gistfile1.rbx

# config
:number => {
  :format => {
    :precision => 3,
    :separator => '.',
    :delimiter => ','
  },
  :currency => {
    :format => {
      :unit => '$',
      :precision => 2,
      :format => '%u%n'
    }
  },
  :human => {
    :format => {
      :precision => 1
    }
  }
}

# test
def test_number_to_human_size_translates_human_formats
  I18n.expects(:translate).with(:'number.format', :locale => 'en-US').returns(@number_defaults)
  I18n.expects(:translate).with(:'number.human.format', :locale => 'en-US').returns(@human_defaults)
  number_to_human_size(1, :locale => 'en-US')
end

# helper
def number_to_human_size(size, *args)
  options = args.extract_options!
  options.symbolize_keys!
  
  defaults = I18n.translate(:'number.format', :locale => options[:locale])
  defaults.merge!(I18n.translate(:'number.human.format', :locale => options[:locale]))
  
  unless args.empty?
    precision = args[0] || defaults[:precision]
  end
  
  precision ||= (options[:precision] || defaults[:precision])

  size = Float(size)
  case
    when size.to_i == 1;    "1 Byte"
    when size < 1.kilobyte; "%d Bytes" % size
    when size < 1.megabyte; "%.#{precision}f KB"  % (size / 1.0.kilobyte)
    when size < 1.gigabyte; "%.#{precision}f MB"  % (size / 1.0.megabyte)
    when size < 1.terabyte; "%.#{precision}f GB"  % (size / 1.0.gigabyte)
    else                    "%.#{precision}f TB"  % (size / 1.0.terabyte)
  end.sub(/([0-9]\.\d*?)0+ /, '\1 ' ).sub(/\. /,' ')
rescue
  nil
end