/*----------------------------------------
   HEXCALC.C -- Hexadecimal Calculator
                (c) Charles Petzold, 1998
  ----------------------------------------*/

#include <windows.h>

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

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("HexCalc") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;
     
     wndclass.style         = CS_HREDRAW | CS_VREDRAW;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = DLGWINDOWEXTRA ;    // Note!
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (hInstance, szAppName) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) (COLOR_BTNFACE + 1) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;
     
     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }
     
     hwnd = CreateDialog (hInstance, szAppName, 0, NULL) ;
     
     ShowWindow (hwnd, iCmdShow) ;
     
     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}

void ShowNumber (HWND hwnd, UINT iNumber)
{
     TCHAR szBuffer[20] ;

     wsprintf (szBuffer, TEXT ("%X"), iNumber) ;
     SetDlgItemText (hwnd, VK_ESCAPE, szBuffer) ;
}

DWORD CalcIt (UINT iFirstNum, int iOperation, UINT iNum)
{
     switch (iOperation)
     {
     case '=': return iNum ;
     case '+': return iFirstNum +  iNum ;
     case '-': return iFirstNum -  iNum ;
     case '*': return iFirstNum *  iNum ;
     case '&': return iFirstNum &  iNum ;
     case '|': return iFirstNum |  iNum ;
     case '^': return iFirstNum ^  iNum ;
     case '<': return iFirstNum << iNum ;
     case '>': return iFirstNum >> iNum ;
     case '/': return iNum ? iFirstNum / iNum: MAXDWORD ;
     case '%': return iNum ? iFirstNum % iNum: MAXDWORD ;
     default : return 0 ;
     }
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static BOOL  bNewNumber = TRUE ;
     static int   iOperation = '=' ;
     static UINT  iNumber, iFirstNum ;
     HWND         hButton ;
     
     switch (message)
     {
     case WM_KEYDOWN:                   // left arrow --> backspace
          if (wParam != VK_LEFT)
               break ;
          wParam = VK_BACK ;
                                        // fall through
     case WM_CHAR:
          if ((wParam = (WPARAM) CharUpper ((TCHAR *) wParam)) == VK_RETURN)
               wParam = '=' ;
          
          if (hButton = GetDlgItem (hwnd, wParam))
          {
               SendMessage (hButton, BM_SETSTATE, 1, 0) ;
               Sleep (100) ;
               SendMessage (hButton, BM_SETSTATE, 0, 0) ;
          }
          else
          {
               MessageBeep (0) ;
               break ;
          }
                                        // fall through
     case WM_COMMAND:
          SetFocus (hwnd) ;
          
          if (LOWORD (wParam) == VK_BACK)         // backspace
               ShowNumber (hwnd, iNumber /= 16) ;
          
          else if (LOWORD (wParam) == VK_ESCAPE)  // escape
               ShowNumber (hwnd, iNumber = 0) ;
          
          else if (isxdigit (LOWORD (wParam)))    // hex digit
          {
               if (bNewNumber)
               {
                    iFirstNum = iNumber ;
                    iNumber = 0 ;
               }
               bNewNumber = FALSE ;
               
               if (iNumber <= MAXDWORD >> 4)
                    ShowNumber (hwnd, iNumber = 16 * iNumber + wParam -
                    (isdigit (wParam) ? '0': 'A' - 10)) ;
               else
                    MessageBeep (0) ;
          }
          else                                    // operation
          {
               if (!bNewNumber)
                    ShowNumber (hwnd, iNumber =
                         CalcIt (iFirstNum, iOperation, iNumber)) ;
               bNewNumber = TRUE ;
               iOperation = LOWORD (wParam) ;
          }
          return 0 ;
          
     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}