merged metadata extension improvement from libtorrent_aio

src/ut_metadata.cpp

@@ -64,6 +64,25 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent { namespace
 {
+	enum
+	{
+		// this is the max number of bytes we'll
+		// queue up in the send buffer. If we exceed this,
+		// we'll wait another second before checking
+		// the send buffer size again. So, this may limit
+		// the rate at which we can server metadata to
+		// 160 kiB/s
+		send_buffer_limit = 0x4000 * 10,
+
+		// this is the max number of requests we'll queue
+		// up. If we get more requests tha this, we'll
+		// start rejecting them, claiming we don't have
+		// metadata. If the torrent is greater than 16 MiB,
+		// we may hit this case (and the client requesting
+		// doesn't throttle its requests)
+		max_incoming_requests = 1024,
+	};
+
 	int div_round_up(int numerator, int denominator)
 	{
 		return (numerator + denominator - 1) / denominator;
@@ -326,8 +345,12 @@ namespace libtorrent { namespace
 						write_metadata_packet(2, piece);
 						return true;
 					}
-					// TODO: put the request on the queue in some cases
+					if (m_pc.send_buffer_size() < send_buffer_limit)
-					write_metadata_packet(1, piece);
+						write_metadata_packet(1, piece);
+					else if (m_incoming_requests.size() < max_incoming_requests)
+						m_incoming_requests.push_back(piece);
+					else
+						write_metadata_packet(2, piece);
 				}
 				break;
 			case 1: // data
@@ -371,6 +394,13 @@ namespace libtorrent { namespace
 		virtual void tick()
 		{
 			maybe_send_request();
+			while (!m_incoming_requests.empty()
+				&& m_pc.send_buffer_size() < send_buffer_limit)
+			{
+				int piece = m_incoming_requests.front();
+				m_incoming_requests.erase(m_incoming_requests.begin());
+				write_metadata_packet(1, piece);
+			}
 		}
 
 		void maybe_send_request()