CCloudStorageBucket::CompileExtentionRule

static function CompileExtentionRule($str)
{
	$res = array();
	$ar = explode(",", $str);
	foreach($ar as $s)
	{
		$s = trim($s);
		if($s !== '')
			$res[$s] = preg_quote(".".$s, '/');
	}
	if(!empty($res))
		return "/(".implode("|", $res).")$/i";
	else
		return "";
}