 message body for serialization.
                </p>
              </td>
</tr>
<tr>
<td>
<pre class="programlisting"><span class="identifier">B</span><span class="special">::</span><span class="identifier">size</span><span class="special">(</span>
  <span class="identifier">B</span><span class="special">::</span><span class="identifier">value_type</span> <span class="identifier">body</span><span class="special">)</span>
</pre>
              </td>
<td>
                <p>
                  <code class="comp