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EventEmitterTrait.php
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<?php
namespace Sabre\Event;
/**
* Event Emitter Trait
*
* This trait contains all the basic functions to implement an
* EventEmitterInterface.
*
* Using the trait + interface allows you to add EventEmitter capabilities
* without having to change your base-class.
*
* @copyright Copyright (C) 2013-2015 fruux GmbH (https://fruux.com/).
* @author Evert Pot (http://evertpot.com/)
* @license http://sabre.io/license/ Modified BSD License
*/
trait EventEmitterTrait {
/**
* The list of listeners
*
* @var array
*/
protected $listeners = [];
/**
* Subscribe to an event.
*
* @param string $eventName
* @param callable $callBack
* @param int $priority
* @return void
*/
function on($eventName, callable $callBack, $priority = 100) {
if (!isset($this->listeners[$eventName])) {
$this->listeners[$eventName] = [
true, // If there's only one item, it's sorted
[$priority],
[$callBack]
];
} else {
$this->listeners[$eventName][0] = false; // marked as unsorted
$this->listeners[$eventName][1][] = $priority;
$this->listeners[$eventName][2][] = $callBack;
}
}
/**
* Subscribe to an event exactly once.
*
* @param string $eventName
* @param callable $callBack
* @param int $priority
* @return void
*/
function once($eventName, callable $callBack, $priority = 100) {
$wrapper = null;
$wrapper = function() use ($eventName, $callBack, &$wrapper) {
$this->removeListener($eventName, $wrapper);
return call_user_func_array($callBack, func_get_args());
};
$this->on($eventName, $wrapper, $priority);
}
/**
* Emits an event.
*
* This method will return true if 0 or more listeners were succesfully
* handled. false is returned if one of the events broke the event chain.
*
* If the continueCallBack is specified, this callback will be called every
* time before the next event handler is called.
*
* If the continueCallback returns false, event propagation stops. This
* allows you to use the eventEmitter as a means for listeners to implement
* functionality in your application, and break the event loop as soon as
* some condition is fulfilled.
*
* Note that returning false from an event subscriber breaks propagation
* and returns false, but if the continue-callback stops propagation, this
* is still considered a 'successful' operation and returns true.
*
* Lastly, if there are 5 event handlers for an event. The continueCallback
* will be called at most 4 times.
*
* @param string $eventName
* @param array $arguments
* @param callback $continueCallBack
* @return bool
*/
function emit($eventName, array $arguments = [], callable $continueCallBack = null) {
if (is_null($continueCallBack)) {
foreach ($this->listeners($eventName) as $listener) {
$result = call_user_func_array($listener, $arguments);
if ($result === false) {
return false;
}
}
} else {
$listeners = $this->listeners($eventName);
$counter = count($listeners);
foreach ($listeners as $listener) {
$counter--;
$result = call_user_func_array($listener, $arguments);
if ($result === false) {
return false;
}
if ($counter > 0) {
if (!$continueCallBack()) break;
}
}
}
return true;
}
/**
* Returns the list of listeners for an event.
*
* The list is returned as an array, and the list of events are sorted by
* their priority.
*
* @param string $eventName
* @return callable[]
*/
function listeners($eventName) {
if (!isset($this->listeners[$eventName])) {
return [];
}
// The list is not sorted
if (!$this->listeners[$eventName][0]) {
// Sorting
array_multisort($this->listeners[$eventName][1], SORT_NUMERIC, $this->listeners[$eventName][2]);
// Marking the listeners as sorted
$this->listeners[$eventName][0] = true;
}
return $this->listeners[$eventName][2];
}
/**
* Removes a specific listener from an event.
*
* If the listener could not be found, this method will return false. If it
* was removed it will return true.
*
* @param string $eventName
* @param callable $listener
* @return bool
*/
function removeListener($eventName, callable $listener) {
if (!isset($this->listeners[$eventName])) {
return false;
}
foreach ($this->listeners[$eventName][2] as $index => $check) {
if ($check === $listener) {
unset($this->listeners[$eventName][1][$index]);
unset($this->listeners[$eventName][2][$index]);
return true;
}
}
return false;
}
/**
* Removes all listeners.
*
* If the eventName argument is specified, all listeners for that event are
* removed. If it is not specified, every listener for every event is
* removed.
*
* @param string $eventName
* @return void
*/
function removeAllListeners($eventName = null) {
if (!is_null($eventName)) {
unset($this->listeners[$eventName]);
} else {
$this->listeners = [];
}
}
}

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