public function getFiles($file = null)
    {
        if ($file !== null) {
            $return = array();
            foreach ($this->_files as $name => $content) {
                if ($name === $file) {
                    $return[$file] = $this->_files[$name];
                }

                if ($content['name'] === $file) {
                    $return[$name] = $this->_files[$name];
                }
            }

            if (count($return) === 0) {
                require_once 'Zend/Validate/Exception.php';
                throw new Zend_Validate_Exception("The file '$file' was not found");
            }

            return $return;
        }

        return $this->_files;
    }