nsion()</span></tt>.</p>
<p>The function should return a <tt class="docutils literal"><span class="pre">std::shared_ptr&lt;torrent_plugin&gt;</span></tt> which
may or may not be 0. If it is a nullptr, the extension is simply ignored
for this torrent. If it is a valid pointer (to a class inheriting
<tt class="docutils literal">torrent_plugin</tt>), it will be associated with this torrent and callbacks
will be made on torrent events.</p>
<p>For more elaborate plugins which require <a class="reference external