Function PyArray_SetBaseObject

numpy/core/src/multiarray/arrayobject.c:154–225

NUMPY_API * Sets the 'base' attribute of the array. This steals a reference * to 'obj'. * * Returns 0 on success, -1 on failure. */

 * Returns 0 on success, -1 on failure.
 */
NPY_NO_EXPORT int
PyArray_SetBaseObject(PyArrayObject *arr, PyObject *obj)
{
    if (obj == NULL) {
        PyErr_SetString(PyExc_ValueError,
                "Cannot set the NumPy array 'base' "
                "dependency to NULL after initialization");
        return -1;
    }
    /*
     * Allow the base to be set only once. Once the object which
     * owns the data is set, it doesn't make sense to change it.
     */
    if (PyArray_BASE(arr) != NULL) {
        Py_DECREF(obj);
        PyErr_SetString(PyExc_ValueError,
                "Cannot set the NumPy array 'base' "
                "dependency more than once");
        return -1;
    }

    /*
     * Don't allow infinite chains of views, always set the base
     * to the first owner of the data.
     * That is, either the first object which isn't an array,
     * or the first object which owns its own data.
     */

    while (PyArray_Check(obj) && (PyObject *)arr != obj) {
        PyArrayObject *obj_arr = (PyArrayObject *)obj;
        PyObject *tmp;

        /* Propagate WARN_ON_WRITE through views. */
        if (PyArray_FLAGS(obj_arr) & NPY_ARRAY_WARN_ON_WRITE) {
            PyArray_ENABLEFLAGS(arr, NPY_ARRAY_WARN_ON_WRITE);
        }

        /* If this array owns its own data, stop collapsing */
        if (PyArray_CHKFLAGS(obj_arr, NPY_ARRAY_OWNDATA)) {
            break;
        }

        tmp = PyArray_BASE(obj_arr);
        /* If there's no base, stop collapsing */
        if (tmp == NULL) {
            break;
        }
        /* Stop the collapse new base when the would not be of the same
         * type (i.e. different subclass).
         */
        if (Py_TYPE(tmp) != Py_TYPE(arr)) {
            break;
        }


        Py_INCREF(tmp);
        Py_DECREF(obj);
        obj = tmp;