Use SDL Input without window

#include <Windows.h>
#include <stdlib.h>
#include "Input.h"
#ifndef __SDL_H_I__
	#define __SDL_H_I__
	#include "SDL.h"
#endif
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow)
{
	SDL_Init(SDL_INIT_EVERYTHING);
	Input::Init();
	while(1)
	{
		Input::Update();
		if(Input::GetKey(SDLKey::SDLK_u))
		{
			SDL_Quit();
			return 0;
		}
	}
	return 0;
}

#ifndef __INPUT_H__
#define __INPUT_H__
#ifndef __SDL_H_I__
	#define __SDL_H_I__
	#include "SDL.h"
#endif

class Input
{
public:
	static void Init();
	static void Update();
	static bool GetKey(SDLKey key);
	static bool GetKeyDown(SDLKey key);
	static bool GetKeyUp(SDLKey key);
	static bool GetButton(int btn);
	static bool GetButtonDown(int btn);
	static bool GetButtonUp(int btn);
private:
	static bool _curKey[322];
	static bool _preKey[322];
	static bool _curBtn[3];
	static bool _preBtn[3];
	static SDL_Event _event;
};

#endif

#include "Input.h"

bool Input::_curKey[322];
bool Input::_preKey[322];
bool Input::_curBtn[3];
bool Input::_preBtn[3];
SDL_Event Input::_event;

void Input::Init()
{
    memset(_curKey,0,sizeof(bool)*322);
    memset(_preKey,0,sizeof(bool)*322);
    memset(_curBtn,0,sizeof(bool)*322);
    memset(_preBtn,0,sizeof(bool)*322);
}

void Input::Update()
{
    memcpy(_preKey,_curKey,sizeof(bool)*322);
    memcpy(_preBtn,_curBtn,sizeof(bool)*3);

    while(SDL_PollEvent(&_event))
    {
        switch(_event.type)
        {
        case SDL_KEYDOWN:
            {
                _curKey[_event.key.keysym.sym] = true;
                break;
            }
        case SDL_KEYUP:
            {
                _curKey[_event.key.keysym.sym] = false;
                break;
            }
        case SDL_MOUSEBUTTONDOWN:
            {
                _curBtn[_event.button.button]=true;
                break;
            }
        case SDL_MOUSEBUTTONUP:
            {
                _curBtn[_event.button.button]=false;
                break;
            }
        }
    }
}

bool Input::GetKey(SDLKey key)
{
    return _curKey[key];
}
bool Input::GetKeyDown(SDLKey key)
{
    return _curKey[key] && !_preKey[key];
}
bool Input::GetKeyUp(SDLKey key)
{
    return !_curKey[key] && _preKey[key];
}

bool Input::GetButton( int btn )
{
    return _curBtn[btn];
}

bool Input::GetButtonDown( int btn )
{
    return _curBtn[btn]==true && _curBtn[btn]==false;
}

bool Input::GetButtonUp( int btn )
{
    return _curBtn[btn]==false && _curBtn[btn]==true;
}