code: private void updateSize()
  	{
  		int length = frames.getLength();
  
  		if (head.getExtendedHeader())
  		{
  			length += ext_head.getSize();
  		}
  
  		head.setTagSize(length);
  
  		if (head.getFooter())
  		{
  			foot.setTagSize(length);
  		}
  	}
docs: Updates the size field of the id3 header and footer (if it exists)
  from the current size of the id3v2 frames plus the extended header
  size (if it exists).