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Date: Fri, 23 Sep 2011 05:37:56 +0200
From: magnum <>
Subject: Re: user-defined character class samples

On 2011-09-23 03:24, Solar Designer wrote:
> On Wed, Sep 21, 2011 at 10:57:33PM +0200, magnum wrote:
>> Dang, now I remember I should have revised that sample, it's not doing
>> what it was supposed to.
> I guess you're referring to this one? -
> # This silly example rule use the user-defined character class
> # example ?1 above. It will prepend any hex-string of at least
> # 4 digits within a candidate with 0x as well as with  \x like
> # this:
> #  'hello'   ->  rejected
> #  'alibaba' ->  'ali0xbaba' and 'ali\xbaba'
> [List.Rules:Example]
> %4?1vap2Aa"[\\0]x"
> If so, that's not what I meant, although we should have removed it (feel
> free to submit a patch such that we don't forget).

Yes, that rule only does the right thing when the hex-digits are 
consecutive. %N?C is "reject the word unless it contains at least N 
characters of class C" but I did the mistake of assuming " least N 
consecutive...". By the way, such a command might be useful.

> These examples are correct, right? -
> # This is a couple of example classes:
> # ?0 matches (one version of) base64 characters
> # ?1 matches hex digits
> # ?2 matches the TAB character (never try to use \x00!)
> [UserClasses]
> 0 = [a-zA-Z0-9/.]
> 1 = [0-9a-fA-F]
> 2 = \x09
> Hmm, did you implement the \x09 thing?  I am not sure.

Yes, they are correct and \x09 works fine. This works in ranges too, eg 
[\x80-\xff]. But the \x thing only works in that very section: I'm still 
pondering how to implement something similar for rules in a clever way.


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