includes/libs/objectcache/HashBagOStuff.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  * Simple store for keeping values in an associative array for the current process.
  26  *
  27  * Data will not persist and is not shared with other processes.
  28  *
  29  * @ingroup Cache
  30  */
  31 class HashBagOStuff extends BagOStuff {
  32         /** @var mixed[] */
  33         protected $bag = [];
  34         /** @var int Max entries allowed */
  35         protected $maxCacheKeys;
  36
  37         /** @var string CAS token prefix for this instance */
  38         private $token;
  39
  40         /** @var int CAS token counter */
  41         private static $casCounter = 0;
  42
  43         const KEY_VAL = 0;
  44         const KEY_EXP = 1;
  45         const KEY_CAS = 2;
  46
  47         /**
  48          * @param array $params Additional parameters include:
  49          *   - maxKeys : only allow this many keys (using oldest-first eviction)
  50          */
  51         function __construct( $params = [] ) {
  52                 parent::__construct( $params );
  53
  54                 $this->token = microtime( true ) . ':' . mt_rand();
  55                 $this->maxCacheKeys = $params['maxKeys'] ?? INF;
  56                 if ( $this->maxCacheKeys <= 0 ) {
  57                         throw new InvalidArgumentException( '$maxKeys parameter must be above zero' );
  58                 }
  59         }
  60
  61         protected function doGet( $key, $flags = 0, &$casToken = null ) {
  62                 $casToken = null;
  63
  64                 if ( !$this->hasKey( $key ) || $this->expire( $key ) ) {
  65                         return false;
  66                 }
  67
  68                 // Refresh key position for maxCacheKeys eviction
  69                 $temp = $this->bag[$key];
  70                 unset( $this->bag[$key] );
  71                 $this->bag[$key] = $temp;
  72
  73                 $casToken = $this->bag[$key][self::KEY_CAS];
  74
  75                 return $this->bag[$key][self::KEY_VAL];
  76         }
  77
  78         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
  79                 // Refresh key position for maxCacheKeys eviction
  80                 unset( $this->bag[$key] );
  81                 $this->bag[$key] = [
  82                         self::KEY_VAL => $value,
  83                         self::KEY_EXP => $this->convertToExpiry( $exptime ),
  84                         self::KEY_CAS => $this->token . ':' . ++self::$casCounter
  85                 ];
  86
  87                 if ( count( $this->bag ) > $this->maxCacheKeys ) {
  88                         reset( $this->bag );
  89                         $evictKey = key( $this->bag );
  90                         unset( $this->bag[$evictKey] );
  91                 }
  92
  93                 return true;
  94         }
  95
  96         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
  97                 if ( $this->get( $key ) === false ) {
  98                         return $this->set( $key, $value, $exptime, $flags );
  99                 }
 100
 101                 return false; // key already set
 102         }
 103
 104         public function delete( $key, $flags = 0 ) {
 105                 unset( $this->bag[$key] );
 106
 107                 return true;
 108         }
 109
 110         public function incr( $key, $value = 1 ) {
 111                 $n = $this->get( $key );
 112                 if ( $this->isInteger( $n ) ) {
 113                         $n = max( $n + intval( $value ), 0 );
 114                         $this->bag[$key][self::KEY_VAL] = $n;
 115
 116                         return $n;
 117                 }
 118
 119                 return false;
 120         }
 121
 122         /**
 123          * Clear all values in cache
 124          */
 125         public function clear() {
 126                 $this->bag = [];
 127         }
 128
 129         /**
 130          * @param string $key
 131          * @return bool
 132          */
 133         protected function expire( $key ) {
 134                 $et = $this->bag[$key][self::KEY_EXP];
 135                 if ( $et == self::TTL_INDEFINITE || $et > $this->getCurrentTime() ) {
 136                         return false;
 137                 }
 138
 139                 $this->delete( $key );
 140
 141                 return true;
 142         }
 143
 144         /**
 145          * Does this bag have a non-null value for the given key?
 146          *
 147          * @param string $key
 148          * @return bool
 149          * @since 1.27
 150          */
 151         protected function hasKey( $key ) {
 152                 return isset( $this->bag[$key] );
 153         }
 154 }