Function PyArray_MapIterArrayCopyIfOverlap

numpy/core/src/multiarray/mapping.c:3321–3408

NUMPY_API * * Same as PyArray_MapIterArray, but: * * If copy_if_overlap != 0, check if `a` has memory overlap with any of the * arrays in `index` and with `extra_op`. If yes, make copies as appropriate * to avoid problems if `a` is modified during the iteration. * `iter->array` may contain a copied array (WRITEBACKIFCOPY set). */

 * `iter->array` may contain a copied array (WRITEBACKIFCOPY set).
 */
NPY_NO_EXPORT PyObject *
PyArray_MapIterArrayCopyIfOverlap(PyArrayObject * a, PyObject * index,
                                  int copy_if_overlap, PyArrayObject *extra_op)
{
    PyArrayMapIterObject * mit = NULL;
    PyArrayObject *subspace = NULL;
    npy_index_info indices[NPY_MAXDIMS * 2 + 1];
    int i, index_num, ndim, fancy_ndim, index_type;
    PyArrayObject *a_copy = NULL;

    index_type = prepare_index(a, index, indices, &index_num,
                               &ndim, &fancy_ndim, 0);

    if (index_type < 0) {
        return NULL;
    }

    if (copy_if_overlap && index_has_memory_overlap(a, index_type, indices,
                                                    index_num,
                                                    (PyObject *)extra_op)) {
        /* Make a copy of the input array */
        a_copy = (PyArrayObject *)PyArray_NewLikeArray(a, NPY_ANYORDER,
                                                       NULL, 0);
        if (a_copy == NULL) {
            goto fail;
        }

        if (PyArray_CopyInto(a_copy, a) != 0) {
            goto fail;
        }

        Py_INCREF(a);
        if (PyArray_SetWritebackIfCopyBase(a_copy, a) < 0) {
            goto fail;
        }

        a = a_copy;
    }

    /* If it is not a pure fancy index, need to get the subspace */
    if (index_type != HAS_FANCY) {
        if (get_view_from_index(a, &subspace, indices, index_num, 1) < 0) {
            goto fail;
        }
    }

    mit = (PyArrayMapIterObject *)PyArray_MapIterNew(indices, index_num,
                                                     index_type, ndim,
                                                     fancy_ndim,
                                                     a, subspace, 0,
                                                     NPY_ITER_READWRITE,
                                                     0, NULL, NULL);
    if (mit == NULL) {
        goto fail;
    }

    /* Required for backward compatibility */
    mit->ait = (PyArrayIterObject *)PyArray_IterNew((PyObject *)a);