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Add a spacing saving heuristic to deque's extend methods

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Raymond Hettinger 2013-07-09 00:13:21 -07:00
parent bbf8ce5b87
commit d9c116ca40
2 changed files with 18 additions and 2 deletions
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16
Modules/_collectionsmodule.c
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@ -332,6 +332,14 @@ deque_extend(dequeobject *deque, PyObject *iterable)
return result;
}
/* Space saving heuristic. Start filling from the left */
if (Py_SIZE(deque) == 0) {
assert(deque->leftblock == deque->rightblock);
assert(deque->leftindex == deque->rightindex+1);
deque->leftindex = 1;
deque->rightindex = 0;
}
it = PyObject_GetIter(iterable);
if (it == NULL)
return NULL;
@ -385,6 +393,14 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
return result;
}
/* Space saving heuristic. Start filling from the right */
if (Py_SIZE(deque) == 0) {
assert(deque->leftblock == deque->rightblock);
assert(deque->leftindex == deque->rightindex+1);
deque->leftindex = BLOCKLEN - 1;
deque->rightindex = BLOCKLEN - 2;
}
it = PyObject_GetIter(iterable);
if (it == NULL)
return NULL;