Function _IsWriteable

numpy/core/src/multiarray/common.c:131–185

NPY_NO_EXPORT npy_bool
_IsWriteable(PyArrayObject *ap)
{
    PyObject *base = PyArray_BASE(ap);
    Py_buffer view;

    /*
     * C-data wrapping arrays may not own their data while not having a base;
     * WRITEBACKIFCOPY arrays have a base, but do own their data.
     */
    if (base == NULL || PyArray_CHKFLAGS(ap, NPY_ARRAY_OWNDATA)) {
        /*
         * This is somewhat unsafe for directly wrapped non-writable C-arrays,
         * which do not know whether the memory area is writable or not and
         * do not own their data (but have no base).
         * It would be better if this returned PyArray_ISWRITEABLE(ap).
         * Since it is hard to deprecate, this is deprecated only on the Python
         * side, but not on in PyArray_UpdateFlags.
         */
        return NPY_TRUE;
    }

    /*
     * Get to the final base object.
     * If it is a writeable array, then return True if we can
     * find an array object or a writeable buffer object as
     * the final base object.
     */
    while (PyArray_Check(base)) {
        ap = (PyArrayObject *)base;
        base = PyArray_BASE(ap);

        if (PyArray_ISWRITEABLE(ap)) {
            /*
             * If any base is writeable, it must be OK to switch, note that
             * bases are typically collapsed to always point to the most
             * general one.
             */
            return NPY_TRUE;
        }

        if (base == NULL || PyArray_CHKFLAGS(ap, NPY_ARRAY_OWNDATA)) {
            /* there is no further base to test the writeable flag for */
            return NPY_FALSE;
        }
        assert(!PyArray_CHKFLAGS(ap, NPY_ARRAY_OWNDATA));
    }

    if (PyObject_GetBuffer(base, &view, PyBUF_WRITABLE|PyBUF_SIMPLE) < 0) {
        PyErr_Clear();
        return NPY_FALSE;
    }
    PyBuffer_Release(&view);
    return NPY_TRUE;
}


/**