code: func (e *RawV4Event) SetExtraHeadersSize(size int) error {
  	newFixedSize := (size +
  		sizeOfBasicV4EventHeader +
  		e.fixedLengthDataSize +
  		e.checksumSize)
  	if size < 0 || newFixedSize > len(e.data) {
  		return errors.Newf(
  			"Invalid extra headers size (data size: %d basic header size: %d"+
  				"fixed length data size: %d checksum size: %d input: %d)",
  			len(e.data),
  			sizeOfBasicV4EventHeader,
  			e.fixedLengthDataSize,
  			e.checksumSize,
  			size)
  	}
  	e.extraHeadersSize = size
  	return nil
  }
docs: // Set the extra headers' size.