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<?php
/**
* Per-process memory cache for storing items.
*
* 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
*/
/**
* Handles a simple LRU key/value map with a maximum number of entries
*
* Use ProcessCacheLRU if hierarchical purging is needed or objects can become stale
*
* @see ProcessCacheLRU
* @ingroup Cache
* @since 1.23
*/
class MapCacheLRU {
/** @var array */
protected $cache = array(); // (key => value)
protected $maxCacheKeys; // integer; max entries
/**
* @param int $maxKeys Maximum number of entries allowed (min 1).
* @throws MWException When $maxCacheKeys is not an int or =< 0.
*/
public function __construct( $maxKeys ) {
if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
throw new MWException( __METHOD__ . " must be given an integer and >= 1" );
}
$this->maxCacheKeys = $maxKeys;
}
/**
* Set a key/value pair.
* This will prune the cache if it gets too large based on LRU.
* If the item is already set, it will be pushed to the top of the cache.
*
* @param string $key
* @param mixed $value
* @return void
*/
public function set( $key, $value ) {
if ( array_key_exists( $key, $this->cache ) ) {
$this->ping( $key ); // push to top
} elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
reset( $this->cache );
$evictKey = key( $this->cache );
unset( $this->cache[$evictKey] );
}
$this->cache[$key] = $value;
}
/**
* Check if a key exists
*
* @param string $key
* @return bool
*/
public function has( $key ) {
return array_key_exists( $key, $this->cache );
}
/**
* Get the value for a key.
* This returns null if the key is not set.
* If the item is already set, it will be pushed to the top of the cache.
*
* @param string $key
* @return mixed
*/
public function get( $key ) {
if ( array_key_exists( $key, $this->cache ) ) {
$this->ping( $key ); // push to top
return $this->cache[$key];
} else {
return null;
}
}
/**
* Clear one or several cache entries, or all cache entries
*
* @param string|array $keys
* @return void
*/
public function clear( $keys = null ) {
if ( $keys === null ) {
$this->cache = array();
} else {
foreach ( (array)$keys as $key ) {
unset( $this->cache[$key] );
}
}
}
/**
* Push an entry to the top of the cache
*
* @param string $key
*/
protected function ping( $key ) {
$item = $this->cache[$key];
unset( $this->cache[$key] );
$this->cache[$key] = $item;
}
}
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