protected function getHandlerFunctionName(AbstractEvent $event) {
        $name = array_search($event, $this->handlerFunctionNames);
        if ($name === false) {
            $functionPrefix = $this->builder->getOptions()->getFunctionPrefix();
            $parts = explode('\\', get_class($event));
            $class = end($parts);
            $name = $functionPrefix . '_Handle' . $class . count($this->handlerFunctionNames);
            $this->handlerFunctionNames[$name] = $event;
        }
        return $name;
    }