Added MapCacheLRU class, a simpler cousin to ProcessCacheLRU

Change-Id: Ibe1b44c8e168a086afb3481b4bb7660dc7d31ae7

diff --git a/includes/AutoLoader.php b/includes/AutoLoader.php
index 60ee2a8..6ee62e0 100644 (file)
--- 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 (file)
index 0000000..3539d8f
--- /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;
+       }
+}