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Re: please keep 'memmem' module simple
From: |
Simon Josefsson |
Subject: |
Re: please keep 'memmem' module simple |
Date: |
Wed, 09 Jan 2008 15:53:35 +0100 |
User-agent: |
Gnus/5.110007 (No Gnus v0.7) Emacs/22.1 (gnu/linux) |
Eric Blake <address@hidden> writes:
> According to Simon Josefsson on 1/9/2008 3:16 AM:
> |
> | For gnutls, the strings are always the same (X.509 PEM headers), and we
> | haven't seen such slowdowns even on large inputs (searching for a 10
> | byte needle in a 500kb input is, while not typical, not uncommon). What
> | properties do unlucky strings have?
>
> The quadratic nature of the brute force algorithm (which glibc currently
..
Thanks for the explanation.
> So I'm okay with the idea of adding a memmem-simple module that skips the
> quadratic check if the system memmem is otherwise working
Sounds like a plan, then. I'll see if I can produce a patch.
> (remember, however, that the system memmem may be broken, as on
> cygwin).
Did the old check find that brokenness? Has this brokenness been
discussed before, and was a m4 test to detect it produced? I can't see
anything in memmem.m4 about it now.
> But I think it should be done solely through m4 magic - in other
> words, split gl_FUNC_MEMMEM into two macros, where the behavioral
> check is called for both memmem and memmem-simple, but the speed check
> is called only for memmem; both modules can share the lib/memmem.c
> implementation.
Sure.
/Simon
- please keep 'memmem' module simple, Simon Josefsson, 2008/01/08
- Re: please keep 'memmem' module simple, Paul Eggert, 2008/01/08
- Re: please keep 'memmem' module simple, Simon Josefsson, 2008/01/08
- Re: please keep 'memmem' module simple, Bruno Haible, 2008/01/08
- Re: please keep 'memmem' module simple, Simon Josefsson, 2008/01/09
- Re: please keep 'memmem' module simple, Eric Blake, 2008/01/09
- Re: please keep 'memmem' module simple,
Simon Josefsson <=
- Re: please keep 'memmem' module simple, Eric Blake, 2008/01/09
- Re: please keep 'memmem' module simple, Simon Josefsson, 2008/01/09
- Re: please keep 'memmem' module simple, Simon Josefsson, 2008/01/09
- Re: please keep 'memmem' module simple, Bruno Haible, 2008/01/09
- Re: please keep 'memmem' module simple, Eric Blake, 2008/01/09
- Re: please keep 'memmem' module simple, Simon Josefsson, 2008/01/09
- Re: please keep 'memmem' module simple, Bruno Haible, 2008/01/09
- Re: please keep 'memmem' module simple, Eric Blake, 2008/01/09