includes/cache/ProcessCacheLRU.php

   1 <?php
   2 /**
   3  * Per-process memory cache for storing items.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 /**
  25  * Handles per process caching of items
  26  * @ingroup Cache
  27  */
  28 class ProcessCacheLRU {
  29         /** @var Array */
  30         protected $cache = array(); // (key => prop => value)
  31
  32         protected $maxCacheKeys; // integer; max entries
  33
  34         /**
  35          * @param $maxKeys integer Maximum number of entries allowed (min 1).
  36          * @throws MWException When $maxCacheKeys is not an int or =< 0.
  37          */
  38         public function __construct( $maxKeys ) {
  39                 if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
  40                         throw new MWException( __METHOD__ . " must be given an integer and >= 1" );
  41                 }
  42                 $this->maxCacheKeys = $maxKeys;
  43         }
  44
  45         /**
  46          * Set a property field for a cache entry.
  47          * This will prune the cache if it gets too large.
  48          * If the item is already set, it will be pushed to the top of the cache.
  49          *
  50          * @param $key string
  51          * @param $prop string
  52          * @param $value mixed
  53          * @return void
  54          */
  55         public function set( $key, $prop, $value ) {
  56                 if ( isset( $this->cache[$key] ) ) {
  57                         $this->ping( $key ); // push to top
  58                 } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
  59                         reset( $this->cache );
  60                         unset( $this->cache[key( $this->cache )] );
  61                 }
  62                 $this->cache[$key][$prop] = $value;
  63         }
  64
  65         /**
  66          * Check if a property field exists for a cache entry.
  67          *
  68          * @param $key string
  69          * @param $prop string
  70          * @return bool
  71          */
  72         public function has( $key, $prop ) {
  73                 return isset( $this->cache[$key][$prop] );
  74         }
  75
  76         /**
  77          * Get a property field for a cache entry.
  78          * This returns null if the property is not set.
  79          * If the item is already set, it will be pushed to the top of the cache.
  80          *
  81          * @param $key string
  82          * @param $prop string
  83          * @return mixed
  84          */
  85         public function get( $key, $prop ) {
  86                 if ( isset( $this->cache[$key][$prop] ) ) {
  87                         $this->ping( $key ); // push to top
  88                         return $this->cache[$key][$prop];
  89                 } else {
  90                         return null;
  91                 }
  92         }
  93
  94         /**
  95          * Clear one or several cache entries, or all cache entries
  96          *
  97          * @param $keys string|Array
  98          * @return void
  99          */
 100         public function clear( $keys = null ) {
 101                 if ( $keys === null ) {
 102                         $this->cache = array();
 103                 } else {
 104                         foreach ( (array)$keys as $key ) {
 105                                 unset( $this->cache[$key] );
 106                         }
 107                 }
 108         }
 109
 110         /**
 111          * Push an entry to the top of the cache
 112          *
 113          * @param $key string
 114          */
 115         protected function ping( $key ) {
 116                 $item = $this->cache[$key];
 117                 unset( $this->cache[$key] );
 118                 $this->cache[$key] = $item;
 119         }
 120 }