" title="Short-hand for flow::Error_code which is very common.">Error_code()</a></code> if non-null. This indicates 1 or more (<code>N</code>) bytes were placed at the start of the buffer, and <em>if</em> exactly 1 native handle handle was transmitted along with some subset of those <code>N</code> bytes, <em>then</em> it was successfully received into <code>*target_payload_hndl</code>; or else the fact there were exactly 0 such handles was successfully determined and reflected via <code>target_payload_hndl-