1 files changed, 131 insertions, 0 deletions
diff --git a/includes/libs/MapCacheLRU.php b/includes/libs/MapCacheLRU.php
new file mode 100644
index 00000000..0b6db32e
--- /dev/null
+++ b/includes/libs/MapCacheLRU.php
@@ -0,0 +1,131 @@
+<?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;
+	}
+}