fixed piece picker problem when a downloading piece could not be picked with the right speed category

examples/client_test.cpp

@@ -303,7 +303,7 @@ int peer_index(libtorrent::tcp::endpoint addr, std::vector<libtorrent::peer_info
 void print_peer_info(std::ostream& out, std::vector<libtorrent::peer_info> const& peers)
 {
 	using namespace libtorrent;
-	out << " down    (total)   up      (total)  que req flags       source fail hshf sndb inactive wait disk block-progress "
+	out << " down    (total)   up      (total)  sent-req recv flags       source fail hshf sndb inactive wait disk block-progress "
 #ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES
 		"country "
 #endif
@@ -321,7 +321,8 @@ void print_peer_info(std::ostream& out, std::vector<libtorrent::peer_info> const
 			<< "(" << add_suffix(i->total_download) << ") " << esc("0")
 			<< esc("31") << (i->up_speed > 0 ? add_suffix(i->up_speed) + "/s ": "         ")
 			<< "(" << add_suffix(i->total_upload) << ") " << esc("0")
-			<< to_string(i->download_queue_length, 3) << " "
+			<< to_string(i->download_queue_length, 3) << " ("
+			<< to_string(i->target_dl_queue_length, 3) << ") "
 			<< to_string(i->upload_queue_length, 3) << " "
 			<< ((i->flags & peer_info::interesting)?'I':'.')
 			<< ((i->flags & peer_info::choked)?'C':'.')

include/libtorrent/peer_connection.hpp

@@ -155,8 +155,7 @@ namespace libtorrent
 
 		int prefer_whole_pieces() const
 		{
-			if (m_prefer_whole_pieces == 0)
-				return peer_info_struct() && peer_info_struct()->on_parole ? 1 : 0;
+			if (on_parole()) return 1;
 			return m_prefer_whole_pieces;
 		}
 

include/libtorrent/peer_info.hpp

@@ -117,6 +117,11 @@ namespace libtorrent
 		// for yet
 		int download_queue_length;
 
+		// the number of requests that is
+		// tried to be maintained (this is
+		// typically a function of download speed)
+		int target_dl_queue_length;
+
 		// this is the number of requests
 		// the peer has sent to us
 		// that we haven't sent yet

src/peer_connection.cpp

@@ -2019,8 +2019,9 @@ namespace libtorrent
 
 		p.load_balancing = total_free_upload();
 
-		p.download_queue_length = (int)download_queue().size();
-		p.upload_queue_length = (int)upload_queue().size();
+		p.download_queue_length = int(download_queue().size() + m_request_queue.size());
+		p.target_dl_queue_length = int(desired_queue_size());
+		p.upload_queue_length = int(upload_queue().size());
 
 		if (boost::optional<piece_block_progress> ret = downloading_piece_progress())
 		{

src/piece_picker.cpp

@@ -1125,7 +1125,7 @@ namespace libtorrent
 			, interesting_blocks, backup_blocks, num_blocks
 			, prefer_whole_pieces, peer, speed, on_parole);
 
-		if (num_blocks == 0) return;
+		if (num_blocks <= 0) return;
 
 		if (rarest_first)
 		{
@@ -1364,6 +1364,13 @@ namespace libtorrent
 
 			if (prefer_whole_pieces > 0 && !exclusive_active) continue;
 
+			// don't pick too many back-up blocks
+			if (i->state != none
+				&& i->state != speed
+				&& !exclusive_active
+				&& int(backup_blocks.size()) >= num_blocks)
+				continue;
+
 			for (int j = 0; j < num_blocks_in_piece; ++j)
 			{
 				// ignore completed blocks and already requested blocks
@@ -1412,9 +1419,15 @@ namespace libtorrent
 		if (num_blocks <= 0) return 0;
 		if (on_parole) return num_blocks;
 
+		int to_copy;
+		if (prefer_whole_pieces == 0)
+			to_copy = (std::min)(int(backup_blocks.size()), num_blocks);
+		else
+			to_copy = int(backup_blocks.size());
+
 		interesting_blocks.insert(interesting_blocks.end()
-			, backup_blocks.begin(), backup_blocks.end());
-		num_blocks -= int(backup_blocks.size());
+			, backup_blocks.begin(), backup_blocks.begin() + to_copy);
+		num_blocks -= to_copy;
 		backup_blocks.clear();
 
 		if (num_blocks <= 0) return 0;

src/policy.cpp

@@ -284,6 +284,8 @@ namespace libtorrent
 		for (std::vector<piece_block>::iterator i = interesting_pieces.begin();
 			i != interesting_pieces.end(); ++i)
 		{
+			if (prefer_whole_pieces == 0 && num_requests <= 0) break;
+
 			if (p.is_requested(*i))
 			{
 				if (num_requests <= 0) break;