static public String ParseSrcPos() {
      if (Pos == null) {
         return null;
      }
      if (Pos.length() >= 3) {
         String srcpos = Pos.subSequence(0, 3).toString();
         if (ParsePosition.IsPos(srcpos)) {
            Pos = Pos.subSequence(3, Pos.length()).toString();
            return srcpos;
         }
      }
      if (Pos.length() >= 2) {
         String srcpos = Pos.subSequence(0, 2).toString();
         if (ParsePosition.IsPos(srcpos)) {
            Pos = Pos.subSequence(2, Pos.length()).toString();
            return srcpos;
         }
      }
      return null;
   }