c# - 从 C# 访问 COM vtable

Question

在 C# 中有没有什么方法可以访问 COM 对象的虚方法表以获得函数的地址？

Answer 1

经过大量搜索和拼凑不同的部分解决方案后，我想出了如何去做。

首先您需要为您尝试访问的对象定义 COM 组件类:

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

接下来您需要实例化 COM 对象。有几种方法可以做到这一点。因为我对 DirectSound 感兴趣，所以我使用了:

[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);

既然我现在有了我的 COM 对象，我就可以使用 Hans 关于 Marshal.GetComInterfaceForObject() 的建议:

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

作为额外的好处，您可以像这样遍历 vtable 函数:

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/引用资料:

• http://msdn.microsoft.com/en-us/library/aa645736(VS.71).aspx [关于 COM 组件类声明的信息]
• http://www.codeproject.com/KB/COM/com_in_c1.aspx [关于 VTable 和 COM 的一般信息]
• http://naudio.codeplex.com/ [特定于 DirectSound COM 接口(interface)的信息]