Re: [pve-devel] [PATCH installer 2/5] common: fqdn: implement case-insensitive comparison as per RFC 952

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 15/02/2024 um 13:39 schrieb Christoph Heiss:
> +impl PartialEq for Fqdn {
> +    fn eq(&self, other: &Self) -> bool {
> +        // Case-insensitive comparison, as per RFC 952 "ASSUMPTIONS",
> +        // RFC 1035 sec. 2.3.3. "Character Case" and RFC 4343 as a whole
> +        let a = self
> +            .parts
> +            .iter()
> +            .map(|s| s.to_lowercase())
> +            .collect::<Vec<String>>();
> +
> +        let b = other
> +            .parts
> +            .iter()
> +            .map(|s| s.to_lowercase())
> +            .collect::<Vec<String>>();
> +
> +        a == b

could be probably more efficiently done by doing the comparison part wise, not
on the whole thing, and with an early abort for mismatching part count, e.g.,
something like:

if self.parts.len() != other.parts.len() {             
    return false;                                      
}                                                      
                                                       
self.parts                                             
    .iter()                                            
    .zip(other.parts.iter())                           
    .all(|(a, b)| a.to_lowercase() == b.to_lowercase())

> @@ -309,4 +329,10 @@ mod tests {
>              "foo.example.com"
>          );
>      }
> +
> +    #[test]
> +    fn fqdn_compare() {
> +        assert_eq!(Fqdn::from("example.com"), Fqdn::from("ExAmPle.Com"));
> +        assert_eq!(Fqdn::from("ExAmPle.Com"), Fqdn::from("example.com"));

I always like throwing in some assert_ne ones for sanity checking (e.g., such
optimization tries like above), as otherwise one won't notice if this is broken,
like by just always returning false..