gistfile1.rbx

def number_to_human_size(number, *args)
  return number.nil? ? nil : pluralize(number.to_i, "Byte") if number.to_i < 1024
  
  options = args.extract_options!
  options.symbolize_keys!
  
  defaults, human = I18n.translate([:'number.format', :'number.human.format'], :locale => options[:locale]) || [{},{}]
  defaults = defaults.merge(human)
  
  unless args.empty?
    ActiveSupport::Deprecation.warn('number_to_human_size takes an option hash instead of a separate precision argument.', caller)
    precision = args[0] || defaults[:precision]
  end
  
  precision ||= (options[:precision] || defaults[:precision])
  separator ||= (options[:separator] || defaults[:separator])
  delimiter ||= (options[:delimiter] || defaults[:delimiter])
  
  number, unit = number_and_unit_for_human_size(number)
  
  number_with_precision(number, :precision => precision,
    :separator => separator, :delimiter => delimiter
  ).sub(/(\d)(#{Regexp.escape(separator)}[1-9]*)?0+\z/, '\1') + " #{unit}"
rescue
  number
end

private
def number_and_unit_for_human_size(number)
  units    = [ "Bytes", "KB", "MB", "GB", "TB" ].freeze

  number   = Float(number)
  exponent = (Math.log(number)/Math.log(1024)).to_i # calculate logarithm for base 1024
  exponent = units.size - 1 if exponent > units.size - 1 # we need this to avoid overflow for the highest unit
  number  /= 1024**exponent
  unit     = units[exponent]

  [ number, unit ]
end