includes/historyblob/HistoryBlobStub.php

   1 <?php
   2 /**
   3  * Efficient concatenated text storage.
   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  */
  22
  23 use MediaWiki\MediaWikiServices;
  24
  25 /**
  26  * Pointer object for an item within a CGZ blob stored in the text table.
  27  */
  28 class HistoryBlobStub {
  29         /**
  30          * @var array One-step cache variable to hold base blobs; operations that
  31          * pull multiple revisions may often pull multiple times from the same
  32          * blob. By keeping the last-used one open, we avoid redundant
  33          * unserialization and decompression overhead.
  34          */
  35         protected static $blobCache = [];
  36
  37         /** @var int */
  38         public $mOldId;
  39
  40         /** @var string */
  41         public $mHash;
  42
  43         /** @var string */
  44         public $mRef;
  45
  46         /**
  47          * @param string $hash The content hash of the text
  48          * @param int $oldid The old_id for the CGZ object
  49          */
  50         function __construct( $hash = '', $oldid = 0 ) {
  51                 $this->mHash = $hash;
  52         }
  53
  54         /**
  55          * Sets the location (old_id) of the main object to which this object
  56          * points
  57          * @param int $id
  58          */
  59         function setLocation( $id ) {
  60                 $this->mOldId = $id;
  61         }
  62
  63         /**
  64          * Sets the location (old_id) of the referring object
  65          * @param string $id
  66          */
  67         function setReferrer( $id ) {
  68                 $this->mRef = $id;
  69         }
  70
  71         /**
  72          * Gets the location of the referring object
  73          * @return string
  74          */
  75         function getReferrer() {
  76                 return $this->mRef;
  77         }
  78
  79         /**
  80          * @return string|false
  81          */
  82         function getText() {
  83                 if ( isset( self::$blobCache[$this->mOldId] ) ) {
  84                         $obj = self::$blobCache[$this->mOldId];
  85                 } else {
  86                         $dbr = wfGetDB( DB_REPLICA );
  87                         $row = $dbr->selectRow(
  88                                 'text',
  89                                 [ 'old_flags', 'old_text' ],
  90                                 [ 'old_id' => $this->mOldId ]
  91                         );
  92
  93                         if ( !$row ) {
  94                                 return false;
  95                         }
  96
  97                         $flags = explode( ',', $row->old_flags );
  98                         if ( in_array( 'external', $flags ) ) {
  99                                 $url = $row->old_text;
 100                                 $parts = explode( '://', $url, 2 );
 101                                 if ( !isset( $parts[1] ) || $parts[1] == '' ) {
 102                                         return false;
 103                                 }
 104                                 $row->old_text = MediaWikiServices::getInstance()
 105                                         ->getExternalStoreAccess()
 106                                         ->fetchFromURL( $url );
 107                         }
 108
 109                         if ( !in_array( 'object', $flags ) ) {
 110                                 return false;
 111                         }
 112
 113                         if ( in_array( 'gzip', $flags ) ) {
 114                                 // This shouldn't happen, but a bug in the compress script
 115                                 // may at times gzip-compress a HistoryBlob object row.
 116                                 $obj = unserialize( gzinflate( $row->old_text ) );
 117                         } else {
 118                                 $obj = unserialize( $row->old_text );
 119                         }
 120
 121                         if ( !is_object( $obj ) ) {
 122                                 // Correct for old double-serialization bug.
 123                                 $obj = unserialize( $obj );
 124                         }
 125
 126                         // Save this item for reference; if pulling many
 127                         // items in a row we'll likely use it again.
 128                         $obj->uncompress();
 129                         self::$blobCache = [ $this->mOldId => $obj ];
 130                 }
 131
 132                 return $obj->getItem( $this->mHash );
 133         }
 134
 135         /**
 136          * Get the content hash
 137          *
 138          * @return string
 139          */
 140         function getHash() {
 141                 return $this->mHash;
 142         }
 143 }
 144
 145 // phpcs:ignore Generic.CodeAnalysis.UnconditionalIfStatement.Found
 146 if ( false ) {
 147         // Blobs generated by MediaWiki < 1.5 on PHP 4 were serialized with the
 148         // class name coerced to lowercase. We can improve efficiency by adding
 149         // autoload entries for the lowercase variants of these classes (T166759).
 150         // The code below is never executed, but it is picked up by the AutoloadGenerator
 151         // parser, which scans for class_alias() calls.
 152         class_alias( HistoryBlobStub::class, 'historyblobstub' );
 153 }