正则表达式，用于检测的base64 EN codeD字符串 [英] RegEx for detecting base64 encoded strings

问题描述

我需要检测与形式的 @的base64 （例如 @ VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw == ）在我的应用程序。

I need to detect strings with the form @base64 (e.g. @VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw==) in my application.

该@必须在开始和进行的base64 EN codeD字符串的字符集是 AZ ， AZ ， 0-9 ， + ， / 和 = 。将此时，相应的普通前presion公司检测到它们？

The @ has to be at the beginning and the charset for base64 encoded strings is a-z, A-Z, 0-9, +, / and =. Would be the appropiate regular expresion to detect them?

感谢

推荐答案

像这样的东西应该做的（不进行适当的长度检查！）

Something like this should do (does not check for proper length!):

^@[a-zA-Z0-9+/]+={0,2}$

---

任何的base64 EN codeD字符串的长度必须是4的倍数，因此额外的。

---

The length of any base64 encoded string must be a multiple of 4, hence the additional.

在这里看到，检查对适当长度的解决方案：<一href=\"http://stackoverflow.com/questions/475074/regex-to-parse-or-validate-base64-data/475217#475217\">RegEx解析或验证Base64编码数据

See here for a solution that checks against proper length: RegEx to parse or validate Base64 data

从链接的答案正则表达式的快速解释：

A quick explanation of the regex from the linked answer:

^@ #match "@" at beginning of string
(?:[A-Za-z0-9+/]{4})* #match any number of 4-letter blocks of the base64 char set
(?:
    [A-Za-z0-9+/]{2}== #match 2-letter block of the base64 char set followed by "==", together forming a 4-letter block
| # or
    [A-Za-z0-9+/]{3}= #match 3-letter block of the base64 char set followed by "=", together forming a 4-letter block
)?
$ #match end of string

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