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bug#16966: [PATCH] grep: optimization with the superset of DFA

From: Paolo Bonzini
Subject: bug#16966: [PATCH] grep: optimization with the superset of DFA
Date: Tue, 01 Apr 2014 10:16:32 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

Il 28/03/2014 18:20, Norihiro Tanaka ha scritto:
I rebased this patch, and added four fixes to it.

 1. Fix for the conditions that the superset is used.  No longer use it
    when don't include any normal chars and CSETs. (dfasuperset)

 2. Ignore any letter constrations.  Otherwise, it mayn't be able to be
    a superset of the original dfa. (dfasuperset)

 3. Change return type of dfahint().  It can check whether used or not
    from caller.(dfahint)

 4. If both kwset and dfahint() aren't used, run DFA matcher in whole
    range still.

For ANYCHAR, you can convert it to CSET{1,mb_cur_max} or, even better, (single-CSET | lead-CSET full-CSET{0,mb_cur_max-1}).

Single-CSET and lead-CSET can be computed by looping over the 256 characters with mbrtowc and looking respectively for non-negative or -2 return values.


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