[Python-checkins] python/dist/src/Objects listobject.c,2.199,2.200

[arigo at users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Objects
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv10655

Modified Files:
	listobject.c 
Log Message:
Get rid of listextend_internal() and explain why the special case
'a.extend(a)' isn't so special anyway.



Index: listobject.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/listobject.c,v
retrieving revision 2.199
retrieving revision 2.200
diff -C2 -d -r2.199 -r2.200
*** listobject.c	18 Mar 2004 22:43:09 -0000	2.199
--- listobject.c	20 Mar 2004 22:19:23 -0000	2.200
***************
*** 648,701 ****
  }
  
- 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)
--- 648,651 ----
***************
*** 713,721 ****
  	*/
  	if (PyList_CheckExact(b) || PyTuple_CheckExact(b) || (PyObject *)self == b) {
  		b = PySequence_Fast(b, "argument must be iterable");
  		if (!b)
  			return NULL;
! 		if (listextend_internal(self, b) < 0)
  			return NULL;
  		Py_RETURN_NONE;
  	}
--- 663,695 ----
  	*/
  	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;
! 		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;
  	}