traverse(dequeobject *deque, visitproc visit, void *arg)
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 @@ deque_copy(PyObject *deque)
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 @@ deque_copy(PyObject *deque)
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.");