Convert byte counts to SI units

si_byte_count.rb

  class SiByteCount

    def initialize(n)
      @n = n
    end

    def to_s
      n = signif(@n, 3)
      UNITS.each do |coef, abbrev|
        if n >= coef
          n = n / coef unless coef.infinite?
          return "#{remove_trailing_decimal_zeros(n)} #{abbrev}"
        end
      end
    end

    private

    UNITS = [
      [1E12, "TB"],
      [1E9, "GB"],
      [1E6, "MB"],
      [1E3, "kB"],
      [-Float::INFINITY, "B"],
    ]
    private_constant :UNITS

    # From https://stackoverflow.com/a/44891822/238886
    def signif(f, significant_digits)
      return 0 if f.zero?
      f.round(-(Math.log10(f).ceil - significant_digits))
    end

    def remove_trailing_decimal_zeros(n)
      n
        .to_s
        .gsub(/(\.\d*)0+$/, '\1')
        .gsub(/\.$/, "")
    end

  end