base60 (en|de)coding - see http://tantek.pbworks.com/w/page/19402946/NewBase60

gistfile1.rb

class String
  def base60_decode
    n = 0
    self.each_byte do |c|
      case
      when c >= 48 && c <= 57
        c -= 48
      when c >= 65 && c <= 72
        c -= 55
      when c == 73 || c == 108
        c = 1
      when c >= 74 && c <= 78
        c -= 56
      when c == 79
        c = 0
      when c >= 80 && c <= 90
        c -= 57
      when c == 95
        c = 34
      when c >= 97 && c <= 107
        c -= 62
      when c >= 109 && c <= 122
        c -= 63
      else
        c = 0
      end
      n = (60 * n) + c
    end
    n
  end
end

class Integer
  BASE60_MAP = "0123456789ABCDEFGHJKLMNPQRSTUVWXYZ_abcdefghijkmnopqrstuvwxyz"
  def base60_encode
    return self if self == 0
    s = ""
    n = self
    while n > 0 do
      d = n % 60;
      s = BASE60_MAP[d] + s;
      n = (n-d)/60;
    end
    s
  end
end