#define SpaceLeft(bufPtr) ((bufPtr)->bufLength - (bufPtr)->nextAdded)

#define IsBufferReady(bufPtr) ((bufPtr)->nextAdded > (bufPtr)->nextRemoved)

#define IsBufferEmpty(bufPtr) ((bufPtr)->nextAdded == (bufPtr)->nextRemoved)

#define IsBufferFull(bufPtr) ((bufPtr)->nextAdded >= (bufPtr)->bufLength)

#define IsBufferOverflowing(bufPtr) ((bufPtr)->nextAdded > (bufPtr)->bufLength)

#define InsertPoint(bufPtr) ((bufPtr)->buf + (bufPtr)->nextAdded)

#define RemovePoint(bufPtr) ((bufPtr)->buf + (bufPtr)->nextRemoved)

    CheckForStdChannelsBeingClosed(chan);

    /*
     * If the refCount reached zero, close the actual channel.
     */

    if (statePtr->refCount <= 0) {
	/*
	 * Ensure that if there is another buffer, it gets flushed whether or
	 * not we are doing a background flush.
	 */

	if ((statePtr->curOutPtr != NULL) &&
		IsBufferReady(statePtr->curOutPtr)) {
	    SetFlag(statePtr, BUFFER_READY);
	}
	Tcl_Preserve((ClientData)statePtr);
	if (!GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    /*
	     * We don't want to re-enter Tcl_Close().
	     */

	    if (!GotFlag(statePtr, CHANNEL_CLOSED)) {

    Channel *chanPtr,		/* The channel to flush on. */
    int calledFromAsyncFlush)	/* If nonzero then we are being called from an
				 * asynchronous flush callback. */
{
    ChannelState *statePtr = chanPtr->state;
				/* State of the channel stack. */
    ChannelBuffer *bufPtr;	/* Iterates over buffered output queue. */
    int toWrite;		/* Amount of output data in current buffer
				 * available to be written. */
    int written;		/* Amount of output data actually written in
				 * current round. */
    int errorCode = 0;		/* Stores POSIX error codes from channel
				 * driver operations. */
    int wroteSome = 0;		/* Set to one if any data was written to the
				 * driver. */

    /*
     * Prevent writing on a dead channel -- a channel that has been closed but
     * not yet deallocated. This can occur if the exit handler for the channel
     * deallocation runs before all channels are deregistered in all
     * interpreters.
     */

    if (CheckForDeadChannel(interp, statePtr)) {
	return -1;
    }

    /*
     * Loop over the queued buffers and attempt to flush as much as possible
     * of the queued output to the channel.
     */

    while (1) {
	/*
	 * If the queue is empty and there is a ready current buffer, OR if

	 * the current buffer is full, then move the current buffer to the





	 * queue.
	 */

	if (((statePtr->curOutPtr != NULL) &&
		IsBufferFull(statePtr->curOutPtr))
		|| (GotFlag(statePtr, BUFFER_READY) &&

			(statePtr->outQueueHead == NULL))) {
	    ResetFlag(statePtr, BUFFER_READY);
	    statePtr->curOutPtr->nextPtr = NULL;
	    if (statePtr->outQueueHead == NULL) {
		statePtr->outQueueHead = statePtr->curOutPtr;
	    } else {
		statePtr->outQueueTail->nextPtr = statePtr->curOutPtr;
	    }
	    statePtr->outQueueTail = statePtr->curOutPtr;
	    statePtr->curOutPtr = NULL;
	}


















	bufPtr = statePtr->outQueueHead;

	/*
	 * If we are not being called from an async flush and an async flush
	 * is active, we just return without producing any output.
	 */

	if (!calledFromAsyncFlush && GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    return 0;
	}

	/*
	 * If the output queue is still empty, break out of the while loop.
	 */

	if (bufPtr == NULL) {
	    break;	/* Out of the "while (1)". */
	}

	/*
	 * Produce the output on the channel.
	 */

	PreserveChannelBuffer(bufPtr);
	toWrite = BytesLeft(bufPtr);
	if (toWrite == 0) {
	    written = 0;
	} else {
	    written = (chanPtr->typePtr->outputProc)(chanPtr->instanceData,
		RemovePoint(bufPtr), toWrite, &errorCode);
	}

	/*
	 * If the write failed completely attempt to start the asynchronous
	 * flush mechanism and break out of this loop - do not attempt to
	 * write any more output at this time.
	 */

	    /*
	     * When we get an error we throw away all the output currently
	     * queued.
	     */

	    DiscardOutputQueued(statePtr);
	    ReleaseChannelBuffer(bufPtr);
	    continue;
	} else {


	    wroteSome = 1;
	}

	bufPtr->nextRemoved += written;

	/*
	 * If this buffer is now empty, recycle it.
	 */

	if (IsBufferEmpty(bufPtr)) {
	    statePtr->outQueueHead = bufPtr->nextPtr;
	    if (statePtr->outQueueHead == NULL) {
		statePtr->outQueueTail = NULL;
	    }
	    RecycleBuffer(statePtr, bufPtr, 0);
	}
	ReleaseChannelBuffer(bufPtr);
    }	/* Closes "while (1)". */

    /*
     * If we wrote some data while flushing in the background, we are done.
     * We can't finish the background flush until we run out of data and the
     * channel becomes writable again. This ensures that all of the pending
     * data has been flushed at the system level.
     */

    if (GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	if (wroteSome) {
	    return errorCode;
	} else if (statePtr->outQueueHead == NULL) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData,
		    statePtr->interestMask);






	}
    }

    /*
     * If the channel is flagged as closed, delete it when the refCount drops
     * to zero, the output queue is empty and there is no output in the
     * current output buffer.

	statePtr->closeCbPtr = cbPtr->nextPtr;
	(cbPtr->proc)(cbPtr->clientData);
	ckfree((char *) cbPtr);
    }

    ResetFlag(statePtr, CHANNEL_INCLOSE);

    /*
     * Ensure that the last output buffer will be flushed.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    /*
     * If this channel supports it, close the read side, since we don't need
     * it anymore and this will help avoid deadlocks on some channel types.
     */

    if (chanPtr->typePtr->closeProc == TCL_CLOSE2PROC) {
	result = (chanPtr->typePtr->close2Proc)(chanPtr->instanceData, interp,

	/* Prevent read attempts on a closed channel */
        DiscardInputQueued(chanPtr->state, 0);
	Tcl_SetErrno(EINVAL);
	return -1;
    }
    if ((chanPtr->typePtr->seekProc != NULL)
        && (Tcl_OutputBuffered((Tcl_Channel) chanPtr) > 0)) {
        if ((chanPtr->state->curOutPtr != NULL)
            && IsBufferReady(chanPtr->state->curOutPtr)) {

            SetFlag(chanPtr->state, BUFFER_READY);







        }
        if (FlushChannel(NULL, chanPtr, 0) != 0) {
            return -1;
        }
    }
    return 0;
}


		needNlFlush = 0;
	    }
	}
	ReleaseChannelBuffer(bufPtr);
    }
    if ((flushed < total) && (GotFlag(statePtr, CHANNEL_UNBUFFERED) ||
	    (needNlFlush && GotFlag(statePtr, CHANNEL_LINEBUFFERED)))) {
	SetFlag(statePtr, BUFFER_READY);
	if (FlushChannel(NULL, chanPtr, 0) != 0) {
	    return -1;
	}
    }

    return total;
}

    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    /*
     * Force current output buffer to be output also.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    result = FlushChannel(NULL, chanPtr, 0);
    if (result != 0) {
	return TCL_ERROR;
    }

    return TCL_OK;
}

    /*
     * See if we can fill an existing buffer. If we can, read only as much as
     * will fit in it. Otherwise allocate a new buffer, add it to the input
     * queue and attempt to fill it to the max.
     */

    bufPtr = statePtr->inQueueTail;
    if ((bufPtr != NULL) && !IsBufferFull(bufPtr)) {
	toRead = SpaceLeft(bufPtr);
    } else {
	bufPtr = statePtr->saveInBufPtr;
	statePtr->saveInBufPtr = NULL;

	/*
	 * Check the actual buffersize against the requested buffersize.
	 * Saved buffers of the wrong size are squashed. This is done
	 * to honor dynamic changes of the buffersize made by the user.

	if (statePtr->inQueueTail == NULL) {
	    statePtr->inQueueHead = bufPtr;
	} else {
	    statePtr->inQueueTail->nextPtr = bufPtr;
	}
	statePtr->inQueueTail = bufPtr;


    }

    PreserveChannelBuffer(bufPtr);
    nread = ChanRead(chanPtr, InsertPoint(bufPtr), toRead);

    if (nread < 0) {
	result = Tcl_GetErrno();

	}
	ResetFlag(statePtr, CHANNEL_NONBLOCKING);
	if (GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	}
    }

    /*
     * If there is data buffered in statePtr->curOutPtr then mark the channel
     * as ready to flush before invoking FlushChannel.
     */

    if ((statePtr->curOutPtr != NULL) && IsBufferReady(statePtr->curOutPtr)) {
	SetFlag(statePtr, BUFFER_READY);
    }

    /*
     * If the flush fails we cannot recover the original position. In that
     * case the seek is not attempted because we do not know where the access
     * position is - instead we return the error. FlushChannel has already
     * called Tcl_SetErrno() to report the error upwards. If the flush
     * succeeds we do the seek also.
     */

	if (GotFlag(statePtr, CHANNEL_EOF)
		&& (bufPtr == NULL || IsBufferEmpty(bufPtr))) {
	    break;
	}

	/* If there is no full buffer, attempt to create and/or fill one. */

	while (bufPtr == NULL || !IsBufferFull(bufPtr)) {
	    int code;

	moreData:
	    code = GetInput(chanPtr);
	    bufPtr = statePtr->inQueueHead;

	    assert (bufPtr != NULL);

#define ChanFlag(chr,bit) (buf[i++] = ((flags & (bit)) ? (chr) : '_'))

    ChanFlag('r', TCL_READABLE);
    ChanFlag('w', TCL_WRITABLE);
    ChanFlag('n', CHANNEL_NONBLOCKING);
    ChanFlag('l', CHANNEL_LINEBUFFERED);
    ChanFlag('u', CHANNEL_UNBUFFERED);
    ChanFlag('R', BUFFER_READY);
    ChanFlag('F', BG_FLUSH_SCHEDULED);
    ChanFlag('c', CHANNEL_CLOSED);
    ChanFlag('E', CHANNEL_EOF);
    ChanFlag('S', CHANNEL_STICKY_EOF);
    ChanFlag('B', CHANNEL_BLOCKED);
    ChanFlag('/', INPUT_SAW_CR);
    ChanFlag('D', CHANNEL_DEAD);

#define CHANNEL_NONBLOCKING	(1<<3)	/* Channel is currently in nonblocking
					 * mode. */
#define CHANNEL_LINEBUFFERED	(1<<4)	/* Output to the channel must be
					 * flushed after every newline. */
#define CHANNEL_UNBUFFERED	(1<<5)	/* Output to the channel must always
					 * be flushed immediately. */
#define BUFFER_READY		(1<<6)	/* Current output buffer (the
					 * curOutPtr field in the channel
					 * structure) should be output as soon
					 * as possible even though it may not
					 * be full. */
#define BG_FLUSH_SCHEDULED	(1<<7)	/* A background flush of the queued
					 * output buffers has been
					 * scheduled. */
#define CHANNEL_CLOSED		(1<<8)	/* Channel has been closed. No further
					 * Tcl-level IO on the channel is
					 * allowed. */
#define CHANNEL_EOF		(1<<9)	/* EOF occurred on this channel. This

    set r
} "hello\nbye\nstrange\n"
test io-29.34 {Tcl_Close, async flush on close, using sockets} {socket tempNotMac fileevent} {
    variable c 0
    variable x running
    set l abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz
    proc writelots {s l} {
	for {set i 0} {$i < 2000} {incr i} {
	    puts $s $l
	}
    }
    proc accept {s a p} {
	variable x
	fileevent $s readable [namespace code [list readit $s]]
	fconfigure $s -blocking off

    vwait [namespace which -variable x]
    fconfigure $cs -blocking off
    writelots $cs $l
    close $cs
    close $ss
    vwait [namespace which -variable x]
    set c
} 2000
test io-29.35 {Tcl_Close vs fileevent vs multiple interpreters} {socket tempNotMac fileevent} {
    # On Mac, this test screws up sockets such that subsequent tests using port 2828
    # either cause errors or panic().

    catch {interp delete x}
    catch {interp delete y}
    interp create x