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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Cache
*/
namespace MediaWiki\Cache;
use LogicException;
use MediaWiki\Page\PageReference;
use Wikimedia\Parsoid\Core\LinkTarget;
/**
* Helper class for mapping value objects representing basic entities to cache keys.
*
* Rationale:
* The logic for deriving the cache key should not be in the value object themselves for two reasons:
* Firstly, the value object should not contain knowledge about caching or keys in general.
* Secondly, all implementations of a given interface must have the exact same logic for deriving
* the cache key. Otherwise, caches will break when different implementations are used when
* interacting with a cache.
*
* Furthermore, the logic for deriving cache keys should not be in a service instance: there can
* only ever be one implementation, it must not depend on configuration, and it should never change.
*
* @ingroup Cache
*/
abstract class CacheKeyHelper {
/**
* Private constructor to defy instantiation.
* @return never
*/
private function __construct() {
// we should never even get here...
throw new LogicException( 'Should not instantiate ' . __CLASS__ );
}
/**
* @param LinkTarget|PageReference $page
*
* @return string
*/
public static function getKeyForPage( $page ): string {
return 'ns' . $page->getNamespace() . ':' . $page->getDBkey();
}
}
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