Represents an UUID in a shorter and still URL compatible string (from 36 to 22 chars)

uuid_shortner.rb

class UUIDShortner
    IGNORE = '-'
    BASE6_SLAB = ' ' * 22
    
    # 64 (6 bits) items dictionary
    DICT = 'a'.upto('z').to_a +
           'A'.upto('Z').to_a +
           '0'.upto('9').to_a +
           ['_', '-'] 

    def self.uuid_to_base6 uuid
        uuid_bits = 0
        
        uuid.each_char do |c|
            next if c == IGNORE
            uuid_bits = (uuid_bits << 4) | c.hex
        end

        base6 = BASE6_SLAB.dup

        base6.size.times { |i|
            base6[i] = DICT[uuid_bits & 0b111111]
            uuid_bits >>= 6
        }

        base6
    end
end

# Examples:

require 'securerandom'
uuid = ARGV[0] || SecureRandom.uuid
short = UUIDShortner.uuid_to_base6 uuid
puts "#{uuid}\n#{short}"

# ruby uuid_to_base6.rb
# c7e6a9e5-1fc6-4d5a-b889-4734e42b9ecc
# m75kKtZrjIRwnz8hLNQ5hd

# ruby uuid_to_base6.rb
# 6107f0c3-e980-4d66-9190-b9f1b9af2622
# IyYR5gFUqgPznby6dd-bHb

# ruby uuid_to_base6.rb
# 94e66cad-3f12-45f3-982d-73dbfbb88da3
# J2iU7V9CTG58fjXpTYM5uc