public function doLog(common_log_Item $item)
    {
        if (is_null($this->filehandle)) {
            $this->initFile();
        }
        if ($this->filehandle !== false) {
            $map = array(
                '%d' => gmdate('Y-m-d H:i:s', $item->getDateTime()),
                '%m' => $item->getDescription(),
                '%p' => $this->prefix,
                '%s' => $item->getSeverityDescriptionString(),
                '%t' => $item->getDateTime(),
                '%r' => $item->getRequest(),
                '%f' => $item->getCallerFile(),
                '%g' => implode(',', $item->getTags()),
                '%l' => $item->getCallerLine()
            );
            if (strpos($this->format, '%b')) {
                $map['%b'] = 'Backtrace not yet supported';
            }
            $str = strtr($this->format, $map) . PHP_EOL;
            @fwrite($this->filehandle, $str);
        }
    }