public function getByteSize(): int
    {
        if ($this->test(\sndsgd\Fs::READABLE) !== true) {
            $this->error = "failed to stat filesize; {$this->error}";
            return -1;
        }
        $bytes = @filesize($this->path);
        if ($bytes === false) {
            $this->setError("failed to stat filesize for '{$this->path}'");
            return -1;
        }
        return $bytes;
    }