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@oyvindio
Created March 28, 2011 14:26
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/* a[ilow:ihigh] = v if v != NULL.
* del a[ilow:ihigh] if v == NULL.
*
* Special speed gimmick: when v is NULL and ihigh - ilow <= 8, it's
* guaranteed the call cannot fail.
*/
static int
list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
{
/* Because [X]DECREF can recursively invoke list operations on
this list, we must postpone all [X]DECREF activity until
after the list is back in its canonical shape. Therefore
we must allocate an additional array, 'recycle', into which
we temporarily copy the items that are deleted from the
list. :-( */
PyObject *recycle_on_stack[8];
PyObject **recycle = recycle_on_stack; /* will allocate more if needed */
PyObject **item;
PyObject **vitem = NULL;
PyObject *v_as_SF = NULL; /* PySequence_Fast(v) */
Py_ssize_t n; /* # of elements in replacement list */
Py_ssize_t norig; /* # of elements in list getting replaced */
Py_ssize_t d; /* Change in size */
Py_ssize_t k;
size_t s;
int result = -1; /* guilty until proved innocent */
#define b ((PyListObject *)v)
if (v == NULL)
n = 0;
else {
if (a == b) {
/* Special case "a[i:j] = a" -- copy b first */
v = list_slice(b, 0, Py_SIZE(b));
if (v == NULL)
return result;
result = list_ass_slice(a, ilow, ihigh, v);
Py_DECREF(v);
return result;
}
v_as_SF = PySequence_Fast(v, "can only assign an iterable");
if(v_as_SF == NULL)
goto Error;
n = PySequence_Fast_GET_SIZE(v_as_SF);
vitem = PySequence_Fast_ITEMS(v_as_SF);
}
if (ilow < 0)
ilow = 0;
else if (ilow > Py_SIZE(a))
ilow = Py_SIZE(a);
if (ihigh < ilow)
ihigh = ilow;
else if (ihigh > Py_SIZE(a))
ihigh = Py_SIZE(a);
norig = ihigh - ilow;
assert(norig >= 0);
d = n - norig;
if (Py_SIZE(a) + d == 0) {
Py_XDECREF(v_as_SF);
return list_clear(a);
}
item = a->ob_item;
/* recycle the items that we are about to remove */
s = norig * sizeof(PyObject *);
if (s > sizeof(recycle_on_stack)) {
recycle = (PyObject **)PyMem_MALLOC(s);
if (recycle == NULL) {
PyErr_NoMemory();
goto Error;
}
}
memcpy(recycle, &item[ilow], s);
if (d < 0) { /* Delete -d items */
memmove(&item[ihigh+d], &item[ihigh],
(Py_SIZE(a) - ihigh)*sizeof(PyObject *));
list_resize(a, Py_SIZE(a) + d);
item = a->ob_item;
}
else if (d > 0) { /* Insert d items */
k = Py_SIZE(a);
if (list_resize(a, k+d) < 0)
goto Error;
item = a->ob_item;
memmove(&item[ihigh+d], &item[ihigh],
(k - ihigh)*sizeof(PyObject *));
}
for (k = 0; k < n; k++, ilow++) {
PyObject *w = vitem[k];
Py_XINCREF(w);
item[ilow] = w;
}
for (k = norig - 1; k >= 0; --k)
Py_XDECREF(recycle[k]);
result = 0;
Error:
if (recycle != recycle_on_stack)
PyMem_FREE(recycle);
Py_XDECREF(v_as_SF);
return result;
#undef b
}
int
PyList_SetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
{
if (!PyList_Check(a)) {
PyErr_BadInternalCall();
return -1;
}
return list_ass_slice((PyListObject *)a, ilow, ihigh, v);
}
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