UserCache.php

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<?php
class UserCache {
    protected $cache = array(); // (uid => property => value)
    protected $typesCached = array(); // (uid => cache type => 1)

    public static function singleton() {
        static $instance = null;
        if ( $instance === null ) {
            $instance = new self();
        }

        return $instance;
    }

    protected function __construct() {
    }

    public function getProp( $userId, $prop ) {
        if ( !isset( $this->cache[$userId][$prop] ) ) {
            wfDebug( __METHOD__ . ": querying DB for prop '$prop' for user ID '$userId'.\n" );
            $this->doQuery( array( $userId ) ); // cache miss
        }

        return isset( $this->cache[$userId][$prop] )
            ? $this->cache[$userId][$prop]
            : false; // user does not exist?
    }

    public function getUserName( $userId, $ip ) {
        return $userId > 0 ? $this->getProp( $userId, 'name' ) : $ip;
    }

    public function doQuery( array $userIds, $options = array(), $caller = '' ) {
        wfProfileIn( __METHOD__ );

        $usersToCheck = array();
        $usersToQuery = array();

        $userIds = array_unique( $userIds );

        foreach ( $userIds as $userId ) {
            $userId = (int)$userId;
            if ( $userId <= 0 ) {
                continue; // skip anons
            }
            if ( isset( $this->cache[$userId]['name'] ) ) {
                $usersToCheck[$userId] = $this->cache[$userId]['name']; // already have name
            } else {
                $usersToQuery[] = $userId; // we need to get the name
            }
        }

        // Lookup basic info for users not yet loaded...
        if ( count( $usersToQuery ) ) {
            $dbr = wfGetDB( DB_SLAVE );
            $table = array( 'user' );
            $conds = array( 'user_id' => $usersToQuery );
            $fields = array( 'user_name', 'user_real_name', 'user_registration', 'user_id' );

            $comment = __METHOD__;
            if ( strval( $caller ) !== '' ) {
                $comment .= "/$caller";
            }

            $res = $dbr->select( $table, $fields, $conds, $comment );
            foreach ( $res as $row ) { // load each user into cache
                $userId = (int)$row->user_id;
                $this->cache[$userId]['name'] = $row->user_name;
                $this->cache[$userId]['real_name'] = $row->user_real_name;
                $this->cache[$userId]['registration'] = $row->user_registration;
                $usersToCheck[$userId] = $row->user_name;
            }
        }

        $lb = new LinkBatch();
        foreach ( $usersToCheck as $userId => $name ) {
            if ( $this->queryNeeded( $userId, 'userpage', $options ) ) {
                $lb->add( NS_USER, str_replace( ' ', '_', $row->user_name ) );
                $this->typesCached[$userId]['userpage'] = 1;
            }
            if ( $this->queryNeeded( $userId, 'usertalk', $options ) ) {
                $lb->add( NS_USER_TALK, str_replace( ' ', '_', $row->user_name ) );
                $this->typesCached[$userId]['usertalk'] = 1;
            }
        }
        $lb->execute();

        wfProfileOut( __METHOD__ );
    }

    protected function queryNeeded( $uid, $type, array $options ) {
        return ( in_array( $type, $options ) && !isset( $this->typesCached[$uid][$type] ) );
    }
}