正则表达式超时

Question

我正在尝试匹配类似的东西

foo: anything after the colon can be matched with (.*)+
foo.bar1.BAZ: balh5317{}({}(

这是我正在使用的正则表达式:

/^((?:(?:(?:[A-Za-z_]+)(?:[0-9]+)?)+[\.]?)+)(?:\s)?(?:\:)(?:\s)?((?:.*)+)$/

请原谅不匹配的组和额外的括号，这是从构建器类编译的

这适用于示例。当我尝试放入这样的字符串时出现问题:

foo.bar.baz.beef.stew.ect.and.forward

我需要能够像这样检查字符串，但正则表达式引擎在一定数量的 foo. 后超时或运行无穷大(据我所知)。 s 每次。

我确信这是一个我可以解决的逻辑问题，但不幸的是我还远未掌握正则表达式，我希望更有经验的用户可以对我如何提高效率有所了解。

此外，这里是我需要匹配的更详细的描述:

Property Name: can contain A-z, numbers, and underscores but can't start with a number

<Property Name>.<Property Name>.<Prop...:<Anything after the colon>

谢谢你的时间!

Answer 1

从您的正则表达式开始:

^((?:(?:(?:[A-Za-z_]+)(?:[0-9]+)?)+[\.]?)+)(?:\s)?(?:\:)(?:\s)?((?:.*)+)$


 ^                                  # Anchors to the beginning to the string.
 (                                  # Opens CG1
     (?:                            # Opens NCG
         (?:                        # Opens NCG
             (?:                    # Opens NCG
                 [A-Za-z_]+         # Character class (any of the characters within)
             )                      # Closes NCG
             (?:                    # Opens NCG
                 [0-9]+             # Character class (any of the characters within)
             )?                     # Closes NCG
         )+                         # Closes NCG
         [\.]?                      # Character class (any of the characters within)
     )+                             # Closes NCG
 )                                  # Closes CG1
 (?:                                # Opens NCG
     \s                             # Token: \s (white space)
 )?                                 # Closes NCG
 (?:                                # Opens NCG
     \:                             # Literal :
 )                                  # Closes NCG
 (?:                                # Opens NCG
     \s                             # Token: \s (white space)
 )?                                 # Closes NCG
 (                                  # Opens CG2
     (?:                            # Opens NCG
         .*                         # . denotes any single character, except for newline
     )+                             # Closes NCG
 )                                  # Closes CG2
 $                                  # Anchors to the end to the string.

我转换了 [0-9]至 \d ，只是为了更容易阅读(两者都匹配相同的东西)。我还删除了许多非捕获组，因为它们并没有真正被使用。

^((?:(?:[A-Za-z_]+\d*)+\.?)+)\s?\:\s?((?:.*)+)$

我也合并了 \s和 .* 到 [\s\S]* ，但看到后面跟着一个 +签名，我删除了该组并刚刚创建了 [\s\S] .

^((?:(?:[A-Za-z_]+\d*)+\.?)+)\s?\:([\s\S]+)$
                      ^

现在我不确定是什么 +以上克拉是应该做的。我们可以移除它，从而移除它周围的非捕获组。

^((?:[A-Za-z_]+\d*\.?)+)\s?\:([\s\S]+)$

解释:

 ^                          # Anchors to the beginning to the string.
 (                          # Opens CG1
     (?:                    # Opens NCG
         [A-Za-z_]+         # Character class (any of the characters within)
         \d*                # Token: \d (digit)
         \.?                # Literal .
     )+                     # Closes NCG
 )                          # Closes CG1
 \s?                        # Token: \s (white space)
 \:                         # Literal :
 (                          # Opens CG2
     [\s\S]+                # Character class (any of the characters within)
 )                          # Closes CG2
 $                          # Anchors to the end to the string.

现在，您可能想要更改 [\s\S]+返回 .*如果您正在处理多行。对此有几种不同的选择，但您使用的语言很重要。

老实说，我是分步完成的，但最大的问题是 (?:.*)+这告诉引擎 match 0 or more characters 1 or more times catastrophic backtracking (as xufox linked to in comments) .

生成的正则表达式以及您的原始正则表达式允许以 . 结尾的变量我会使用更像这样的东西，你的正则表达式真的离它不远。

这将匹配 foo.ba5r 之类的名称，如果可以接受，则您之前的正则表达式不会。

^([A-Za-z_]\w*(?:\.[A-Za-z_]+\w*)*)\s?\:([\s\S]+)$

解释:

 ^                          # Anchors to the beginning to the string.
 (                          # Opens CG1
     [A-Za-z_]              # Character class (any of the characters within)
     \w*                    # Token: \w (a-z, A-Z, 0-9, _)
     (?:                    # Opens NCG
         \.                 # Literal .
         [A-Za-z_]          # Character class (any of the characters within)
         \w*                # Token: \w (a-z, A-Z, 0-9, _)
     )*                     # Closes NCG
 )                          # Closes CG1
 \s?                        # Token: \s (white space)
 \:                         # Literal :
 (                          # Opens CG2
     [\s\S]+                # Character class (any of the characters within)
 )                          # Closes CG2
 $                          # Anchors to the end to the string.