Function PyArray_SetWritebackIfCopyBase

numpy/core/src/multiarray/arrayobject.c:108–146

NUMPY_API * * Precondition: 'arr' is a copy of 'base' (though possibly with different * strides, ordering, etc.). This function sets the WRITEBACKIFCOPY flag and the * ->base pointer on 'arr', call PyArray_ResolveWritebackIfCopy to copy any * changes back to 'base' before deallocating the array. * * Steals a reference to 'base'. * * Returns 0 on success, -1 on failure. */

 * Returns 0 on success, -1 on failure.
 */
NPY_NO_EXPORT int
PyArray_SetWritebackIfCopyBase(PyArrayObject *arr, PyArrayObject *base)
{
    if (base == NULL) {
        PyErr_SetString(PyExc_ValueError,
                  "Cannot WRITEBACKIFCOPY to NULL array");
        return -1;
    }
    if (PyArray_BASE(arr) != NULL) {
        PyErr_SetString(PyExc_ValueError,
                  "Cannot set array with existing base to WRITEBACKIFCOPY");
        goto fail;
    }
    if (PyArray_FailUnlessWriteable(base, "WRITEBACKIFCOPY base") < 0) {
        goto fail;
    }

    /*
     * Any writes to 'arr' will magically turn into writes to 'base', so we
     * should warn if necessary.
     */
    if (PyArray_FLAGS(base) & NPY_ARRAY_WARN_ON_WRITE) {
        PyArray_ENABLEFLAGS(arr, NPY_ARRAY_WARN_ON_WRITE);
    }

    /*
     * Unlike PyArray_SetBaseObject, we do not compress the chain of base
     * references.
     */
    ((PyArrayObject_fields *)arr)->base = (PyObject *)base;
    PyArray_ENABLEFLAGS(arr, NPY_ARRAY_WRITEBACKIFCOPY);
    PyArray_CLEARFLAGS(base, NPY_ARRAY_WRITEABLE);

    return 0;

  fail:
    Py_DECREF(base);
    return -1;
}

/*NUMPY_API
 * Sets the 'base' attribute of the array. This steals a reference