human_readable_size.rb

IEC_PREFIXES = ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi', 'Yi']
SI_PREFIXES  = ['', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y']
def human_readable_size(size, precision = 2, use_iec_prefix = false)
  size = size.to_f
  if use_iec_prefix
    prefixes = IEC_PREFIXES
    base = 1024
  else
    prefixes = SI_PREFIXES
    base = 1000
  end
  if size == 0
    prefix_index = 0
  else
    prefix_index = [(Math.log(size.abs) / Math.log(base)).floor, prefixes.length - 1].min
  end
  beautified_size = (size / (base ** prefix_index)).round(precision)
  "#{beautified_size} #{prefixes[prefix_index]}B"
end

puts human_readable_size(0, 2, true)
puts human_readable_size(-53687091200, 2, true)
puts human_readable_size(536870912000000000000000000000000000000000000)