LinkCache.php

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<?php
class LinkCache {
    private $mGoodLinks;
    private $mBadLinks;
    private $mForUpdate = false;

    const MAX_SIZE = 10000;

    protected static $instance;

    public function __construct() {
        $this->mGoodLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
        $this->mBadLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
    }

    public static function singleton() {
        if ( !self::$instance ) {
            self::$instance = new LinkCache;
        }

        return self::$instance;
    }

    public static function destroySingleton() {
        self::$instance = null;
    }

    public static function setSingleton( LinkCache $instance ) {
        self::$instance = $instance;
    }

    public function forUpdate( $update = null ) {
        return wfSetVar( $this->mForUpdate, $update );
    }

    public function getGoodLinkID( $title ) {
        $info = $this->mGoodLinks->get( $title );
        if ( !$info ) {
            return 0;
        }
        return $info['id'];
    }

    public function getGoodLinkFieldObj( Title $title, $field ) {
        $dbkey = $title->getPrefixedDBkey();
        $info = $this->mGoodLinks->get( $dbkey );
        if ( !$info ) {
            return null;
        }
        return $info[$field];
    }

    public function isBadLink( $title ) {
        // Use get() to ensure it records as used for LRU.
        return $this->mBadLinks->get( $title ) !== false;
    }

    public function addGoodLinkObj( $id, Title $title, $len = -1, $redir = null,
        $revision = 0, $model = null, $lang = null
    ) {
        $dbkey = $title->getPrefixedDBkey();
        $this->mGoodLinks->set( $dbkey, [
            'id' => (int)$id,
            'length' => (int)$len,
            'redirect' => (int)$redir,
            'revision' => (int)$revision,
            'model' => $model ? (string)$model : null,
            'lang' => $lang ? (string)$lang : null,
        ] );
    }

    public function addGoodLinkObjFromRow( Title $title, $row ) {
        $dbkey = $title->getPrefixedDBkey();
        $this->mGoodLinks->set( $dbkey, [
            'id' => intval( $row->page_id ),
            'length' => intval( $row->page_len ),
            'redirect' => intval( $row->page_is_redirect ),
            'revision' => intval( $row->page_latest ),
            'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
            'lang' => !empty( $row->page_lang ) ? strval( $row->page_lang ) : null,
        ] );
    }

    public function addBadLinkObj( Title $title ) {
        $dbkey = $title->getPrefixedDBkey();
        if ( !$this->isBadLink( $dbkey ) ) {
            $this->mBadLinks->set( $dbkey, 1 );
        }
    }

    public function clearBadLink( $title ) {
        $this->mBadLinks->delete( $title );
    }

    public function clearLink( Title $title ) {
        $dbkey = $title->getPrefixedDBkey();
        $this->mBadLinks->delete( $dbkey );
        $this->mGoodLinks->delete( $dbkey );
    }

    public function addLink( $title ) {
        $nt = Title::newFromDBkey( $title );
        if ( !$nt ) {
            return 0;
        }
        return $this->addLinkObj( $nt );
    }

    public function addLinkObj( Title $nt ) {
        global $wgContentHandlerUseDB, $wgPageLanguageUseDB;

        $key = $nt->getPrefixedDBkey();
        if ( $this->isBadLink( $key ) || $nt->isExternal() ) {
            return 0;
        }
        $id = $this->getGoodLinkID( $key );
        if ( $id != 0 ) {
            return $id;
        }

        if ( $key === '' ) {
            return 0;
        }

        // Some fields heavily used for linking...
        $db = $this->mForUpdate ? wfGetDB( DB_MASTER ) : wfGetDB( DB_SLAVE );

        $fields = [ 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ];
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'page_content_model';
        }
        if ( $wgPageLanguageUseDB ) {
            $fields[] = 'page_lang';
        }

        $row = $db->selectRow( 'page', $fields,
            [ 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ],
            __METHOD__
        );

        if ( $row !== false ) {
            $this->addGoodLinkObjFromRow( $nt, $row );
            $id = intval( $row->page_id );
        } else {
            $this->addBadLinkObj( $nt );
            $id = 0;
        }

        return $id;
    }

    public function clear() {
        $this->mGoodLinks->clear();
        $this->mBadLinks->clear();
    }
}