访问COM vtable从C＃ | vtable从C＃

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问题描述

C＃中是否有任何方法访问COM对象的虚方法表以获取函数的地址？

Is there any way in C# to access a COM object's virtual method table in order to get a function's address?

推荐答案

经过大量的搜索和拼凑不同的部分解决方案，我想出了如何做。

After a lot of searching and piecing together different partial solutions, I figured out how to do it.

首先，您需要为要尝试访问的对象定义COM coclass：

First you need to define the COM coclass for the object you're trying to access:

[ComImport, Guid("..."), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface ISomeCOMInterface
{
   // Define interface methods here, using PInvoke conversion between types
}

接下来需要实例化COM对象。有几种方法可以做到这一点。由于我对DirectSound感兴趣，我使用了：

Next you need to instantiate the COM object. There are a couple of ways to do that. Since I was interested in DirectSound, I used:

[DllImport("dsound.dll", EntryPoint = "DirectSoundCreate", ...]
static extern void DirectSoundCreate(IntPtr GUID, [Out, MarshalAs(UnmanagedType.Interface)] out IDirectSound directSound, IntPtr pUnkOuter);

IDirectSound directSound;
DirectSoundCreate(IntPtr.Zero, out directSound, IntPtr.Zero);

由于我现在有我的COM对象可以使用Hans的建议 Marshal.GetComInterfaceForObject（）：

Since I now had my COM object, I could then use Hans' suggestion of Marshal.GetComInterfaceForObject():

IntPtr comPtr = Marshal.GetComInterfaceForObject(directSound, typeof(IDirectSound));
IntPtr vTable = Marshal.ReadIntPtr(comPtr);

作为一个额外的好处，你可以这样遍历vtable函数：

As an added bonus, you can then iterate through the vtable functions like this:

int start = Marshal.GetStartComSlot(typeof(IDirectSound));
int end = Marshal.GetEndComSlot(typeof(IDirectSound));

ComMemberType mType = 0;
for (int i = start; i < end; i++)
{
    System.Reflection.MemberInfo mi = Marshal.GetMethodInfoForComSlot(typeof(IDirectSound), i, ref mType);
    Console.WriteLine("Method {0} at address 0x{1:X}", mi.Name, Marshal.ReadIntPtr(vTable, i * Marshal.SizeOf(typeof(IntPtr))).ToInt64());
}

额外阅读/参考：

[关于COM coclass声明的信息]

[有关VTables和COM in general]

[特定于DirectSound COM接口的信息]

http://msdn.microsoft.com/en-us/library/aa645736(VS.71).aspx [Info on COM coclass declarations]
http://www.codeproject.com/KB/COM/com_in_c1.aspx [Info on VTables and COM in general]
http://naudio.codeplex.com/ [Info specific to the DirectSound COM Interfaces]

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