write_file.cpp

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#if defined (WIN32)
#define IS_WIN32 TRUE
#else
#define IS_WIN32 FALSE
#endif

#define IS_NT IS_WIN32 && (BOOL)(GetVersion() < 0x80000000)
#define IS_WIN32S IS_WIN32 && (BOOL)(!(IS_NT) && (LOBYTE(LOWORD(GetVersion()))<4))
#define IS_WIN95 (BOOL)(!(IS_NT) && !(IS_WIN32S)) && IS_WIN32

HINSTANCE hInst; // current instance

LPCTSTR lpszAppName = "MyApp";
LPCTSTR lpszTitle = "My Application";

BOOL RegisterWin95( CONST WNDCLASS* lpwc );

int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance,
                      LPTSTR lpCmdLine, int nCmdShow)
{
   MSG      msg;
   HWND     hWnd;
   WNDCLASS wc;

   // Register the main application window class.
   //............................................
   wc.style         = CS_HREDRAW | CS_VREDRAW;
   wc.lpfnWndProc   = (WNDPROC)WndProc;
   wc.cbClsExtra    = 0;
   wc.cbWndExtra    = 0;
   wc.hInstance     = hInstance;
   wc.hIcon         = LoadIcon( hInstance, lpszAppName );
   wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
   wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
   wc.lpszMenuName = lpszAppName;
   wc.lpszClassName = lpszAppName;

   if ( IS_WIN95 )
   {
      if ( !RegisterWin95( &wc ) )
         return( FALSE );
   }
   else if ( !RegisterClass( &wc ) )
      return( FALSE );

hInst = hInstance;

   // Create the main application window.
   //....................................
   hWnd = CreateWindow( lpszAppName,
                        lpszTitle,
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT, 0,
                        CW_USEDEFAULT, 0,
                        NULL,
                        NULL,
                        hInstance,
                        NULL
                      );

if ( !hWnd )
return( FALSE );

ShowWindow( hWnd, nCmdShow );
UpdateWindow( hWnd );

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

return( msg.wParam );
}

BOOL RegisterWin95( CONST WNDCLASS* lpwc )
{
WNDCLASSEX wcex;

   wcex.style         = lpwc->style;
   wcex.lpfnWndProc   = lpwc->lpfnWndProc;
   wcex.cbClsExtra    = lpwc->cbClsExtra;
   wcex.cbWndExtra    = lpwc->cbWndExtra;
   wcex.hInstance     = lpwc->hInstance;
   wcex.hIcon         = lpwc->hIcon;
   wcex.hCursor       = lpwc->hCursor;
   wcex.hbrBackground = lpwc->hbrBackground;
   wcex.lpszMenuName = lpwc->lpszMenuName;
   wcex.lpszClassName = lpwc->lpszClassName;

   // Added elements for Windows 95.
   //...............................
   wcex.cbSize = sizeof(WNDCLASSEX);
   wcex.hIconSm = LoadImage(wcex.hInstance, lpwc->lpszClassName,
                            IMAGE_ICON, 16, 16,
                            LR_DEFAULTCOLOR );

   return RegisterClassEx( &wcex );
}

LPCTSTR lpBuffer = "This is the string that will be written to the file.";

LRESULT CALLBACK WndProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
static HANDLE hFile;

   switch( uMsg )
   {
      case WM_CREATE :
              {
                 DWORD dwWritten;

                 // Open/create a file.
                 //....................
                 hFile = CreateFile( "FILE.DAT", GENERIC_READ | GENERIC_WRITE,
                                     0, NULL, OPEN_ALWAYS,
                                     FILE_ATTRIBUTE_NORMAL, NULL );

                 // Write a string to the file.
                 //............................
                 WriteFile( hFile, lpBuffer, strlen( lpBuffer )+1,
                            &dwWritten, NULL );
              }
              break;

      case WM_COMMAND :
              switch( LOWORD( wParam ) )
              {
                 case IDM_TEST :
                        {
                           char szBuf[128];
                           DWORD dwRead;

                           // Make sure the file pointer
                           // is at the beginning of the file.
                           //.................................
                           SetFilePointer( hFile, 0, NULL, FILE_BEGIN );

                           // Read the string from the file and display it.
                           //..............................................
                           if ( ReadFile( hFile, szBuf, strlen( lpBuffer )+1,
                                          &dwRead, NULL ) )
                           {
                              szBuf[dwRead] = 0;

                              MessageBox( hWnd, szBuf, "Read File", MB_OK );

                              // Change the end of the file and truncate
                              // the contents for the next read.
                              //........................................
                              SetFilePointer( hFile, 40, NULL, FILE_BEGIN );
                              SetEndOfFile( hFile );                           }
                        }
                        break;

                 case IDM_ABOUT :
                        DialogBox( hInst, "AboutBox", hWnd, (DLGPROC)About );
                        break;

                 case IDM_EXIT :
                        DestroyWindow( hWnd );
                        break;
              }
              break;

      case WM_DESTROY :
              // Close the file.
              //................
              CloseHandle( hFile );

PostQuitMessage(0);
break;

      default :
            return( DefWindowProc( hWnd, uMsg, wParam, lParam ) );
   }

return( 0L );
}

LRESULT CALLBACK About( HWND hDlg,
                        UINT message,
                        WPARAM wParam,
                        LPARAM lParam)
{
   switch (message)
   {
       case WM_INITDIALOG:
               return (TRUE);

       case WM_COMMAND:
               if (   LOWORD(wParam) == IDOK
                   || LOWORD(wParam) == IDCANCEL)
               {
                       EndDialog(hDlg, TRUE);
                       return (TRUE);
               }
               break;
   }

return (FALSE);
}