Catastrophic backtracking #820
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bemself
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Sep 5, 2020
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| The typical symptom -- a regular expression works fine sometimes, but for certain strings it "hangs", consuming 100% of CPU. | ||
| 典型的症状就是 -- 一个正则表达式有时能正常工作，但在某些特定字符串中就会消耗 100% 的 CPU 算力，出现「挂起」现象，。 |
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| 典型的症状就是 -- 一个正则表达式有时能正常工作，但在某些特定字符串中就会消耗 100% 的 CPU 算力，出现「挂起」现象，。 | |
| 典型的症状就是 － 一个正则表达式有时能正常工作，但在某些特定字符串中就会消耗 100% 的 CPU 算力，出现「挂起」现象。 |
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| Let's say we have a string, and we'd like to check if it consists of words `pattern:\w+` with an optional space `pattern:\s?` after each. | ||
| 比如我们现在有一个字符串，我们想检查其中是否包含一些字符 `pattern:\w+` ，我们允许字符后跟着可选的空格符 `pattern:\s?` 。 |
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| 比如我们现在有一个字符串，我们想检查其中是否包含一些字符 `pattern:\w+` ，我们允许字符后跟着可选的空格符 `pattern:\s?` 。 | |
| 比如我们现在有一个字符串，我们想检查其中是否包含一些字符 `pattern:\w+`，我们允许字符后跟着可选的空格符 `pattern:\s?`。 |
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能否翻译如下，因为根据下面的例子来看这里的words应该理解为单词更贴切：
比如我们现在有一个字符串，我们想检查该字符串是不是由一些后面带有可选空格pattern:\s?的单词pattern:\w+所组成 。
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| We'll use a regexp `pattern:^(\w+\s?)*$`, it specifies 0 or more such words. | ||
| 我们使用一个这样的正则 `pattern:^(\w+\s?)*$` ，它指定了 0 个或更多个此类的字符。 |
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| 我们使用一个这样的正则 `pattern:^(\w+\s?)*$` ，它指定了 0 个或更多个此类的字符。 | |
| 我们使用一个这样的正则 `pattern:^(\w+\s?)*$`，它指定了 0 个或更多个此类的字符。 |
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| And, to make things more obvious, let's replace `pattern:\w` with `pattern:\d`. The resulting regular expression still hangs, for instance: | ||
| 同时为了让问题更显著，再用 `pattern:\d` 替换掉 `pattern:\w` 。这个新的正则表达式执行时仍然会挂起，比如： |
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| 同时为了让问题更显著，再用 `pattern:\d` 替换掉 `pattern:\w` 。这个新的正则表达式执行时仍然会挂起，比如： | |
| 同时为了让问题更显著，再用 `pattern:\d` 替换掉 `pattern:\w`。这个新的正则表达式执行时仍然会挂起，比如： |
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| ``` | ||
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| \d+.......\d+ | ||
| (12345678)(9)! | ||
| ``` | ||
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| The engine tries to match `pattern:$` again, but fails, because meets `subject:!`: | ||
| 引擎再次去尝试匹配 `pattern:$` ，但是失败了，因为它遇到了 `subject:!` ： |
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| 引擎再次去尝试匹配 `pattern:$` ，但是失败了，因为它遇到了 `subject:!` ： | |
| 引擎再次去尝试匹配 `pattern:$`，但是失败了，因为它遇到了 `subject:!` ： |
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| For example, the previous pattern `pattern:(\w+\s?)*` could match the word `subject:string` as two `pattern:\w+`: | ||
| 举个例子，之前那个模式 `pattern:(\w+\s?)*` 可能以两个 `pattern:\w+` 的方式来匹配单词 `subject:string` ： |
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| 举个例子，之前那个模式 `pattern:(\w+\s?)*` 可能以两个 `pattern:\w+` 的方式来匹配单词 `subject:string` ： | |
| 举个例子，之前那个模式 `pattern:(\w+\s?)*` 可能以两个 `pattern:\w+` 的方式来匹配单词 `subject:string`： |
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| ```js run | ||
| \w+\w+ | ||
| string | ||
| ``` | ||
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| The previous pattern, due to the optional `pattern:\s` allowed variants `pattern:\w+`, `pattern:\w+\s`, `pattern:\w+\w+` and so on. | ||
| 之前那个模式，由于存在可选的 `pattern:\s` ，它允许 `pattern:\w+`，`pattern:\w+\s`，`pattern:\w+\w+` 等等的变体形式。 |
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| 之前那个模式，由于存在可选的 `pattern:\s` ，它允许 `pattern:\w+`，`pattern:\w+\s`，`pattern:\w+\w+` 等等的变体形式。 | |
| 之前那个模式，由于存在可选的 `pattern:\s`，它允许 `pattern:\w+`、`pattern:\w+\s` 和 `pattern:\w+\w+` 等等的变体形式。 |
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| E.g. in the regexp `pattern:(\d+)*$` it's obvious for a human, that `pattern:+` shouldn't backtrack. If we replace one `pattern:\d+` with two separate `pattern:\d+\d+`, nothing changes: | ||
| 比如，正则 `pattern:(\d+)*$` 中 `pattern:+` 对于我们人类来说很明显不应去回溯，就算我们用两个独立的 `pattern:\d+\d+` 去替换一个 `pattern:\d+`， 也是根本没作用的： |
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| 比如，正则 `pattern:(\d+)*$` 中 `pattern:+` 对于我们人类来说很明显不应去回溯，就算我们用两个独立的 `pattern:\d+\d+` 去替换一个 `pattern:\d+`， 也是根本没作用的： | |
| 比如，正则 `pattern:(\d+)*$` 中 `pattern:+` 对于我们人类来说很明显不应去回溯，就算我们用两个独立的 `pattern:\d+\d+` 去替换一个 `pattern:\d+`，也是根本没作用的： |
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| For instance, in the word `subject:JavaScript` it may not only match `match:Java`, but leave out `match:Script` to match the rest of the pattern. | ||
| 例如，在单词 `subject:JavaScript` 不仅可以匹配 `match:Java`，而且可以忽略 `match:Script` ，匹配模式的其余部分。 |
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| 例如，在单词 `subject:JavaScript` 不仅可以匹配 `match:Java`，而且可以忽略 `match:Script` ，匹配模式的其余部分。 | |
| 例如，在单词 `subject:JavaScript` 中不仅可以匹配 `match:Java`，而且可以忽略 `match:Script`，匹配模式的其余部分。 |
| ``` | ||
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| Here `pattern:\2` is used instead of `pattern:\1`, because there are additional outer parentheses. To avoid messing up with the numbers, we can give the parentheses a name, e.g. `pattern:(?<word>\w+)`. | ||
| 这里我们用 `pattern:\2` 代替 `pattern:\1`，因为这里附加了额外的外部括号。为了防止数字产生混淆，，我们可以给括号命名，例如 `pattern:(?<word>\w+)`。 |
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| 这里我们用 `pattern:\2` 代替 `pattern:\1`，因为这里附加了额外的外部括号。为了防止数字产生混淆，，我们可以给括号命名，例如 `pattern:(?<word>\w+)`。 | |
| 这里我们用 `pattern:\2` 代替 `pattern:\1`，因为这里附加了额外的外部括号。为了防止数字产生混淆，我们可以给括号命名，例如 `pattern:(?<word>\w+)`。 |
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Please make the requested changes. After it, add a comment "/done". |
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格式已修正，更新了 PR。 @bemself |
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/done |
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/done |
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Thank you 💖 I updated the Progress Issue #324 🎉 🎉 🎉 |
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感谢翻译和校对 👍 后面的内容有些更新和变动，我先合并了，后续再做更新优化。欢迎继续 PR 更多内容。 |
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目标章节：9-regular-expressions/15-regexp-catastrophic-backtracking
当前上游最新 commit：javascript-tutorial/en.javascript.info@32e20fc#diff-daa73ffcb00f33284c228961daab9209
本 PR 所做更改如下：