added feature to ask a torrent if it needs to save its resume data or not

ChangeLog

@@ -1,3 +1,4 @@
+	* added feature to ask a torrent if it needs to save its resume data or not
 	* added setting to ignore file modification time when loading resume files
 	* support more fine-grained torrent states between which peer sources it
 	  announces to

bindings/python/src/torrent_handle.cpp

@@ -335,6 +335,7 @@ void bind_torrent_handle()
         .def("file_priorities", &file_priorities)
         .def("use_interface", &torrent_handle::use_interface)
         .def("save_resume_data", _(&torrent_handle::save_resume_data))
+        .def("need_save_resume_data", _(&torrent_handle::need_save_resume_data))
         .def("force_reannounce", _(force_reannounce0))
         .def("force_reannounce", &force_reannounce)
         .def("force_dht_announce", _(&torrent_handle::force_dht_announce))

docs/manual.rst

@@ -1979,6 +1979,7 @@ Its declaration looks like this::
 		std::string name() const;
 
 		void save_resume_data() const;
+		bool need_save_resume_data() const;
 		void force_reannounce() const;
 		void force_dht_announce() const;
 		void force_reannounce(boost::posix_time::time_duration) const;
@@ -2857,6 +2858,17 @@ Example code to pause and save resume data for all torrents and wait for the ale
 	}
 	
 
+need_save_resume_data()
+-----------------------
+
+	::
+
+		bool need_save_resume_data() const;
+
+This function returns true if any whole chunk has been downloaded since the
+torrent was first loaded or since the last time the resume data was saved. When
+saving resume data periodically, it makes sense to skip any torrent which hasn't
+downloaded anything since the last time.
 
 status()
 --------

include/libtorrent/torrent.hpp

@@ -266,6 +266,7 @@ namespace libtorrent
 		bool is_torrent_paused() const { return !m_allow_peers; }
 		void force_recheck();
 		void save_resume_data();
+		bool need_save_resume_data() const { return m_need_save_resume_data; }
 
 		bool is_auto_managed() const { return m_auto_managed; }
 		void auto_managed(bool a);
@@ -1070,8 +1071,10 @@ namespace libtorrent
 #else
 		unsigned int m_dummy_padding_bits_to_align:2;
 #endif
-		// TODO: Add new bools here!
-		unsigned int m_dummy_padding_bit_to_alignt:1;
+
+		// set to false when saving resume data. Set to true
+		// whenever something is downloaded
+		bool m_need_save_resume_data:1;
 
 		// total time we've been available as a seed on this torrent
 		// does not count when the torrent is stopped or paused

include/libtorrent/torrent_handle.hpp

@@ -466,6 +466,7 @@ namespace libtorrent
 
 		void force_recheck() const;
 		void save_resume_data() const;
+		bool need_save_resume_data() const;
 
 		bool is_auto_managed() const;
 		void auto_managed(bool m) const;

src/torrent.cpp

@@ -354,6 +354,7 @@ namespace libtorrent
 		, m_resolving_country(false)
 		, m_resolve_countries(false)
 #endif
+		, m_need_save_resume_data(false)
 		, m_seeding_time(0)
 		, m_time_scaler(0)
 		, m_max_uploads(~0)
@@ -713,7 +714,7 @@ namespace libtorrent
 		mutex::scoped_lock l(m_ses.m_mutex);
 
 		INVARIANT_CHECK;
-	
+
 		if (is_seed()) return;
 
 		if (m_abort)
@@ -735,6 +736,8 @@ namespace libtorrent
 		// add_piece() multiple times
 		if (picker().is_finished(block_finished)) return;
 
+		m_need_save_resume_data = true;
+
 		picker().mark_as_finished(block_finished, 0);
 
 		// did we just finish the piece?
@@ -2557,6 +2560,7 @@ namespace libtorrent
 		}
 		else
 		{
+			m_need_save_resume_data = false;
 			write_resume_data(*j.resume_data);
 			alerts().post_alert(save_resume_data_alert(j.resume_data
 				, get_handle()));
@@ -5227,6 +5231,8 @@ namespace libtorrent
 			return;
 		}
 
+		m_need_save_resume_data = false;
+
 		TORRENT_ASSERT(m_storage);
 		if (m_state == torrent_status::queued_for_checking
 			|| m_state == torrent_status::checking_files

src/torrent_handle.cpp

@@ -304,6 +304,12 @@ namespace libtorrent
 		TORRENT_FORWARD(save_resume_data());
 	}
 
+	bool torrent_handle::need_save_resume_data() const
+	{
+		INVARIANT_CHECK;
+		TORRENT_FORWARD_RETURN(need_save_resume_data(), false);
+	}
+
 	void torrent_handle::force_recheck() const
 	{
 		INVARIANT_CHECK;