wikimedia/mediawiki-core

<?php
/**
 * Efficient concatenated text storage.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

use MediaWiki\MediaWikiServices;

/**
 * Pointer object for an item within a CGZ blob stored in the text table.
 *
 * WARNING: Objects of this class are serialized and permanently stored in the DB.
 * Do not change the name or visibility of any property!
 *
 * Note: the property visibility was changed in 2020 from public to protected.
 * This may cause problems in future.
 */
class HistoryBlobStub {
    /**
     * @var array One-step cache variable to hold base blobs; operations that
     * pull multiple revisions may often pull multiple times from the same
     * blob. By keeping the last-used one open, we avoid redundant
     * unserialization and decompression overhead.
     */
    protected static $blobCache = [];

    /** @var int */
    protected $mOldId;

    /** @var string */
    protected $mHash;

    /** @var string */
    protected $mRef;

    /**
     * @param string $hash The content hash of the text
     * @param int $oldid The old_id for the CGZ object
     */
    public function __construct( $hash = '', $oldid = 0 ) {
        $this->mHash = $hash;
    }

    /**
     * Sets the location (old_id) of the main object to which this object
     * points
     * @param int $id
     */
    public function setLocation( $id ) {
        $this->mOldId = $id;
    }

    /**
     * Gets the location of the main object
     * @return int
     */
    public function getLocation() {
        return $this->mOldId;
    }

    /**
     * Sets the location (old_id) of the referring object
     * @param string $id
     */
    public function setReferrer( $id ) {
        $this->mRef = $id;
    }

    /**
     * Gets the location of the referring object
     * @return string
     */
    public function getReferrer() {
        return $this->mRef;
    }

    /**
     * @return string|false
     */
    public function getText() {
        if ( isset( self::$blobCache[$this->mOldId] ) ) {
            $obj = self::$blobCache[$this->mOldId];
        } else {
            $dbr = MediaWikiServices::getInstance()->getConnectionProvider()->getReplicaDatabase();
            $row = $dbr->newSelectQueryBuilder()
                ->select( [ 'old_flags', 'old_text' ] )
                ->from( 'text' )
                ->where( [ 'old_id' => $this->mOldId ] )
                ->caller( __METHOD__ )->fetchRow();

            if ( !$row ) {
                return false;
            }

            $flags = explode( ',', $row->old_flags );
            if ( in_array( 'external', $flags ) ) {
                $url = $row->old_text;
                $parts = explode( '://', $url, 2 );
                if ( !isset( $parts[1] ) || $parts[1] == '' ) {
                    return false;
                }
                $row->old_text = MediaWikiServices::getInstance()
                    ->getExternalStoreAccess()
                    ->fetchFromURL( $url );
            }

            if ( !in_array( 'object', $flags ) ) {
                return false;
            }

            if ( in_array( 'gzip', $flags ) ) {
                // This shouldn't happen, but a bug in the compress script
                // may at times gzip-compress a HistoryBlob object row.
                $obj = HistoryBlobUtils::unserialize( gzinflate( $row->old_text ), true );
            } else {
                $obj = HistoryBlobUtils::unserialize( $row->old_text, true );
            }

            // Save this item for reference; if pulling many
            // items in a row we'll likely use it again.
            self::$blobCache = [ $this->mOldId => $obj ];
        }

        if ( method_exists( $obj, 'getItem' ) ) {
            return $obj->getItem( $this->mHash );
        }

        return false;
    }

    /**
     * Get the content hash
     *
     * @return string
     */
    public function getHash() {
        return $this->mHash;
    }
}

// Blobs generated by MediaWiki < 1.5 on PHP 4 were serialized with the
// class name coerced to lowercase. We can improve efficiency by adding
// autoload entries for the lowercase variants of these classes (T166759).
// The code below is never executed, but it is picked up by the AutoloadGenerator
// parser, which scans for class_alias() calls.
/*
class_alias( HistoryBlobStub::class, 'historyblobstub' );
*/