lt sync 2642

libtorrent/include/libtorrent/magnet_uri.hpp

@@ -46,6 +46,7 @@ namespace libtorrent
 	struct torrent_handle;
 
 	std::string TORRENT_EXPORT make_magnet_uri(torrent_handle const& handle);
+	std::string TORRENT_EXPORT make_magnet_uri(torrent_info const& info);
 
 #ifndef TORRENT_NO_DEPRECATE
 	// deprecated in 0.14

libtorrent/src/magnet_uri.cpp

@@ -69,6 +69,26 @@ namespace libtorrent
 		return ret.str();
 	}
 
+	std::string make_magnet_uri(torrent_info const& info)
+	{
+		std::stringstream ret;
+		if (!info.is_valid()) return ret.str();
+
+		std::string name = info.name();
+
+		ret << "magnet:?xt=urn:btih:" << base32encode(
+			std::string((char*)info.info_hash().begin(), 20));
+		if (!name.empty())
+			ret << "&dn=" << escape_string(name.c_str(), name.length());
+		std::vector<announce_entry> const& tr = info.trackers();
+		if (!tr.empty())
+		{
+			ret << "&tr=" << escape_string(tr[0].url.c_str()
+				, tr[0].url.length());
+		}
+		return ret.str();
+	}
+
 #ifndef TORRENT_NO_DEPRECATE
 	torrent_handle add_magnet_uri(session& ses, std::string const& uri
 		, fs::path const& save_path

libtorrent/src/peer_connection.cpp

@@ -1706,9 +1706,8 @@ namespace libtorrent
 			}
 		
 			if (t->alerts().should_post<file_error_alert>())
-			{
 				t->alerts().post_alert(file_error_alert(j.error_file, t->get_handle(), j.str));
-			}
+			t->set_error(j.str);
 			t->pause();
 			return;
 		}

libtorrent/src/torrent.cpp

@@ -330,7 +330,11 @@ namespace libtorrent
 
 	void torrent::start()
 	{
+		// we need to start announcing since we don't have any
+		// metadata. To receive peers to ask for it.
 		if (m_torrent_file->is_valid()) init();
+		else if (!m_trackers.empty()) start_announcing();
+
 		if (m_abort) return;
 	}
 
@@ -3919,7 +3923,10 @@ namespace libtorrent
 	void torrent::start_announcing()
 	{
 		if (is_paused()) return;
-		if (!m_files_checked) return;
+		// if we don't have metadata, we need to announce
+		// before checking files, to get peers to
+		// request the metadata from
+		if (!m_files_checked && valid_metadata()) return;
 		if (m_announcing) return;
 
 		m_announcing = true;