added subfile existence check

matlab/@ustar/ustar.m

@@ -131,6 +131,13 @@ classdef ustar < handle
       end
       fclose(fidw);
     end
+    function [flag] = isSubfile(obj,fname)
+      % [flag] = obj.isSubfile(fname)
+      % Checks if a subfile exists within tar-ball.
+      % Input
+      %   fname           name of subfile
+      flag = any(ismember(obj.subFile,fname));
+    end
   end
   %% ------------------------------------------------------------------------%%
   %%                          PRIVATE METHODS                                %%