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<?php |
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/** |
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* @author Jared King <[email protected]> |
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* |
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* @see http://jaredtking.com |
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* |
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* @copyright 2015 Jared King |
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* @license MIT |
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*/ |
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namespace Pulsar; |
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final class Iterator implements \Iterator, \Countable, \ArrayAccess |
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{ |
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/** |
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* @var Query |
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*/ |
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private $query; |
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/** |
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* @var int |
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*/ |
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private $start; |
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/** |
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* @var int |
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*/ |
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private $pointer; |
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/** |
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* @var int |
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*/ |
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private $limit; |
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/** |
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* @var int|bool |
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*/ |
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private $loadedStart; |
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/** |
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* @var array |
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*/ |
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private $models; |
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/** |
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* @var int|bool |
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*/ |
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private $count; |
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public function __construct(Query $query) |
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{ |
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$this->query = $query; |
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$this->models = []; |
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$this->start = $query->getStart(); |
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$this->limit = $query->getLimit(); |
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$this->pointer = $this->start; |
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$sort = $query->getSort(); |
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if (empty($sort)) { |
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$model = $query->getModel(); |
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$idProperties = $model::getIDProperties(); |
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foreach ($idProperties as &$property) { |
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$property .= ' asc'; |
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} |
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$query->sort(implode(',', $idProperties)); |
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} |
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} |
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public function getQuery(): Query |
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{ |
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return $this->query; |
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} |
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////////////////////////// |
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// Iterator Interface |
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////////////////////////// |
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/** |
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* Rewind the Iterator to the first element. |
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*/ |
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public function rewind() |
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{ |
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$this->pointer = $this->start; |
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$this->loadedStart = false; |
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$this->models = []; |
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$this->count = false; |
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} |
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/** |
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* Returns the current element. |
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* |
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* @return mixed |
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*/ |
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public function current() |
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{ |
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if ($this->pointer >= $this->count()) { |
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return null; |
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} |
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$this->loadModels(); |
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$k = $this->pointer % $this->limit; |
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if (isset($this->models[$k])) { |
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return $this->models[$k]; |
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} |
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return null; |
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} |
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/** |
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* Return the key of the current element. |
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* |
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* @return int |
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*/ |
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public function key() |
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{ |
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return $this->pointer; |
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} |
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/** |
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* Move forward to the next element. |
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*/ |
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public function next() |
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{ |
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++$this->pointer; |
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} |
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/** |
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* Checks if current position is valid. |
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* |
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* @return bool |
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*/ |
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public function valid() |
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{ |
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return $this->pointer < $this->count(); |
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} |
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////////////////////////// |
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// Countable Interface |
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////////////////////////// |
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/** |
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* Get total number of models matching query. |
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* |
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* @return int |
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*/ |
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public function count() |
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{ |
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$this->updateCount(); |
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return $this->count; |
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} |
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////////////////////////// |
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// ArrayAccess Interface |
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////////////////////////// |
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public function offsetExists($offset) |
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{ |
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return is_numeric($offset) && $offset < $this->count(); |
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} |
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public function offsetGet($offset) |
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{ |
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if (!$this->offsetExists($offset)) { |
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throw new \OutOfBoundsException("$offset does not exist on this Iterator"); |
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} |
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$this->pointer = $offset; |
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return $this->current(); |
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} |
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public function offsetSet($offset, $value) |
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{ |
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// iterators are immutable |
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throw new \Exception('Cannot perform set on immutable Iterator'); |
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} |
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public function offsetUnset($offset) |
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{ |
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// iterators are immutable |
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throw new \Exception('Cannot perform unset on immutable Iterator'); |
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} |
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////////////////////////// |
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// Private Methods |
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////////////////////////// |
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/** |
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* Load the next round of models. |
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*/ |
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private function loadModels() |
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{ |
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$start = $this->rangeStart($this->pointer, $this->limit); |
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if ($this->loadedStart !== $start) { |
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$this->query->start($start); |
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$this->models = $this->query->execute(); |
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$this->loadedStart = $start; |
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} |
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} |
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/** |
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* Updates the total count of models. For better performance |
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* the count is only updated on edges, which is when new models |
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* need to be loaded. |
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*/ |
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private function updateCount() |
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{ |
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// The count only needs to be updated when the pointer is |
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// on the edges |
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if (0 != $this->pointer % $this->limit && |
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$this->pointer < $this->count) { |
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return; |
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} |
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$newCount = $this->query->count(); |
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// It's possible when iterating over models that something |
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// is modified or deleted that causes the model count |
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// to decrease. If the count has decreased then we |
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// shift the pointer to prevent overflow. |
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// This calculation is based on the assumption that |
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// the first N (count - count') models are deleted. |
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if (0 != $this->count && $newCount < $this->count) { |
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$this->pointer = max(0, $this->pointer - ($this->count - $newCount)); |
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} |
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// If the count has increased then the pointer is still |
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// valid. Update the count to include the extra models. |
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$this->count = $newCount; |
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} |
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/** |
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* Generates the starting page given a pointer and limit. |
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*/ |
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private function rangeStart(int $pointer, int $limit) |
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{ |
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return floor($pointer / $limit) * $limit; |
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} |
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/** |
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* Cast Iterator to array. |
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*/ |
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public function toArray(): array |
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{ |
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return iterator_to_array($this); |
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} |
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} |
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