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<?php
namespace ipl\Stdlib;
use Generator;
use SplPriorityQueue;
/**
* Stable priority queue that also maintains insertion order for items with the same priority
*/
class PriorityQueue extends SplPriorityQueue
{
/** @var int */
protected $serial = PHP_INT_MAX;
/**
* @inheritDoc
*
* Maintains insertion order for items with the same priority.
*/
public function insert($value, $priority): bool
{
return parent::insert($value, [$priority, $this->serial--]);
}
/**
* Yield all items as priority-value pairs
*
* @return Generator
*/
public function yieldAll()
{
// Clone queue because the SplPriorityQueue acts as a heap and thus items are removed upon iteration
$queue = clone $this;
$queue->setExtractFlags(static::EXTR_BOTH);
foreach ($queue as $item) {
yield $item['priority'][0] => $item['data'];
}
}
}
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