outlaw love song

Quick, local short_urls

Cross-posted from http://engineering.patch.com/quick-local-shorturls

On patch.com, we generate short_urls for our editors to use on services like Twitter. The benefit of generating the short URL internally is three-fold:

1. We get to maintain the Patch branding
2. We don’t have to rely on an external shortening service
3. We can be in control of how our links are created

The last one is really fun, because it means that we can cleverly name our short_urls in a way that they don’t need to make an extra request to the database for lookup. So, instead of a user requesting http://patch.com/bE582, and us looking up in a table what page that references, we can created a short URL like: http://patch.com/L-dbrB and serve the user Listing 281923.

Its really simple, as is the code to support it:

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# John Crepezzi  April 22, 2010  
class ShortId  
 
  # We cut out vowels to avoid shortened strings from mistakenly 
  # forming words  
  Alphabet = 'bcdfghjklmnpqrstvwxyz0123456789BCDFGHJKLMNPQRSTVWXYZ'  
  AlphabetLength = Alphabet.length  
 
  # Encode a numeric ID  
  def self.encode(id)  
    alpha = ''  
    while id != 0  
      alpha = Alphabet[id % AlphabetLength].chr + alpha  
      id /= AlphabetLength  
    end  
    alpha  
  end  
 
  # Decode an ID created with self.encode  
  def self.decode(alpha)  
    alpha = alpha.dup; id = 0  
    0.upto(alpha.length - 1) do |i|  
      id += Alphabet.index(alpha[-1]) * (AlphabetLength ** i)  
      alpha.chop!  
    end  
    id  
  end  
 
end

Enjoy!