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Re: Efficient method to replace middle lines only when no match

by AnomalousMonk (Archbishop)
on Mar 19, 2014 at 03:55 UTC ( [id://1078892]=note: print w/replies, xml ) Need Help??


in reply to Efficient method to replace middle lines only when no match

Ok, with a better understanding of the requirements, here's a solution that seems sufficiently fast: I'm just timing to 1 sec resolution, but in general,  s/// with replacements is a little over 1 sec, without replacements a little under. To me, that seems pretty fast for a 21M timing test string.

use warnings; use strict; local $/; my $slurp = do { local $/; <DATA>; }; print qq{[[$slurp]] \n\n}; my $replace = qq{field2: valueB\n}; my $text = $slurp; $text =~ s{ ^ field1: [^\n]* \n \K (?! ^ \Q$replace\E) .*? (?= ^ field3: [^\n]* \n) } {$replace}xmsg; print qq{[[$text]] \n\n}; $text = $slurp; $text = $text x 100_000; printf qq{length of timing string: %d \n\n}, length $text; print qq{begin timings \n}; my $start = time(); # start timing for replacements $text =~ s{ ^ field1: [^\n]* \n \K (?! ^ \Q$replace\E) .*? (?= ^ field3: [^\n]* \n) } {$replace}xmsg; printf qq{replacements: %ds elapsed \n}, time() - $start; $start = time(); # start timing for no replacements $text =~ s{ ^ field1: [^\n]* \n \K (?! ^ \Q$replace\E) .*? (?= ^ field3: [^\n]* \n) } {$replace}xmsg; printf qq{no replacements: %ds elapsed \n}, time() - $start; print qq{\n}; print substr($text, 0, 250), qq{\n... \n}, substr($text, -250), qq{\n} +; __DATA__ yada field1: replace following A some lines here field3: replace previous A blah blah field1: do not replace field2: valueB field3: do not replace field1: replace after B hoo ha fee fie foe field3: replace before B

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