Windows API: Convert Decimal to Binary

Convert very large decimal numbers to binary ones.

#ifndef UNICODE
#define UNICODE
#endif

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
unsigned long long AlphaToUnsignedInt(WCHAR* sz);
void CopyString(WCHAR* dst, const WCHAR* src);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
	static const WCHAR szAppName[] = L"BinaryWin";
	HWND		hwnd;
	MSG		 msg;
	WNDCLASSEX	wndclass;

	wndclass.cbSize = sizeof(wndclass);
	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = WndProc;
	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hInstance = hInstance;
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
	wndclass.lpszMenuName = NULL;
	wndclass.lpszClassName = szAppName;
	wndclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

	RegisterClassEx(&wndclass);

	hwnd = CreateWindowEx(WS_EX_STATICEDGE, // extended window style
		szAppName,                          // window class name
		L"Convert Decimal to Binary",       // window caption
		0,                                  // window style
		CW_USEDEFAULT,                      // initial x position
		CW_USEDEFAULT,                      // initial y position
		600,                                // initial x size
		380,                                // initial y size
		NULL,                               // parent window handle
		NULL,                               // window menu handle
		hInstance,                          // program instance handle
		NULL);                              // creation parameters

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
	HDC				hdc;
	PAINTSTRUCT		ps;
	RECT			 rect;
	static HWND		hwndEdit;
	static WCHAR	 szResult[100];

#define ID_EDIT		 123
#define ID_BUTTON	 456
#define ID_BTNEXIT	789

	switch (iMsg)
	{
	case WM_CREATE:
		hwndEdit = CreateWindowEx(WS_EX_CLIENTEDGE, L"EDIT", NULL, WS_CHILD | WS_VISIBLE | ES_NUMBER,
			100, 100, 475, 22, hwnd, (HMENU)ID_EDIT, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
		CreateWindowEx(0, L"BUTTON", L"Convert to Binary", WS_CHILD | WS_VISIBLE,
			400, 250, 150, 25, hwnd, (HMENU)ID_BUTTON, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
		CreateWindowEx(0, L"BUTTON", L"Exit Program", WS_CHILD | WS_VISIBLE,
			400, 285, 150, 25, hwnd, (HMENU)ID_BTNEXIT, ((LPCREATESTRUCT)lParam)->hInstance, NULL);
		return 0;

	case WM_CLOSE:
		DestroyWindow(hwnd);
		return 0;

	case WM_COMMAND:
		if (LOWORD(wParam) == ID_BUTTON && HIWORD(wParam) == BN_CLICKED)
		{
			unsigned long long num;
			int i = GetWindowTextLength(hwndEdit);
			WCHAR* sz = new WCHAR[i + 1];
			GetWindowText(hwndEdit, sz, i + 1);
			for (num = AlphaToUnsignedInt(sz), sz = &szResult[98]; num > 0 && sz >= szResult; sz--)
			{
				*sz = (WCHAR)(num & 1) + '0';
				num >>= 1;
			}
			if (sz == szResult && num)
				MessageBox(hwnd, L"Number too great!", L"Binary Converter", 0);
			else if (sz > szResult)
				CopyString(szResult, sz + 1);
			GetClientRect(hwnd, &rect);
			InvalidateRect(hwnd, &rect, TRUE);
		}
		else if (LOWORD(wParam) == ID_BTNEXIT && HIWORD(wParam) == BN_CLICKED)
			SendMessage(hwnd, WM_CLOSE, 0, 0);
		return 0;

	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);

		SetBkMode(hdc, TRANSPARENT);
		rect.left = 10;
		rect.top = 100;
		rect.bottom = 122;
		rect.right = 90;
		DrawText(hdc, L"Number:", -1, &rect, DT_SINGLELINE | DT_RIGHT | DT_VCENTER);
		GetClientRect(hwnd, &rect);
		rect.top = 150;
		rect.bottom = 172;
		DrawText(hdc, szResult, -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;
	}

	return DefWindowProc(hwnd, iMsg, wParam, lParam);
}

unsigned long long AlphaToUnsignedInt(WCHAR* sz)
{
	int c;
	unsigned long long total;

	while (*sz == ' ' || *sz == '\r' || *sz == '\n') ++sz;
	total = 0;
	while (c = *sz++)
		total = 10 * total + (c - '0');

	return total;
}

void CopyString(WCHAR* dst, const WCHAR* src)
{
	while (*dst++ = *src++);
}

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