From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Dmitry Gutov Newsgroups: gmane.emacs.bugs Subject: bug#60953: The :match predicate with large regexp in tree-sitter font-lock seems inefficient Date: Mon, 30 Jan 2023 20:20:46 +0200 Message-ID: <33cad4c1-4af5-37bb-05bc-79a4d9c1a700@yandex.ru> References: <7624dddc-4600-9a03-ac8b-d3c9e0ab618c@yandex.ru> <04729838-b7d4-8a08-2b71-12536a28aebb@yandex.ru> <83wn5ag4nc.fsf@gnu.org> <01b5d074-fb12-6b1f-cbfb-5e759833b854@yandex.ru> <838rhpg57n.fsf@gnu.org> <5026D975-983F-4D18-8690-BE139C92825D@gmail.com> <83pmb1emxi.fsf@gnu.org> <6f318afc-ca71-8b7e-c822-52e6635b5718@yandex.ru> <83sffxcfxw.fsf@gnu.org> <83pmb1cbg5.fsf@gnu.org> <2da844d3-ea31-289e-2821-aa174e365ffd@yandex.ru> <6784f9e7-844b-374d-2a1e-8a61cebe0d7e@yandex.ru> <83zga03yne.fsf@gnu.org> <373a575f-c683-1581-c3e6-502e9897fb04@yandex.ru> <83mt603vrc.fsf@gnu.org> <83e58a1b-2e4a-356a-36d8-c756ff105b62@yandex.ru> <83bkmf52va.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; 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Mon, 30 Jan 2023 10:20:48 -0800 (PST) Content-Language: en-US In-Reply-To: <83bkmf52va.fsf@gnu.org> X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.bugs:254468 Archived-At: On 30/01/2023 19:49, Eli Zaretskii wrote: >> Date: Mon, 30 Jan 2023 19:15:07 +0200 >> Cc: casouri@gmail.com, 60953@debbugs.gnu.org >> From: Dmitry Gutov >> >>> fast_looking_at already does an anchored match, so I'm not sure I >>> follow. I don't even understand why you need th \` part, when the >>> match will either always start from the first position or fail. >> >> The regexp might include the anchors, or it might not. >> >> It might also use a different anchor like ^ or $ or \b. > > OK, but it always goes only forward, so narrowing to the beginning > shouldn't be necessary. Right? Are you saying that fast_looking_at ("\\`", ...) will always succeed? And fast_looking_at ("^", ...), etc. I would imagine that only fast_looking_at ("\\=", ...) is guaranteed to succeed. > And you can use the LIMIT argument to > limit how far it goes forward, right? So once again, why narrow? I tried to explain that there is a certain expectation (on the part of the user/programmer) which anchors are allowed in the :match regexp, and what their effects are, and those seem hard to support without narrowing. >>> And for \', just compare the length of the match returned by >>> fast_looking_at with the length of the text. >> >> This seems to work, i.e. even when before "carpet", >> >> (and (looking-at (regexp-opt '("car" "cardigan" "carpet"))) >> (match-string 0)) >> >> returns the full match. I was expecting that it could return just "car" >> -- not sure why it doesn't stop there. > > Because regex search is greedy? Cool. TIL, thanks. That's not going to help here, but might in other situations when my code controls the regexp as well. >> One possible alternative, I suppose, would be to create a raw pointer to >> a part of the buffer text and call re_search directly specifying the >> known length of the node in bytes. If buffer text is one contiguous >> region in memory, that is. > > It isn't, though: there's the gap. Which is why doing this is not > recommended; instead, use something like search_buffer_re, which > already handles this complication for you. (Except that > search_buffer_re is a static function, so only code in search.c can > use it. So you'd need to make it non-static.) Interesting. Does search_buffer_re match the \` anchor at POS and \' at LIM? IOW, does in treat the rest of the buffer as non-existing? Or could it?