如何使HTML5电子邮件验证正则表达式在C ++中工作？ [英] How to make HTML5 email validation regex work in C++?

问题描述

我正在尝试在客户端和服务器端都验证电子邮件。客户端是JavaScript（Web前端）。服务器端是用C ++ 11编写的。

I am trying to validate email both on the client-side and on the server-side. The client-side is JavaScript(web front-end). The server-side is written in C++11.

我用来验证电子邮件的正则表达式由HTML标准提供（此处）[ https://html.spec.whatwg.org/ multipage / input.html＃e-mail-state-（type = email）] 。我在这里复制它以供快速参考：

The regex I am using to validate email is provided by the HTML standard (here)[https://html.spec.whatwg.org/multipage/input.html#e-mail-state-(type=email)]. I am reproducing it here for quick reference:

/^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/

验证在客户端使用JavaScript。但是使用 std :: regex_match 的服务器端验证失败。

The validation works on the client-side using JavaScript. But the server-side validation using std::regex_match fails.

以下是用于检查有效电子邮件的C ++代码：

Following is the C++ code to check valid email:

bool is_valid_email(std::string email)
{
    // Regex from HTML5 spec.
    static std::regex const email_regex {R"(/^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/)"};

    return std::regex_match(email, email_regex);
}

我在做什么错了？

推荐答案

JavaScript regex文字两端的 / 是 regex分隔符字符，它们不是正则表达式模式的一部分。

The / at both ends of the JavaScript regex literal are regex delimiter characters, they are not part of a regular expression pattern.

在C ++中，您使用正则或原始字符串文字设置了正则表达式，

In C++, you set the regex using either regular or raw string literals, do you do not need to include regex delimiters into the pattern.

因此，如果您有 const regex = / abc / JavaScript，您可以使用

So, if you have const regex = /abc/ in JavaScript, you may use

std::regex const regex {R"(abc)"};

在您的情况下，您甚至不需要 ^ 在模式的开头， $ 在模式的结尾，因为 regex_match 需要完整的字符串匹配：

In your case, you do not even need the ^ at the start and $ at the end of the pattern since regex_match requires a full string match:

bool is_valid_email(std::string email)
{
    // Regex from HTML5 spec.
    static std::regex const email_regex {R"([a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*)"};
    return std::regex_match(email, email_regex);
}

此外， / 不是一个特殊的正则表达式元字符，您不需要对其进行转义。

Also, / is not a special regex metacharacter, you do not need to escape it.

注意由于最新的JavaScript ECMAScript实现支持更多正则表达式功能，就像无限宽的后向命名捕捉组一样，将JavaScript regex模式转换为C ++兼容的regex模式并不总是那么简单。

NOTE Since the latest JavaScript ECMAScript implementations support many more regex feature, like infinite-width lookbehind, named capturing groups, it is not always so straight-forward to convert a JavaScript regex pattern to a C++ compatible regex pattern.

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