Messages in this thread | | | Date | Sun, 19 Aug 2007 03:57:58 +0100 | From | Al Viro <> | Subject | Re: Thinking outside the box on file systems |
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On Sat, Aug 18, 2007 at 07:03:06PM -0700, david@lang.hm wrote: > >>I suspect you will find it somewhat hard to convince *anybody* on > >>this list to put either a regex engine or a Perl interpreter into the > >>kernel. I doubt you could even get a simple shell-style pattern > >>matcher in. First of all, both of the former chew up enormous gobs > >>of stack space *AND* they're NP-complete.
Eh? regex via NFA is O(expression size * string length) time and O(expression size) space. If you can show that regex matching is NP-complete, you've got a good shot at Nevanlinna Prize...
Not that it made regex in kernel a good idea, but fair is fair - unless you can show any mentioning of backrefs upthread...[1]
> You just can't do such > >>matching even in polynomial time, let alone something that scales > >>appropriately for an OS kernel like, say, O(log(n)). > > > >Already been done. Take a look at "AppArmor" aka "Immunix". > > don't forget the ACPI interpreter.
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