gistfile1.txt

def smallAsciiRepresentation(digest)

  digestParts = digest.unpack("Q2") # digest is a 128 bit buffer, cut it into two 64 bits ruby Integer
  smallDigestPart = digestParts[0] ^ digestParts[1] # XOR the two 64 bits parts
  smallDigest = [smallDigestPart].pack("Q") # and transform the result into a 64 bits binary buffer 
  smallDigestB64 = [smallDigest].pack("m") # b64-encode the result 
  smallID = smallDigestB64.gsub(/[\n=]/, '').gsub(/\+/,'-').gsub(/\//,'_') # and make it URL-friendly by shortening it (no '=' at the end, no '+', no '/')

  return smallID
end