tclxtnotify.c

tcl是工具命令语言

 *
 *----------------------------------------------------------------------
 */

static void
CreateFileHandler(fd, mask, proc, clientData)
    int fd;			/* Handle of stream to watch. */
    int mask;			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, and TCL_EXCEPTION:
				 * indicates conditions under which
				 * proc should be called. */
    Tcl_FileProc *proc;		/* Procedure to call for each
				 * selected event. */
    ClientData clientData;	/* Arbitrary data to pass to proc. */
{
    FileHandler *filePtr;

    if (!initialized) {
	InitNotifier();
    }

    TclSetAppContext(NULL);

    for (filePtr = notifier.firstFileHandlerPtr; filePtr != NULL;
	    filePtr = filePtr->nextPtr) {
	if (filePtr->fd == fd) {
	    break;
	}
    }
    if (filePtr == NULL) {
	filePtr = (FileHandler*) ckalloc(sizeof(FileHandler));
	filePtr->fd = fd;
	filePtr->read = 0;
	filePtr->write = 0;
	filePtr->except = 0;
	filePtr->readyMask = 0;
	filePtr->mask = 0;
	filePtr->nextPtr = notifier.firstFileHandlerPtr;
	notifier.firstFileHandlerPtr = filePtr;
    }
    filePtr->proc = proc;
    filePtr->clientData = clientData;

    /*
     * Register the file with the Xt notifier, if it hasn't been done yet.
     */

    if (mask & TCL_READABLE) {
	if (!(filePtr->mask & TCL_READABLE)) {
	    filePtr->read =
                XtAppAddInput(notifier.appContext, fd, XtInputReadMask,
                        FileProc, filePtr);
	}
    } else {
	if (filePtr->mask & TCL_READABLE) {
	    XtRemoveInput(filePtr->read);
	}
    }
    if (mask & TCL_WRITABLE) {
	if (!(filePtr->mask & TCL_WRITABLE)) {
	    filePtr->write =
                XtAppAddInput(notifier.appContext, fd, XtInputWriteMask,
                        FileProc, filePtr);
	}
    } else {
	if (filePtr->mask & TCL_WRITABLE) {
	    XtRemoveInput(filePtr->write);
	}
    }
    if (mask & TCL_EXCEPTION) {
	if (!(filePtr->mask & TCL_EXCEPTION)) {
	    filePtr->except =
                XtAppAddInput(notifier.appContext, fd, XtInputExceptMask,
                        FileProc, filePtr);
	}
    } else {
	if (filePtr->mask & TCL_EXCEPTION) {
	    XtRemoveInput(filePtr->except);
	}
    }
    filePtr->mask = mask;
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteFileHandler --
 *
 *	Cancel a previously-arranged callback arrangement for
 *	a file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a callback was previously registered on file, remove it.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteFileHandler(fd)
    int fd;			/* Stream id for which to remove
				 * callback procedure. */
{
    FileHandler *filePtr, *prevPtr;

    if (!initialized) {
	InitNotifier();
    }

    TclSetAppContext(NULL);

    /*
     * Find the entry for the given file (and return if there
     * isn't one).
     */

    for (prevPtr = NULL, filePtr = notifier.firstFileHandlerPtr; ;
	    prevPtr = filePtr, filePtr = filePtr->nextPtr) {
	if (filePtr == NULL) {
	    return;
	}
	if (filePtr->fd == fd) {
	    break;
	}
    }

    /*
     * Clean up information in the callback record.
     */

    if (prevPtr == NULL) {
	notifier.firstFileHandlerPtr = filePtr->nextPtr;
    } else {
	prevPtr->nextPtr = filePtr->nextPtr;
    }
    if (filePtr->mask & TCL_READABLE) {
	XtRemoveInput(filePtr->read);
    }
    if (filePtr->mask & TCL_WRITABLE) {
	XtRemoveInput(filePtr->write);
    }
    if (filePtr->mask & TCL_EXCEPTION) {
	XtRemoveInput(filePtr->except);
    }
    ckfree((char *) filePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * FileProc --
 *
 *	These procedures are called by Xt when a file becomes readable,
 *	writable, or has an exception.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Makes an entry on the Tcl event queue if the event is
 *	interesting.
 *
 *----------------------------------------------------------------------
 */

static void
FileProc(clientData, fd, id)
    caddr_t clientData;
    int *fd;
    XtInputId *id;
{
    FileHandler *filePtr = (FileHandler *)clientData;
    FileHandlerEvent *fileEvPtr;
    int mask = 0;

    /*
     * Determine which event happened.
     */

    if (*id == filePtr->read) {
	mask = TCL_READABLE;
    } else if (*id == filePtr->write) {
	mask = TCL_WRITABLE;
    } else if (*id == filePtr->except) {
	mask = TCL_EXCEPTION;
    }

    /*
     * Ignore unwanted or duplicate events.
     */

    if (!(filePtr->mask & mask) || (filePtr->readyMask & mask)) {
	return;
    }
    
    /*
     * This is an interesting event, so put it onto the event queue.
     */

    filePtr->readyMask |= mask;
    fileEvPtr = (FileHandlerEvent *) ckalloc(sizeof(FileHandlerEvent));
    fileEvPtr->header.proc = FileHandlerEventProc;
    fileEvPtr->fd = filePtr->fd;
    Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);

    /*
     * Process events on the Tcl event queue before returning to Xt.
     */

    Tcl_ServiceAll();
}

/*
 *----------------------------------------------------------------------
 *
 * FileHandlerEventProc --
 *
 *	This procedure is called by Tcl_ServiceEvent when a file event
 *	reaches the front of the event queue.  This procedure is
 *	responsible for actually handling the event by invoking the
 *	callback for the file handler.
 *
 * Results:
 *	Returns 1 if the event was handled, meaning it should be removed
 *	from the queue.  Returns 0 if the event was not handled, meaning
 *	it should stay on the queue.  The only time the event isn't
 *	handled is if the TCL_FILE_EVENTS flag bit isn't set.
 *
 * Side effects:
 *	Whatever the file handler's callback procedure does.
 *
 *----------------------------------------------------------------------
 */

static int
FileHandlerEventProc(evPtr, flags)
    Tcl_Event *evPtr;		/* Event to service. */
    int flags;			/* Flags that indicate what events to
				 * handle, such as TCL_FILE_EVENTS. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr = (FileHandlerEvent *) evPtr;
    int mask;

    if (!(flags & TCL_FILE_EVENTS)) {
	return 0;
    }

    /*
     * Search through the file handlers to find the one whose handle matches
     * the event.  We do this rather than keeping a pointer to the file
     * handler directly in the event, so that the handler can be deleted
     * while the event is queued without leaving a dangling pointer.
     */

    for (filePtr = notifier.firstFileHandlerPtr; filePtr != NULL;
	    filePtr = filePtr->nextPtr) {
	if (filePtr->fd != fileEvPtr->fd) {
	    continue;
	}

	/*
	 * The code is tricky for two reasons:
	 * 1. The file handler's desired events could have changed
	 *    since the time when the event was queued, so AND the
	 *    ready mask with the desired mask.
	 * 2. The file could have been closed and re-opened since
	 *    the time when the event was queued.  This is why the
	 *    ready mask is stored in the file handler rather than
	 *    the queued event:  it will be zeroed when a new
	 *    file handler is created for the newly opened file.
	 */

	mask = filePtr->readyMask & filePtr->mask;
	filePtr->readyMask = 0;
	if (mask != 0) {
	    (*filePtr->proc)(filePtr->clientData, mask);
	}
	break;
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * WaitForEvent --
 *
 *	This function is called by Tcl_DoOneEvent to wait for new
 *	events on the message queue.  If the block time is 0, then
 *	Tcl_WaitForEvent just polls without blocking.
 *
 * Results:
 *	Returns 1 if an event was found, else 0.  This ensures that
 *	Tcl_DoOneEvent will return 1, even if the event is handled
 *	by non-Tcl code.
 *
 * Side effects:
 *	Queues file events that are detected by the select.
 *
 *----------------------------------------------------------------------
 */

static int
WaitForEvent(
    Tcl_Time *timePtr)		/* Maximum block time, or NULL. */
{
    int timeout;

    if (!initialized) {
	InitNotifier();
    }

    TclSetAppContext(NULL);

    if (timePtr) {
        timeout = timePtr->sec * 1000 + timePtr->usec / 1000;
        if (timeout == 0) {
            if (XtAppPending(notifier.appContext)) {
                goto process;
            } else {
                return 0;
            }
        } else {
            Tcl_SetTimer(timePtr);
        }
    }
process:
    XtAppProcessEvent(notifier.appContext, XtIMAll);
    return 1;
}