linux-kernel - Re: [PATCH 1/5] lib: add find_nth(,and,andnot)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAAH8bW9qP8YY8k_JOE+oezU0iFCZq6H2W6dv8sL2kr3Q_eLQ8Q@mail.gmail.com>
Date:   Fri, 8 Jul 2022 09:40:48 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>, David Gow <davidgow@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Isabella Basso <isabbasso@...eup.net>,
        Kees Cook <keescook@...omium.org>,
        Keith Busch <kbusch@...nel.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH 1/5] lib: add find_nth(,and,andnot)_bit()

On Fri, Jul 8, 2022 at 2:13 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Fri, Jul 8, 2022 at 10:55 AM Rasmus Villemoes
> <linux@...musvillemoes.dk> wrote:
> > On 07/07/2022 23.03, Yury Norov wrote:
> >
> > >> And I don't
> > >> like that the index is apparently 1-based (and that surprising API isn't
> > >> spelled out anywhere).
> > >
> > > Yeah... My motivation to start counting from 1 is to keep consistency
> > > with ffs: __ffs(word) <=> fns(word, 1).
> >
> > I understand that you're translating that second f in ffs (find First
> > set) to a 1. But I disagree that that's necessarily a logical thing to
> > do. Everybody understands that (given a C or python or... context) when
> > some prose talks about "the first element in an array", it's the one at
> > [0]. So I find it much more natural that the set bits in a word are
> > enumerated 0, 1, ..., popcount(w)-1.
>
> I agree that here we operate with an array of bits, which naturally
> starts from bit 0.

OK, I'll send v2 shortly