tclunixnotfy.c

tcl是工具命令语言

    if (filePtr->mask & TCL_WRITABLE) {
	(tsdPtr->checkMasks+MASK_SIZE)[index] &= ~bit;
    }
    if (filePtr->mask & TCL_EXCEPTION) {
	(tsdPtr->checkMasks+2*(MASK_SIZE))[index] &= ~bit;
    }

    /*
     * Find current max fd.
     */

    if (fd+1 == tsdPtr->numFdBits) {
	for (tsdPtr->numFdBits = 0; index >= 0; index--) {
	    flags = tsdPtr->checkMasks[index]
		| (tsdPtr->checkMasks+MASK_SIZE)[index]
		| (tsdPtr->checkMasks+2*(MASK_SIZE))[index];
	    if (flags) {
		for (i = (NBBY*sizeof(fd_mask)); i > 0; i--) {
		    if (flags & (((unsigned long)1) << (i-1))) {
			break;
		    }
		}
		tsdPtr->numFdBits = index * (NBBY*sizeof(fd_mask)) + i;
		break;
	    }
	}
    }

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

    if (prevPtr == NULL) {
	tsdPtr->firstFileHandlerPtr = filePtr->nextPtr;
    } else {
	prevPtr->nextPtr = filePtr->nextPtr;
    }
    ckfree((char *) filePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * 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. */
{
    int mask;
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr = (FileHandlerEvent *) evPtr;
    ThreadSpecificData *tsdPtr;

    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.
     */

    tsdPtr = TCL_TSD_INIT(&dataKey);
    for (filePtr = tsdPtr->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;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_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 the select would block forever, otherwise
 *	returns 0.
 *
 * Side effects:
 *	Queues file events that are detected by the select.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WaitForEvent(timePtr)
    Tcl_Time *timePtr;		/* Maximum block time, or NULL. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr;
    struct timeval timeout, *timeoutPtr;
    int bit, index, mask;
#ifdef TCL_THREADS
    int waitForFiles;
#else
    int numFound;
#endif
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (tclStubs.tcl_WaitForEvent != Tcl_WaitForEvent) {
	return tclStubs.tcl_WaitForEvent(timePtr);
    }

    /*
     * Set up the timeout structure.  Note that if there are no events to
     * check for, we return with a negative result rather than blocking
     * forever.
     */

    if (timePtr) {
	timeout.tv_sec = timePtr->sec;
	timeout.tv_usec = timePtr->usec;
	timeoutPtr = &timeout;
#ifndef TCL_THREADS
    } else if (tsdPtr->numFdBits == 0) {
	/*
	 * If there are no threads, no timeout, and no fds registered,
	 * then there are no events possible and we must avoid deadlock.
	 * Note that this is not entirely correct because there might
	 * be a signal that could interrupt the select call, but we
	 * don't handle that case if we aren't using threads.
	 */

	return -1;
#endif
    } else {
	timeoutPtr = NULL;
    }

#ifdef TCL_THREADS
    /*
     * Place this thread on the list of interested threads, signal the
     * notifier thread, and wait for a response or a timeout.
     */

    Tcl_MutexLock(&notifierMutex);

    waitForFiles = (tsdPtr->numFdBits > 0);
    if (timePtr != NULL && timePtr->sec == 0 && timePtr->usec == 0) {
	/*
	 * Cannot emulate a polling select with a polling condition variable.
	 * Instead, pretend to wait for files and tell the notifier
	 * thread what we are doing.  The notifier thread makes sure
	 * it goes through select with its select mask in the same state
	 * as ours currently is.  We block until that happens.
	 */

	waitForFiles = 1;
	tsdPtr->pollState = POLL_WANT;
	timePtr = NULL;
    } else {
	tsdPtr->pollState = 0;
    }

    if (waitForFiles) {
        /*
         * Add the ThreadSpecificData structure of this thread to the list
         * of ThreadSpecificData structures of all threads that are waiting
         * on file events.
         */


        tsdPtr->nextPtr = waitingListPtr;
        if (waitingListPtr) {
            waitingListPtr->prevPtr = tsdPtr;
        }
        tsdPtr->prevPtr = 0;
        waitingListPtr = tsdPtr;
	tsdPtr->onList = 1;
	
	write(triggerPipe, "", 1);
    }

    memset((VOID *) tsdPtr->readyMasks, 0, 3*MASK_SIZE*sizeof(fd_mask));

    if (!tsdPtr->eventReady) {
        Tcl_ConditionWait(&tsdPtr->waitCV, &notifierMutex, timePtr);
    }
    tsdPtr->eventReady = 0;

    if (waitForFiles && tsdPtr->onList) {
	/*
	 * Remove the ThreadSpecificData structure of this thread from the
	 * waiting list.  Alert the notifier thread to recompute its select
	 * masks - skipping this caused a hang when trying to close a pipe
	 * which the notifier thread was still doing a select on.
	 */

        if (tsdPtr->prevPtr) {
            tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
        } else {
            waitingListPtr = tsdPtr->nextPtr;
        }
        if (tsdPtr->nextPtr) {
            tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;
        }
        tsdPtr->nextPtr = tsdPtr->prevPtr = NULL;
	tsdPtr->onList = 0;
	write(triggerPipe, "", 1);
    }

    
#else
    memcpy((VOID *) tsdPtr->readyMasks, (VOID *) tsdPtr->checkMasks,
	    3*MASK_SIZE*sizeof(fd_mask));
    numFound = select(tsdPtr->numFdBits,
	    (SELECT_MASK *) &tsdPtr->readyMasks[0],
	    (SELECT_MASK *) &tsdPtr->readyMasks[MASK_SIZE],
	    (SELECT_MASK *) &tsdPtr->readyMasks[2*MASK_SIZE], timeoutPtr);

    /*
     * Some systems don't clear the masks after an error, so
     * we have to do it here.
     */

    if (numFound == -1) {
	memset((VOID *) tsdPtr->readyMasks, 0, 3*MASK_SIZE*sizeof(fd_mask));
    }
#endif

    /*
     * Queue all detected file events before returning.
     */

    for (filePtr = tsdPtr->firstFileHandlerPtr; (filePtr != NULL);
	 filePtr = filePtr->nextPtr) {
	index = filePtr->fd / (NBBY*sizeof(fd_mask));
	bit = 1 << (filePtr->fd % (NBBY*sizeof(fd_mask)));
	mask = 0;

	if (tsdPtr->readyMasks[index] & bit) {
	    mask |= TCL_READABLE;
	}
	if ((tsdPtr->readyMasks+MASK_SIZE)[index] & bit) {
	    mask |= TCL_WRITABLE;
	}
	if ((tsdPtr->readyMasks+2*(MASK_SIZE))[index] & bit) {
	    mask |= TCL_EXCEPTION;
	}

	if (!mask) {
	    continue;
	}

	/*
	 * Don't bother to queue an event if the mask was previously
	 * non-zero since an event must still be on the queue.
	 */

	if (filePtr->readyMask == 0) {
	    fileEvPtr = (FileHandlerEvent *) ckalloc(
		sizeof(FileHandlerEvent));
	    fileEvPtr->header.proc = FileHandlerEventProc;
	    fileEvPtr->fd = filePtr->fd;
	    Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
	}
	filePtr->readyMask = mask;
    }
#ifdef TCL_THREADS
    Tcl_MutexUnlock(&notifierMutex);
#endif
    return 0;
}

#ifdef TCL_THREADS
/*
 *----------------------------------------------------------------------
 *
 * NotifierThreadProc --
 *
 *	This routine is the initial (and only) function executed by the
 *	special notifier thread.  Its job is to wait for file descriptors
 *	to become readable or writable or to have an exception condition
 *	and then to notify other threads who are interested in this
 *	information by signalling a condition variable.  Other threads
 *	can signal this notifier thread of a change in their interests
 *	by writing a single byte to a special pipe that the notifier
 *	thread is monitoring.
 *
 * Result:
 *	None.  Once started, this routine never exits.  It dies with
 *	the overall process.
 *
 * Side effects:
 *	The trigger pipe used to signal the notifier thread is created
 *	when the notifier thread first starts.
 *
 *----------------------------------------------------------------------
 */

static void
NotifierThreadProc(clientData)
    ClientData clientData;	/* Not used. */
{
    ThreadSpecificData *tsdPtr;
    fd_mask masks[3*MASK_SIZE];
    long *maskPtr = (long *)masks;	/* masks[] cast to type long[] */
    int fds[2];
    int i, status, index, bit, numFdBits, found, receivePipe, word;
    struct timeval poll = {0., 0.}, *timePtr;
    int maskSize = 3 * ((MASK_SIZE) / sizeof(long)) * sizeof(fd_mask);
    char buf[2];

    if (pipe(fds) != 0) {
	panic("NotifierThreadProc: could not create trigger pipe.");
    }

    receivePipe = fds[0];

#ifndef USE_FIONBIO
    status = fcntl(receivePipe, F_GETFL);
    status |= O_NONBLOCK;
    if (fcntl(receivePipe, F_SETFL, status) < 0) {
	panic("NotifierThreadProc: could not make receive pipe non blocking.");
    }
    status = fcntl(fds[1], F_GETFL);
    status |= O_NONBLOCK;
    if (fcntl(fds[1], F_SETFL, status) < 0) {
	panic("NotifierThreadProc: could not make trigger pipe non blocking.");
    }
#else
    if (ioctl(receivePipe, (int) FIONBIO, &status) < 0) {
	panic("NotifierThreadProc: could not make receive pipe non blocking.");
    }
    if (ioctl(fds[1], (int) FIONBIO, &status) < 0) {
	panic("NotifierThreadProc: could not make trigger pipe non blocking.");
    }
#endif

    /*
     * Install the write end of the pipe into the global variable.
     */

    Tcl_MutexLock(&notifierMutex);
    triggerPipe = fds[1];

    /*
     * Signal any threads that are waiting.
     */

    Tcl_ConditionNotify(&notifierCV);
    Tcl_MutexUnlock(&notifierMutex);

    /*
     * Look for file events and report them to interested threads.
     */

    while (1) {
	/*
	 * Set up the select mask to include the receive pipe.
	 */

	memset((VOID *)masks, 0, 3*MASK_SIZE*sizeof(fd_mask));
        numFdBits = receivePipe + 1;
	index = receivePipe / (NBBY*sizeof(fd_mask));
	bit = 1 << (receivePipe % (NBBY*sizeof(fd_mask)));
	masks[index] |= bit;

	/*
	 * Add in the check masks from all of the waiting notifiers.
	 */
	
	Tcl_MutexLock(&notifierMutex);
	timePtr = NULL;
        for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
            for (i = 0; i < maskSize; i++) {
                maskPtr[i] |= ((long*)tsdPtr->checkMasks)[i];
            }
            if (tsdPtr->numFdBits > numFdBits) {
                numFdBits = tsdPtr->numFdBits;
            }
	    if (tsdPtr->pollState & POLL_WANT) {
		/*
		 * Here we make sure we go through select() with the same
		 * mask bits that were present when the thread tried to poll.
		 */

		tsdPtr->pollState |= POLL_DONE;
		timePtr = &poll;
	    }
        }
	Tcl_MutexUnlock(&notifierMutex);

	maskSize = 3 * ((MASK_SIZE) / sizeof(long)) * sizeof(fd_mask);

	if (select(numFdBits, (SELECT_MASK *) &masks[0],
		(SELECT_MASK *) &masks[MASK_SIZE],
		(SELECT_MASK *) &masks[2*MASK_SIZE], timePtr) == -1) {
	    /*
	     * Try again immediately on an error.
	     */

	    continue;
        }

	/*
	 * Alert any threads that are waiting on a ready file descriptor.
	 */

	Tcl_MutexLock(&notifierMutex);
        for (tsdPtr = waitingListPtr; tsdPtr; tsdPtr = tsdPtr->nextPtr) {
	    found = 0;

            for (i = 0; i < maskSize; i++) {
                word = maskPtr[i] & ((long*)tsdPtr->checkMasks)[i];
                found |= word;
                (((long*)(tsdPtr->readyMasks))[i]) = word;
	    }
            if (found || (tsdPtr->pollState & POLL_DONE)) {
                tsdPtr->eventReady = 1;
		if (tsdPtr->onList) {
		    /*
		     * Remove the ThreadSpecificData structure of this
		     * thread from the waiting list. This prevents us from
		     * continuously spining on select until the other
		     * threads runs and services the file event.
		     */
	    
		    if (tsdPtr->prevPtr) {
			tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr;
		    } else {
			waitingListPtr = tsdPtr->nextPtr;
		    }
		    if (tsdPtr->nextPtr) {
			tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr;
		    }
		    tsdPtr->nextPtr = tsdPtr->prevPtr = NULL;
		    tsdPtr->onList = 0;
		    tsdPtr->pollState = 0;
		}
		Tcl_ConditionNotify(&tsdPtr->waitCV);
            }
        }
	Tcl_MutexUnlock(&notifierMutex);
	
	/*
	 * Consume the next byte from the notifier pipe if the pipe was
	 * readable.  Note that there may be multiple bytes pending, but
	 * to avoid a race condition we only read one at a time.
	 */

	if (masks[index] & bit) {
	    i = read(receivePipe, buf, 1);

	    if ((i == 0) || ((i == 1) && (buf[0] == 'q'))) {
		/*
		 * Someone closed the write end of the pipe or sent us a
		 * Quit message [Bug: 4139] and then closed the write end
		 * of the pipe so we need to shut down the notifier thread.
		 */

		break;
	    }
	}
    }

    /*
     * Clean up the read end of the pipe and signal any threads waiting on
     * termination of the notifier thread.
     */

    close(receivePipe);
    Tcl_MutexLock(&notifierMutex);
    triggerPipe = -1;
    Tcl_ConditionNotify(&notifierCV);
    Tcl_MutexUnlock(&notifierMutex);
}
#endif