在大文本中找到某种模式的有效方法是什么? [英] What is the efficient way to find some pattern in a big text?

问题描述

我想从大型文本文件中提取电子邮件地址.最好的方法是什么?

I want to extract email addresses from a large text file. what is the best way to do it?

我的想法是在文本中找到 '@' 并使用Regex"将电子邮件地址查找到子字符串中(例如)此位置之前的 256 个字符和 512 的长度.

My idea is to find '@' in the text and use "Regex" to find email address into substring at (for example) 256 chars before this position and length of 512.

P.S.:坦率地说，我想知道在 巨大 文本中找到某种模式(如电子邮件地址)的最佳和最有效的方法.

P.S.: Straightforwardly I want to know the best and most efficient way to find some pattern (like email addresses) in a huge text.

推荐答案

如果你绝对需要最有效的方式，我认为不应该使用正则表达式.

If you absolutely need the most efficient way, I don't think regular expressions should be used.

假设您的文本中几乎所有 @ 实例都是电子邮件地址，并且您使用的是一种快速向前和向后字符串遍历的语言，这种方法可能会接近最快:

Assuming almost all instances of @ in your text are email addresses and you are working in a language with fast forward and backward string traversal, this method will probably be close to the fastest:

1. 搜索@
2. 手动比较 @ 后面的每个字符以确保它们在允许的 ASCII 范围内
3. 跟踪是否在第一个空格或其他有效终止字符之前找到了有效域
4. 再次从 @ 符号向后搜索，比较每个字符以确保它们在本地组件的有效字符范围内

1. Search for @
2. Manually compare each character after the @ to make sure they are within the allowed ASCII ranges
3. Keep track of whether a valid domain was found before the first space or other valid terminating character
4. Search again from the @ symbol backwards, comparing each character to make sure they fall within the valid character ranges for the local component

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