added option to not recheck on missing or incomplete resume data

ChangeLog

@@ -1,3 +1,4 @@
+	* added option to not recheck on missing or incomplete resume data
 	* extended stats logging with statistics=on builds
 	* added new session functions to more efficiently query torrent status
 	* added alerts for added and removed torrents

docs/manual.rst

@@ -4263,6 +4263,7 @@ session_settings
 		bool enable_incoming_tcp;
 		int max_pex_peers;
 		bool ignore_resume_timestamps;
+		bool no_recheck_incomplete_resume;
 		bool anonymous_mode;
 		int tick_interval;
 		int share_mode_target;
@@ -4981,6 +4982,13 @@ It might be useful to set this to true if your network is faster than your
 disk, and it would be faster to redownload potentially missed pieces than
 to go through the whole storage to look for them.
 
+``no_recheck_incomplete_resume`` determines if the storage should check
+the whole files when resume data is incomplete or missing or whether
+it should simply assume we don't have any of the data. By default, this
+is determined by the existance of any of the files. By setting this setting
+to true, the files won't be checked, but will go straight to download
+mode.
+
 ``anonymous_mode`` defaults to false. When set to true, the client tries
 to hide its identity to a certain degree. The peer-ID will no longer
 include the client's fingerprint. The user-agent will be reset to an

include/libtorrent/session_settings.hpp

@@ -233,6 +233,7 @@ namespace libtorrent
 			, enable_incoming_tcp(true)
 			, max_pex_peers(200)
 			, ignore_resume_timestamps(false)
+			, no_recheck_incomplete_resume(false)
 			, anonymous_mode(false)
 			, tick_interval(100)
 			, report_web_seed_downloads(true)
@@ -912,6 +913,12 @@ namespace libtorrent
 		// since the last session
 		bool ignore_resume_timestamps;
 
+		// normally, if a resume file is incomplete (typically there's no
+		// "file sizes" field) the torrent is queued for a full check. If
+		// this settings is set to true, instead libtorrent will assume
+		// we have none of the files and go straight to download
+		bool no_recheck_incomplete_resume;
+
 		// when this is true, libtorrent will take actions to make sure any
 		// privacy sensitive information is leaked out from the client. This
 		// mode is assumed to be combined with using a proxy for all your

src/session_impl.cpp

@@ -331,6 +331,7 @@ namespace aux {
 		TORRENT_SETTING(boolean, enable_incoming_tcp)
 		TORRENT_SETTING(integer, max_pex_peers)
 		TORRENT_SETTING(boolean, ignore_resume_timestamps)
+		TORRENT_SETTING(boolean, no_recheck_incomplete_resume)
 		TORRENT_SETTING(boolean, anonymous_mode)
 		TORRENT_SETTING(integer, tick_interval)
 		TORRENT_SETTING(integer, upload_rate_limit)
@@ -1491,6 +1492,7 @@ namespace aux {
 			|| m_settings.volatile_read_cache != s.volatile_read_cache
 			|| m_settings.no_atime_storage!= s.no_atime_storage
 			|| m_settings.ignore_resume_timestamps != s.ignore_resume_timestamps
+			|| m_settings.no_recheck_incomplete_resume != s.no_recheck_incomplete_resume
 			|| m_settings.low_prio_disk != s.low_prio_disk)
 			update_disk_io_thread = true;
 

src/storage.cpp

@@ -1971,25 +1971,28 @@ ret:
 
 	int piece_manager::check_no_fastresume(error_code& error)
 	{
-		bool has_files = m_storage->has_any_file();
-
-		if (m_storage->error())
-			return fatal_disk_error;
-
-		if (has_files)
+		bool has_files = false;
+		if (!m_storage->settings().no_recheck_incomplete_resume)
 		{
-			m_state = state_full_check;
-			m_piece_to_slot.clear();
-			m_piece_to_slot.resize(m_files.num_pieces(), has_no_slot);
-			m_slot_to_piece.clear();
-			m_slot_to_piece.resize(m_files.num_pieces(), unallocated);
-			if (m_storage_mode == storage_mode_compact)
+			m_storage->has_any_file();
+			if (m_storage->error())
+				return fatal_disk_error;
+
+			if (has_files)
 			{
-				m_unallocated_slots.clear();
-				m_free_slots.clear();
+				m_state = state_full_check;
+				m_piece_to_slot.clear();
+				m_piece_to_slot.resize(m_files.num_pieces(), has_no_slot);
+				m_slot_to_piece.clear();
+				m_slot_to_piece.resize(m_files.num_pieces(), unallocated);
+				if (m_storage_mode == storage_mode_compact)
+				{
+					m_unallocated_slots.clear();
+					m_free_slots.clear();
+				}
+				TORRENT_ASSERT(int(m_piece_to_slot.size()) == m_files.num_pieces());
+				return need_full_check;
 			}
-			TORRENT_ASSERT(int(m_piece_to_slot.size()) == m_files.num_pieces());
-			return need_full_check;
 		}
 
 		if (m_storage_mode == storage_mode_compact)