Readable Base 62 encoder

fixnum+base62.rb

# Use this for your URL shortening needs
# Base 62 is as good as you can easily get for URL shortening
# And it's effective: 1_000_000 => '4c92'
# Challenge: fork and speed up the implementation!

class Fixnum
  TOKENS = ('0'..'9').to_a + ('a'..'z').to_a + ('A'..'Z').to_a

  # NOTE returns nil for 0
  def to_62_s
    i = self
    s = ''
    while i > 0
      s << TOKENS[i.modulo(62)]
      i /= 62
    end
    s.reverse
  end

  def self.base62(s)
    i = 0
    n = 1
    s.reverse.each_byte do |c|
      i += TOKENS.index(c.chr) * n
      n *= 62
    end
    return i
  end
end


if __FILE__ == $0
  s = 1_000_000.to_62_s
  assert Fixnum.base62(s) == 1_000_000
end