gistfile1.rb

module Base62
  BASE_CHARS = '0SKVnQFHhGs9qo7p8cRW54duMYNXTCErx2tDmwO3kabfUB1elLvjiIgyJAZ6Pz'.split('')
  BASE = BASE_CHARS.length
  BASE_ENCODED_MIN_LENGTH = 1
  
  def self.decode(number)
    # assure string
    number = number.to_s.reverse.split('')
    
    decoded = 0
    digits = number.length
    
    # decode
    digits.times do |i|
      decoded+= BASE_CHARS.index(number[i]) * BASE**i
    end
    
    decoded
  end

  def self.encode(number)
    if number.nil?
      return nil
    end
    
    # assure numerical
    number = number.to_i(10) unless number.is_a? Integer
    
    encoded = ''
    digits = (number > 0) ? 1 + (Math.log(number)/Math.log(BASE)).to_i : 0
    
    # fill with leading zeros
    (BASE_ENCODED_MIN_LENGTH - digits).times do
      encoded << BASE_CHARS[0]
    end
    
    # convert the number
    digits.times do |i|
      divider = BASE**(digits - 1 - i)
      encoded << BASE_CHARS[(number / divider).to_i]
      number = number % divider
    end
    
    encoded
  end
  
end

# extend Integer and String
class Integer
  def to_base62
    Base62.encode self
  end
  def from_base62
    Base62.decode self
  end
end

class String
  def to_base62
    Base62.encode self
  end
  def from_base62
    Base62.decode self
  end
end