LinkCache.php

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<?php
class LinkCache {
    // Increment $mClassVer whenever old serialized versions of this class
    // becomes incompatible with the new version.
    private $mClassVer = 4;

    private $mGoodLinks = array();
    private $mGoodLinkFields = array();
    private $mBadLinks = array();
    private $mForUpdate = false;
    private $useDatabase = true;

    protected static $instance;

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

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

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

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

    public function getGoodLinkID( $title ) {
        if ( array_key_exists( $title, $this->mGoodLinks ) ) {
            return $this->mGoodLinks[$title];
        } else {
            return 0;
        }
    }

    public function getGoodLinkFieldObj( $title, $field ) {
        $dbkey = $title->getPrefixedDBkey();
        if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
            return $this->mGoodLinkFields[$dbkey][$field];
        } else {
            return null;
        }
    }

    public function isBadLink( $title ) {
        return array_key_exists( $title, $this->mBadLinks );
    }

    public function addGoodLinkObj( $id, $title, $len = -1, $redir = null, $revision = false, $model = false ) {
        $dbkey = $title->getPrefixedDBkey();
        $this->mGoodLinks[$dbkey] = intval( $id );
        $this->mGoodLinkFields[$dbkey] = array(
            'length' => intval( $len ),
            'redirect' => intval( $redir ),
            'revision' => intval( $revision ),
            'model' => intval( $model ) );
    }

    public function addGoodLinkObjFromRow( $title, $row ) {
        $dbkey = $title->getPrefixedDBkey();
        $this->mGoodLinks[$dbkey] = intval( $row->page_id );
        $this->mGoodLinkFields[$dbkey] = array(
            '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,
        );
    }

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

    public function clearBadLink( $title ) {
        unset( $this->mBadLinks[$title] );
    }

    public function clearLink( $title ) {
        $dbkey = $title->getPrefixedDBkey();
        unset( $this->mBadLinks[$dbkey] );
        unset( $this->mGoodLinks[$dbkey] );
        unset( $this->mGoodLinkFields[$dbkey] );
    }

    public function getGoodLinks() {
        return $this->mGoodLinks;
    }

    public function getBadLinks() {
        return array_keys( $this->mBadLinks );
    }

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

    public function useDatabase( $value = null ) {
        if ( $value !== null ) {
            $this->useDatabase = (bool)$value;
        }
        return $this->useDatabase;
    }

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

        wfProfileIn( __METHOD__ );

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

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

        if( !$this->useDatabase ) {
            return 0;
        }

        # Some fields heavily used for linking...
        if ( $this->mForUpdate ) {
            $db = wfGetDB( DB_MASTER );
            if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
                $options = array( 'FOR UPDATE' );
            } else {
                $options = array();
            }
        } else {
            $db = wfGetDB( DB_SLAVE );
            $options = array();
        }

        $f = array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' );
        if ( $wgContentHandlerUseDB ) {
            $f[] = 'page_content_model';
        }

        $s = $db->selectRow( 'page', $f,
            array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
            __METHOD__, $options );
        # Set fields...
        if ( $s !== false ) {
            $this->addGoodLinkObjFromRow( $nt, $s );
            $id = intval( $s->page_id );
        } else {
            $this->addBadLinkObj( $nt );
            $id = 0;
        }

        wfProfileOut( __METHOD__ );
        return $id;
    }

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