<?php

class tx_example_convertTask extends tx_scheduler_Task {

        public function execute() {

                set_time_limit(0);
                $offset = 0;
                do {
                        $res = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
                                'md5hash, md5filename, filename',
                                'cache_imagesizes',
                                'TRUE',
                                '',
                                'md5filename',
                                $offset . ', 10000'
                        );
                        if ($GLOBALS['TYPO3_DB']->sql_num_rows($res)) {
                                while ($row = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($res)) {
                                                // could be either absolute path or relative to site root
                                        $fileName = $row['filename'];
                                        if (strpos($fileName, PATH_site) === false) {
                                                $fileName = PATH_site . $fileName;
                                        }
                                        if (file_exists($fileName)) {
                                                $hash = md5(filemtime($fileName) . filesize($fileName));
                                                if ($row['md5hash'] !== $hash) {
                                                        $GLOBALS['TYPO3_DB']->exec_UPDATEquery(
                                                                'cache_imagesizes',
                                                                'md5filename = ' . $GLOBALS['TYPO3_DB']->fullQuoteStr($row['md5filename'], 'cache_imagesizes'),
                                                                array(
                                                                        'md5hash' => $hash,
                                                                        'tstamp' => $GLOBALS['EXEC_TIME']
                                                                )
                                                        );
                                                }
                                        }
                                }
                                $GLOBALS['TYPO3_DB']->sql_free_result($res);
                                $offset += 10000;

                        } else {
                                break;
                        }
                } while (true);
                return true;
        }
}

?>