public function chown($uid, $gid = -1, $cb = null, $pri = EIO_PRI_DEFAULT)
    {
        $cb = CallbackWrapper::forceWrap($cb);
        if (!$this->fd) {
            if ($cb) {
                $cb($this, false);
            }
            return false;
        }
        if (!FileSystem::$supported) {
            $r = chown($this->path, $uid);
            if ($gid !== -1) {
                $r = $r && chgrp($this->path, $gid);
            }
            if ($cb) {
                $cb($this, $r);
            }
            return false;
        }
        return eio_fchown($this->fd, $uid, $gid, $pri, $cb, $this);
    }