code: function parseTopDict(reader, start, length, strings) {
              var dict = parseCFFDict(reader, start || 0, length || reader.length);
              return interpretDict(dict, TOP_DICT_META, strings);
          }
docs: 解析cff top字典
  
  @param  {Reader} reader  读取器
  @param  {number} start 开始offset
  @param  {number} length 大小
  @param  {Object} strings 字符串集合
  @return {Object}         字典数据