On Mon, Nov 20, 2023 at 07:03:13PM -0800, Linus Torvalds wrote: > On Mon, 20 Nov 2023 at 18:29, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > It's a bit complicated, yes. But no, doing things one unicode > > character at a time is just bad bad bad. > > Put another way: the _point_ of UTF-8 is that ASCII is still ASCII. > It's literally why UTF-8 doesn't suck. > > So you can still compare ASCII strings as-is. > > No, that doesn't help people who are really using other locales, and > are actively using complicated characters. > > But it very much does mean that you can compare "Bad" and "bad" and > never ever look at any unicode translation ever. Yeah, agreed, that would be a nice optimization. However, in the unfortunate case where (a) it's non-ASCII, and (b) the input string is non-normalized and/or differs in case, we end up scanning some portion of the two strings twice; once doing the strcmp, and once doing the Unicode slow path. That being said, given that even in the case where we're dealing with non-ASCII strings, in the fairly common case where the program is doing a readdir() followed by a open() or stat(), the filename will be byte-identical and so a strcmp() will suffice. So I agree that it's a nice optimization. It'd be interesting how much such an optimization would actually show up in various benchmarks. It'd have to be something that was really metadata-heavy, or else the filenamea lookups would get drowned out. - Ted
