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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 Exception When $maxCacheKeys is not an int or =< 0.
+ */
+ public function __construct( $maxKeys ) {
+ if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
+ throw new Exception( __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;
+ }
+ }
+
+ /**
+ * @return array
+ * @since 1.25
+ */
+ public function getAllKeys() {
+ return array_keys( $this->cache );
+ }
+
+ /**
+ * 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;
+ }
+}