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