code: function parseCFFIndex(reader, offset, conversionFn) {
              if (offset) {
                  reader.seek(offset);
              }
              var start = reader.offset;
              var offsets = [];
              var objects = [];
              var count = reader.readUint16();
              var i;
              var l;
              if (count !== 0) {
                  var offsetSize = reader.readUint8();
                  for (i = 0, l = count + 1; i < l; i++) {
                      offsets.push(getOffset(reader, offsetSize));
                  }
  
                  for (i = 0, l = count; i < l; i++) {
                      var value = reader.readBytes(offsets[i + 1] - offsets[i]);
                      if (conversionFn) {
                          value = conversionFn(value);
                      }
                      objects.push(value);
                  }
              }
  
              return {
                  objects: objects,
                  startOffset: start,
                  endOffset: reader.offset
              };
          }
docs: 解析`CFF`表索引
  @param  {Reader} reader       读取器
  @param  {number} offset       偏移
  @param  {Funciton} conversionFn 转换函数
  @return {Object}              表对象