add rvalue reference overloads for add_torrent_params, settings_pack and session_params. Those structures are pretty large so being able to take them by rvalue reference may be beneficial

bindings/python/src/session.cpp

@@ -979,8 +979,8 @@ void bind_session()
 #endif // TORRENT_DISABLE_DHT
         .def("add_torrent", &add_torrent)
         .def("async_add_torrent", &async_add_torrent)
-        .def("async_add_torrent", &lt::session::async_add_torrent)
+        .def("async_add_torrent", static_cast<void (session_handle::*)(lt::add_torrent_params const&)>(&lt::session::async_add_torrent))
-        .def("add_torrent", allow_threads((lt::torrent_handle (session_handle::*)(add_torrent_params const&))&lt::session::add_torrent))
+        .def("add_torrent", allow_threads(static_cast<lt::torrent_handle (session_handle::*)(add_torrent_params const&)>(&lt::session::add_torrent)))
 #ifndef BOOST_NO_EXCEPTIONS
 #if TORRENT_ABI_VERSION == 1
         .def(

include/libtorrent/aux_/session_impl.hpp

@@ -395,7 +395,11 @@ namespace aux {
 			void add_dht_router(std::pair<std::string, int> const& node);
 			void set_dht_settings(dht::dht_settings const& s);
 			dht::dht_settings const& get_dht_settings() const { return m_dht_settings; }
-			void set_dht_state(dht::dht_state state);
+
+			// you must give up ownership of the dht state
+			void set_dht_state(dht::dht_state&& state);
+			void set_dht_state(dht::dht_state const& state) = delete;
+
 			void set_dht_storage(dht::dht_storage_constructor_type sc);
 			void start_dht();
 			void stop_dht();

include/libtorrent/kademlia/dht_tracker.hpp

@@ -72,7 +72,16 @@ namespace libtorrent { namespace dht {
 			, dht_settings const& settings
 			, counters& cnt
 			, dht_storage_interface& storage
-			, dht_state state);
+			, dht_state&& state);
+
+		// the dht_state must be moved in!
+		dht_tracker(dht_observer* observer
+			, io_service& ios
+			, send_fun_t const& send_fun
+			, dht_settings const& settings
+			, counters& cnt
+			, dht_storage_interface& storage
+			, dht_state const& state) = delete;
 
 #if defined(_MSC_VER) && _MSC_VER < 1910
 		// workaround for a bug in msvc 14.0

include/libtorrent/session.hpp

@@ -131,10 +131,15 @@ namespace aux {
 		// (ut_metadata, ut_pex and smart_ban). The default values in the
 		// settings is to start the default features like upnp, NAT-PMP,
 		// and dht for example.
-		explicit session_params(settings_pack sp = settings_pack());
+		explicit session_params(settings_pack&& sp);
+		explicit session_params(settings_pack const& sp);
+		session_params();
+
 		// This constructor helps to configure the set of initial plugins
 		// to be added to the session before it's started.
-		session_params(settings_pack sp
+		session_params(settings_pack&& sp
+			, std::vector<std::shared_ptr<plugin>> exts);
+		session_params(settings_pack const& sp
 			, std::vector<std::shared_ptr<plugin>> exts);
 
 		session_params(session_params const&) = default;
@@ -178,8 +183,13 @@ namespace aux {
 		// In order to avoid a race condition between starting the session and
 		// configuring it, you can pass in a session_params object. Its settings
 		// will take effect before the session starts up.
-		explicit session(session_params params = session_params())
+		explicit session(session_params const& params)
+		{ start(session_params(params), nullptr); }
+		explicit session(session_params&& params)
+		{ start(std::move(params), nullptr); }
+		session()
 		{
+			session_params params;
 			start(std::move(params), nullptr);
 		}
 
@@ -196,10 +206,10 @@ namespace aux {
 		// 	call session::abort() and save the session_proxy first, then
 		// 	destruct the session object, then sync with the io_service, then
 		// 	destruct the session_proxy object.
-		session(session_params params, io_service& ios)
+		session(session_params&& params, io_service& ios)
-		{
+		{ start(std::move(params), &ios); }
-			start(std::move(params), &ios);
+		session(session_params const& params, io_service& ios)
-		}
+		{ start(session_params(params), &ios); }
 
 		// Constructs the session objects which acts as the container of torrents.
 		// It provides configuration options across torrents (such as rate limits,
@@ -212,11 +222,12 @@ namespace aux {
 		// NAT-PMP) and default plugins (ut_metadata, ut_pex and smart_ban). The
 		// default is to start those features. If you do not want them to start,
 		// pass 0 as the flags parameter.
-		session(settings_pack pack
+		session(settings_pack&& pack
 			, session_flags_t const flags = start_default_features | add_default_plugins)
-		{
+		{ start(flags, std::move(pack), nullptr); }
-			start(flags, std::move(pack), nullptr);
+		session(settings_pack const& pack
-		}
+			, session_flags_t const flags = start_default_features | add_default_plugins)
+		{ start(flags, settings_pack(pack), nullptr); }
 
 		// movable
 		session(session&&) = default;
@@ -239,12 +250,14 @@ namespace aux {
 		// 	call session::abort() and save the session_proxy first, then
 		// 	destruct the session object, then sync with the io_service, then
 		// 	destruct the session_proxy object.
-		session(settings_pack pack
+		session(settings_pack&& pack
 			, io_service& ios
 			, session_flags_t const flags = start_default_features | add_default_plugins)
-		{
+		{ start(flags, std::move(pack), &ios); }
-			start(flags, std::move(pack), &ios);
+		session(settings_pack const& pack
-		}
+			, io_service& ios
+			, session_flags_t const flags = start_default_features | add_default_plugins)
+		{ start(flags, settings_pack(pack), &ios); }
 
 #if TORRENT_ABI_VERSION == 1
 #ifdef __GNUC__
@@ -348,8 +361,11 @@ namespace aux {
 
 	private:
 
-		void start(session_params params, io_service* ios);
+		void start(session_params&& params, io_service* ios);
-		void start(session_flags_t flags, settings_pack sp, io_service* ios);
+		void start(session_flags_t flags, settings_pack&& sp, io_service* ios);
+
+		void start(session_params const& params, io_service* ios) = delete;
+		void start(session_flags_t flags, settings_pack const& sp, io_service* ios) = delete;
 
 		// data shared between the main thread
 		// and the working thread

include/libtorrent/session_handle.hpp

@@ -215,7 +215,8 @@ namespace libtorrent {
 		torrent_handle add_torrent(add_torrent_params const& params);
 #endif
 		torrent_handle add_torrent(add_torrent_params const& params, error_code& ec);
-		void async_add_torrent(add_torrent_params params);
+		void async_add_torrent(add_torrent_params&& params);
+		void async_add_torrent(add_torrent_params const& params);
 
 #ifndef BOOST_NO_EXCEPTIONS
 #if TORRENT_ABI_VERSION == 1

simulation/test_dht_rate_limit.cpp

@@ -124,7 +124,7 @@ TORRENT_TEST(dht_rate_limit)
 	std::unique_ptr<lt::dht::dht_storage_interface> dht_storage(dht::dht_default_storage_constructor(dhtsett));
 	auto dht = std::make_shared<lt::dht::dht_tracker>(
 		&o, dht_ios, std::bind(&send_packet, std::ref(sock), _1, _2, _3, _4, _5)
-		, dhtsett, cnt, *dht_storage, state);
+		, dhtsett, cnt, *dht_storage, std::move(state));
 	dht->new_socket(ls);
 
 	bool stop = false;
@@ -245,7 +245,7 @@ TORRENT_TEST(dht_delete_socket)
 	std::unique_ptr<lt::dht::dht_storage_interface> dht_storage(dht::dht_default_storage_constructor(dhtsett));
 	auto dht = std::make_shared<lt::dht::dht_tracker>(
 		&o, dht_ios, std::bind(&send_packet, std::ref(sock), _1, _2, _3, _4, _5)
-		, dhtsett, cnt, *dht_storage, state);
+		, dhtsett, cnt, *dht_storage, std::move(state));
 
 	dht->start([](std::vector<std::pair<dht::node_entry, std::string>> const&){});
 	dht->new_socket(ls);

src/kademlia/dht_tracker.cpp

@@ -88,7 +88,7 @@ namespace libtorrent { namespace dht {
 		, dht_settings const& settings
 		, counters& cnt
 		, dht_storage_interface& storage
-		, dht_state state)
+		, dht_state&& state)
 		: m_counters(cnt)
 		, m_storage(storage)
 		, m_state(std::move(state))

src/session.cpp

@@ -319,7 +319,7 @@ namespace {
 		return params;
 	}
 
-	void session::start(session_params params, io_service* ios)
+	void session::start(session_params&& params, io_service* ios)
 	{
 		bool const internal_executor = ios == nullptr;
 
@@ -334,16 +334,18 @@ namespace {
 		*static_cast<session_handle*>(this) = session_handle(m_impl);
 
 #ifndef TORRENT_DISABLE_EXTENSIONS
-		for (auto const& ext : params.extensions)
+		for (auto& ext : params.extensions)
 		{
-			m_impl->add_ses_extension(ext);
+			m_impl->add_ses_extension(std::move(ext));
 		}
 #endif
 
 #ifndef TORRENT_DISABLE_DHT
-		m_impl->set_dht_settings(params.dht_settings);
+		m_impl->set_dht_settings(std::move(params.dht_settings));
 		m_impl->set_dht_state(std::move(params.dht_state));
-		m_impl->set_dht_storage(params.dht_storage_constructor);
+
+		TORRENT_ASSERT(params.dht_storage_constructor);
+		m_impl->set_dht_storage(std::move(params.dht_storage_constructor));
 #endif
 
 		m_impl->start_session();
@@ -376,7 +378,7 @@ namespace {
 		}
 	}
 
-	void session::start(session_flags_t const flags, settings_pack sp, io_service* ios)
+	void session::start(session_flags_t const flags, settings_pack&& sp, io_service* ios)
 	{
 		start({std::move(sp),
 			default_plugins(!(flags & add_default_plugins))}, ios);
@@ -431,16 +433,36 @@ namespace {
 		}
 	}
 
-	session_params::session_params(settings_pack sp)
+	session_params::session_params(settings_pack&& sp)
 		: session_params(std::move(sp), default_plugins())
 	{}
 
-	session_params::session_params(settings_pack sp
+	session_params::session_params(settings_pack const& sp)
+		: session_params(sp, default_plugins())
+	{}
+
+	session_params::session_params()
+		: extensions(default_plugins())
+#ifndef TORRENT_DISABLE_DHT
+		, dht_storage_constructor(dht::dht_default_storage_constructor)
+#endif
+	{}
+
+	session_params::session_params(settings_pack&& sp
 		, std::vector<std::shared_ptr<plugin>> exts)
 		: settings(std::move(sp))
 		, extensions(std::move(exts))
 #ifndef TORRENT_DISABLE_DHT
 		, dht_storage_constructor(dht::dht_default_storage_constructor)
+#endif
+	{}
+
+	session_params::session_params(settings_pack const& sp
+		, std::vector<std::shared_ptr<plugin>> exts)
+		: settings(sp)
+		, extensions(std::move(exts))
+#ifndef TORRENT_DISABLE_DHT
+		, dht_storage_constructor(dht::dht_default_storage_constructor)
 #endif
 	{}
 }

src/session_handle.cpp

@@ -393,7 +393,12 @@ namespace {
 		return sync_call_ret<torrent_handle>(&session_impl::add_torrent, p, ecr);
 	}
 
-	void session_handle::async_add_torrent(add_torrent_params params)
+	void session_handle::async_add_torrent(add_torrent_params const& params)
+	{
+		async_add_torrent(add_torrent_params(params));
+	}
+
+	void session_handle::async_add_torrent(add_torrent_params&& params)
 	{
 		TORRENT_ASSERT_PRECOND(!params.save_path.empty());
 

src/session_impl.cpp

@@ -5860,7 +5860,7 @@ namespace aux {
 		m_dht_settings = settings;
 	}
 
-	void session_impl::set_dht_state(dht::dht_state state)
+	void session_impl::set_dht_state(dht::dht_state&& state)
 	{
 		m_dht_state = std::move(state);
 	}