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<?php |
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namespace VDB\Spider; |
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use Exception; |
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use Symfony\Component\EventDispatcher\Event; |
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use Symfony\Component\EventDispatcher\EventDispatcher; |
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use Symfony\Component\EventDispatcher\EventDispatcherInterface; |
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use Symfony\Component\EventDispatcher\GenericEvent; |
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use VDB\Spider\Discoverer\DiscovererSet; |
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use VDB\Spider\Event\SpiderEvents; |
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use VDB\Spider\Exception\QueueException; |
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use VDB\Spider\QueueManager\QueueManagerInterface; |
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use VDB\Spider\QueueManager\InMemoryQueueManager; |
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use VDB\Spider\Uri\DiscoveredUri; |
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use VDB\Spider\Downloader\DownloaderInterface; |
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use VDB\Spider\Downloader\Downloader; |
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use VDB\Uri\UriInterface; |
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use VDB\Uri\Uri; |
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/** |
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* |
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*/ |
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class Spider |
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{ |
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/** @var DownloaderInterface */ |
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private $downloader; |
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/** @var QueueManagerInterface */ |
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private $queueManager; |
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/** @var EventDispatcherInterface */ |
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private $dispatcher; |
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/** @var DiscovererSet */ |
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private $discovererSet; |
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/** @var DiscoveredUri The URI of the site to spider */ |
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private $seed = array(); |
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/** @var string the unique id of this spider instance */ |
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private $spiderId; |
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/** |
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* @param string $seed the URI to start crawling |
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* @param string|null $spiderId |
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*/ |
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public function __construct($seed, $spiderId = null) |
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{ |
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$this->setSeed($seed); |
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if (null !== $spiderId) { |
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$this->spiderId = $spiderId; |
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} else { |
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$this->spiderId = md5($seed . microtime(true)); |
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} |
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// This makes the spider handle signals gracefully and allows us to do cleanup |
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if (php_sapi_name() == 'cli') { |
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declare(ticks = 1); |
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if (function_exists('pcntl_signal')) { |
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pcntl_signal(SIGTERM, array($this, 'handleSignal')); |
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pcntl_signal(SIGINT, array($this, 'handleSignal')); |
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pcntl_signal(SIGHUP, array($this, 'handleSignal')); |
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pcntl_signal(SIGQUIT, array($this, 'handleSignal')); |
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} |
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} |
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} |
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/** |
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* Starts crawling the URI provided on instantiation |
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* |
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* @return void |
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*/ |
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public function crawl() |
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{ |
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$this->getQueueManager()->addUri($this->seed); |
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$this->getDownloader()->getPersistenceHandler()->setSpiderId($this->spiderId); |
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$this->doCrawl(); |
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} |
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/** |
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* param DiscovererSet $discovererSet |
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*/ |
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public function setDiscovererSet(DiscovererSet $discovererSet) |
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{ |
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$this->discovererSet = $discovererSet; |
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} |
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/** |
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* @return DiscovererSet |
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*/ |
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public function getDiscovererSet() |
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{ |
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if (!$this->discovererSet) { |
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$this->discovererSet = new DiscovererSet(); |
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} |
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return $this->discovererSet; |
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} |
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/** |
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* param QueueManagerInterface $queueManager |
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*/ |
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public function setQueueManager(QueueManagerInterface $queueManager) |
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{ |
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$this->queueManager = $queueManager; |
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} |
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/** |
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* @return QueueManagerInterface |
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*/ |
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public function getQueueManager() |
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{ |
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if (!$this->queueManager) { |
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$this->queueManager = new InMemoryQueueManager(); |
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} |
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return $this->queueManager; |
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} |
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/** |
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* @param DownloaderInterface $downloader |
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* @return $this |
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*/ |
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public function setDownloader(DownloaderInterface $downloader) |
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{ |
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$this->downloader = $downloader; |
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return $this; |
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} |
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/** |
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* @return DownloaderInterface |
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*/ |
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public function getDownloader() |
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{ |
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if (!$this->downloader) { |
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$this->downloader = new Downloader(); |
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} |
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return $this->downloader; |
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} |
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/** |
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* @param EventDispatcherInterface $eventDispatcher |
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* @return $this |
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*/ |
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public function setDispatcher(EventDispatcherInterface $eventDispatcher) |
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{ |
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$this->dispatcher = $eventDispatcher; |
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return $this; |
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} |
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/** |
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* @return EventDispatcherInterface |
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*/ |
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public function getDispatcher() |
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{ |
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if (!$this->dispatcher) { |
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$this->dispatcher = new EventDispatcher(); |
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} |
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return $this->dispatcher; |
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} |
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public function handleSignal($signal) |
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{ |
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switch ($signal) { |
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case SIGTERM: |
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case SIGKILL: |
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case SIGINT: |
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case SIGQUIT: |
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$this->dispatch(SpiderEvents::SPIDER_CRAWL_USER_STOPPED); |
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} |
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} |
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/** |
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* Function that crawls each provided URI |
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* It applies all processors and listeners set on the Spider |
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* |
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* This is a either depth first algorithm as explained here: |
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* https://en.wikipedia.org/wiki/Depth-first_search#Example |
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* Note that because we don't do it recursive, but iteratively, |
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* results will be in a different order from the example, because |
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* we always take the right-most child first, whereas a recursive |
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* variant would always take the left-most child first |
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* |
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* or |
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* |
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* a breadth first algorithm |
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* |
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* @return void |
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*/ |
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private function doCrawl() |
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{ |
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while ($currentUri = $this->getQueueManager()->next()) { |
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if ($this->getDownloader()->isDownLoadLimitExceeded()) { |
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break; |
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} |
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if (!$resource = $this->getDownloader()->download($currentUri)) { |
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continue; |
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} |
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$this->dispatch( |
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SpiderEvents::SPIDER_CRAWL_RESOURCE_PERSISTED, |
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new GenericEvent($this, array('uri' => $currentUri)) |
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); |
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// Once the document is enqueued, apply the discoverers to look for more links to follow |
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$discoveredUris = $this->getDiscovererSet()->discover($resource); |
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foreach ($discoveredUris as $uri) { |
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try { |
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$this->getQueueManager()->addUri($uri); |
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} catch (QueueException $e) { |
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// when the queue size is exceeded, we stop discovering |
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break; |
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} |
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} |
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} |
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} |
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/** |
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* A shortcut for EventDispatcher::dispatch() |
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* |
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* @param string $eventName |
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* @param null|Event $event |
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*/ |
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private function dispatch($eventName, Event $event = null) |
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{ |
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$this->getDispatcher()->dispatch($eventName, $event); |
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} |
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/** |
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* @param string $uri |
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*/ |
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private function setSeed($uri) |
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{ |
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$this->seed = new DiscoveredUri(new Uri($uri)); |
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$this->seed->setDepthFound(0); |
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} |
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} |
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