[Summary view] [Print] [Text view]

   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 a simple LRU key/value map with a maximum number of entries
  26   *
  27   * Use ProcessCacheLRU if hierarchical purging is needed or objects can become stale
  28   *
  29   * @see ProcessCacheLRU
  30   * @ingroup Cache
  31   * @since 1.23
  32   */
  33  class MapCacheLRU {
  34      /** @var array */
  35      protected $cache = array(); // (key => value)
  36  
  37      protected $maxCacheKeys; // integer; max entries
  38  
  39      /**
  40       * @param int $maxKeys Maximum number of entries allowed (min 1).
  41       * @throws MWException When $maxCacheKeys is not an int or =< 0.
  42       */
  43  	public function __construct( $maxKeys ) {
  44          if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
  45              throw new MWException( __METHOD__ . " must be given an integer and >= 1" );
  46          }
  47          $this->maxCacheKeys = $maxKeys;
  48      }
  49  
  50      /**
  51       * Set a key/value pair.
  52       * This will prune the cache if it gets too large based on LRU.
  53       * If the item is already set, it will be pushed to the top of the cache.
  54       *
  55       * @param string $key
  56       * @param mixed $value
  57       * @return void
  58       */
  59  	public function set( $key, $value ) {
  60          if ( array_key_exists( $key, $this->cache ) ) {
  61              $this->ping( $key ); // push to top
  62          } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
  63              reset( $this->cache );
  64              $evictKey = key( $this->cache );
  65              unset( $this->cache[$evictKey] );
  66          }
  67          $this->cache[$key] = $value;
  68      }
  69  
  70      /**
  71       * Check if a key exists
  72       *
  73       * @param string $key
  74       * @return bool
  75       */
  76  	public function has( $key ) {
  77          return array_key_exists( $key, $this->cache );
  78      }
  79  
  80      /**
  81       * Get the value for a key.
  82       * This returns null if the key is not set.
  83       * If the item is already set, it will be pushed to the top of the cache.
  84       *
  85       * @param string $key
  86       * @return mixed
  87       */
  88  	public function get( $key ) {
  89          if ( array_key_exists( $key, $this->cache ) ) {
  90              $this->ping( $key ); // push to top
  91              return $this->cache[$key];
  92          } else {
  93              return null;
  94          }
  95      }
  96  
  97      /**
  98       * Clear one or several cache entries, or all cache entries
  99       *
 100       * @param string|array $keys
 101       * @return void
 102       */
 103  	public function clear( $keys = null ) {
 104          if ( $keys === null ) {
 105              $this->cache = array();
 106          } else {
 107              foreach ( (array)$keys as $key ) {
 108                  unset( $this->cache[$key] );
 109              }
 110          }
 111      }
 112  
 113      /**
 114       * Push an entry to the top of the cache
 115       *
 116       * @param string $key
 117       */
 118  	protected function ping( $key ) {
 119          $item = $this->cache[$key];
 120          unset( $this->cache[$key] );
 121          $this->cache[$key] = $item;
 122      }
 123  }