_get_osfhandle

Remonter à Io.h - Index

Header File

io.h

Category

Input/output Routines

Prototype

long _get_osfhandle(int filehandle);

Description

Associates file handles.

The _get_osfhandle function associates an operating system file handle with an existing runtime file handle. The variable filehandle is the file handle of your program.

Return value

On success, _get_osfhandle returns an operating system file handle corresponding to the variable filehandle.

On error, the function returns -1 and sets the global variable errno to

EBADF

an invalid file handle

Example

 #include <windows.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <io.h>
 //Example for _get_osfhandle() and _open_osfhandle()
 BOOL InitApplication(HINSTANCE hInstance);
 HWND InitInstance(HINSTANCE hInstance, int nCmdShow);
 LRESULT FAR PASCAL _export MainWndProc(HWND hWnd, UINT message,
             WPARAM wParam, LPARAM lParam);
 Example_get_osfhandle(HWND hWnd);
 #pragma argsused
 int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
         LPSTR lpCmdLine, int nCmdShow)
 {
 MSG msg;      // message
   if (!InitApplication(hInstance))  // Initialize shared things
    return (FALSE); // Exits if unable to initialize
   /* Perform initializations that apply to a specific instance */
   if (!(InitInstance(hInstance, nCmdShow)))
    return (FALSE);
   /* Acquire and dispatch messages until a WM_QUIT message is received. */
   while (GetMessage(&msg, // message structure
    NULL, // handle of window receiving the message
    NULL, // lowest message to examine
    NULL))  // highest message to examine
   {
   TranslateMessage(&msg); // Translates virtual key codes
   DispatchMessage(&msg);  // Dispatches message to window
   }
   return (msg.wParam);  // Returns the value from PostQuitMessage
 }
 BOOL InitApplication(HINSTANCE hInstance)
 {
   WNDCLASS  wc;
   // Fill in window class structure with parameters that describe the
   // main window.
   wc.style = CS_HREDRAW | CS_VREDRAW; // Class style(s).
   wc.lpfnWndProc = (long (FAR PASCAL*)(void *,unsigned int,unsigned int, long ))MainWndProc; // Function to retrieve messages for
                 // windows of this class.
   wc.cbClsExtra = 0;  // No per-class extra data.
   wc.cbWndExtra = 0;  // No per-window extra data.
   wc.hInstance = hInstance; // Application that owns the class.
   wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
   wc.hCursor = LoadCursor(NULL, IDC_ARROW);
   wc.hbrBackground = GetStockObject(WHITE_BRUSH);
   wc.lpszMenuName = NULL;  // Name of menu resource in .RC file.
   wc.lpszClassName = "Example"; // Name used in call to CreateWindow.
   /* Register the window class and return success/failure code. */
   return (RegisterClass(&wc));
 }
 HWND InitInstance(HINSTANCE hInstance, int nCmdShow)
 {
   HWND  hWnd; // Main window handle.
   /* Create a main window for this application instance.  */
   hWnd = CreateWindow(
    "Example",                 // See RegisterClass() call.
    "Example _get_osfhandle _open_osfhandle (32 bit)",  // Text for window title bar.
    WS_OVERLAPPEDWINDOW,        // Window style.
    CW_USEDEFAULT,         // Default horizontal position.
    CW_USEDEFAULT,          // Default vertical position.
    CW_USEDEFAULT,            // Default width.
    CW_USEDEFAULT,        // Default height.
    NULL,                  // Overlapped windows have no parent.
    NULL,                  // Use the window class menu.
    hInstance,              // This instance owns this window.
    NULL                   // Pointer not needed.
   );
   /* If window could not be created, return "failure" */
   if (!hWnd)
    return (FALSE);
   /* Make the window visible; update its client area; and return "success" */
   ShowWindow(hWnd, nCmdShow); // Show the window
   UpdateWindow(hWnd);     // Sends WM_PAINT message
   return (hWnd);        // Returns the value from PostQuitMessage
 }
 #pragma argsused
 LRESULT FAR PASCAL _export MainWndProc(HWND hWnd, UINT message,
             WPARAM wParam, LPARAM lParam)
 {
   switch (message)
   {
     case WM_CREATE:
     {
       Example_get_osfhandle(hWnd);
       return NULL;
     }
     case WM_QUIT:
     case WM_DESTROY:  // message: window being destroyed
       PostQuitMessage(0);
     break;
     default:      // Passes it on if unprocessed
       return (DefWindowProc(hWnd, message, wParam, lParam));
   }
 }
 Example_get_osfhandle(HWND hWnd)
 {
     long osfHandle;
     char str[128];
     int fHandle = open("file1.c", O_CREAT|O_TEXT);
     if(fHandle != -1)
     {
       osfHandle = _get_osfhandle(fHandle);
       sprintf(str, "file handle = %lx OS file handle = %lx", fHandle, osfHandle);
       MessageBox(hWnd,str,"_get_osfhandle",MB_OK|MB_ICONINFORMATION);
       close(fHandle);
       fHandle = _open_osfhandle(osfHandle, O_TEXT );
       sprintf(str, "file handle = %lx OS file handle = %lx", fHandle, osfHandle);
       MessageBox(hWnd,str,"_open_osfhandle",MB_OK|MB_ICONINFORMATION);
          close(fHandle);
     }
     else
       MessageBox(hWnd,"File Open Error","WARNING",MB_OK|MB_ICONSTOP);
 return 0;
 }

Portability

POSIX	Win32	ANSI C	ANSI C++
	+