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;

        static function &singleton() {
                static $instance;
                if ( !isset( $instance ) ) {
                        $instance = new LinkCache;
                }
                return $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 ) {
                $dbkey = $title->getPrefixedDbKey();
                $this->mGoodLinks[$dbkey] = intval( $id );
                $this->mGoodLinkFields[$dbkey] = array(
                        'length' => intval( $len ),
                        'redirect' => intval( $redir ),
                        'revision' => intval( $revision ) );
        }

        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 ),
                );
        }

        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 addLinkObj( $nt ) {
                global $wgAntiLockFlags;
                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;
                }

                # 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();
                }

                $s = $db->selectRow( 'page',
                        array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ),
                        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();
        }
}