code: function(allowQuestionMark){
          var reader  = this._reader,
              part = "",
              c       = reader.peek();
  
          //first read hex digits
          while(isHexDigit(c) && part.length < 6){
              reader.read();
              part += c;
              c = reader.peek();
          }
  
          //then read question marks if allowed
          if (allowQuestionMark){
              while(c == "?" && part.length < 6){
                  reader.read();
                  part += c;
                  c = reader.peek();
              }
          }
  
          //there can't be any other characters after this point
  
          return part;
      }
docs: ------------------------------------------------------------------------- Methods to read values from the string stream -------------------------------------------------------------------------