base62.rb

class B62
  CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".split('')
  BASE = 62
  def self.encode(value)
    s = []
    while value >= BASE
      value, rem = value.divmod(BASE)
      s << CHARS[rem]
    end
    s << CHARS[value]
    s.reverse.to_s
  end
   
  def self.decode(str)
    str = str.split('').reverse
    total = 0
    str.each_with_index do |v,k|
      total += (CHARS.index(v) * (BASE ** k))
    end
    total
  end
end