はじめに 皆さんこんにちは．3回生のらん（@ran350jp）です． 文字列マッチングに便利な正規表現ですが，テキトーに書くと脆弱になり得るという情報を耳にしてから色々と原因や対策を調べていました． しかし，多くの記事で紹介されていた対策方法は，「独自の正規表現を使用しないー」とか「 * や + などの繰り返し表現はなるべく使わないー」とかいう なんともふわっとしたものでした．これでは「いやぁ確かにそうなんかもしれんけど…そうゆう訳にはいかんやんか…」と納得できません． つまり，「本質的に何が問題」で，「具体的にどんな特徴のある正規表現が脆弱になり得るのか」を知りたい訳です． そこで，様々な文献を調査してみました．本記事では調査して溜まった知見を紹介していきます． 本記事は， Purdue大学のJames Davis教授による “The Regular Expression Denial
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Show navigation Starting with v8.8, V8 ships with a new experimental non-backtracking RegExp engine (in addition to the existing Irregexp engine) which guarantees execution in linear time with respect to the size of the subject string. The experimental engine is available behind the feature flags mentioned below. Runtime of /(a*)*b/.exec('a'.repeat(n)) for n ≤ 100Here’s how you can configure the n
Implementing Regular Expressions Russ Cox rsc@swtch.com This page collects resources about implementing regular expression search efficiently. Articles and Notes “Regular Expression Matching Can Be Simple And Fast” An introduction to using finite automata to implement regular expression matching, and why the standard backtracking implementation is a bad idea. Supporting programs: NFA | DFA | bound
Background: RegExps in SpiderMonkey Regular expressions – commonly known as RegExps – are a powerful tool in JavaScript for manipulating strings. They provide a rich syntax to describe and capture character information. They’re also heavily used, so it’s important for SpiderMonkey (the JavaScript engine in Firefox) to optimize them well. Over the years, we’ve had several approaches to RegExps. Con
Regular Expression Matching with a Trigram Index or How Google Code Search Worked Russ Cox rsc@swtch.com January 2012 Introduction In the summer of 2006, I was lucky enough to be an intern at Google. At the time, Google had an internal tool called gsearch that acted as if it ran grep over all the files in the Google source tree and printed the results. Of course, that implementation would be fairl
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