code: protected String formatFileSize(BigInteger fileLength, BigInteger divisor, String unit) {
  		BigDecimal size = new BigDecimal(fileLength);
  		size = size.setScale(config.getFileSizeDisplayScale()).divide(new BigDecimal(divisor), BigDecimal.ROUND_HALF_EVEN);
  		return String.format("%s %s", size.doubleValue(), unit);
  	}
docs: calculates the and formats files size
  @see #getFileSize(long)
  @param fileLength
  @param divisor
  @param unit the Unit for the divisor
  @return