函数指针-DInput8.dll挂钩代码的参数用途

我一直试图弄清楚DirectInput8挂钩项目中一个参数的用途。我正在生产 opensource 这里的代码。为了简洁起见,我只发布了几个函数。

ULONG oldCreateDevice;
HRESULT WINAPI xCreateDevice(DWORD d1, DWORD d2, DWORD d3, DWORD d4)
{
    HRESULT hr = ((HRESULT(WINAPI*)(DWORD,DWORD,DWORD,DWORD))oldCreateDevice)(d1,d2,d3,d4);

    // hook only if keyboard requested
    if(*(DWORD*)d2 != GUID_SysKeyboard)
        return hr;

    DWORD dwKeybTable = *(DWORD*)(*(DWORD*)d3);

    DWORD oldprot;
    VirtualProtect((LPVOID)dwKeybTable, 0x2C, PAGE_EXECUTE_READWRITE, &oldprot);

    // already hooked?
    if((DWORD)xGetDeviceState == *((DWORD*)(dwKeybTable+0x24))) goto ex1;
    // hook it!
    oldGetDeviceState = *((DWORD*)(dwKeybTable+0x24));
    *((DWORD*)(dwKeybTable+0x24)) = (DWORD)xGetDeviceState;

ex1:
    // already hooked?
    if((DWORD)xGetDeviceData == *((DWORD*)(dwKeybTable+0x28))) goto ex2;
    // hook it!
    oldGetDeviceData = *((DWORD*)(dwKeybTable+0x28));
    *((DWORD*)(dwKeybTable+0x28)) = (DWORD)xGetDeviceData;

ex2:

    return hr;

}


ULONG oldDirectInput8Create;
HRESULT WINAPI xDirectInput8Create(HINSTANCE hinst, DWORD dwVersion, REFIID riidltf, VOID **ppvOut, LPUNKNOWN punkOuter)
{
    HRESULT ret = ((HRESULT(WINAPI*)(HINSTANCE,DWORD,REFIID,VOID**,LPUNKNOWN))oldDirectInput8Create)(hinst,dwVersion,riidltf,ppvOut,punkOuter);

    DWORD dwFuncTable = (DWORD)*((DWORD*)*ppvOut);

    DWORD oldprot;
    VirtualProtect((LPVOID)dwFuncTable, 0x10, PAGE_EXECUTE_READWRITE, &oldprot);

    //already hooked?
    if((DWORD)xCreateDevice == *((DWORD*)(dwFuncTable + 0x0C))) goto ex;
    //hook it
    oldCreateDevice = *((DWORD*)(dwFuncTable + 0x0C));
    *((DWORD*)(dwFuncTable + 0x0C)) = (DWORD)xCreateDevice;

ex:
    return ret;
}


DWORD WINAPI RemoteMain(LPVOID lpParam)
{

    LoadLibrary("user32.dll");
    LoadLibrary("advapi32.dll");

    Splice_Init();

    Splice((ULONG)GetProcAddress(LoadLibrary("dinput8.dll"),"DirectInput8Create"), xDirectInput8Create, &oldDirectInput8Create);

    ThreadControl(FALSE); // resume all
    return 0;
}

正如您可能注意到的那样,代码正在用重定向(挂钩)函数替换函数。我的问题是xCreateDevice函数中的第一个参数 对于DirectInput8,CreateDevice函数根据我所理解的文档使用3个参数。但我不确定为什么这里使用4个参数。它是否指向原始的“oldCreateDevice”?还是其他原因?

我希望有人能指导我。谢谢