在 C# 中调用 UnmanagedFunctionPointer 以实现自定义调用约定

发布于 2024-12-06 09:27:30 字数 1117 浏览 1 评论 0原文

我在 DLL 中有一个函数：

char __usercall MyUserCallFunction<al>(int arg1<esi>)

因为我讨厌自己，所以我想使用 P/Invoke 从 C# 中调用它。

通常，这可以通过获取函数委托来完成，例如：

    [UnmanagedFunctionPointer(CallingConvention.ThisCall, CharSet = CharSet.Auto, SetLastError = true)]
    public delegate char DMyUserCallFunction(IntPtr a1);

然后通过执行以下操作来调用它：

var MyFunctionPointer = (DMyUserCallFunction)Marshal.GetDelegateForFunctionPointer(AddressOfFunction, typeof(DMyUserCallFunction));

MyFunctionPointer(IntPtr.Zero);

但是，对于自定义用户调用约定，这将导致程序崩溃。是否有某种方法可以使用不安全代码或某种包装函数来完成此操作，将委托放置到位，但不会强迫我编写 C++ DLL？

谢谢！

编辑：

按照 dtb 的建议，我创建了一个非常小的 C++ DLL，通过 P/Invoke 使用它来调用该函数。对于任何好奇的人来说，C++ 中的函数最终看起来像这样：

extern "C" __declspec(dllexport) int __stdcall callUsercallFunction(int functionPointer, int arg1 )
{
    int retVal;

    _asm 
    {
        mov esi, arg1
        call functionPointer
        mov retVal, eax
    }

    //Fake returning al, the lower byte of eax
    return retVal & 0x000000FF;
}

原文

I have a function in a DLL:

char __usercall MyUserCallFunction<al>(int arg1<esi>)

Because I hate myself I'd like to call this from within C# using P/Invoke.

Normally this can be done by getting a function delegate, a la:

    [UnmanagedFunctionPointer(CallingConvention.ThisCall, CharSet = CharSet.Auto, SetLastError = true)]
    public delegate char DMyUserCallFunction(IntPtr a1);

And then invoking it by doing:

var MyFunctionPointer = (DMyUserCallFunction)Marshal.GetDelegateForFunctionPointer(AddressOfFunction, typeof(DMyUserCallFunction));

MyFunctionPointer(IntPtr.Zero);

For custom user calling conventions, however, this will cause the program to crash. Is there some sort of way I can do this using unsafe code or some sort of wrapper function that puts the delegates in place, but doesn't force me to write a C++ DLL?

Thanks!

Edit:

As suggested by dtb, I created a very small C++ DLL which I use via P/Invoke to call the function. For anyone curious the function in C++ ends up looking like:

extern "C" __declspec(dllexport) int __stdcall callUsercallFunction(int functionPointer, int arg1 )
{
    int retVal;

    _asm 
    {
        mov esi, arg1
        call functionPointer
        mov retVal, eax
    }

    //Fake returning al, the lower byte of eax
    return retVal & 0x000000FF;
}

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