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[perl #131211] fixup File::Glob degenerate matching
The old code would go quadratic with recursion and backtracking when doing patterns like "a*a*a*a*a*a*a*x" on a file like "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa". This patch changes the code to not recurse, and to not backtrack, as per this article from Russ Cox: https://research.swtch.com/glob It also adds a micro-optimisation for M_ONE and M_SET under the new code. Thanks to Avar and Russ Cox for helping with this patch, along with Jilles Tjoelker and the rest of the FreeBSD community.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| use strict; | ||
| use warnings; | ||
| use v5.16.0; | ||
| use File::Temp 'tempdir'; | ||
| use File::Spec::Functions; | ||
| use Test::More; | ||
| use Time::HiRes qw(time); | ||
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| plan tests => 13; | ||
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| my $path = tempdir uc cleanup => 1; | ||
| my @files= ( | ||
| "x".("a" x 50)."b", # 0 | ||
| "abbbbbbbbbbbbc", # 1 | ||
| "abbbbbbbbbbbbd", # 2 | ||
| "aaabaaaabaaaabc", # 3 | ||
| "pq", # 4 | ||
| "r", # 5 | ||
| "rttiiiiiii", # 6 | ||
| "wewewewewewe", # 7 | ||
| "weeeweeeweee", # 8 | ||
| "weewweewweew", # 9 | ||
| "wewewewewewewewewewewewewewewewewq", # 10 | ||
| "wtttttttetttttttwr", # 11 | ||
| ); | ||
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| foreach (@files) { | ||
| open(my $f, ">", catfile $path, $_); | ||
| } | ||
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| my $elapsed_fail= 0; | ||
| my $elapsed_match= 0; | ||
| my @got_files; | ||
| my @no_files; | ||
| my $count = 0; | ||
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| while (++$count < 10) { | ||
| $elapsed_match -= time; | ||
| @got_files= glob catfile $path, "x".("a*" x $count) . "b"; | ||
| $elapsed_match += time; | ||
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| $elapsed_fail -= time; | ||
| @no_files= glob catfile $path, "x".("a*" x $count) . "c"; | ||
| $elapsed_fail += time; | ||
| last if $elapsed_fail > $elapsed_match * 100; | ||
| } | ||
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| is $count,10, | ||
| "tried all the patterns without bailing out"; | ||
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| cmp_ok $elapsed_fail/$elapsed_match,"<",2, | ||
| "time to fail less than twice the time to match"; | ||
| is "@got_files", catfile($path, $files[0]), | ||
| "only got the expected file for xa*..b"; | ||
| is "@no_files", "", "shouldnt have files for xa*..c"; | ||
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| @got_files= glob catfile $path, "a*b*b*b*bc"; | ||
| is "@got_files", catfile($path, $files[1]), | ||
| "only got the expected file for a*b*b*b*bc"; | ||
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| @got_files= sort glob catfile $path, "a*b*b*bc"; | ||
| is "@got_files", catfile($path, $files[3])." ".catfile($path,$files[1]), | ||
| "got the expected two files for a*b*b*bc"; | ||
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| @got_files= sort glob catfile $path, "p*"; | ||
| is "@got_files", catfile($path, $files[4]), | ||
| "p* matches pq"; | ||
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| @got_files= sort glob catfile $path, "r*???????"; | ||
| is "@got_files", catfile($path, $files[6]), | ||
| "r*??????? works as expected"; | ||
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| @got_files= sort glob catfile $path, "w*e*w??e"; | ||
| is "@got_files", join(" ", sort map { catfile($path, $files[$_]) } (7,8)), | ||
| "w*e*w??e works as expected"; | ||
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| @got_files= sort glob catfile $path, "w*e*we??"; | ||
| is "@got_files", join(" ", sort map { catfile($path, $files[$_]) } (7,8,9,10)), | ||
| "w*e*we?? works as expected"; | ||
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| @got_files= sort glob catfile $path, "w**e**w"; | ||
| is "@got_files", join(" ", sort map { catfile($path, $files[$_]) } (9)), | ||
| "w**e**w works as expected"; | ||
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| @got_files= sort glob catfile $path, "*wee*"; | ||
| is "@got_files", join(" ", sort map { catfile($path, $files[$_]) } (8,9)), | ||
| "*wee* works as expected"; | ||
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| @got_files= sort glob catfile $path, "we*"; | ||
| is "@got_files", join(" ", sort map { catfile($path, $files[$_]) } (7,8,9,10)), | ||
| "we* works as expected"; | ||
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