vcap_key_field_set
vcap_key_field_set(data, offset, length, value, mask);
vcap_key_field_set(data, offset, n, value, mask);
vcap_key_field_set(data, offset, length, port->value, port->mask);
vcap_key_field_set(data, offset, length, value, msk);
vcap_key_field_set(&data, i, min(32u, count - i), 0, 0);