经典ASP解决方案

大多数现代浏览器现在都支持将文件名作为UTF-8传递，但我使用的文件上传解决方案是基于FreeASPUpload的。Net(站点已经不存在了，链接指向archive.org)，它不会工作，因为二进制解析依赖于读取单字节ASCII编码的字符串，当您传递UTF-8编码的数据时，它工作得很好，直到您得到ASCII不支持的字符。

然而，我能够找到一个解决方案，使代码读取和解析二进制为UTF-8。

Public Function BytesToString(bytes)    'UTF-8..
  Dim bslen
  Dim i, k , N 
  Dim b , count 
  Dim str

  bslen = LenB(bytes)
  str=""

  i = 0
  Do While i < bslen
    b = AscB(MidB(bytes,i+1,1))

    If (b And &HFC) = &HFC Then
      count = 6
      N = b And &H1
    ElseIf (b And &HF8) = &HF8 Then
      count = 5
      N = b And &H3
    ElseIf (b And &HF0) = &HF0 Then
      count = 4
      N = b And &H7
    ElseIf (b And &HE0) = &HE0 Then
      count = 3
      N = b And &HF
    ElseIf (b And &HC0) = &HC0 Then
      count = 2
      N = b And &H1F
    Else
      count = 1
      str = str & Chr(b)
    End If

    If i + count - 1 > bslen Then
      str = str&"?"
      Exit Do
    End If

    If count>1 then
      For k = 1 To count - 1
        b = AscB(MidB(bytes,i+k+1,1))
        N = N * &H40 + (b And &H3F)
      Next
      str = str & ChrW(N)
    End If
    i = i + count
  Loop

  BytesToString = str
End Function

通过在我自己的代码中实现include_aspuploader.asp中的by睾string()函数，我能够获得UTF-8文件名。

有用的链接

一个ASP经典应用程序中的Multipart/form-data和UTF-8 Unicode, UTF, ASCII, ANSI格式的差异

我最终在“download.php”脚本中编写了以下代码(基于这篇博文和这些测试用例)。

$il1_filename = utf8_decode($filename);
$to_underscore = "\"\\#*;:|<>/?";
$safe_filename = strtr($il1_filename, $to_underscore, str_repeat("_", strlen($to_underscore)));

header("Content-Disposition: attachment; filename=\"$safe_filename\""
.( $safe_filename === $filename ? "" : "; filename*=UTF-8''".rawurlencode($filename) ));

只要只使用iso-latin1和“safe”字符，就使用标准的filename="…";如果不是，它会添加文件名*=UTF-8 " url编码的方式。根据这个具体的测试用例，它应该从MSIE9起，并在最近的FF, Chrome, Safari;在较低的MSIE版本中，它应该提供包含ISO8859-1版本的文件名，在非此编码的字符上使用下划线。

最后注意:最大值。在apache上，每个报头字段的大小为8190字节。UTF-8每个字符最多可以有四个字节;在rawurlencode之后，每个字符是x3 = 12字节。非常低效，但理论上仍然可以在文件名中有超过600个“smiles”%F0%9F%98%81。

我通常对文件名进行url编码(使用%xx)，它似乎在所有浏览器中都可以工作。你还是得做些检查。

在。net 4.5(和Core 1.0)中，你可以使用ContentDispositionHeaderValue来为你格式化。

var fileName = "Naïve file.txt";
var h = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
h.FileNameStar = fileName;
h.FileName = "fallback-ascii-name.txt";

Response.Headers.Add("Content-Disposition", h.ToString());

h.ToString()将导致:

attachment; filename*=utf-8''Na%C3%AFve%20file.txt; filename=fallback-ascii-name.txt

只是一个更新，因为我今天为了回应一个客户的问题而尝试了所有这些东西

With the exception of Safari configured for Japanese, all browsers our customer tested worked best with filename=text.pdf - where text is a customer value serialized by ASP.Net/IIS in utf-8 without url encoding. For some reason, Safari configured for English would accept and properly save a file with utf-8 Japanese name but that same browser configured for Japanese would save the file with the utf-8 chars uninterpreted. All other browsers tested seemed to work best/fine (regardless of language configuration) with the filename utf-8 encoded without url encoding. I could not find a single browser implementing Rfc5987/8187 at all. I tested with the latest Chrome, Firefox builds plus IE 11 and Edge. I tried setting the header with just filename*=utf-8''texturlencoded.pdf, setting it with both filename=text.pdf; filename*=utf-8''texturlencoded.pdf. Not one feature of Rfc5987/8187 appeared to be getting processed correctly in any of the above.

对于那些需要JavaScript方式编码头的人，我发现这个函数工作得很好:

function createContentDispositionHeader(filename:string) {
    const encoded = encodeURIComponent(filename);
    return `attachment; filename*=UTF-8''${encoded}; filename="${encoded}"`;
}

这是基于Nextcloud在下载文件时的操作。文件名首先以UTF-8编码的形式出现，并且可能为了与某些浏览器兼容，文件名也不带UTF-8前缀。