什么是最好的候选填充字符的url安全和文件名安全base64？ [英] What's the best candidate padding char for url-safe and filename-safe base64?

问题描述

官方base64的padding char为'='，在URL中使用时可能需要进行百分比编码。我试图找到最好的填充字符，所以我的编码字符串可以是url的安全（我将使用编码的字符串作为参数值，如id = encodedString）和文件名安全（我将使用编码字符串直接作为文件名）。

The padding char for the official base64 is '=', which might need to be percent-encoded when used in a URL. I'm trying to find the best padding char so that my encoded string can be both url safe (I'll be using the encoded string as parameter value, such as id=encodedString) AND filename safe (I'll be using the encoded string directly as filename).

Dot（'。'）是一个受欢迎的候选人，它的网址安全，但并不完全是文件名安全： Windows不会允许以尾随点结尾的文件名。

Dot ('.') is a popular candidate, it's url safe but it's not exactly filename safe: Windows won't allow a file name which ends with a trailing dot.

'！'似乎是一个可行的选择，虽然我googled，我从来没有看到任何人使用它作为填充字符。有任何想法吗？谢谢！

'!' seems to be a viable choice, although I googled and I've never seen anybody using it as the padding char. Any ideas? Thanks!

更新：我用 - （减号）替换+，将/替换为_（下划线）在我自定义的base64编码中，所以' - '或'_'不再适用于填充字符。

Update: I replaced "+" with "-" (minus) and replaced "/" with "_" (underscore) in my customized base64 encoding already, so '-' or '_' is not available for the padding char any more.

推荐答案

最好的解决方案（我上个月在电子邮件发送网站上处理这个问题）是不要使用填充字符（=）在所有

The best solution (I've spent last month working on this problem with an email sending website) is to not use padding character (=) at all

唯一的原因是因为懒的解码器是填补字符。你可以非常容易地添加缺少= - >只是在文本上做％4，并减去你从4获得的数字，这是多少=你需要添加到字符串结尾。这是C＃代码：

The only reason why padding character is there is because of "lazy" decoders. You can extremely easy add missing = -> just do %4 on text and subtract the number you get from 4 and that is how many = you need to add in string end. Here is C# code:

    var pad = 4 - (text.Length % 4);
    if (pad < 4)
        text = text.PadRight(text.Length + pad, '=');

此外，大多数人都有兴趣用其他URL安全字符替换+和/我建议：

Also, most people who do this are interested in replacing + and / with other URL safe character... I propose:

• 替换为 -
  /替换为_

不要使用。因为它可以在不同的系统/ Web服务器上产生疯狂的结果（例如在IIS Base64编码的字符串不能结束，或IIS将搜索文件）

DO NOT USE . as it can produce crazy results on different systems / web servers (for example on IIS Base64 encoded string can't end with . or IIS will search for the file)

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