 returned.  With textual data this can be detected by testing
       whether the last returned byte is <code class="literal">\n</code> or not.  (In a binary
       <code class="command">COPY</code>, actual parsing of the <code class="command">COPY</code> data format will be needed to make the
       equivalent determination.)
       The returned string is not null-terminated.  (If you want to add a
       terminating null, be sure to pass a <em class="parameter"><code>bufsize</code></em> one smaller
       