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                 $this->resize( $maxKeys );
  42         }
  43
  44         /**
  45          * Set a property field for a cache entry.
  46          * This will prune the cache if it gets too large based on LRU.
  47          * If the item is already set, it will be pushed to the top of the cache.
  48          *
  49          * @param $key string
  50          * @param $prop string
  51          * @param $value mixed
  52          * @return void
  53          */
  54         public function set( $key, $prop, $value ) {
  55                 if ( isset( $this->cache[$key] ) ) {
  56                         $this->ping( $key ); // push to top
  57                 } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
  58                         reset( $this->cache );
  59                         $evictKey = key( $this->cache );
  60                         unset( $this->cache[$evictKey] );
  61                         unset( $this->cacheTimes[$evictKey] );
  62                 }
  63                 $this->cache[$key][$prop] = $value;
  64                 $this->cacheTimes[$key][$prop] = microtime( true );
  65         }
  66
  67         /**
  68          * Check if a property field exists for a cache entry.
  69          *
  70          * @param $key string
  71          * @param $prop string
  72          * @param $maxAge float Ignore items older than this many seconds (since 1.21)
  73          * @return bool
  74          */
  75         public function has( $key, $prop, $maxAge = 0.0 ) {
  76                 if ( isset( $this->cache[$key][$prop] ) ) {
  77                         return ( $maxAge <= 0 ||
  78                                 ( microtime( true ) - $this->cacheTimes[$key][$prop] ) <= $maxAge );
  79                 }
  80
  81                 return false;
  82         }
  83
  84         /**
  85          * Get a property field for a cache entry.
  86          * This returns null if the property is not set.
  87          * If the item is already set, it will be pushed to the top of the cache.
  88          *
  89          * @param $key string
  90          * @param $prop string
  91          * @return mixed
  92          */
  93         public function get( $key, $prop ) {
  94                 if ( isset( $this->cache[$key][$prop] ) ) {
  95                         $this->ping( $key ); // push to top
  96                         return $this->cache[$key][$prop];
  97                 } else {
  98                         return null;
  99                 }
 100         }
 101
 102         /**
 103          * Clear one or several cache entries, or all cache entries
 104          *
 105          * @param $keys string|Array
 106          * @return void
 107          */
 108         public function clear( $keys = null ) {
 109                 if ( $keys === null ) {
 110                         $this->cache = array();
 111                         $this->cacheTimes = array();
 112                 } else {
 113                         foreach ( (array)$keys as $key ) {
 114                                 unset( $this->cache[$key] );
 115                                 unset( $this->cacheTimes[$key] );
 116                         }
 117                 }
 118         }
 119
 120         /**
 121          * Resize the maximum number of cache entries, removing older entries as needed
 122          *
 123          * @param $maxKeys integer
 124          * @return void
 125          * @throws UnexpectedValueException
 126          */
 127         public function resize( $maxKeys ) {
 128                 if ( !is_int( $maxKeys ) || $maxKeys < 1 ) {
 129                         throw new UnexpectedValueException( __METHOD__ . " must be given an integer >= 1" );
 130                 }
 131                 $this->maxCacheKeys = $maxKeys;
 132                 while ( count( $this->cache ) > $this->maxCacheKeys ) {
 133                         reset( $this->cache );
 134                         $evictKey = key( $this->cache );
 135                         unset( $this->cache[$evictKey] );
 136                         unset( $this->cacheTimes[$evictKey] );
 137                 }
 138         }
 139
 140         /**
 141          * Push an entry to the top of the cache
 142          *
 143          * @param $key string
 144          */
 145         protected function ping( $key ) {
 146                 $item = $this->cache[$key];
 147                 unset( $this->cache[$key] );
 148                 $this->cache[$key] = $item;
 149         }
 150 }