      </li>
<li class="listitem">
              An error occurs.
            </li>
</ul></div>
<p>
          This operation is implemented in terms of one or more calls to the next
          layer's <code class="computeroutput"><span class="identifier">async_write_some</span></code>
          functions, and is known as a <span class="emphasis"><em>composed operation</em></span>. The
          program must ensure that the stream performs no other write operations
          (such as <a class="link" href="asyn