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Implement Linear glob match #4094 #4579

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HazemSamir commented Dec 6, 2017

As Noted in #4094 that glob expansion is exponential. A near linear implementation is discussed in this article on glob expansion in various shells and platforms.

Changes in wildcard.cpp:

The function that is responsible for this behavior is wildcard_match and its wildcard_match_internal which matches the wildcard recursively with the string. I changed it to the near linear implementation discussed in the article.

The wildcard "**" is not affected by this function because wildcard_expand_string is the one that is responsible for it and it is still doing it recursively.

tested using:

cd (mktemp -d)
touch (printf 'a%.0s' (seq 100))
for n in (seq 1 10)
   set -l pattern (printf 'a*%.0s' (seq $n))b
   time fish -c "echo $pattern"
end
n (a*) User time exponential User time linear
1 0.01 0.008
2 0.00 0.000
3 0.00 0.004
4 0.03 0.008
5 0.57 0.004
6 9.13 0.004
7 126.32 0.004
8 1521.75 0.008
9 16055.30 0.008
10 152573.24 0.004

Fixes issue #4094

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ridiculousfish commented Dec 11, 2017

Reviewed, this looks awesome!! Merged as c45d4ab.

ridiculousfish added a commit that referenced this pull request Dec 11, 2017

Add glob changes to CHANGELOG
This records the glob changes from #4579 in the changelog
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ridiculousfish commented Dec 11, 2017

Noted in changelog as c077aae

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