Devristo\Phpws\Framing\WebSocketFrame::rotMask PHP Method

    protected static function rotMask($data, $key, $offset = 0)
    {
        // Rotate key for example if $offset=1 and $key=abcd then output will be bcda
        $rotated_key = substr($key, $offset) . substr($key, 0, $offset);
        // Repeat key until it is at least the size of the $data
        $key_pad = str_repeat($rotated_key, ceil(1.0 * strlen($data) / strlen($key)));
        return $data ^ substr($key_pad, 0, strlen($data));
    }