Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php

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+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher.
+ */
+
+namespace Drupal\Component\EventDispatcher;
+
+use Symfony\Component\DependencyInjection\IntrospectableContainerInterface;
+use Symfony\Component\EventDispatcher\Event;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * A performance optimized container aware event dispatcher.
+ *
+ * This version of the event dispatcher contains the following optimizations
+ * in comparison to the Symfony event dispatcher component:
+ *
+ * <dl>
+ *   <dt>Faster instantiation of the event dispatcher service</dt>
+ *   <dd>
+ *     Instead of calling <code>addSubscriberService</code> once for each
+ *     subscriber, a precompiled array of listener definitions is passed
+ *     directly to the constructor. This is faster by roughly an order of
+ *     magnitude. The listeners are collected and prepared using a compiler
+ *     pass.
+ *   </dd>
+ *   <dt>Lazy instantiation of listeners</dt>
+ *   <dd>
+ *     Services are only retrieved from the container just before invocation.
+ *     Especially when dispatching the KernelEvents::REQUEST event, this leads
+ *     to a more timely invocation of the first listener. Overall dispatch
+ *     runtime is not affected by this change though.
+ *   </dd>
+ * </dl>
+ */
+class ContainerAwareEventDispatcher implements EventDispatcherInterface {
+
+  /**
+   * The service container.
+   *
+   * @var \Symfony\Component\DependencyInjection\IntrospectableContainerInterface;
+   */
+  protected $container;
+
+  /**
+   * Listener definitions.
+   *
+   * A nested array of listener definitions keyed by event name and priority.
+   * A listener definition is an associative array with one of the following key
+   * value pairs:
+   * - callable: A callable listener
+   * - service: An array of the form [service id, method]
+   *
+   * A service entry will be resolved to a callable only just before its
+   * invocation.
+   *
+   * @var array
+   */
+  protected $listeners;
+
+  /**
+   * Whether listeners need to be sorted prior to dispatch, keyed by event name.
+   *
+   * @var TRUE[]
+   */
+  protected $unsorted;
+
+  /**
+   * Constructs a container aware event dispatcher.
+   *
+   * @param \Symfony\Component\EventDispatcher\IntrospectableContainerInterface $container
+   *   The service container.
+   * @param array $listeners
+   *   A nested array of listener definitions keyed by event name and priority.
+   *   The array is expected to be ordered by priority. A listener definition is
+   *   an associative array with one of the following key value pairs:
+   *   - callable: A callable listener
+   *   - service: An array of the form [service id, method]
+   *   A service entry will be resolved to a callable only just before its
+   *   invocation.
+   */
+  public function __construct(IntrospectableContainerInterface $container, array $listeners = []) {
+    $this->container = $container;
+    $this->listeners = $listeners;
+    $this->unsorted = [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function dispatch($event_name, Event $event = NULL) {
+    if ($event === NULL) {
+      $event = new Event();
+    }
+
+    $event->setDispatcher($this);
+    $event->setName($event_name);
+
+    if (isset($this->listeners[$event_name])) {
+      // Sort listeners if necessary.
+      if (isset($this->unsorted[$event_name])) {
+        krsort($this->listeners[$event_name]);
+        unset($this->unsorted[$event_name]);
+      }
+
+      // Invoke listeners and resolve callables if necessary.
+      foreach ($this->listeners[$event_name] as $priority => &$definitions) {
+        foreach ($definitions as $key => &$definition) {
+          if (!isset($definition['callable'])) {
+            $definition['callable'] = [$this->container->get($definition['service'][0]), $definition['service'][1]];
+          }
+
+          $definition['callable']($event, $event_name, $this);
+          if ($event->isPropagationStopped()) {
+            return $event;
+          }
+        }
+      }
+    }
+
+    return $event;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getListeners($event_name = NULL) {
+    $result = [];
+
+    if ($event_name === NULL) {
+      // If event name was omitted, collect all listeners of all events.
+      foreach (array_keys($this->listeners) as $event_name) {
+        $listeners = $this->getListeners($event_name);
+        if (!empty($listeners)) {
+          $result[$event_name] = $listeners;
+        }
+      }
+    }
+    elseif (isset($this->listeners[$event_name])) {
+      // Sort listeners if necessary.
+      if (isset($this->unsorted[$event_name])) {
+        krsort($this->listeners[$event_name]);
+        unset($this->unsorted[$event_name]);
+      }
+
+      // Collect listeners and resolve callables if necessary.
+      foreach ($this->listeners[$event_name] as $priority => &$definitions) {
+        foreach ($definitions as $key => &$definition) {
+          if (!isset($definition['callable'])) {
+            $definition['callable'] = [$this->container->get($definition['service'][0]), $definition['service'][1]];
+          }
+
+          $result[] = $definition['callable'];
+        }
+      }
+    }
+
+    return $result;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasListeners($event_name = NULL) {
+    return (bool) count($this->getListeners($event_name));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addListener($event_name, $listener, $priority = 0) {
+    $this->listeners[$event_name][$priority][] = ['callable' => $listener];
+    $this->unsorted[$event_name] = TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeListener($event_name, $listener) {
+    if (!isset($this->listeners[$event_name])) {
+      return;
+    }
+
+    foreach ($this->listeners[$event_name] as $priority => $definitions) {
+      foreach ($definitions as $key => $definition) {
+        if (!isset($definition['callable'])) {
+          if (!$this->container->initialized($definition['service'][0])) {
+            continue;
+          }
+          $definition['callable'] = [$this->container->get($definition['service'][0]), $definition['service'][1]];
+        }
+
+        if ($definition['callable'] === $listener) {
+          unset($this->listeners[$event_name][$priority][$key]);
+        }
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addSubscriber(EventSubscriberInterface $subscriber) {
+    foreach ($subscriber->getSubscribedEvents() as $event_name => $params) {
+      if (is_string($params)) {
+        $this->addListener($event_name, array($subscriber, $params));
+      }
+      elseif (is_string($params[0])) {
+        $this->addListener($event_name, array($subscriber, $params[0]), isset($params[1]) ? $params[1] : 0);
+      }
+      else {
+        foreach ($params as $listener) {
+          $this->addListener($event_name, array($subscriber, $listener[0]), isset($listener[1]) ? $listener[1] : 0);
+        }
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeSubscriber(EventSubscriberInterface $subscriber) {
+    foreach ($subscriber->getSubscribedEvents() as $event_name => $params) {
+      if (is_array($params) && is_array($params[0])) {
+        foreach ($params as $listener) {
+          $this->removeListener($event_name, array($subscriber, $listener[0]));
+        }
+      }
+      else {
+        $this->removeListener($event_name, array($subscriber, is_string($params) ? $params : $params[0]));
+      }
+    }
+  }
+
+}