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Get rid of listextend_internal() and explain why the special case 

'a.extend(a)' isn't so special anyway.
This commit is contained in:
Armin Rigo 2004-03-20 22:19:23 +00:00
parent 70ec0b42b5
commit 70d172dda4
1 changed files with 25 additions and 51 deletions
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76
Objects/listobject.c
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@ -647,56 +647,6 @@ listappend(PyListObject *self, PyObject *v)
return ins(self, (int) self->ob_size, v);
}
static int
listextend_internal(PyListObject *self, PyObject *b)
{
int selflen = PyList_GET_SIZE(self);
int blen;
register int i;
PyObject **src, **dest;
blen = PyObject_Size(b);
if (blen == 0) {
/* short circuit when b is empty */
Py_DECREF(b);
return 0;
}
if (self == (PyListObject*)b) {
/* as in list_ass_slice() we must special case the
* situation: a.extend(a)
*
* XXX: I think this way ought to be faster than using
* list_slice() the way list_ass_slice() does.
*/
Py_DECREF(b);
b = PyList_New(selflen);
if (!b)
return -1;
for (i = 0; i < selflen; i++) {
PyObject *o = PyList_GET_ITEM(self, i);
Py_INCREF(o);
PyList_SET_ITEM(b, i, o);
}
}
if (list_resize(self, selflen + blen) == -1) {
Py_DECREF(b);
return -1;
}
/* populate the end of self with b's items */
src = PySequence_Fast_ITEMS(b);
dest = self->ob_item + selflen;
for (i = 0; i < blen; i++) {
PyObject *o = src[i];
Py_INCREF(o);
dest[i] = o;
}
Py_DECREF(b);
return 0;
}
static PyObject *
listextend(PyListObject *self, PyObject *b)
{
@ -712,11 +662,35 @@ listextend(PyListObject *self, PyObject *b)
2) extending self to self requires making a copy first
*/
if (PyList_CheckExact(b) || PyTuple_CheckExact(b) || (PyObject *)self == b) {
PyObject **src, **dest;
b = PySequence_Fast(b, "argument must be iterable");
if (!b)
return NULL;
if (listextend_internal(self, b) < 0)
n = PySequence_Fast_GET_SIZE(b);
if (n == 0) {
/* short circuit when b is empty */
Py_DECREF(b);
Py_RETURN_NONE;
}
m = self->ob_size;
if (list_resize(self, m + n) == -1) {
Py_DECREF(b);
return NULL;
}
/* note that we may still have self == b here for the
* situation a.extend(a), but the following code works
* in that case too. Just make sure to resize self
* before calling PySequence_Fast_ITEMS.
*/
/* populate the end of self with b's items */
src = PySequence_Fast_ITEMS(b);
dest = self->ob_item + m;
for (i = 0; i < n; i++) {
PyObject *o = src[i];
Py_INCREF(o);
dest[i] = o;
}
Py_DECREF(b);
Py_RETURN_NONE;
}