Re: [Boost-bugs] [Boost C++ Libraries] #11776: Effective way to find all regex matches in large file (was: Need way to find all regex matches in large file)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11776: Effective way to find all regex matches in large file (was: Need way to find all regex matches in large file)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-03-15 17:06:50

#11776: Effective way to find all regex matches in large file
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  Reporter:  der-storch-85@…   |      Owner:  johnmaddock
      Type:  Feature Requests  |     Status:  reopened
 Milestone:  To Be Determined  |  Component:  regex
   Version:  Boost 1.59.0      |   Severity:  Optimization
Resolution:                    |   Keywords:
-------------------------------+--------------------------
Changes (by der-storch-85@…):

 * status:  closed => reopened
 * resolution:  wontfix =>

Comment:

 Replying to [comment:1 johnmaddock]:
 > Documentation updated.

 Great. But, as I wrote, an additional update of
 [http://www.boost.org/doc/libs/1_59_0/libs/regex/doc/html/boost_regex/partial_matches.html

 Partial Matches] is really necessary, because it’s one of the first
 answers when searching a solution for this special problem. For a
 (tortuous) workaround see attached file `main.cpp` that can be compiled
 with
 {{{
 g++ main.cpp -std=c++11 -lboost_regex -o regex
 }}}

 > Note that this particular case can be detected by checking whether the
 end of the match is at the end of the current string.

 In the ''above very particular'' case: yes, but normally: no. That would
 be to easy ;-)
 Example: buffer size 4, regex "(ab)+", and input 1abab2.

 > However, there are expression such as "abc.*123" that actually need the
 whole input string (no matter how long it may be) to determine the longest
 match.

 Correct, you have to keep that in mind, especially when parsing large
 files. Nevertheless: Erroneous or senseless regexes lead to unwanted or
 erroneous program executions.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11776#comment:2>
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