includes/libs/objectcache/APCBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using PHP's APC accelerator.
   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  * This is a wrapper for APC's shared memory functions
  26  *
  27  * Use PHP serialization to avoid bugs and easily create CAS tokens.
  28  * APCu has a memory corruption bug when the serializer is set to 'default'.
  29  * See T120267, and upstream bug reports:
  30  *  - https://github.com/krakjoe/apcu/issues/38
  31  *  - https://github.com/krakjoe/apcu/issues/35
  32  *  - https://github.com/krakjoe/apcu/issues/111
  33  *
  34  * @ingroup Cache
  35  */
  36 class APCBagOStuff extends MediumSpecificBagOStuff {
  37         /** @var bool Whether to trust the APC implementation to serialization */
  38         private $nativeSerialize;
  39
  40         /**
  41          * @var string String to append to each APC key. This may be changed
  42          *  whenever the handling of values is changed, to prevent existing code
  43          *  from encountering older values which it cannot handle.
  44          */
  45         const KEY_SUFFIX = ':4';
  46
  47         public function __construct( array $params = [] ) {
  48                 $params['segmentationSize'] = $params['segmentationSize'] ?? INF;
  49                 parent::__construct( $params );
  50                 // The extension serializer is still buggy, unlike "php" and "igbinary"
  51                 $this->nativeSerialize = ( ini_get( 'apc.serializer' ) !== 'default' );
  52         }
  53
  54         protected function doGet( $key, $flags = 0, &$casToken = null ) {
  55                 $casToken = null;
  56
  57                 $blob = apc_fetch( $key . self::KEY_SUFFIX );
  58                 $value = $this->nativeSerialize ? $blob : $this->unserialize( $blob );
  59                 if ( $value !== false ) {
  60                         $casToken = $blob; // don't bother hashing this
  61                 }
  62
  63                 return $value;
  64         }
  65
  66         protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
  67                 apc_store(
  68                         $key . self::KEY_SUFFIX,
  69                         $this->nativeSerialize ? $value : $this->serialize( $value ),
  70                         $exptime
  71                 );
  72
  73                 return true;
  74         }
  75
  76         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
  77                 return apc_add(
  78                         $key . self::KEY_SUFFIX,
  79                         $this->nativeSerialize ? $value : $this->serialize( $value ),
  80                         $exptime
  81                 );
  82         }
  83
  84         protected function doDelete( $key, $flags = 0 ) {
  85                 apc_delete( $key . self::KEY_SUFFIX );
  86
  87                 return true;
  88         }
  89
  90         public function incr( $key, $value = 1 ) {
  91                 return apc_inc( $key . self::KEY_SUFFIX, $value );
  92         }
  93
  94         public function decr( $key, $value = 1 ) {
  95                 return apc_dec( $key . self::KEY_SUFFIX, $value );
  96         }
  97 }