英文:
Regex to Glob and vice-versa conversion
问题
我们有一个需求，我们想将正则表达式转换为支持CloudFront的Glob格式，反之亦然。有什么建议可以实现这个需求吗？首先，是否可能实现这个需求？特别是从正则表达式到Glob的转换，因为我了解正则表达式是一种超集，所以可能无法将所有的正则表达式转换为相应的Glob格式。
英文:
We have a requirement where we want to convert Regex to cloudfront supported Glob and vice-versa. Any suggestion how can we achieve that and first of all whether it's possible?especially from Regex to Glob, as I understand regex is kind of superset so it might not be possible to convert all the Regex to corresponding Glob?
答案1
得分: 2
要从通配符转换为glob，您需要编写一个解析器，将模式拆分为抽象语法树。例如，通配符*-{[0-9],draft}.docx可能解析为[Anything(), "-", OneOf([Range("0", "9"), "draft"]), ".docx"]。
然后，您需要遍历AST并为每个节点输出等效的正则表达式。例如，您可能会使用以下规则：
Anything() -> .*
Range(x, y) -> [x-y]
OneOf(x, y) -> (x|y)
生成的正则表达式为.*-([0-9]|draft).docx。
这还不完美，因为您还必须记住转义任何特殊字符；.是正则表达式中的特殊字符，因此您应该转义它，最终得到.*-([0-9]|draft)\.docx。
严格来说，不是所有的正则表达式都可以转换为glob模式。通配符中不存在Kleene星号操作；简单的正则表达式a*（即任意数量的a字符）无法转换为glob模式。
我不确定CloudFront支持哪些类型的glob（文档中没有找到“glob”一词），但是这里有一些关于常见的shell glob模式通配符的文档。
以下是一些等效序列的总结：
| Glob通配符 | 正则表达式 | 含义 |
|---|---|---|
? |
. |
任意单个字符 |
* |
.* |
零个或多个字符 |
[a-z] |
[a-z] |
范围内的任意字符 |
[!a-m] |
[^a-m] |
不在范围内的字符 |
[a,b,c] |
[abc] |
给定字符中的任意一个 |
{cat,dog,bat} |
`(cat | dog |
{*.tar,*.gz} |
`(.*.tar | .*.gz)` |
英文:
To convert from a glob you would need to write a parser that split the pattern into an abstract syntax tree. For example, the glob *-{[0-9],draft}.docx might parse to [Anything(), "-", OneOf([Range("0", "9"), "draft"]), ".docx"].
Then you would walk the AST and output the equivalent regular expression for each node. For example, the rules you might use for this could be:
Anything() -> .*
Range(x, y) -> [x-y]
OneOf(x, y) -> (x|y)
resulting in the regular expression .*-([0-9]|draft).docx.
That's not perfect, because you also have to remember to escape any special characters; . is a special character in regular expressions, so you should escape it, yielding finally .*-([0-9]|draft)\.docx.
Strictly speaking regular expression cannot all be translated to glob patterns. The Kleene star operation does not exist in globbing; the simple regular expression a* (i.e., any number of a characters) cannot be translated to a glob pattern.
I'm not sure what types of globs CloudFront supports (the documentation returned no hits for the term "glob"), but here is some documentation on commonly-supported shell glob pattern wildcards.
Here is a summarization of the some equivalent sequences:
| Glob Wildcard | Regular Expression | Meaning |
|---|---|---|
? |
. |
Any single character |
* |
.* |
Zero or more characters |
[a-z] |
[a-z] |
Any character from the range |
[!a-m] |
[^a-m] |
A character not in the range |
[a,b,c] |
[abc] |
One of the given characters |
{cat,dog,bat} |
`(cat | dog |
{*.tar,*.gz} |
`(.*.tar | .*.gz)` |
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