tclio.c

来自「tcl是工具命令语言」· C语言 代码 · 共 2,110 行 · 第 1/5 页

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

int
Tcl_GetChannelMode(chan)
    Tcl_Channel chan;		/* The channel for which the mode is
                                 * being computed. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
					/* State of actual channel. */

    return (statePtr->flags & (TCL_READABLE | TCL_WRITABLE));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelName --
 *
 *	Returns the string identifying the channel name.
 *
 * Results:
 *	The string containing the channel name. This memory is
 *	owned by the generic layer and should not be modified by
 *	the caller.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

CONST char *
Tcl_GetChannelName(chan)
    Tcl_Channel chan;		/* The channel for which to return the name. */
{
    ChannelState *statePtr;	/* State of actual channel. */

    statePtr = ((Channel *) chan)->state;
    return statePtr->channelName;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelHandle --
 *
 *	Returns an OS handle associated with a channel.
 *
 * Results:
 *	Returns TCL_OK and places the handle in handlePtr, or returns
 *	TCL_ERROR on failure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetChannelHandle(chan, direction, handlePtr)
    Tcl_Channel chan;		/* The channel to get file from. */
    int direction;		/* TCL_WRITABLE or TCL_READABLE. */
    ClientData *handlePtr;	/* Where to store handle */
{
    Channel *chanPtr;		/* The actual channel. */
    ClientData handle;
    int result;

    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    result = (chanPtr->typePtr->getHandleProc)(chanPtr->instanceData,
	    direction, &handle);
    if (handlePtr) {
	*handlePtr = handle;
    }
    return result;
}

/*
 *---------------------------------------------------------------------------
 *
 * AllocChannelBuffer --
 *
 *	A channel buffer has BUFFER_PADDING bytes extra at beginning to
 *	hold any bytes of a native-encoding character that got split by
 *	the end of the previous buffer and need to be moved to the
 *	beginning of the next buffer to make a contiguous string so it
 *	can be converted to UTF-8.
 *
 *	A channel buffer has BUFFER_PADDING bytes extra at the end to
 *	hold any bytes of a native-encoding character (generated from a
 *	UTF-8 character) that overflow past the end of the buffer and
 *	need to be moved to the next buffer.
 *
 * Results:
 *	A newly allocated channel buffer.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static ChannelBuffer *
AllocChannelBuffer(length)
    int length;			/* Desired length of channel buffer. */
{
    ChannelBuffer *bufPtr;
    int n;

    n = length + CHANNELBUFFER_HEADER_SIZE + BUFFER_PADDING + BUFFER_PADDING;
    bufPtr = (ChannelBuffer *) ckalloc((unsigned) n);
    bufPtr->nextAdded	= BUFFER_PADDING;
    bufPtr->nextRemoved	= BUFFER_PADDING;
    bufPtr->bufLength	= length + BUFFER_PADDING;
    bufPtr->nextPtr	= (ChannelBuffer *) NULL;
    return bufPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * RecycleBuffer --
 *
 *	Helper function to recycle input and output buffers. Ensures
 *	that two input buffers are saved (one in the input queue and
 *	another in the saveInBufPtr field) and that curOutPtr is set
 *	to a buffer. Only if these conditions are met is the buffer
 *	freed to the OS.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May free a buffer to the OS.
 *
 *----------------------------------------------------------------------
 */

static void
RecycleBuffer(statePtr, bufPtr, mustDiscard)
    ChannelState *statePtr;	/* ChannelState in which to recycle buffers. */
    ChannelBuffer *bufPtr;	/* The buffer to recycle. */
    int mustDiscard;		/* If nonzero, free the buffer to the
                                 * OS, always. */
{
    /*
     * Do we have to free the buffer to the OS?
     */

    if (mustDiscard) {
        ckfree((char *) bufPtr);
        return;
    }

    /*
     * Only save buffers which are at least as big as the requested
     * buffersize for the channel. This is to honor dynamic changes
     * of the buffersize made by the user.
     */

    if ((bufPtr->bufLength - BUFFER_PADDING) < statePtr->bufSize) {
        ckfree((char *) bufPtr);
        return;
    }

    /*
     * Only save buffers for the input queue if the channel is readable.
     */
    
    if (statePtr->flags & TCL_READABLE) {
        if (statePtr->inQueueHead == (ChannelBuffer *) NULL) {
            statePtr->inQueueHead = bufPtr;
            statePtr->inQueueTail = bufPtr;
            goto keepit;
        }
        if (statePtr->saveInBufPtr == (ChannelBuffer *) NULL) {
            statePtr->saveInBufPtr = bufPtr;
            goto keepit;
        }
    }

    /*
     * Only save buffers for the output queue if the channel is writable.
     */

    if (statePtr->flags & TCL_WRITABLE) {
        if (statePtr->curOutPtr == (ChannelBuffer *) NULL) {
            statePtr->curOutPtr = bufPtr;
            goto keepit;
        }
    }

    /*
     * If we reached this code we return the buffer to the OS.
     */

    ckfree((char *) bufPtr);
    return;

    keepit:
    bufPtr->nextRemoved = BUFFER_PADDING;
    bufPtr->nextAdded = BUFFER_PADDING;
    bufPtr->nextPtr = (ChannelBuffer *) NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * DiscardOutputQueued --
 *
 *	Discards all output queued in the output queue of a channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Recycles buffers.
 *
 *----------------------------------------------------------------------
 */

static void
DiscardOutputQueued(statePtr)
    ChannelState *statePtr;	/* ChannelState for which to discard output. */
{
    ChannelBuffer *bufPtr;
    
    while (statePtr->outQueueHead != (ChannelBuffer *) NULL) {
        bufPtr = statePtr->outQueueHead;
        statePtr->outQueueHead = bufPtr->nextPtr;
        RecycleBuffer(statePtr, bufPtr, 0);
    }
    statePtr->outQueueHead = (ChannelBuffer *) NULL;
    statePtr->outQueueTail = (ChannelBuffer *) NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CheckForDeadChannel --
 *
 *	This function checks is a given channel is Dead.
 *      (A channel that has been closed but not yet deallocated.)
 *
 * Results:
 *	True (1) if channel is Dead, False (0) if channel is Ok
 *
 * Side effects:
 *      None
 *
 *----------------------------------------------------------------------
 */

static int
CheckForDeadChannel(interp, statePtr)
    Tcl_Interp *interp;		/* For error reporting (can be NULL) */
    ChannelState *statePtr;	/* The channel state to check. */
{
    if (statePtr->flags & CHANNEL_DEAD) {
        Tcl_SetErrno(EINVAL);
	if (interp) {
	    Tcl_AppendResult(interp,
		    "unable to access channel: invalid channel",
		    (char *) NULL);   
	}
	return 1;
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * FlushChannel --
 *
 *	This function flushes as much of the queued output as is possible
 *	now. If calledFromAsyncFlush is nonzero, it is being called in an
 *	event handler to flush channel output asynchronously.
 *
 * Results:
 *	0 if successful, else the error code that was returned by the
 *	channel type operation.
 *
 * Side effects:
 *	May produce output on a channel. May block indefinitely if the
 *	channel is synchronous. May schedule an async flush on the channel.
 *	May recycle memory for buffers in the output queue.
 *
 *----------------------------------------------------------------------
 */

static int
FlushChannel(interp, chanPtr, calledFromAsyncFlush)
    Tcl_Interp *interp;			/* For error reporting during close. */
    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 != (ChannelBuffer *) NULL) &&
                (statePtr->curOutPtr->nextAdded == statePtr->curOutPtr->bufLength))
                || ((statePtr->flags & BUFFER_READY) &&
                        (statePtr->outQueueHead == (ChannelBuffer *) NULL))) {
            statePtr->flags &= (~(BUFFER_READY));
            statePtr->curOutPtr->nextPtr = (ChannelBuffer *) NULL;
            if (statePtr->outQueueHead == (ChannelBuffer *) NULL) {
                statePtr->outQueueHead = statePtr->curOutPtr;
            } else {
                statePtr->outQueueTail->nextPtr = statePtr->curOutPtr;
            }
            statePtr->outQueueTail = statePtr->curOutPtr;
            statePtr->curOutPtr = (ChannelBuffer *) 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) &&
                (statePtr->flags & BG_FLUSH_SCHEDULED)) {
            return 0;
        }

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

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

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

        toWrite = bufPtr->nextAdded - bufPtr->nextRemoved;
        written = (chanPtr->typePtr->outputProc) (chanPtr->instanceData,
                bufPtr->buf + bufPtr->nextRemoved, 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.
         */

        if (written < 0) {
            
            /*
             * If the last attempt to write was interrupted, simply retry.
             */
            
            if (errorCode == EINTR) {
                errorCode = 0;
                continue;
            }

            /*
             * If the channel is non-blocking and we would have blocked,
             * start a background flushing handler and break out of the loop.
             */

            if ((errorCode == EWOULDBLOCK) || (errorCode == EAGAIN)) {
		/*
		 * This used to check for CHANNEL_NONBLOCKING, and panic
		 * if the channel was blocking.  However, it appears
		 * that setting stdin to -blocking 0 has some effect on
		 * the stdout when it's a tty channel (dup'ed underneath)
		 */
		if (!(statePtr->flags & BG_FLUSH_SCHEDULED)) {
		    statePtr->flags |= BG_FLUSH_SCHEDULED;
		    UpdateInterest(chanPtr);
		}
		errorCode = 0;
		break;
            }

            /*
             * Decide whether to report the error upwards or defer it.
             */

            if (calledFromAsyncFlush) {
                if (statePtr->unreportedError =