add_extension on torrent_handle, to add an extension on an already running torrent

include/libtorrent/torrent.hpp

@@ -128,6 +128,8 @@ namespace libtorrent
 
 #ifndef TORRENT_DISABLE_EXTENSIONS
 		void add_extension(boost::shared_ptr<torrent_plugin>);
+		void add_extension(boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> const& ext
+			, void* userdata);
 #endif
 
 		// this is called when the torrent has metadata.

include/libtorrent/torrent_handle.hpp

@@ -64,6 +64,8 @@ namespace libtorrent
 		struct checker_impl;
 	}
 
+	struct torrent_plugin;
+
 	struct TORRENT_EXPORT duplicate_torrent: std::exception
 	{
 		virtual const char* what() const throw()
@@ -279,6 +281,11 @@ namespace libtorrent
 		void remove_url_seed(std::string const& url) const;
 		std::set<std::string> url_seeds() const;
 
+#ifndef TORRENT_DISABLE_EXTENSIONS
+		void add_extension(boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> const& ext
+			, void* userdata = 0);
+#endif
+
 		bool has_metadata() const;
 		const torrent_info& get_torrent_info() const;
 		bool is_valid() const;

src/torrent.cpp

@@ -346,10 +346,34 @@ namespace libtorrent
 	}
 
 #ifndef TORRENT_DISABLE_EXTENSIONS
+
 	void torrent::add_extension(boost::shared_ptr<torrent_plugin> ext)
 	{
 		m_extensions.push_back(ext);
 	}
+
+	void torrent::add_extension(boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> const& ext
+		, void* userdata)
+	{
+		boost::shared_ptr<torrent_plugin> tp(ext(this, userdata));
+		if (!tp) return;
+
+		add_extension(tp);
+		
+		for (peer_iterator i = m_connections.begin();
+			i != m_connections.end(); ++i)
+		{
+			peer_connection* p = *i;
+			boost::shared_ptr<peer_plugin> pp(tp->new_connection(p));
+			if (pp) p->add_extension(pp);
+		}
+
+		// if files are checked for this torrent, call the extension
+		// to let it initialize itself
+		if (m_connections_initialized)
+			tp->on_files_checked();
+	}
+
 #endif
 
 	// this may not be called from a constructor because of the call to

src/torrent_handle.cpp

@@ -247,6 +247,20 @@ namespace libtorrent
 		find_torrent(m_ses, m_chk, m_info_hash)->move_storage(save_path);
 	}
 
+	void torrent_handle::add_extension(
+		boost::function<boost::shared_ptr<torrent_plugin>(torrent*, void*)> const& ext
+		, void* userdata)
+	{
+		INVARIANT_CHECK;
+
+		if (m_ses == 0) throw_invalid_handle();
+		TORRENT_ASSERT(m_chk);
+
+		session_impl::mutex_t::scoped_lock l1(m_ses->m_mutex);
+		mutex::scoped_lock l2(m_chk->m_mutex);
+		return find_torrent(m_ses, m_chk, m_info_hash)->add_extension(ext, userdata);
+	}
+
 	bool torrent_handle::has_metadata() const
 	{
 		INVARIANT_CHECK;