Re: Formal review request for Hash2

From: Ivan Matek (libbooze_at_[hidden])
Date: 2024-12-05 21:59:43

On Thu, Dec 5, 2024 at 10:53 PM Andrey Semashev via Boost <
boost_at_[hidden]> wrote:

> Technically, it doesn't need to be size to separate the two fields. You
> can use any kind of separator, including a fixed one (i.e. not depending
> on either of the fields it separates). I.e. instead of this:
>
>   "ab" | 2 | "c" | 1
>
> you could have this:
>
>   "ab" | separator_t{} | "c" | separator_t{}
>
> An empty sequence could simply be hashed as separator_t{}.
>
> The question is how separator_t would hash and whether it could be made
> any faster than just hashing the size. I suppose, it could be smaller
> (e.g. 1 byte of data instead of sizeof(size_t)), but I'm not sure if
> that would mean anything in terms of performance.
>
>
>
As far as I understand that will not work. Assume separator is char 'x'
although it does not really matter what the value is, it is just for ease
of writing.

now
"a" | "xc"
hashes same
as
"ax" | "c"
because both produce axxc