利用Win32API 读取文件头获取Mime-Type

最新推荐文章于 2024-09-17 16:50:18 发布

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最新推荐文章于 2024-09-17 16:50:18 发布

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本文介绍了两种方法来获取文件的Mime-Type：第一种方法通过调用Win32API的FindMimeFromData函数从文件头中解析；第二种方法则利用Windows系统的注册表查找已定义的Mime-Type。

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第一个种方式利用Win32API 读取文件头获取Mime-Type

[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private extern static System.UInt32 FindMimeFromData(
System.UInt32 pBC,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
[MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
System.UInt32 cbSize,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
System.UInt32 dwMimeFlags,
out System.UInt32 ppwzMimeOut,
System.UInt32 dwReserverd
);

public string getMimeFromFile(string filename)
{
if (!File.Exists(filename))
throw new FileNotFoundException(filename + " not found");

byte[] buffer = new byte[256];
using (FileStream fs = new FileStream(filename, FileMode.Open))
{
if (fs.Length >= 256)
fs.Read(buffer, 0, 256);
else
fs.Read(buffer, 0, (int)fs.Length);
}
try
{
System.UInt32 mimetype;
FindMimeFromData(0, null, buffer, 256, null, 0, out mimetype, 0);
System.IntPtr mimeTypePtr = new IntPtr(mimetype);
string mime = Marshal.PtrToStringUni(mimeTypePtr);
Marshal.FreeCoTaskMem(mimeTypePtr);
return mime;
}
catch (Exception e)
{
return "unknown/unknown";
}
}

第二种方式利用系统注册表查找Mime-Type

using System.IO;
using Microsoft.Win32;

string GetMimeType(FileInfo fileInfo)
{
string mimeType = "application/unknown";

RegistryKey regKey = Registry.ClassesRoot.OpenSubKey(
fileInfo.Extension.ToLower()
);

if(regKey != null)
{
object contentType = regKey.GetValue("Content Type");

if(contentType != null)
mimeType = contentType.ToString();
}

return mimeType;
}