From 77f7e9ba654058617f97e84563d2fa0061dc72a1 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Fri, 4 Oct 2013 20:47:33 -0700
Subject: [PATCH] Added MapCacheLRU class, a simpler cousin to ProcessCacheLRU

Change-Id: Ibe1b44c8e168a086afb3481b4bb7660dc7d31ae7
---
 includes/AutoLoader.php        |   1 +
 includes/cache/MapCacheLRU.php | 113 +++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+)
 create mode 100644 includes/cache/MapCacheLRU.php

diff --git a/includes/AutoLoader.php b/includes/AutoLoader.php
index 60ee2a866b..6ee62e0424 100644
--- a/includes/AutoLoader.php
+++ b/includes/AutoLoader.php
@@ -390,6 +390,7 @@ $wgAutoloadLocalClasses = array(
 	'HTMLFileCache' => 'includes/cache/HTMLFileCache.php',
 	'LinkBatch' => 'includes/cache/LinkBatch.php',
 	'LinkCache' => 'includes/cache/LinkCache.php',
+	'MapCacheLRU' => 'includes/cache/MapCacheLRU.php',
 	'MessageCache' => 'includes/cache/MessageCache.php',
 	'ObjectFileCache' => 'includes/cache/ObjectFileCache.php',
 	'ProcessCacheLRU' => 'includes/cache/ProcessCacheLRU.php',
diff --git a/includes/cache/MapCacheLRU.php b/includes/cache/MapCacheLRU.php
new file mode 100644
index 0000000000..3539d8fca2
--- /dev/null
+++ b/includes/cache/MapCacheLRU.php
@@ -0,0 +1,113 @@
+<?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
+ */
+class MapCacheLRU {
+	/** @var Array */
+	protected $cache = array(); // (key => value)
+
+	protected $maxCacheKeys; // integer; max entries
+
+	/**
+	 * @param $maxKeys integer 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 $key string
+	 * @param $value mixed
+	 * @return void
+	 */
+	public function set( $key, $value ) {
+		if ( isset( $this->cache[$key] ) ) {
+			$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;
+	}
+
+	/**
+	 * 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 $key string
+	 * @param $prop string
+	 * @return mixed
+	 */
+	public function get( $key ) {
+		if ( isset( $this->cache[$key] ) ) {
+			$this->ping( $key ); // push to top
+			return $this->cache[$key];
+		} else {
+			return null;
+		}
+	}
+
+	/**
+	 * Clear one or several cache entries, or all cache entries
+	 *
+	 * @param $keys string|Array
+	 * @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 $key string
+	 */
+	protected function ping( $key ) {
+		$item = $this->cache[$key];
+		unset( $this->cache[$key] );
+		$this->cache[$key] = $item;
+	}
+}
-- 
2.20.1