windows客户端开发--获取windows系统中文件的MIME

Posted 2020-06-23 江南-一苇渡江

首先，什么是MIME，是不是文件的后缀名呢？

当然不是。

有时候我们需要获取某个文件的后缀名，这也许对你来说太小case了，你可能不加思考的写了一个函数，更加文件名字符串查找最后一个’.’，然后取最有一个’.’之后的字符串，即为我们要得到的后缀名。

看似非常完美，但确实漏洞百出。

如果我的文件没有后缀名怎么办？
如果我的一张png图片，我强制把后缀名改为jpg怎么办？
这样你根据文件名字方法就不能获得百分百正确的后缀名。

所以，就该MIME出场了！

何为MIME？

MIME (Multipurpose Internet Mail Extensions) 是描述消息内容类型的因特网标准。
MIME 消息能包含文本、图像、音频、视频以及其他应用程序专用的数据。

接下来的工作就是在windows系统上，如何根据一个文件名路径，获取这个文件的mime呢？

起初，我觉得应该找一个第三方库来实现这个小小的功能，比如libmagic。

但是暮然回首，发现windows为我们提供了api。这里要插一句：windows确实是最复杂的操作系统。有时候我们再忽略了太多windows api给我们提供的函数。

FindMimeFromData
作用：
Determines the MIME type from the data provided.
原型：

HRESULT FindMimeFromData(
             LPBC    pBC,
             LPCWSTR pwzUrl,
             LPVOID  pBuffer,
             DWORD   cbSize,
             LPCWSTR pwzMimeProposed,
             DWORD   dwMimeFlags,
             LPWSTR  *ppwzMimeOut,
  _Reserved_ DWORD   dwReserved
);

参数：

pBC
A pointer to the IBindCtx interface. Can be set to NULL.
pwzUrl
A pointer to a string value that contains the URL of the data. Can be set to NULL if pBuffer contains the data to be sniffed.
pBuffer
A pointer to the buffer that contains the data to be sniffed. Can be set to NULL if pwzUrl contains a valid URL.
cbSize
An unsigned long integer value that contains the size of the buffer.
pwzMimeProposed
A pointer to a string value that contains the proposed MIME type. This value is authoritative if type cannot be determined from the data. If the proposed type contains a semi-colon (;) it is removed. This parameter can be set to NULL.

下面看看如何应用，首先是读一个文件，然后调用FindMimeFromData函数即可：

#include <urlmon.h>
#include <stdio.h>
#include <Windows.h>
#include <iostream>
#pragma comment(lib, "Urlmon.lib")

int main(int argc, char* argv[])
{
    char buff[256];
    LPWSTR out;

    FILE *in = fopen("D:\\libsakura.lib", "rb");

    fread(buff, 1, 256, in);

    FindMimeFromData(NULL, NULL, buff, 256, NULL, FMFD_DEFAULT, &out, 0);

    printf("%ls\n", out);

    return 0;
}

下面是文件类型对应的MIME，仅供参考：

application/envoy   evy
application/fractals    fif
application/futuresplash    spl
application/hta hta
application/internet-property-stream    acx
application/mac-binhex40    hqx
application/msword  doc
application/msword  dot
application/octet-stream    *
application/octet-stream    bin
application/octet-stream    class
application/octet-stream    dms
application/octet-stream    exe
application/octet-stream    lha
application/octet-stream    lzh
application/oda oda
application/olescript   axs
application/pdf pdf
application/pics-rules  prf
application/pkcs10  p10
application/pkix-crl    crl
application/postscript  ai
application/postscript  eps
application/postscript  ps
application/rtf rtf
application/set-payment-initiation  setpay
application/set-registration-initiation setreg
application/vnd.ms-excel    xla
application/vnd.ms-excel    xlc
application/vnd.ms-excel    xlm
application/vnd.ms-excel    xls
application/vnd.ms-excel    xlt
application/vnd.ms-excel    xlw
application/vnd.ms-outlook  msg
application/vnd.ms-pkicertstore sst
application/vnd.ms-pkiseccat    cat
application/vnd.ms-pkistl   stl
application/vnd.ms-powerpoint   pot
application/vnd.ms-powerpoint   pps
application/vnd.ms-powerpoint   ppt
application/vnd.ms-project  mpp
application/vnd.ms-works    wcm
application/vnd.ms-works    wdb
application/vnd.ms-works    wks
application/vnd.ms-works    wps
application/winhlp  hlp
application/x-bcpio bcpio
application/x-cdf   cdf
application/x-compress  z
application/x-compressed    tgz
application/x-cpio  cpio
application/x-csh   csh
application/x-director  dcr
application/x-director  dir
application/x-director  dxr
application/x-dvi   dvi
application/x-gtar  gtar
application/x-gzip  gz
application/x-hdf   hdf
application/x-internet-signup   ins
application/x-internet-signup   isp
application/x-iphone    iii
application/x-javascript    js
application/x-latex latex
application/x-msaccess  mdb
application/x-mscardfile    crd
application/x-msclip    clp
application/x-msdownload    dll
application/x-msmediaview   m13
application/x-msmediaview   m14
application/x-msmediaview   mvb
application/x-msmetafile    wmf
application/x-msmoney   mny
application/x-mspublisher   pub
application/x-msschedule    scd
application/x-msterminal    trm
application/x-mswrite   wri
application/x-netcdf    cdf
application/x-netcdf    nc
application/x-perfmon   pma
application/x-perfmon   pmc
application/x-perfmon   pml
application/x-perfmon   pmr
application/x-perfmon   pmw
application/x-pkcs12    p12
application/x-pkcs12    pfx
application/x-pkcs7-certificates    p7b
application/x-pkcs7-certificates    spc
application/x-pkcs7-certreqresp p7r
application/x-pkcs7-mime    p7c
application/x-pkcs7-mime    p7m
application/x-pkcs7-signature   p7s
application/x-sh    sh
application/x-shar  shar
application/x-shockwave-flash   swf
application/x-stuffit   sit
application/x-sv4cpio   sv4cpio
application/x-sv4crc    sv4crc
application/x-tar   tar
application/x-tcl   tcl
application/x-tex   tex
application/x-texinfo   texi
application/x-texinfo   texinfo
application/x-troff roff
application/x-troff t
application/x-troff tr
application/x-troff-man man
application/x-troff-me  me
application/x-troff-ms  ms
application/x-ustar ustar
application/x-wais-source   src
application/x-x509-ca-cert  cer
application/x-x509-ca-cert  crt
application/x-x509-ca-cert  der
application/ynd.ms-pkipko   pko
application/zip zip
audio/basic au
audio/basic snd
audio/mid   mid
audio/mid   rmi
audio/mpeg  mp3
audio/x-aiff    aif
audio/x-aiff    aifc
audio/x-aiff    aiff
audio/x-mpegurl m3u
audio/x-pn-realaudio    ra
audio/x-pn-realaudio    ram
audio/x-wav wav
image/bmp   bmp
image/cis-cod   cod
image/gif   gif
image/ief   ief
image/jpeg  jpe
image/jpeg  jpeg
image/jpeg  jpg
image/pipeg jfif
image/svg+xml   svg
image/tiff  tif
image/tiff  tiff
image/x-cmu-raster  ras
image/x-cmx cmx
image/x-icon    ico
image/x-portable-anymap pnm
image/x-portable-bitmap pbm
image/x-portable-graymap    pgm
image/x-portable-pixmap ppm
image/x-rgb rgb
image/x-xbitmap xbm
image/x-xpixmap xpm
image/x-xwindowdump xwd
message/rfc822  mht
message/rfc822  mhtml
message/rfc822  nws
text/css    css
text/h323   323
text/html   htm
text/html   html
text/html   stm
text/iuls   uls
text/plain  bas
text/plain  c
text/plain  h
text/plain  txt
text/richtext   rtx
text/scriptlet  sct
text/tab-separated-values   tsv
text/webviewhtml    htt
text/x-component    htc
text/x-setext   etx
text/x-vcard    vcf
video/mpeg  mp2
video/mpeg  mpa
video/mpeg  mpe
video/mpeg  mpeg
video/mpeg  mpg
video/mpeg  mpv2
video/quicktime mov
video/quicktime qt
video/x-la-asf  lsf
video/x-la-asf  lsx
video/x-ms-asf  asf
video/x-ms-asf  asr
video/x-ms-asf  asx
video/x-msvideo avi
video/x-sgi-movie   movie
x-world/x-vrml  flr
x-world/x-vrml  vrml
x-world/x-vrml  wrl
x-world/x-vrml  wrz
x-world/x-vrml  xaf
x-world/x-vrml  xof