protected function _guessAdapterType()
    {
        $this->_cleanFilesStack();
        if (!empty($this->files_stack)) {
            $_fs = $this->files_stack;
            $_file = array_shift($_fs);
            $this->setAdapterType($_file->getExtension());
            return true;
        } elseif (false===$this->silent) {
            throw new \RuntimeException(
                '[Compressor] Trying to guess adapter from an empty files stack!'
            );
        }
        return false;
    }