How can I move this custom code out of drupal core user module?

Question

I am in the process of trying to get our custom code out of core.

In this function I capture the old session ID to update a project the user may have been working on while not logged in.

function user_authenticate_finalize(&$edit) {
  global $user;
  watchdog('user', 'Session opened for %name.', array('%name' => $user->name));
  // Update the user table timestamp noting user has logged in.
  // This is also used to invalidate one-time login links.
  $user->login = time();
  db_query("UPDATE {users} SET login = %d WHERE uid = %d", $user->login, $user->uid);

  $old_session_id = session_id(); //THIS LINE NEEDS TO BE MOVED

  // Regenerate the session ID to prevent against session fixation attacks.
  sess_regenerate();

  tf_user_new_session_id($user, $old_session_id); //THIS LINE NEEDS TO BE MOVED

  user_module_invoke('login', $edit, $user);
}

The lines right before and right after sess_regenerate();

Answer 1

function tf_user_user($op, &$edit, &$account, $category = NULL)
{
  $current_session = session_id();

  if ('login' == $op)
  {
    setcookie('session_id_anonymous', $current_session, time() + 86400);
  }
  if ('load' == $op)
  {
    if (isset($_COOKIE['session_id_anonymous']) && $_COOKIE['session_id_anonymous'] != $current_session)
    {
      tf_user_new_session_id($account->uid, $_COOKIE['session_id_anonymous'], $current_session);

      setcookie('session_id_anonymous', $current_session, time() - 3600);
    }
  }
  //more code
}