Function time_to_string_resolve_descriptors

numpy/core/src/multiarray/datetime.c:3942–3990

In the current setup both strings and unicode casts support all outputs */

/* In the current setup both strings and unicode casts support all outputs */
static NPY_CASTING
time_to_string_resolve_descriptors(
        PyArrayMethodObject *NPY_UNUSED(self),
        PyArray_DTypeMeta *dtypes[2],
        PyArray_Descr **given_descrs,
        PyArray_Descr **loop_descrs,
        npy_intp *NPY_UNUSED(view_offset))
{
    if (given_descrs[1] != NULL && dtypes[0]->type_num == NPY_DATETIME) {
        /*
         * At the time of writing, NumPy does not check the length here,
         * but will error if filling fails.
         */
        Py_INCREF(given_descrs[1]);
        loop_descrs[1] = given_descrs[1];
    }
    else {
        /* Find the correct string length, possibly based on the unit */
        int size;
        if (given_descrs[0]->type_num == NPY_DATETIME) {
            PyArray_DatetimeMetaData *meta = get_datetime_metadata_from_dtype(given_descrs[0]);
            assert(meta != NULL);
            size = get_datetime_iso_8601_strlen(0, meta->base);
        }
        else {
            /*
             * This is arguably missing space for the unit, e.g. for:
             * `np.timedelta64(1231234342124, 'ms')`
             */
            size = 21;
        }
        if (dtypes[1]->type_num == NPY_UNICODE) {
            size *= 4;
        }
        loop_descrs[1] = PyArray_DescrNewFromType(dtypes[1]->type_num);
        if (loop_descrs[1] == NULL) {
            return -1;
        }
        loop_descrs[1]->elsize = size;
    }

    loop_descrs[0] = NPY_DT_CALL_ensure_canonical(given_descrs[0]);
    if (loop_descrs[0] == NULL) {
        Py_DECREF(loop_descrs[1]);
        return -1;
    }

    return NPY_UNSAFE_CASTING;
}

static int
datetime_to_string_get_loop(