protected function size($args) {
		$size = 0;
		
		foreach ($args['targets'] as $target) {
			if (($volume = $this->volume($target)) == false
			|| ($file = $volume->file($target)) == false
			|| !$file['read']) {
				return array('error' => $this->error(self::ERROR_OPEN, '#'.$target));
			}
			
			$size += $volume->size($target);
		}
		return array('size' => $size);
	}