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Message-ID: <e78791a327cdadf4557c936802066a55@smtp.hushmail.com>
Date: Tue, 05 May 2015 22:40:24 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: get_binary_*() and get_hash_*() methods
On 2015-05-05 21:53, Aleksey Cherepanov wrote:
> I mean, we can implement cmp_all using other methods, something like
> the following:
>
> static int cmp_all(void *binary, int count)
> {
> int i;
> int b = fmt_default_binary_hash_6(binary);
> for (i = 0; i < count; i++) {
> if (get_hash_6(i) == b)
> return 1;
> }
> return 0;
> }
That's a function call inside a hot loop and the compiler can't optimize
it away (but you realized this below).
> Though some formats define get_hash_6 as "return 0;".
Sounds like a bug to me. I think there should be no get_hash_6 in that
case (ie. the function pointer should be NULL).
> Hm, get_hash_6 is in format's file. self is needed to access it in
> default implementation. But then it will not be inlined.
>
> A macro may be used to insert the code of cmp_all into format's file.
> Though get_hash_6 gives only 31 bits, while raw-sha512 checks all 64
> bits in 1 check.
>
> So I think my question about default implementation of cmp_all is
> solved.
>
> Does binary_hash_6() and get_hash_6() functions have to return the
> same values for the same hashes?
Yes that's the whole point of these functions, and the self-tests tries
to verify this.
magnum
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