includes/libs/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         /** @var Array */
  32         protected $cacheTimes = array(); // (key => prop => UNIX timestamp)
  33
  34         protected $maxCacheKeys; // integer; max entries
  35
  36         /**
  37          * @param $maxKeys integer Maximum number of entries allowed (min 1).
  38          * @throws UnexpectedValueException When $maxCacheKeys is not an int or =< 0.
  39          */
  40         public function __construct( $maxKeys ) {
  41                 if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
  42                         throw new UnexpectedValueException( __METHOD__ . " must be given an integer >= 1" );
  43                 }
  44                 $this->maxCacheKeys = $maxKeys;
  45         }
  46
  47         /**
  48          * Set a property field for a cache entry.
  49          * This will prune the cache if it gets too large based on LRU.
  50          * If the item is already set, it will be pushed to the top of the cache.
  51          *
  52          * @param $key string
  53          * @param $prop string
  54          * @param $value mixed
  55          * @return void
  56          */
  57         public function set( $key, $prop, $value ) {
  58                 if ( isset( $this->cache[$key] ) ) {
  59                         $this->ping( $key ); // push to top
  60                 } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
  61                         reset( $this->cache );
  62                         $evictKey = key( $this->cache );
  63                         unset( $this->cache[$evictKey] );
  64                         unset( $this->cacheTimes[$evictKey] );
  65                 }
  66                 $this->cache[$key][$prop] = $value;
  67                 $this->cacheTimes[$key][$prop] = time();
  68         }
  69
  70         /**
  71          * Check if a property field exists for a cache entry.
  72          *
  73          * @param $key string
  74          * @param $prop string
  75          * @param $maxAge integer Ignore items older than this many seconds (since 1.21)
  76          * @return bool
  77          */
  78         public function has( $key, $prop, $maxAge = 0 ) {
  79                 if ( isset( $this->cache[$key][$prop] ) ) {
  80                         return ( $maxAge <= 0 || ( time() - $this->cacheTimes[$key][$prop] ) <= $maxAge );
  81                 }
  82
  83                 return false;
  84         }
  85
  86         /**
  87          * Get a property field for a cache entry.
  88          * This returns null if the property is not set.
  89          * If the item is already set, it will be pushed to the top of the cache.
  90          *
  91          * @param $key string
  92          * @param $prop string
  93          * @return mixed
  94          */
  95         public function get( $key, $prop ) {
  96                 if ( isset( $this->cache[$key][$prop] ) ) {
  97                         $this->ping( $key ); // push to top
  98                         return $this->cache[$key][$prop];
  99                 } else {
 100                         return null;
 101                 }
 102         }
 103
 104         /**
 105          * Clear one or several cache entries, or all cache entries
 106          *
 107          * @param $keys string|Array
 108          * @return void
 109          */
 110         public function clear( $keys = null ) {
 111                 if ( $keys === null ) {
 112                         $this->cache = array();
 113                         $this->cacheTimes = array();
 114                 } else {
 115                         foreach ( (array)$keys as $key ) {
 116                                 unset( $this->cache[$key] );
 117                                 unset( $this->cacheTimes[$key] );
 118                         }
 119                 }
 120         }
 121
 122         /**
 123          * Push an entry to the top of the cache
 124          *
 125          * @param $key string
 126          */
 127         protected function ping( $key ) {
 128                 $item = $this->cache[$key];
 129                 unset( $this->cache[$key] );
 130                 $this->cache[$key] = $item;
 131         }
 132 }