/**
 * Get a uid for anonymous vs. registered voting
 */
function _vote_up_down_get_uid() {
  global $user;

  if ($user->uid) {
    $uid = $user->uid;
  }
  else if (variable_get('vote_up_down_anonymous_vote', 0)) {
    // Fake uid for anonymous users.
    // If the IP is valid turn it into a integer and add the number of the current day.
    // The current day is what limit anonymous voting to one vote per day and IP address.
    $hostname = (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER['REMOTE_ADDR'];
    if ($long = ip2long($hostname)) {
      $uid = abs($long) + date('z');
    }
  }
  else {
    $uid = NULL;
  }

  return $uid;
}