path: root/win/tclWinSerial.c

/*
 * tclWinSerial.c --
 *
 *	This file implements the Windows-specific serial port functions, and
 *	the "serial" channel driver.
 *
 * Copyright (c) 1999 by Scriptics Corp.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * Serial functionality implemented by Rolf.Schroedter@dlr.de
 */

#include "tclWinInt.h"

/*
 * The following variable is used to tell whether this module has been
 * initialized.
 */

static int initialized = 0;

/*
 * The serialMutex locks around access to the initialized variable, and it is
 * used to protect background threads from being terminated while they are
 * using APIs that hold locks.
 */

TCL_DECLARE_MUTEX(serialMutex)

/*
 * Bit masks used in the flags field of the SerialInfo structure below.
 */

#define SERIAL_PENDING	(1<<0)	/* Message is pending in the queue. */
#define SERIAL_ASYNC	(1<<1)	/* Channel is non-blocking. */

/*
 * Bit masks used in the sharedFlags field of the SerialInfo structure below.
 */

#define SERIAL_EOF	(1<<2)	/* Serial has reached EOF. */
#define SERIAL_ERROR	(1<<4)

/*
 * Default time to block between checking status on the serial port.
 */

#define SERIAL_DEFAULT_BLOCKTIME 10	/* 10 msec */

/*
 * Define Win32 read/write error masks returned by ClearCommError()
 */

#define SERIAL_READ_ERRORS \
	(CE_RXOVER | CE_OVERRUN | CE_RXPARITY | CE_FRAME  | CE_BREAK)
#define SERIAL_WRITE_ERRORS \
	(CE_TXFULL | CE_PTO)

/*
 * This structure describes per-instance data for a serial based channel.
 */

typedef struct SerialInfo {
    HANDLE handle;
    struct SerialInfo *nextPtr;	/* Pointer to next registered serial. */
    Tcl_Channel channel;	/* Pointer to channel structure. */
    int validMask;		/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which operations are valid on the file. */
    int watchMask;		/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which events should be reported. */
    int flags;			/* State flags, see above for a list. */
    int readable;		/* Flag that the channel is readable. */
    int writable;		/* Flag that the channel is writable. */
    int blockTime;		/* Maximum blocktime in msec. */
    unsigned int lastEventTime;	/* Time in milliseconds since last readable
				 * event. */
				/* Next readable event only after blockTime */
    DWORD error;		/* pending error code returned by
				 * ClearCommError() */
    DWORD lastError;		/* last error code, can be fetched with
				 * fconfigure chan -lasterror */
    DWORD sysBufRead;		/* Win32 system buffer size for read ops,
				 * default=4096 */
    DWORD sysBufWrite;		/* Win32 system buffer size for write ops,
				 * default=4096 */

    Tcl_ThreadId threadId;	/* Thread to which events should be reported.
				 * This value is used by the reader/writer
				 * threads. */
    OVERLAPPED osRead;		/* OVERLAPPED structure for read operations. */
    OVERLAPPED osWrite;		/* OVERLAPPED structure for write operations */
    HANDLE writeThread;		/* Handle to writer thread. */
    CRITICAL_SECTION csWrite;	/* Writer thread synchronisation. */
    HANDLE evWritable;		/* Manual-reset event to signal when the
				 * writer thread has finished waiting for the
				 * current buffer to be written. */
    HANDLE evStartWriter;	/* Auto-reset event used by the main thread to
				 * signal when the writer thread should
				 * attempt to write to the serial. */
    HANDLE evStopWriter;	/* Auto-reset event used by the main thread to
				 * signal when the writer thread should close.
				 */
    DWORD writeError;		/* An error caused by the last background
				 * write. Set to 0 if no error has been
				 * detected. This word is shared with the
				 * writer thread so access must be
				 * synchronized with the evWritable object. */
    char *writeBuf;		/* Current background output buffer. Access is
				 * synchronized with the evWritable object. */
    int writeBufLen;		/* Size of write buffer. Access is
				 * synchronized with the evWritable object. */
    int toWrite;		/* Current amount to be written. Access is
				 * synchronized with the evWritable object. */
    int writeQueue;		/* Number of bytes pending in output queue.
				 * Offset to DCB.cbInQue. Used to query
				 * [fconfigure -queue] */
} SerialInfo;

typedef struct ThreadSpecificData {
    /*
     * The following pointer refers to the head of the list of serials that
     * are being watched for file events.
     */

    SerialInfo *firstSerialPtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * The following structure is what is added to the Tcl event queue when serial
 * events are generated.
 */

typedef struct SerialEvent {
    Tcl_Event header;		/* Information that is standard for all
				 * events. */
    SerialInfo *infoPtr;	/* Pointer to serial info structure. Note that
				 * we still have to verify that the serial
				 * exists before dereferencing this
				 * pointer. */
} SerialEvent;

/*
 * We don't use timeouts.
 */

static COMMTIMEOUTS no_timeout = {
    0,			/* ReadIntervalTimeout */
    0,			/* ReadTotalTimeoutMultiplier */
    0,			/* ReadTotalTimeoutConstant */
    0,			/* WriteTotalTimeoutMultiplier */
    0,			/* WriteTotalTimeoutConstant */
};

/*
 * Declarations for functions used only in this file.
 */

static int		SerialBlockProc(ClientData instanceData, int mode);
static void		SerialCheckProc(ClientData clientData, int flags);
static int		SerialCloseProc(ClientData instanceData,
			    Tcl_Interp *interp);
static int		SerialEventProc(Tcl_Event *evPtr, int flags);
static void		SerialExitHandler(ClientData clientData);
static int		SerialGetHandleProc(ClientData instanceData,
			    int direction, ClientData *handlePtr);
static ThreadSpecificData *SerialInit(void);
static int		SerialInputProc(ClientData instanceData, char *buf,
			    int toRead, int *errorCode);
static int		SerialOutputProc(ClientData instanceData,
			    const char *buf, int toWrite, int *errorCode);
static void		SerialSetupProc(ClientData clientData, int flags);
static void		SerialWatchProc(ClientData instanceData, int mask);
static void		ProcExitHandler(ClientData clientData);
static int		SerialGetOptionProc(ClientData instanceData,
			    Tcl_Interp *interp, const char *optionName,
			    Tcl_DString *dsPtr);
static int		SerialSetOptionProc(ClientData instanceData,
			    Tcl_Interp *interp, const char *optionName,
			    const char *value);
static DWORD WINAPI	SerialWriterThread(LPVOID arg);
static void		SerialThreadActionProc(ClientData instanceData,
			    int action);
static int		SerialBlockingRead(SerialInfo *infoPtr, LPVOID buf,
			    DWORD bufSize, LPDWORD lpRead, LPOVERLAPPED osPtr);
static int		SerialBlockingWrite(SerialInfo *infoPtr, LPVOID buf,
			    DWORD bufSize, LPDWORD lpWritten,
			    LPOVERLAPPED osPtr);

/*
 * This structure describes the channel type structure for command serial
 * based IO.
 */

static const Tcl_ChannelType serialChannelType = {
    "serial",			/* Type name. */
    TCL_CHANNEL_VERSION_5,	/* v5 channel */
    SerialCloseProc,		/* Close proc. */
    SerialInputProc,		/* Input proc. */
    SerialOutputProc,		/* Output proc. */
    NULL,			/* Seek proc. */
    SerialSetOptionProc,	/* Set option proc. */
    SerialGetOptionProc,	/* Get option proc. */
    SerialWatchProc,		/* Set up notifier to watch the channel. */
    SerialGetHandleProc,	/* Get an OS handle from channel. */
    NULL,			/* close2proc. */
    SerialBlockProc,		/* Set blocking or non-blocking mode.*/
    NULL,			/* flush proc. */
    NULL,			/* handler proc. */
    NULL,			/* wide seek proc */
    SerialThreadActionProc,	/* thread action proc */
    NULL                       /* truncate */
};

/*
 *----------------------------------------------------------------------
 *
 * SerialInit --
 *
 *	This function initializes the static variables for this file.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new event source.
 *
 *----------------------------------------------------------------------
 */

static ThreadSpecificData *
SerialInit(void)
{
    ThreadSpecificData *tsdPtr;

    /*
     * Check the initialized flag first, then check it again in the mutex.
     * This is a speed enhancement.
     */

    if (!initialized) {
	Tcl_MutexLock(&serialMutex);
	if (!initialized) {
	    initialized = 1;
	    Tcl_CreateExitHandler(ProcExitHandler, NULL);
	}
	Tcl_MutexUnlock(&serialMutex);
    }

    tsdPtr = (ThreadSpecificData *) TclThreadDataKeyGet(&dataKey);
    if (tsdPtr == NULL) {
	tsdPtr = TCL_TSD_INIT(&dataKey);
	tsdPtr->firstSerialPtr = NULL;
	Tcl_CreateEventSource(SerialSetupProc, SerialCheckProc, NULL);
	Tcl_CreateThreadExitHandler(SerialExitHandler, NULL);
    }
    return tsdPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialExitHandler --
 *
 *	This function is called to cleanup the serial module before Tcl is
 *	unloaded.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Removes the serial event source.
 *
 *----------------------------------------------------------------------
 */

static void
SerialExitHandler(
    ClientData clientData)	/* Old window proc */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    SerialInfo *infoPtr;

    /*
     * Clear all eventually pending output. Otherwise Tcl's exit could totally
     * block, because it performs a blocking flush on all open channels. Note
     * that serial write operations may be blocked due to handshake.
     */

    for (infoPtr = tsdPtr->firstSerialPtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	PurgeComm(infoPtr->handle,
		PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
    }
    Tcl_DeleteEventSource(SerialSetupProc, SerialCheckProc, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * ProcExitHandler --
 *
 *	This function is called to cleanup the process list before Tcl is
 *	unloaded.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Resets the process list.
 *
 *----------------------------------------------------------------------
 */

static void
ProcExitHandler(
    ClientData clientData)	/* Old window proc */
{
    Tcl_MutexLock(&serialMutex);
    initialized = 0;
    Tcl_MutexUnlock(&serialMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * SerialBlockTime --
 *
 *	Wrapper to set Tcl's block time in msec
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Updates the maximum blocking time.
 *
 *----------------------------------------------------------------------
 */

static void
SerialBlockTime(
    int msec)			/* milli-seconds */
{
    Tcl_Time blockTime;

    blockTime.sec  =  msec / 1000;
    blockTime.usec = (msec % 1000) * 1000;
    Tcl_SetMaxBlockTime(&blockTime);
}

/*
 *----------------------------------------------------------------------
 *
 * SerialGetMilliseconds --
 *
 *	Get current time in milliseconds,ignoring integer overruns.
 *
 * Results:
 *	The current time.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static unsigned int
SerialGetMilliseconds(void)
{
    Tcl_Time time;

    Tcl_GetTime(&time);

    return (time.sec * 1000 + time.usec / 1000);
}

/*
 *----------------------------------------------------------------------
 *
 * SerialSetupProc --
 *
 *	This procedure is invoked before Tcl_DoOneEvent blocks waiting for an
 *	event.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

void
SerialSetupProc(
    ClientData data,		/* Not used. */
    int flags)			/* Event flags as passed to Tcl_DoOneEvent. */
{
    SerialInfo *infoPtr;
    int block = 1;
    int msec = INT_MAX;		/* min. found block time */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

    /*
     * Look to see if any events handlers installed. If they are, do not
     * block.
     */

    for (infoPtr=tsdPtr->firstSerialPtr ; infoPtr!=NULL ;
	    infoPtr=infoPtr->nextPtr) {
	if (infoPtr->watchMask & TCL_WRITABLE) {
	    if (WaitForSingleObject(infoPtr->evWritable, 0) != WAIT_TIMEOUT) {
		block = 0;
		msec = min(msec, infoPtr->blockTime);
	    }
	}
	if (infoPtr->watchMask & TCL_READABLE) {
	    block = 0;
	    msec = min(msec, infoPtr->blockTime);
	}
    }

    if (!block) {
	SerialBlockTime(msec);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SerialCheckProc --
 *
 *	This procedure is called by Tcl_DoOneEvent to check the serial event
 *	source for events.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May queue an event.
 *
 *----------------------------------------------------------------------
 */

static void
SerialCheckProc(
    ClientData data,		/* Not used. */
    int flags)			/* Event flags as passed to Tcl_DoOneEvent. */
{
    SerialInfo *infoPtr;
    SerialEvent *evPtr;
    int needEvent;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    COMSTAT cStat;
    unsigned int time;

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

    /*
     * Queue events for any ready serials that don't already have events
     * queued.
     */

    for (infoPtr=tsdPtr->firstSerialPtr ; infoPtr!=NULL ;
	    infoPtr=infoPtr->nextPtr) {
	if (infoPtr->flags & SERIAL_PENDING) {
	    continue;
	}

	needEvent = 0;

	/*
	 * If WRITABLE watch mask is set look for infoPtr->evWritable object.
	 */

	if (infoPtr->watchMask & TCL_WRITABLE &&
		WaitForSingleObject(infoPtr->evWritable, 0) != WAIT_TIMEOUT) {
	    infoPtr->writable = 1;
	    needEvent = 1;
	}

	/*
	 * If READABLE watch mask is set call ClearCommError to poll cbInQue.
	 * Window errors are ignored here.
	 */

	if (infoPtr->watchMask & TCL_READABLE) {
	    if (ClearCommError(infoPtr->handle, &infoPtr->error, &cStat)) {
		/*
		 * Look for characters already pending in windows queue. If
		 * they are, poll.
		 */

		if (infoPtr->watchMask & TCL_READABLE) {
		    /*
		     * Force fileevent after serial read error.
		     */

		    if ((cStat.cbInQue > 0) ||
			    (infoPtr->error & SERIAL_READ_ERRORS)) {
			infoPtr->readable = 1;
			time = SerialGetMilliseconds();
			if ((unsigned int) (time - infoPtr->lastEventTime)
				>= (unsigned int) infoPtr->blockTime) {
			    needEvent = 1;
			    infoPtr->lastEventTime = time;
			}
		    }
		}
	    }
	}

	/*
	 * Queue an event if the serial is signaled for reading or writing.
	 */

	if (needEvent) {
	    infoPtr->flags |= SERIAL_PENDING;
	    evPtr = ckalloc(sizeof(SerialEvent));
	    evPtr->header.proc = SerialEventProc;
	    evPtr->infoPtr = infoPtr;
	    Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SerialBlockProc --
 *
 *	Set blocking or non-blocking mode on channel.
 *
 * Results:
 *	0 if successful, errno when failed.
 *
 * Side effects:
 *	Sets the device into blocking or non-blocking mode.
 *
 *----------------------------------------------------------------------
 */

static int
SerialBlockProc(
    ClientData instanceData,    /* Instance data for channel. */
    int mode)			/* TCL_MODE_BLOCKING or
				 * TCL_MODE_NONBLOCKING. */
{
    int errorCode = 0;
    SerialInfo *infoPtr = (SerialInfo *) instanceData;

    /*
     * Only serial READ can be switched between blocking & nonblocking using
     * COMMTIMEOUTS. Serial write emulates blocking & nonblocking by the
     * SerialWriterThread.
     */

    if (mode == TCL_MODE_NONBLOCKING) {
	infoPtr->flags |= SERIAL_ASYNC;
    } else {
	infoPtr->flags &= ~(SERIAL_ASYNC);
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialCloseProc --
 *
 *	Closes a serial based IO channel.
 *
 * Results:
 *	0 on success, errno otherwise.
 *
 * Side effects:
 *	Closes the physical channel.
 *
 *----------------------------------------------------------------------
 */

static int
SerialCloseProc(
    ClientData instanceData,    /* Pointer to SerialInfo structure. */
    Tcl_Interp *interp)		/* For error reporting. */
{
    SerialInfo *serialPtr = (SerialInfo *) instanceData;
    int errorCode, result = 0;
    SerialInfo *infoPtr, **nextPtrPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    DWORD exitCode;

    errorCode = 0;

    if (serialPtr->validMask & TCL_READABLE) {
	PurgeComm(serialPtr->handle, PURGE_RXABORT | PURGE_RXCLEAR);
	CloseHandle(serialPtr->osRead.hEvent);
    }
    serialPtr->validMask &= ~TCL_READABLE;

    if (serialPtr->validMask & TCL_WRITABLE) {
	/*
	 * Generally we cannot wait for a pending write operation because it
	 * may hang due to handshake
	 *    WaitForSingleObject(serialPtr->evWritable, INFINITE);
	 */

	/*
	 * The thread may have already closed on it's own. Check it's exit
	 * code.
	 */

	GetExitCodeThread(serialPtr->writeThread, &exitCode);

	if (exitCode == STILL_ACTIVE) {
	    /*
	     * Set the stop event so that if the writer thread is blocked in
	     * SerialWriterThread on WaitForMultipleEvents, it will exit
	     * cleanly.
	     */

	    SetEvent(serialPtr->evStopWriter);

	    /*
	     * Wait at most 20 milliseconds for the writer thread to close.
	     */

	    if (WaitForSingleObject(serialPtr->writeThread,
		    20) == WAIT_TIMEOUT) {
		/*
		 * Forcibly terminate the background thread as a last resort.
		 * Note that we need to guard against terminating the thread
		 * while it is in the middle of Tcl_ThreadAlert because it
		 * won't be able to release the notifier lock.
		 */

		Tcl_MutexLock(&serialMutex);

		/* BUG: this leaks memory */
		TerminateThread(serialPtr->writeThread, 0);

		Tcl_MutexUnlock(&serialMutex);
	    }
	}

	CloseHandle(serialPtr->writeThread);
	CloseHandle(serialPtr->osWrite.hEvent);
	CloseHandle(serialPtr->evWritable);
	CloseHandle(serialPtr->evStartWriter);
	CloseHandle(serialPtr->evStopWriter);
	serialPtr->writeThread = NULL;

	PurgeComm(serialPtr->handle, PURGE_TXABORT | PURGE_TXCLEAR);
    }
    serialPtr->validMask &= ~TCL_WRITABLE;

    DeleteCriticalSection(&serialPtr->csWrite);

    /*
     * Don't close the Win32 handle if the handle is a standard channel during
     * the thread exit process. Otherwise, one thread may kill the stdio of
     * another.
     */

    if (!TclInThreadExit()
	    || ((GetStdHandle(STD_INPUT_HANDLE) != serialPtr->handle)
	    && (GetStdHandle(STD_OUTPUT_HANDLE) != serialPtr->handle)
	    && (GetStdHandle(STD_ERROR_HANDLE) != serialPtr->handle))) {
	if (CloseHandle(serialPtr->handle) == FALSE) {
	    TclWinConvertError(GetLastError());
	    errorCode = errno;
	}
    }

    serialPtr->watchMask &= serialPtr->validMask;

    /*
     * Remove the file from the list of watched files.
     */

    for (nextPtrPtr=&(tsdPtr->firstSerialPtr), infoPtr=*nextPtrPtr;
	    infoPtr!=NULL;
	    nextPtrPtr=&infoPtr->nextPtr, infoPtr=*nextPtrPtr) {
	if (infoPtr == (SerialInfo *)serialPtr) {
	    *nextPtrPtr = infoPtr->nextPtr;
	    break;
	}
    }

    /*
     * Wrap the error file into a channel and give it to the cleanup routine.
     */

    if (serialPtr->writeBuf != NULL) {
	ckfree(serialPtr->writeBuf);
	serialPtr->writeBuf = NULL;
    }
    ckfree(serialPtr);

    if (errorCode == 0) {
	return result;
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialBlockingRead --
 *
 *	Perform a blocking read into the buffer given. Returns count of how
 *	many bytes were actually read, and an error indication.
 *
 * Results:
 *	A count of how many bytes were read is returned and an error
 *	indication is returned.
 *
 * Side effects:
 *	Reads input from the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
SerialBlockingRead(
    SerialInfo *infoPtr,	/* Serial info structure */
    LPVOID buf,			/* The input buffer pointer */
    DWORD bufSize,		/* The number of bytes to read */
    LPDWORD lpRead,		/* Returns number of bytes read */
    LPOVERLAPPED osPtr)		/* OVERLAPPED structure */
{
    /*
     *  Perform overlapped blocking read.
     *  1. Reset the overlapped event
     *  2. Start overlapped read operation
     *  3. Wait for completion
     */

    /*
     * Set Offset to ZERO, otherwise NT4.0 may report an error.
     */

    osPtr->Offset = osPtr->OffsetHigh = 0;
    ResetEvent(osPtr->hEvent);
    if (!ReadFile(infoPtr->handle, buf, bufSize, lpRead, osPtr)) {
	if (GetLastError() != ERROR_IO_PENDING) {
	    /*
	     * ReadFile failed, but it isn't delayed. Report error.
	     */

	    return FALSE;
	} else {
	    /*
	     * Read is pending, wait for completion, timeout?
	     */

	    if (!GetOverlappedResult(infoPtr->handle, osPtr, lpRead, TRUE)) {
		return FALSE;
	    }
	}
    } else {
	/*
	 * ReadFile completed immediately.
	 */
    }
    return TRUE;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialBlockingWrite --
 *
 *	Perform a blocking write from the buffer given. Returns count of how
 *	many bytes were actually written, and an error indication.
 *
 * Results:
 *	A count of how many bytes were written is returned and an error
 *	indication is returned.
 *
 * Side effects:
 *	Writes output to the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
SerialBlockingWrite(
    SerialInfo *infoPtr,	/* Serial info structure */
    LPVOID buf,			/* The output buffer pointer */
    DWORD bufSize,		/* The number of bytes to write */
    LPDWORD lpWritten,		/* Returns number of bytes written */
    LPOVERLAPPED osPtr)		/* OVERLAPPED structure */
{
    int result;

    /*
     * Perform overlapped blocking write.
     *  1. Reset the overlapped event
     *  2. Remove these bytes from the output queue counter
     *  3. Start overlapped write operation
     *  3. Remove these bytes from the output queue counter
     *  4. Wait for completion
     *  5. Adjust the output queue counter
     */

    ResetEvent(osPtr->hEvent);

    EnterCriticalSection(&infoPtr->csWrite);
    infoPtr->writeQueue -= bufSize;

    /*
     * Set Offset to ZERO, otherwise NT4.0 may report an error
     */

    osPtr->Offset = osPtr->OffsetHigh = 0;
    result = WriteFile(infoPtr->handle, buf, bufSize, lpWritten, osPtr);
    LeaveCriticalSection(&infoPtr->csWrite);

    if (result == FALSE) {
	int err = GetLastError();

	switch (err) {
	case ERROR_IO_PENDING:
	    /*
	     * Write is pending, wait for completion.
	     */

	    if (!GetOverlappedResult(infoPtr->handle, osPtr, lpWritten,
		    TRUE)) {
		return FALSE;
	    }
	    break;
	case ERROR_COUNTER_TIMEOUT:
	    /*
	     * Write timeout handled in SerialOutputProc.
	     */

	    break;
	default:
	    /*
	     * WriteFile failed, but it isn't delayed. Report error.
	     */

	    return FALSE;
	}
    } else {
	/*
	 * WriteFile completed immediately.
	 */
    }

    EnterCriticalSection(&infoPtr->csWrite);
    infoPtr->writeQueue += (*lpWritten - bufSize);
    LeaveCriticalSection(&infoPtr->csWrite);

    return TRUE;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialInputProc --
 *
 *	Reads input from the IO channel into the buffer given. Returns count
 *	of how many bytes were actually read, and an error indication.
 *
 * Results:
 *	A count of how many bytes were read is returned and an error
 *	indication is returned in an output argument.
 *
 * Side effects:
 *	Reads input from the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
SerialInputProc(
    ClientData instanceData,	/* Serial state. */
    char *buf,			/* Where to store data read. */
    int bufSize,		/* How much space is available in the
				 * buffer? */
    int *errorCode)		/* Where to store error code. */
{
    SerialInfo *infoPtr = (SerialInfo *) instanceData;
    DWORD bytesRead = 0;
    COMSTAT cStat;

    *errorCode = 0;

    /*
     * Check if there is a CommError pending from SerialCheckProc
     */

    if (infoPtr->error & SERIAL_READ_ERRORS) {
	goto commError;
    }

    /*
     * Look for characters already pending in windows queue. This is the
     * mainly restored good old code from Tcl8.0
     */

    if (ClearCommError(infoPtr->handle, &infoPtr->error, &cStat)) {
	/*
	 * Check for errors here, but not in the evSetup/Check procedures.
	 */

	if (infoPtr->error & SERIAL_READ_ERRORS) {
	    goto commError;
	}
	if (infoPtr->flags & SERIAL_ASYNC) {
	    /*
	     * NON_BLOCKING mode: Avoid blocking by reading more bytes than
	     * available in input buffer.
	     */

	    if (cStat.cbInQue > 0) {
		if ((DWORD) bufSize > cStat.cbInQue) {
		    bufSize = cStat.cbInQue;
		}
	    } else {
		errno = *errorCode = EAGAIN;
		return -1;
	    }
	} else {
	    /*
	     * BLOCKING mode: Tcl trys to read a full buffer of 4 kBytes here.
	     */

	    if (cStat.cbInQue > 0) {
		if ((DWORD) bufSize > cStat.cbInQue) {
		    bufSize = cStat.cbInQue;
		}
	    } else {
		bufSize = 1;
	    }
	}
    }

    if (bufSize == 0) {
	return bytesRead = 0;
    }

    /*
     * Perform blocking read. Doesn't block in non-blocking mode, because we
     * checked the number of available bytes.
     */

    if (SerialBlockingRead(infoPtr, (LPVOID) buf, (DWORD) bufSize, &bytesRead,
	    &infoPtr->osRead) == FALSE) {
	TclWinConvertError(GetLastError());
	*errorCode = errno;
	return -1;
    }
    return bytesRead;

  commError:
    infoPtr->lastError = infoPtr->error;
				/* save last error code */
    infoPtr->error = 0;		/* reset error code */
    *errorCode = EIO;		/* to return read-error only once */
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialOutputProc --
 *
 *	Writes the given output on the IO channel. Returns count of how many
 *	characters were actually written, and an error indication.
 *
 * Results:
 *	A count of how many characters were written is returned and an error
 *	indication is returned in an output argument.
 *
 * Side effects:
 *	Writes output on the actual channel.
 *
 *----------------------------------------------------------------------
 */

static int
SerialOutputProc(
    ClientData instanceData,	/* Serial state. */
    const char *buf,		/* The data buffer. */
    int toWrite,		/* How many bytes to write? */
    int *errorCode)		/* Where to store error code. */
{
    SerialInfo *infoPtr = (SerialInfo *) instanceData;
    DWORD bytesWritten, timeout;

    *errorCode = 0;

    /*
     * At EXIT Tcl trys to flush all open channels in blocking mode. We avoid
     * blocking output after ExitProc or CloseHandler(chan) has been called by
     * checking the corrresponding variables.
     */

    if (!initialized || TclInExit()) {
	return toWrite;
    }

    /*
     * Check if there is a CommError pending from SerialCheckProc
     */

    if (infoPtr->error & SERIAL_WRITE_ERRORS) {
	infoPtr->lastError = infoPtr->error;
				/* save last error code */
	infoPtr->error = 0;	/* reset error code */
	errno = EIO;
	goto error;
    }

    timeout = (infoPtr->flags & SERIAL_ASYNC) ? 0 : INFINITE;
    if (WaitForSingleObject(infoPtr->evWritable, timeout) == WAIT_TIMEOUT) {
	/*
	 * The writer thread is blocked waiting for a write to complete and
	 * the channel is in non-blocking mode.
	 */

	errno = EAGAIN;
	goto error1;
    }

    /*
     * Check for a background error on the last write.
     */

    if (infoPtr->writeError) {
	TclWinConvertError(infoPtr->writeError);
	infoPtr->writeError = 0;
	goto error1;
    }

    /*
     * Remember the number of bytes in output queue
     */

    EnterCriticalSection(&infoPtr->csWrite);
    infoPtr->writeQueue += toWrite;
    LeaveCriticalSection(&infoPtr->csWrite);

    if (infoPtr->flags & SERIAL_ASYNC) {
	/*
	 * The serial is non-blocking, so copy the data into the output buffer
	 * and restart the writer thread.
	 */

	if (toWrite > infoPtr->writeBufLen) {
	    /*
	     * Reallocate the buffer to be large enough to hold the data.
	     */

	    if (infoPtr->writeBuf) {
		ckfree(infoPtr->writeBuf);
	    }
	    infoPtr->writeBufLen = toWrite;
	    infoPtr->writeBuf = ckalloc(toWrite);
	}
	memcpy(infoPtr->writeBuf, buf, (size_t) toWrite);
	infoPtr->toWrite = toWrite;
	ResetEvent(infoPtr->evWritable);
	SetEvent(infoPtr->evStartWriter);
	bytesWritten = (DWORD) toWrite;

    } else {
	/*
	 * In the blocking case, just try to write the buffer directly. This
	 * avoids an unnecessary copy.
	 */

	if (!SerialBlockingWrite(infoPtr, (LPVOID) buf, (DWORD) toWrite,
		&bytesWritten, &infoPtr->osWrite)) {
	    goto writeError;
	}
	if (bytesWritten != (DWORD) toWrite) {
	    /*
	     * Write timeout.
	     */
	    infoPtr->lastError |= CE_PTO;
	    errno = EIO;
	    goto error;
	}
    }

    return (int) bytesWritten;

  writeError:
    TclWinConvertError(GetLastError());

  error:
    /*
     * Reset the output queue counter on error during blocking output
     */

    /*
     * EnterCriticalSection(&infoPtr->csWrite);
     * infoPtr->writeQueue = 0;
     * LeaveCriticalSection(&infoPtr->csWrite);
     */
  error1:
    *errorCode = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialEventProc --
 *
 *	This function is invoked by Tcl_ServiceEvent when a file event reaches
 *	the front of the event queue. This procedure invokes Tcl_NotifyChannel
 *	on the serial.
 *
 * 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 notifier callback does.
 *
 *----------------------------------------------------------------------
 */

static int
SerialEventProc(
    Tcl_Event *evPtr,		/* Event to service. */
    int flags)			/* Flags that indicate what events to handle,
				 * such as TCL_FILE_EVENTS. */
{
    SerialEvent *serialEvPtr = (SerialEvent *)evPtr;
    SerialInfo *infoPtr;
    int mask;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

    /*
     * Search through the list of watched serials for the one whose handle
     * matches the event. We do this rather than simply dereferencing the
     * handle in the event so that serials can be deleted while the event is
     * in the queue.
     */

    for (infoPtr = tsdPtr->firstSerialPtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (serialEvPtr->infoPtr == infoPtr) {
	    infoPtr->flags &= ~(SERIAL_PENDING);
	    break;
	}
    }

    /*
     * Remove stale events.
     */

    if (!infoPtr) {
	return 1;
    }

    /*
     * Check to see if the serial is readable. Note that we can't tell if a
     * serial is writable, so we always report it as being writable unless we
     * have detected EOF.
     */

    mask = 0;
    if (infoPtr->watchMask & TCL_WRITABLE) {
	if (infoPtr->writable) {
	    mask |= TCL_WRITABLE;
	    infoPtr->writable = 0;
	}
    }

    if (infoPtr->watchMask & TCL_READABLE) {
	if (infoPtr->readable) {
	    mask |= TCL_READABLE;
	    infoPtr->readable = 0;
	}
    }

    /*
     * Inform the channel of the events.
     */

    Tcl_NotifyChannel(infoPtr->channel, infoPtr->watchMask & mask);
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialWatchProc --
 *
 *	Called by the notifier to set up to watch for events on this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
SerialWatchProc(
    ClientData instanceData,	/* Serial state. */
    int mask)			/* What events to watch for, OR-ed combination
				 * of TCL_READABLE, TCL_WRITABLE and
				 * TCL_EXCEPTION. */
{
    SerialInfo **nextPtrPtr, *ptr;
    SerialInfo *infoPtr = (SerialInfo *) instanceData;
    int oldMask = infoPtr->watchMask;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * Since the file is always ready for events, we set the block time so we
     * will poll.
     */

    infoPtr->watchMask = mask & infoPtr->validMask;
    if (infoPtr->watchMask) {
	if (!oldMask) {
	    infoPtr->nextPtr = tsdPtr->firstSerialPtr;
	    tsdPtr->firstSerialPtr = infoPtr;
	}
	SerialBlockTime(infoPtr->blockTime);
    } else if (oldMask) {
	/*
	 * Remove the serial port from the list of watched serial ports.
	 */

	for (nextPtrPtr=&(tsdPtr->firstSerialPtr), ptr=*nextPtrPtr; ptr!=NULL;
		nextPtrPtr=&ptr->nextPtr, ptr=*nextPtrPtr) {
	    if (infoPtr == ptr) {
		*nextPtrPtr = ptr->nextPtr;
		break;
	    }
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SerialGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle to retrieve OS handles from inside a
 *	command serial port based channel.
 *
 * Results:
 *	Returns TCL_OK with the fd in handlePtr, or TCL_ERROR if there is no
 *	handle for the specified direction.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
SerialGetHandleProc(
    ClientData instanceData,	/* The serial state. */
    int direction,		/* TCL_READABLE or TCL_WRITABLE */
    ClientData *handlePtr)	/* Where to store the handle. */
{
    SerialInfo *infoPtr = (SerialInfo *) instanceData;

    *handlePtr = (ClientData) infoPtr->handle;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialWriterThread --
 *
 *	This function runs in a separate thread and writes data onto a serial.
 *
 * Results:
 *	Always returns 0.
 *
 * Side effects:
 *	Signals the main thread when an output operation is completed. May
 *	cause the main thread to wake up by posting a message.
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
SerialWriterThread(
    LPVOID arg)
{
    SerialInfo *infoPtr = (SerialInfo *)arg;
    DWORD bytesWritten, toWrite, waitResult;
    char *buf;
    OVERLAPPED myWrite;		/* Have an own OVERLAPPED in this thread. */
    HANDLE wEvents[2];

    /*
     * The stop event takes precedence by being first in the list.
     */

    wEvents[0] = infoPtr->evStopWriter;
    wEvents[1] = infoPtr->evStartWriter;

    for (;;) {
	/*
	 * Wait for the main thread to signal before attempting to write.
	 */

	waitResult = WaitForMultipleObjects(2, wEvents, FALSE, INFINITE);

	if (waitResult != (WAIT_OBJECT_0 + 1)) {
	    /*
	     * The start event was not signaled. It might be the stop event or
	     * an error, so exit.
	     */

	    break;
	}

	buf = infoPtr->writeBuf;
	toWrite = infoPtr->toWrite;

	myWrite.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

	/*
	 * Loop until all of the bytes are written or an error occurs.
	 */

	while (toWrite > 0) {
	    /*
	     * Check for pending writeError. Ignore all write operations until
	     * the user has been notified.
	     */

	    if (infoPtr->writeError) {
		break;
	    }
	    if (SerialBlockingWrite(infoPtr, (LPVOID) buf, (DWORD) toWrite,
		    &bytesWritten, &myWrite) == FALSE) {
		infoPtr->writeError = GetLastError();
		break;
	    }
	    if (bytesWritten != toWrite) {
		/*
		 * Write timeout.
		 */

		infoPtr->writeError = ERROR_WRITE_FAULT;
		break;
	    }
	    toWrite -= bytesWritten;
	    buf += bytesWritten;
	}

	CloseHandle(myWrite.hEvent);

	/*
	 * Signal the main thread by signalling the evWritable event and then
	 * waking up the notifier thread.
	 */

	SetEvent(infoPtr->evWritable);

	/*
	 * Alert the foreground thread. Note that we need to treat this like a
	 * critical section so the foreground thread does not terminate this
	 * thread while we are holding a mutex in the notifier code.
	 */

	Tcl_MutexLock(&serialMutex);
	if (infoPtr->threadId != NULL) {
	    /*
	     * TIP #218: When in flight ignore the event, no one will receive
	     * it anyway.
	     */

	    Tcl_ThreadAlert(infoPtr->threadId);
	}
	Tcl_MutexUnlock(&serialMutex);
    }

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinSerialReopen --
 *
 *	Reopens the serial port with the OVERLAPPED FLAG set
 *
 * Results:
 *	Returns the new handle, or INVALID_HANDLE_VALUE. Normally there
 *	shouldn't be any error, because the same channel has previously been
 *	succeesfully opened.
 *
 * Side effects:
 *	May close the original handle
 *
 *----------------------------------------------------------------------
 */

HANDLE
TclWinSerialReopen(
    HANDLE handle,
    const TCHAR *name,
    DWORD access)
{
    SerialInit();

    /*
     * Multithreaded I/O needs the overlapped flag set otherwise
     * ClearCommError blocks under Windows NT/2000 until serial output is
     * finished
     */

    if (CloseHandle(handle) == FALSE) {
	return INVALID_HANDLE_VALUE;
    }
    handle = CreateFile(name, access, 0, 0, OPEN_EXISTING,
	    FILE_FLAG_OVERLAPPED, 0);
    return handle;
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinOpenSerialChannel --
 *
 *	Constructs a Serial port channel for the specified standard OS handle.
 *	This is a helper function to break up the construction of channels
 *	into File, Console, or Serial.
 *
 * Results:
 *	Returns the new channel, or NULL.
 *
 * Side effects:
 *	May open the channel
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclWinOpenSerialChannel(
    HANDLE handle,
    char *channelName,
    int permissions)
{
    SerialInfo *infoPtr;
    DWORD id;

    SerialInit();

    infoPtr = ckalloc(sizeof(SerialInfo));
    memset(infoPtr, 0, sizeof(SerialInfo));

    infoPtr->validMask = permissions;
    infoPtr->handle = handle;
    infoPtr->channel = (Tcl_Channel) NULL;
    infoPtr->readable = 0;
    infoPtr->writable = 1;
    infoPtr->toWrite = infoPtr->writeQueue = 0;
    infoPtr->blockTime = SERIAL_DEFAULT_BLOCKTIME;
    infoPtr->lastEventTime = 0;
    infoPtr->lastError = infoPtr->error = 0;
    infoPtr->threadId = Tcl_GetCurrentThread();
    infoPtr->sysBufRead = 4096;
    infoPtr->sysBufWrite = 4096;

    /*
     * Use the pointer to keep the channel names unique, in case the handles
     * are shared between multiple channels (stdin/stdout).
     */

    sprintf(channelName, "file%" TCL_I_MODIFIER "x", (size_t) infoPtr);

    infoPtr->channel = Tcl_CreateChannel(&serialChannelType, channelName,
	    infoPtr, permissions);


    SetupComm(handle, infoPtr->sysBufRead, infoPtr->sysBufWrite);
    PurgeComm(handle,
	    PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);

    /*
     * Default is blocking.
     */

    SetCommTimeouts(handle, &no_timeout);

    InitializeCriticalSection(&infoPtr->csWrite);
    if (permissions & TCL_READABLE) {
	infoPtr->osRead.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    }
    if (permissions & TCL_WRITABLE) {
	/*
	 * Initially the channel is writable and the writeThread is idle.
	 */

	infoPtr->osWrite.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
	infoPtr->evWritable = CreateEvent(NULL, TRUE, TRUE, NULL);
	infoPtr->evStartWriter = CreateEvent(NULL, FALSE, FALSE, NULL);
	infoPtr->evStopWriter = CreateEvent(NULL, FALSE, FALSE, NULL);
	infoPtr->writeThread = CreateThread(NULL, 256, SerialWriterThread,
		infoPtr, 0, &id);
    }

    /*
     * Files have default translation of AUTO and ^Z eof char, which means
     * that a ^Z will be accepted as EOF when reading.
     */

    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");

    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialErrorStr --
 *
 *	Converts a Win32 serial error code to a list of readable errors.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Generates readable errors in the supplied DString.
 *
 *----------------------------------------------------------------------
 */

static void
SerialErrorStr(
    DWORD error,		/* Win32 serial error code. */
    Tcl_DString *dsPtr)		/* Where to store string. */
{
    if (error & CE_RXOVER) {
	Tcl_DStringAppendElement(dsPtr, "RXOVER");
    }
    if (error & CE_OVERRUN) {
	Tcl_DStringAppendElement(dsPtr, "OVERRUN");
    }
    if (error & CE_RXPARITY) {
	Tcl_DStringAppendElement(dsPtr, "RXPARITY");
    }
    if (error & CE_FRAME) {
	Tcl_DStringAppendElement(dsPtr, "FRAME");
    }
    if (error & CE_BREAK) {
	Tcl_DStringAppendElement(dsPtr, "BREAK");
    }
    if (error & CE_TXFULL) {
	Tcl_DStringAppendElement(dsPtr, "TXFULL");
    }
    if (error & CE_PTO) {	/* PTO used to signal WRITE-TIMEOUT */
	Tcl_DStringAppendElement(dsPtr, "TIMEOUT");
    }
    if (error & ~((DWORD) (SERIAL_READ_ERRORS | SERIAL_WRITE_ERRORS))) {
	char buf[TCL_INTEGER_SPACE + 1];

	wsprintfA(buf, "%d", error);
	Tcl_DStringAppendElement(dsPtr, buf);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SerialModemStatusStr --
 *
 *	Converts a Win32 modem status list of readable flags
 *
 * Result:
 *	None.
 *
 * Side effects:
 *	Appends modem status flag strings to the given DString.
 *
 *----------------------------------------------------------------------
 */

static void
SerialModemStatusStr(
    DWORD status,		/* Win32 modem status. */
    Tcl_DString *dsPtr)		/* Where to store string. */
{
    Tcl_DStringAppendElement(dsPtr, "CTS");
    Tcl_DStringAppendElement(dsPtr, (status & MS_CTS_ON)  ?  "1" : "0");
    Tcl_DStringAppendElement(dsPtr, "DSR");
    Tcl_DStringAppendElement(dsPtr, (status & MS_DSR_ON)   ? "1" : "0");
    Tcl_DStringAppendElement(dsPtr, "RING");
    Tcl_DStringAppendElement(dsPtr, (status & MS_RING_ON)  ? "1" : "0");
    Tcl_DStringAppendElement(dsPtr, "DCD");
    Tcl_DStringAppendElement(dsPtr, (status & MS_RLSD_ON)  ? "1" : "0");
}

/*
 *----------------------------------------------------------------------
 *
 * SerialSetOptionProc --
 *
 *	Sets an option on a channel.
 *
 * Results:
 *	A standard Tcl result. Also sets the interp's result on error if
 *	interp is not NULL.
 *
 * Side effects:
 *	May modify an option on a device.
 *
 *----------------------------------------------------------------------
 */

static int
SerialSetOptionProc(
    ClientData instanceData,	/* File state. */
    Tcl_Interp *interp,		/* For error reporting - can be NULL. */
    const char *optionName,	/* Which option to set? */
    const char *value)		/* New value for option. */
{
    SerialInfo *infoPtr;
    DCB dcb;
    BOOL result, flag;
    size_t len, vlen;
    Tcl_DString ds;
    const TCHAR *native;
    int argc;
    const char **argv;

    infoPtr = (SerialInfo *) instanceData;

    /*
     * Parse options. This would be far easier if we had Tcl_Objs to work with
     * as that would let us use Tcl_GetIndexFromObj()...
     */

    len = strlen(optionName);
    vlen = strlen(value);

    /*
     * Option -mode baud,parity,databits,stopbits
     */

    if ((len > 2) && (strncmp(optionName, "-mode", len) == 0)) {
	if (!GetCommState(infoPtr->handle, &dcb)) {
	    goto getStateFailed;
	}
	native = Tcl_WinUtfToTChar(value, -1, &ds);
	result = BuildCommDCB(native, &dcb);
	Tcl_DStringFree(&ds);

	if (result == FALSE) {
	    if (interp != NULL) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"bad value \"%s\" for -mode: should be baud,parity,data,stop",
			value));
		Tcl_SetErrorCode(interp, "TCL", "VALUE", "SERIALMODE", NULL);
	    }
	    return TCL_ERROR;
	}

	/*
	 * Default settings for serial communications.
	 */

	dcb.fBinary = TRUE;
	dcb.fErrorChar = FALSE;
	dcb.fNull = FALSE;
	dcb.fAbortOnError = FALSE;

	if (!SetCommState(infoPtr->handle, &dcb)) {
	    goto setStateFailed;
	}
	return TCL_OK;
    }

    /*
     * Option -handshake none|xonxoff|rtscts|dtrdsr
     */

    if ((len > 1) && (strncmp(optionName, "-handshake", len) == 0)) {
	if (!GetCommState(infoPtr->handle, &dcb)) {
	    goto getStateFailed;
	}

	/*
	 * Reset all handshake options. DTR and RTS are ON by default.
	 */

	dcb.fOutX = dcb.fInX = FALSE;
	dcb.fOutxCtsFlow = dcb.fOutxDsrFlow = dcb.fDsrSensitivity = FALSE;
	dcb.fDtrControl = DTR_CONTROL_ENABLE;
	dcb.fRtsControl = RTS_CONTROL_ENABLE;
	dcb.fTXContinueOnXoff = FALSE;

	/*
	 * Adjust the handshake limits. Yes, the XonXoff limits seem to
	 * influence even hardware handshake.
	 */

	dcb.XonLim = (WORD) (infoPtr->sysBufRead*1/2);
	dcb.XoffLim = (WORD) (infoPtr->sysBufRead*1/4);

	if (strncasecmp(value, "NONE", vlen) == 0) {
	    /*
	     * Leave all handshake options disabled.
	     */
	} else if (strncasecmp(value, "XONXOFF", vlen) == 0) {
	    dcb.fOutX = dcb.fInX = TRUE;
	} else if (strncasecmp(value, "RTSCTS", vlen) == 0) {
	    dcb.fOutxCtsFlow = TRUE;
	    dcb.fRtsControl = RTS_CONTROL_HANDSHAKE;
	} else if (strncasecmp(value, "DTRDSR", vlen) == 0) {
	    dcb.fOutxDsrFlow = TRUE;
	    dcb.fDtrControl = DTR_CONTROL_HANDSHAKE;
	} else {
	    if (interp != NULL) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"bad value \"%s\" for -handshake: must be one of"
			" xonxoff, rtscts, dtrdsr or none", value));
		Tcl_SetErrorCode(interp, "TCL", "VALUE", "HANDSHAKE", NULL);
	    }
	    return TCL_ERROR;
	}

	if (!SetCommState(infoPtr->handle, &dcb)) {
	    goto setStateFailed;
	}
	return TCL_OK;
    }

    /*
     * Option -xchar {\x11 \x13}
     */

    if ((len > 1) && (strncmp(optionName, "-xchar", len) == 0)) {
	if (!GetCommState(infoPtr->handle, &dcb)) {
	    goto getStateFailed;
	}

	if (Tcl_SplitList(interp, value, &argc, &argv) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	if (argc != 2) {
	badXchar:
	    if (interp != NULL) {
		Tcl_SetObjResult(interp, Tcl_NewStringObj(
			"bad value for -xchar: should be a list of"
			" two elements with each a single character", -1));
		Tcl_SetErrorCode(interp, "TCL", "VALUE", "XCHAR", NULL);
	    }
	    ckfree(argv);
	    return TCL_ERROR;
	}

	/*
	 * These dereferences are safe, even in the zero-length string cases,
	 * because that just makes the xon/xoff character into NUL. When the
	 * character looks like it is UTF-8 encoded, decode it before casting
	 * into the format required for the Win guts. Note that this does not
	 * convert character sets; it is expected that when people set the
	 * control characters to something large and custom, they'll know the
	 * hex/octal value rather than the printable form.
	 */

	dcb.XonChar = argv[0][0];
	dcb.XoffChar = argv[1][0];
	if (argv[0][0] & 0x80 || argv[1][0] & 0x80) {
	    Tcl_UniChar character;
	    int charLen;

	    charLen = Tcl_UtfToUniChar(argv[0], &character);
	    if (argv[0][charLen]) {
		goto badXchar;
	    }
	    dcb.XonChar = (char) character;
	    charLen = Tcl_UtfToUniChar(argv[1], &character);
	    if (argv[1][charLen]) {
		goto badXchar;
	    }
	    dcb.XoffChar = (char) character;
	}
	ckfree(argv);

	if (!SetCommState(infoPtr->handle, &dcb)) {
	    goto setStateFailed;
	}
	return TCL_OK;
    }

    /*
     * Option -ttycontrol {DTR 1 RTS 0 BREAK 0}
     */

    if ((len > 4) && (strncmp(optionName, "-ttycontrol", len) == 0)) {
	int i, result = TCL_OK;

	if (Tcl_SplitList(interp, value, &argc, &argv) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	if ((argc % 2) == 1) {
	    if (interp != NULL) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"bad value \"%s\" for -ttycontrol: should be "
			"a list of signal,value pairs", value));
		Tcl_SetErrorCode(interp, "TCL", "VALUE", "TTYCONTROL", NULL);
	    }
	    ckfree(argv);
	    return TCL_ERROR;
	}

	for (i = 0; i < argc - 1; i += 2) {
	    if (Tcl_GetBoolean(interp, argv[i+1], &flag) == TCL_ERROR) {
		result = TCL_ERROR;
		break;
	    }
	    if (strncasecmp(argv[i], "DTR", strlen(argv[i])) == 0) {
		if (!EscapeCommFunction(infoPtr->handle,
			(DWORD) (flag ? SETDTR : CLRDTR))) {
		    if (interp != NULL) {
			Tcl_SetObjResult(interp, Tcl_NewStringObj(
				"can't set DTR signal", -1));
			Tcl_SetErrorCode(interp, "TCL", "OPERATION",
				"FCONFIGURE", "TTY_SIGNAL", NULL);
		    }
		    result = TCL_ERROR;
		    break;
		}
	    } else if (strncasecmp(argv[i], "RTS", strlen(argv[i])) == 0) {
		if (!EscapeCommFunction(infoPtr->handle,
			(DWORD) (flag ? SETRTS : CLRRTS))) {
		    if (interp != NULL) {
			Tcl_SetObjResult(interp, Tcl_NewStringObj(
				"can't set RTS signal", -1));
			Tcl_SetErrorCode(interp, "TCL", "OPERATION",
				"FCONFIGURE", "TTY_SIGNAL", NULL);
		    }
		    result = TCL_ERROR;
		    break;
		}
	    } else if (strncasecmp(argv[i], "BREAK", strlen(argv[i])) == 0) {
		if (!EscapeCommFunction(infoPtr->handle,
			(DWORD) (flag ? SETBREAK : CLRBREAK))) {
		    if (interp != NULL) {
			Tcl_SetObjResult(interp, Tcl_NewStringObj(
				"can't set BREAK signal", -1));
			Tcl_SetErrorCode(interp, "TCL", "OPERATION",
				"FCONFIGURE", "TTY_SIGNAL", NULL);
		    }
		    result = TCL_ERROR;
		    break;
		}
	    } else {
		if (interp != NULL) {
		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			    "bad signal name \"%s\" for -ttycontrol: must be"
			    " DTR, RTS or BREAK", argv[i]));
		    Tcl_SetErrorCode(interp, "TCL", "VALUE", "TTY_SIGNAL",
			    NULL);
		}
		result = TCL_ERROR;
		break;
	    }
	}

	ckfree(argv);
	return result;
    }

    /*
     * Option -sysbuffer {read_size write_size}
     * Option -sysbuffer read_size
     */

    if ((len > 1) && (strncmp(optionName, "-sysbuffer", len) == 0)) {
	/*
	 * -sysbuffer 4096 or -sysbuffer {64536 4096}
	 */

	size_t inSize = (size_t) -1, outSize = (size_t) -1;

	if (Tcl_SplitList(interp, value, &argc, &argv) == TCL_ERROR) {
	    return TCL_ERROR;
	}
	if (argc == 1) {
	    inSize = atoi(argv[0]);
	    outSize = infoPtr->sysBufWrite;
	} else if (argc == 2) {
	    inSize  = atoi(argv[0]);
	    outSize = atoi(argv[1]);
	}
	ckfree(argv);

	if ((argc < 1) || (argc > 2) || (inSize <= 0) || (outSize <= 0)) {
	    if (interp != NULL) {
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"bad value \"%s\" for -sysbuffer: should be "
			"a list of one or two integers > 0", value));
		Tcl_SetErrorCode(interp, "TCL", "VALUE", "SYS_BUFFER", NULL);
	    }
	    return TCL_ERROR;
	}

	if (!SetupComm(infoPtr->handle, inSize, outSize)) {
	    if (interp != NULL) {
		TclWinConvertError(GetLastError());
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"can't setup comm buffers: %s",
			Tcl_PosixError(interp)));
	    }
	    return TCL_ERROR;
	}
	infoPtr->sysBufRead  = inSize;
	infoPtr->sysBufWrite = outSize;

	/*
	 * Adjust the handshake limits. Yes, the XonXoff limits seem to
	 * influence even hardware handshake.
	 */

	if (!GetCommState(infoPtr->handle, &dcb)) {
	    goto getStateFailed;
	}
	dcb.XonLim = (WORD) (infoPtr->sysBufRead*1/2);
	dcb.XoffLim = (WORD) (infoPtr->sysBufRead*1/4);
	if (!SetCommState(infoPtr->handle, &dcb)) {
	    goto setStateFailed;
	}
	return TCL_OK;
    }

    /*
     * Option -pollinterval msec
     */

    if ((len > 1) && (strncmp(optionName, "-pollinterval", len) == 0)) {
	if (Tcl_GetInt(interp, value, &(infoPtr->blockTime)) != TCL_OK) {
	    return TCL_ERROR;
	}
	return TCL_OK;
    }

    /*
     * Option -timeout msec
     */

    if ((len > 2) && (strncmp(optionName, "-timeout", len) == 0)) {
	int msec;
	COMMTIMEOUTS tout = {0,0,0,0,0};

	if (Tcl_GetInt(interp, value, &msec) != TCL_OK) {
	    return TCL_ERROR;
	}
	tout.ReadTotalTimeoutConstant = msec;
	if (!SetCommTimeouts(infoPtr->handle, &tout)) {
	    if (interp != NULL) {
		TclWinConvertError(GetLastError());
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"can't set comm timeouts: %s",
			Tcl_PosixError(interp)));
	    }
	    return TCL_ERROR;
	}

	return TCL_OK;
    }

    return Tcl_BadChannelOption(interp, optionName,
	    "mode handshake pollinterval sysbuffer timeout ttycontrol xchar");

  getStateFailed:
    if (interp != NULL) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't get comm state: %s", Tcl_PosixError(interp)));
    }
    return TCL_ERROR;

  setStateFailed:
    if (interp != NULL) {
	TclWinConvertError(GetLastError());
	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
		"can't set comm state: %s", Tcl_PosixError(interp)));
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * SerialGetOptionProc --
 *
 *	Gets a mode associated with an IO channel. If the optionName arg is
 *	non NULL, retrieves the value of that option. If the optionName arg is
 *	NULL, retrieves a list of alternating option names and values for the
 *	given channel.
 *
 * Results:
 *	A standard Tcl result. Also sets the supplied DString to the string
 *	value of the option(s) returned.
 *
 * Side effects:
 *	The string returned by this function is in static storage and may be
 *	reused at any time subsequent to the call.
 *
 *----------------------------------------------------------------------
 */

static int
SerialGetOptionProc(
    ClientData instanceData,	/* File state. */
    Tcl_Interp *interp,		/* For error reporting - can be NULL. */
    const char *optionName,	/* Option to get. */
    Tcl_DString *dsPtr)		/* Where to store value(s). */
{
    SerialInfo *infoPtr;
    DCB dcb;
    size_t len;
    int valid = 0;		/* Flag if valid option parsed. */

    infoPtr = (SerialInfo *) instanceData;

    if (optionName == NULL) {
	len = 0;
    } else {
	len = strlen(optionName);
    }

    /*
     * Get option -mode
     */

    if (len == 0) {
	Tcl_DStringAppendElement(dsPtr, "-mode");
    }
    if (len==0 || (len>2 && (strncmp(optionName, "-mode", len) == 0))) {
	char parity;
	const char *stop;
	char buf[2 * TCL_INTEGER_SPACE + 16];

	if (!GetCommState(infoPtr->handle, &dcb)) {
	    if (interp != NULL) {
		TclWinConvertError(GetLastError());
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"can't get comm state: %s", Tcl_PosixError(interp)));
	    }
	    return TCL_ERROR;
	}

	valid = 1;
	parity = 'n';
	if (dcb.Parity <= 4) {
	    parity = "noems"[dcb.Parity];
	}
	stop = (dcb.StopBits == ONESTOPBIT) ? "1" :
		(dcb.StopBits == ONE5STOPBITS) ? "1.5" : "2";

	wsprintfA(buf, "%d,%c,%d,%s", dcb.BaudRate, parity,
		dcb.ByteSize, stop);
	Tcl_DStringAppendElement(dsPtr, buf);
    }

    /*
     * Get option -pollinterval
     */

    if (len == 0) {
	Tcl_DStringAppendElement(dsPtr, "-pollinterval");
    }
    if (len==0 || (len>1 && strncmp(optionName, "-pollinterval", len)==0)) {
	char buf[TCL_INTEGER_SPACE + 1];

	valid = 1;
	wsprintfA(buf, "%d", infoPtr->blockTime);
	Tcl_DStringAppendElement(dsPtr, buf);
    }

    /*
     * Get option -sysbuffer
     */

    if (len == 0) {
	Tcl_DStringAppendElement(dsPtr, "-sysbuffer");
	Tcl_DStringStartSublist(dsPtr);
    }
    if (len==0 || (len>1 && strncmp(optionName, "-sysbuffer", len) == 0)) {
	char buf[TCL_INTEGER_SPACE + 1];
	valid = 1;

	wsprintfA(buf, "%d", infoPtr->sysBufRead);
	Tcl_DStringAppendElement(dsPtr, buf);
	wsprintfA(buf, "%d", infoPtr->sysBufWrite);
	Tcl_DStringAppendElement(dsPtr, buf);
    }
    if (len == 0) {
	Tcl_DStringEndSublist(dsPtr);
    }

    /*
     * Get option -xchar
     */

    if (len == 0) {
	Tcl_DStringAppendElement(dsPtr, "-xchar");
	Tcl_DStringStartSublist(dsPtr);
    }
    if (len==0 || (len>1 && strncmp(optionName, "-xchar", len) == 0)) {
	char buf[4];
	valid = 1;

	if (!GetCommState(infoPtr->handle, &dcb)) {
	    if (interp != NULL) {
		TclWinConvertError(GetLastError());
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"can't get comm state: %s", Tcl_PosixError(interp)));
	    }
	    return TCL_ERROR;
	}
	sprintf(buf, "%c", dcb.XonChar);
	Tcl_DStringAppendElement(dsPtr, buf);
	sprintf(buf, "%c", dcb.XoffChar);
	Tcl_DStringAppendElement(dsPtr, buf);
    }
    if (len == 0) {
	Tcl_DStringEndSublist(dsPtr);
    }

    /*
     * Get option -lasterror
     *
     * Option is readonly and returned by [fconfigure chan -lasterror] but not
     * returned by unnamed [fconfigure chan].
     */

    if (len>1 && strncmp(optionName, "-lasterror", len)==0) {
	valid = 1;
	SerialErrorStr(infoPtr->lastError, dsPtr);
    }

    /*
     * get option -queue
     *
     * Option is readonly and returned by [fconfigure chan -queue].
     */

    if (len>1 && strncmp(optionName, "-queue", len)==0) {
	char buf[TCL_INTEGER_SPACE + 1];
	COMSTAT cStat;
	DWORD error;
	int inBuffered, outBuffered, count;

	valid = 1;

	/*
	 * Query the pending data in Tcl's internal queues.
	 */

	inBuffered  = Tcl_InputBuffered(infoPtr->channel);
	outBuffered = Tcl_OutputBuffered(infoPtr->channel);

	/*
	 * Query the number of bytes in our output queue:
	 *     1. The bytes pending in the output thread
	 *     2. The bytes in the system drivers buffer
	 * The writer thread should not interfere this action.
	 */

	EnterCriticalSection(&infoPtr->csWrite);
	ClearCommError(infoPtr->handle, &error, &cStat);
	count = (int) cStat.cbOutQue + infoPtr->writeQueue;
	LeaveCriticalSection(&infoPtr->csWrite);

	wsprintfA(buf, "%d", inBuffered + cStat.cbInQue);
	Tcl_DStringAppendElement(dsPtr, buf);
	wsprintfA(buf, "%d", outBuffered + count);
	Tcl_DStringAppendElement(dsPtr, buf);
    }

    /*
     * get option -ttystatus
     *
     * Option is readonly and returned by [fconfigure chan -ttystatus] but not
     * returned by unnamed [fconfigure chan].
     */

    if (len>4 && strncmp(optionName, "-ttystatus", len)==0) {
	DWORD status;

	if (!GetCommModemStatus(infoPtr->handle, &status)) {
	    if (interp != NULL) {
		TclWinConvertError(GetLastError());
		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
			"can't get tty status: %s", Tcl_PosixError(interp)));
	    }
	    return TCL_ERROR;
	}
	valid = 1;
	SerialModemStatusStr(status, dsPtr);
    }

    if (valid) {
	return TCL_OK;
    }
    return Tcl_BadChannelOption(interp, optionName,
	    "mode pollinterval lasterror queue sysbuffer ttystatus xchar");
}

/*
 *----------------------------------------------------------------------
 *
 * SerialThreadActionProc --
 *
 *	Insert or remove any thread local refs to this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Changes thread local list of valid channels.
 *
 *----------------------------------------------------------------------
 */

static void
SerialThreadActionProc(
    ClientData instanceData,
    int action)
{
    SerialInfo *infoPtr = (SerialInfo *) instanceData;

    /*
     * We do not access firstSerialPtr in the thread structures. This is not
     * for all serials managed by the thread, but only those we are watching.
     * Removal of the filevent handlers before transfer thus takes care of
     * this structure.
     */

    Tcl_MutexLock(&serialMutex);
    if (action == TCL_CHANNEL_THREAD_INSERT) {
	/*
	 * We can't copy the thread information from the channel when the
	 * channel is created. At this time the channel back pointer has not
	 * been set yet. However in that case the threadId has already been
	 * set by TclpCreateCommandChannel itself, so the structure is still
	 * good.
	 */

	SerialInit();
	if (infoPtr->channel != NULL) {
	    infoPtr->threadId = Tcl_GetChannelThread(infoPtr->channel);
	}
    } else {
	infoPtr->threadId = NULL;
    }
    Tcl_MutexUnlock(&serialMutex);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */