code: function (offset, length) {
  
                  if (arguments.length === 1) {
                      length = arguments[0];
                      offset = this.offset;
                  }
  
                  if (length < 0 || offset + length > this.length) {
                      error.raise(10001, this.length, offset + length);
                  }
  
                  var buffer = [];
                  for (var i = 0; i < length; ++i) {
                      buffer.push(this.view.getUint8(offset + i));
                  }
  
                  this.offset = offset + length;
                  return buffer;
              }
docs: 获取指定的字节数组
  @param {number} offset 偏移
  @param {number} length 字节长度
  @return {Array} 字节数组