directinput缓冲模式的疑问，我写的这个代码为什么没有反应呢？

#include <windows.h>
#include <dinput.h>
#include <string.h>
#include <stdio.h>
using namespace std;

#define DINPUT_BUFFERSIZE 4

HWND hwnd;

LPDIRECTINPUT           lpDirectInput;  // DirectInput object
LPDIRECTINPUTDEVICE     lpKeyboard;     // DirectInput device

LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);

void ReleaseDInput()
{
    if (lpKeyboard!=NULL)
    {
        lpKeyboard->Unacquire();
        lpKeyboard->Release();
        lpKeyboard = NULL;
    }
    if (lpDirectInput!=NULL)
    {
        lpDirectInput->Release();
        lpDirectInput = NULL;
    }
}

BOOL InitDInput(HWND hWnd,HINSTANCE hInstance)
{
    HRESULT hr;

    // 创建一个 DIRECTINPUT 对象
    hr = DirectInput8Create(hInstance, DIRECTINPUT_VERSION, IID_IDirectInput8, (void**)&lpDirectInput, NULL);

    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }

    // 创建一个 DIRECTINPUTDEVICE 界面
    hr = lpDirectInput->CreateDevice(GUID_SysKeyboard, &lpKeyboard, NULL);
    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }

    // 设定为通过一个 256 字节的数组返回查询状态值
    hr = lpKeyboard->SetDataFormat(&c_dfDIKeyboard);
    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }

    // 设定协作模式
    hr = lpKeyboard->SetCooperativeLevel(hWnd, DISCL_EXCLUSIVE | DISCL_FOREGROUND);
    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }

    // 设定缓冲区大小
    // 如果不设定，缓冲区大小默认值为 0，程序就只能按立即模式工作
    // 如果要用缓冲模式工作，必须使缓冲区大小超过 0
    DIPROPDWORD     prop;

    prop.diph.dwSize = sizeof(DIPROPDWORD);
    prop.diph.dwHeaderSize = sizeof(DIPROPHEADER);
    prop.diph.dwObj = 0;
    prop.diph.dwHow = DIPH_DEVICE;
    prop.dwData = DINPUT_BUFFERSIZE;

    hr = lpKeyboard->SetProperty(DIPROP_BUFFERSIZE, &prop.diph);

    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }


    hr = lpKeyboard->Acquire();
    if FAILED(hr)
    {
        // 失败
        return FALSE;
    }

    return TRUE;
}

HRESULT UpdateInputState(void)
{
    if(lpKeyboard != NULL)
    {
        DIDEVICEOBJECTDATA  didod[DINPUT_BUFFERSIZE];  // Receives buffered data
        DWORD               dwElements;
        HRESULT             hr;
        ZeroMemory(didod, sizeof(DIDEVICEOBJECTDATA)*DINPUT_BUFFERSIZE);

        hr = DIERR_INPUTLOST;

        while(hr != DI_OK)
        {
            dwElements = DINPUT_BUFFERSIZE;
            hr = lpKeyboard->GetDeviceData(sizeof(DIDEVICEOBJECTDATA), didod, &dwElements, 0);
            if (hr != DI_OK)
            {
                hr = lpKeyboard->Acquire();
                if(FAILED(hr))
                return hr;
            }
        }

        if(FAILED(hr))
            return hr;
        for(int i=0; i<DINPUT_BUFFERSIZE; i++)
        {
            if (didod[i].dwOfs == 0)
                return S_OK;
            // 此处放入处理代码
            // didod[i].dwOfs 表示那个键被按下或松开
            // didod[i].dwData 记录此键的状态，低字节最高位是 1 表示按下，0 表示松开
            // 一般用 didod[i].dwData&0x80 来测试}
        }
        DWORD tmp[20];
        VOID* pDest,*pSrc;
        pDest = &tmp;
        pSrc = &didod;
        memcpy( pDest, pSrc, 80 );
      
        string strResult("test:\n");
        for (int i=0;i<20;i++)
        {
            strResult+=tmp[i];
            strResult+="\n";
        }
        MessageBox( NULL, strResult.c_str(),"提示!", MB_OK) ;
    }
    return S_OK;
}

int _stdcall WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
    HWND hwnd;
    MSG  msg;
    WNDCLASS WindowClass;
    if(!hPrevInstance){
        //not first run, to set the windows class
        WindowClass.style=NULL;
        WindowClass.cbClsExtra=0;
        WindowClass.cbWndExtra=0;
        WindowClass.hbrBackground = HBRUSH(GetStockObject(BLACK_BRUSH));
        WindowClass.hCursor=LoadCursor(hInstance,IDC_ARROW);
        WindowClass.hIcon=LoadIcon(hInstance,IDI_APPLICATION);
        WindowClass.hInstance=hInstance;
        WindowClass.lpfnWndProc=WndProc;
        WindowClass.lpszClassName="DInput_Test";
        WindowClass.lpszMenuName=NULL;
        RegisterClass(&WindowClass);
    }
    // start to create the window when registed the window class
    hwnd=CreateWindow("DInput_Test","DirectInput_Test",WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,NULL,NULL,hInstance,NULL);
    ShowWindow(hwnd,nShowCmd);
    UpdateWindow(hwnd);  

    if FAILED(InitDInput(hwnd,hInstance))
    {
        MessageBox( NULL, "创建DInput设备出错!","Error!", MB_OK) ;
        ReleaseDInput();
        PostQuitMessage( 0 );
        return 0;
    }

    GetMessage(&msg,NULL,NULL,NULL);
    //process the message quenue
    while(msg.message != WM_QUIT)
    {
        UpdateInputState();
        if( GetMessage(&msg,NULL,0,0) )
        {
            //解析消息
            TranslateMessage(&msg);
            //分派消息
            DispatchMessage(&msg);
        }
    }

    ReleaseDInput();
    UnregisterClass( "DInput_Test", hInstance);

    return msg.wParam;
}
//window message process function  
    LRESULT CALLBACK WndProc(HWND hwnd,UINT msg,WPARAM wparam,LPARAM lparam)
    {
        switch(msg)
        {
            //关闭窗口消息的处理
        case WM_CLOSE:
            DestroyWindow( hwnd );
            break;
            //销毁窗口消息的处理
        case WM_DESTROY:
            //退出当前进程
            PostQuitMessage( 0 );
            break;
        default:
            return DefWindowProc(hwnd,msg,wparam,lparam);
        }
        return NULL;
    }