Base32 string encoder, generate a unique shorten string from a long string, such as a url

shorten.rb

require 'digest/md5'
module Shorten
    #base32
    TABLE = %w(a b c d e f g h i j k l m n o p q r s t u v w x y z 2 3 4 6 7 8)
    
    # short('balabala') => Array
    # short('balabala',1) => String, Array[1]
    def self.short long_str, index = nil
      index = (0..3).to_a.include?(index) ? index : nil
      hash_string = Digest::MD5.hexdigest(long_str)
      hashes,strs = [],[]
      
      hashes = (0..31).step(8).collect{|i|hash_string[i,8]}

      strs = hashes.collect do |str|
        i = 0x3FFFFFFF & "0x#{str}".hex
        str =''
        (0..5).each do
          j = 0x0000001F & i
          str << TABLE[j]
          i = i >> 5
        end
        str
      end
      
      index.nil? ? strs : strs[index]
    end
    
end