public function await($timeout = 0, TimeUnit $unit = null)
    {
        if (null !== $unit) {
            $timeout = $unit->toMicros($timeout);
        }
        $timeoutAt = microtime(true) + ($timeout / 1000000);
        while (0 != $this->count) {
            if ($timeout > 0 && (microtime(true) > $timeoutAt)) {
                return false;
            }
            time_nanosleep(0, 1);
        }
        return true;
    }