tclWinChan.c   [plain text]

/* 
 * tclWinChan.c
 *
 *	Channel drivers for Windows channels based on files, command
 *	pipes and TCP sockets.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclWinChan.c,v 1.2 2001/09/14 01:44:24 zlaski Exp $
 */

#include "tclWinInt.h"

/*
 * This is the size of the channel name for File based channels
 */

#define CHANNEL_NAME_SIZE	64
static char channelName[CHANNEL_NAME_SIZE+1];

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

static int initialized = 0;

/*
 * State flags used in the info structures below.
 */

#define FILE_PENDING	(1<<0)	/* Message is pending in the queue. */
#define FILE_ASYNC	(1<<1)	/* Channel is non-blocking. */
#define FILE_APPEND	(1<<2)	/* File is in append mode. */

/*
 * The following structure contains per-instance data for a file based channel.
 */

typedef struct FileInfo {
    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. */
    HANDLE handle;		/* Input/output file. */
    struct FileInfo *nextPtr;	/* Pointer to next registered file. */
} FileInfo;

/*
 * List of all file channels currently open.
 */

static FileInfo *firstFilePtr;

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

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

/*
 * Static routines for this file:
 */

static int		ComGetOptionProc _ANSI_ARGS_((ClientData instanceData, 
			    Tcl_Interp *interp, char *optionName,
			    Tcl_DString *dsPtr));
static int		ComInputProc _ANSI_ARGS_((ClientData instanceData,
	            	    char *buf, int toRead, int *errorCode));
static int		ComSetOptionProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp, char *optionName, 
			    char *value));
static int		FileBlockProc _ANSI_ARGS_((ClientData instanceData,
			    int mode));
static void		FileChannelExitHandler _ANSI_ARGS_((
		            ClientData clientData));
static void		FileCheckProc _ANSI_ARGS_((ClientData clientData,
			    int flags));
static int		FileCloseProc _ANSI_ARGS_((ClientData instanceData,
		            Tcl_Interp *interp));
static int		FileEventProc _ANSI_ARGS_((Tcl_Event *evPtr, 
			    int flags));
static int		FileGetHandleProc _ANSI_ARGS_((ClientData instanceData,
		            int direction, ClientData *handlePtr));
static void		FileInit _ANSI_ARGS_((void));
static int		FileInputProc _ANSI_ARGS_((ClientData instanceData,
	            	    char *buf, int toRead, int *errorCode));
static int		FileOutputProc _ANSI_ARGS_((ClientData instanceData,
			    char *buf, int toWrite, int *errorCode));
static int		FileSeekProc _ANSI_ARGS_((ClientData instanceData,
			    long offset, int mode, int *errorCode));
static void		FileSetupProc _ANSI_ARGS_((ClientData clientData,
			    int flags));
static void		FileWatchProc _ANSI_ARGS_((ClientData instanceData,
		            int mask));

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

static Tcl_ChannelType fileChannelType = {
    "file",			/* Type name. */
    FileBlockProc,		/* Set blocking or non-blocking mode.*/
    FileCloseProc,		/* Close proc. */
    FileInputProc,		/* Input proc. */
    FileOutputProc,		/* Output proc. */
    FileSeekProc,		/* Seek proc. */
    NULL,			/* Set option proc. */
    NULL,			/* Get option proc. */
    FileWatchProc,		/* Set up the notifier to watch the channel. */
    FileGetHandleProc,		/* Get an OS handle from channel. */
};

static Tcl_ChannelType comChannelType = {
    "com",			/* Type name. */
    FileBlockProc,		/* Set blocking or non-blocking mode.*/
    FileCloseProc,		/* Close proc. */
    ComInputProc,		/* Input proc. */
    FileOutputProc,		/* Output proc. */
    NULL,			/* Seek proc. */
    ComSetOptionProc,		/* Set option proc. */
    ComGetOptionProc,		/* Get option proc. */
    FileWatchProc,		/* Set up notifier to watch the channel. */
    FileGetHandleProc		/* Get an OS handle from channel. */
};

/*
 *----------------------------------------------------------------------
 *
 * FileInit --
 *
 *	This function creates the window used to simulate file events.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new window and creates an exit handler. 
 *
 *----------------------------------------------------------------------
 */

static void
FileInit()
{
    initialized = 1;
    firstFilePtr = NULL;
    Tcl_CreateEventSource(FileSetupProc, FileCheckProc, NULL);
    Tcl_CreateExitHandler(FileChannelExitHandler, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * FileChannelExitHandler --
 *
 *	This function is called to cleanup the channel driver before
 *	Tcl is unloaded.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Destroys the communication window.
 *
 *----------------------------------------------------------------------
 */

static void
FileChannelExitHandler(clientData)
    ClientData clientData;	/* Old window proc */
{
    Tcl_DeleteEventSource(FileSetupProc, FileCheckProc, NULL);
    initialized = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * FileSetupProc --
 *
 *	This procedure is invoked before Tcl_DoOneEvent blocks waiting
 *	for an event.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

void
FileSetupProc(data, flags)
    ClientData data;		/* Not used. */
    int flags;			/* Event flags as passed to Tcl_DoOneEvent. */
{
    FileInfo *infoPtr;
    Tcl_Time blockTime = { 0, 0 };

    if (!(flags & TCL_FILE_EVENTS)) {
	return;
    }
    
    /*
     * Check to see if there is a ready file.  If so, poll.
     */

    for (infoPtr = firstFilePtr; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
	if (infoPtr->watchMask) {
	    Tcl_SetMaxBlockTime(&blockTime);
	    break;
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileCheckProc --
 *
 *	This procedure is called by Tcl_DoOneEvent to check the file
 *	event source for events. 
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May queue an event.
 *
 *----------------------------------------------------------------------
 */

static void
FileCheckProc(data, flags)
    ClientData data;		/* Not used. */
    int flags;			/* Event flags as passed to Tcl_DoOneEvent. */
{
    FileEvent *evPtr;
    FileInfo *infoPtr;

    if (!(flags & TCL_FILE_EVENTS)) {
	return;
    }
    
    /*
     * Queue events for any ready files that don't already have events
     * queued (caused by persistent states that won't generate WinSock
     * events).
     */

    for (infoPtr = firstFilePtr; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
	if (infoPtr->watchMask && !(infoPtr->flags & FILE_PENDING)) {
	    infoPtr->flags |= FILE_PENDING;
	    evPtr = (FileEvent *) ckalloc(sizeof(FileEvent));
	    evPtr->header.proc = FileEventProc;
	    evPtr->infoPtr = infoPtr;
	    Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
	}
    }
}

/*----------------------------------------------------------------------
 *
 * FileEventProc --
 *
 *	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 file.
 *
 * 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
FileEventProc(evPtr, flags)
    Tcl_Event *evPtr;		/* Event to service. */
    int flags;			/* Flags that indicate what events to
				 * handle, such as TCL_FILE_EVENTS. */
{
    FileEvent *fileEvPtr = (FileEvent *)evPtr;
    FileInfo *infoPtr;

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

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

    for (infoPtr = firstFilePtr; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
	if (fileEvPtr->infoPtr == infoPtr) {
	    infoPtr->flags &= ~(FILE_PENDING);
	    Tcl_NotifyChannel(infoPtr->channel, infoPtr->watchMask);
	    break;
	}
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileBlockProc --
 *
 *	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
FileBlockProc(instanceData, mode)
    ClientData instanceData;	/* Instance data for channel. */
    int mode;			/* TCL_MODE_BLOCKING or
                                 * TCL_MODE_NONBLOCKING. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    
    /*
     * Files on Windows can not be switched between blocking and nonblocking,
     * hence we have to emulate the behavior. This is done in the input
     * function by checking against a bit in the state. We set or unset the
     * bit here to cause the input function to emulate the correct behavior.
     */

    if (mode == TCL_MODE_NONBLOCKING) {
	infoPtr->flags |= FILE_ASYNC;
    } else {
	infoPtr->flags &= ~(FILE_ASYNC);
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * FileCloseProc --
 *
 *	Closes the IO channel.
 *
 * Results:
 *	0 if successful, the value of errno if failed.
 *
 * Side effects:
 *	Closes the physical channel
 *
 *----------------------------------------------------------------------
 */

static int
FileCloseProc(instanceData, interp)
    ClientData instanceData;	/* Pointer to FileInfo structure. */
    Tcl_Interp *interp;		/* Not used. */
{
    FileInfo *fileInfoPtr = (FileInfo *) instanceData;
    FileInfo **nextPtrPtr;
    int errorCode = 0;

    /*
     * Remove the file from the watch list.
     */

    FileWatchProc(instanceData, 0);

    if (CloseHandle(fileInfoPtr->handle) == FALSE) {
	TclWinConvertError(GetLastError());
	errorCode = errno;
    }
    for (nextPtrPtr = &firstFilePtr; (*nextPtrPtr) != NULL;
	 nextPtrPtr = &((*nextPtrPtr)->nextPtr)) {
	if ((*nextPtrPtr) == fileInfoPtr) {
	    (*nextPtrPtr) = fileInfoPtr->nextPtr;
	    break;
	}
    }
    ckfree((char *)fileInfoPtr);
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * FileSeekProc --
 *
 *	Seeks on a file-based channel. Returns the new position.
 *
 * Results:
 *	-1 if failed, the new position if successful. If failed, it
 *	also sets *errorCodePtr to the error code.
 *
 * Side effects:
 *	Moves the location at which the channel will be accessed in
 *	future operations.
 *
 *----------------------------------------------------------------------
 */

static int
FileSeekProc(instanceData, offset, mode, errorCodePtr)
    ClientData instanceData;			/* File state. */
    long offset;				/* Offset to seek to. */
    int mode;					/* Relative to where
                                                 * should we seek? */
    int *errorCodePtr;				/* To store error code. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    DWORD moveMethod;
    DWORD newPos;

    *errorCodePtr = 0;
    if (mode == SEEK_SET) {
        moveMethod = FILE_BEGIN;
    } else if (mode == SEEK_CUR) {
        moveMethod = FILE_CURRENT;
    } else {
        moveMethod = FILE_END;
    }

    newPos = SetFilePointer(infoPtr->handle, offset, NULL, moveMethod);
    if (newPos == 0xFFFFFFFF) {
        TclWinConvertError(GetLastError());
        return -1;
    }
    return newPos;
}

/*
 *----------------------------------------------------------------------
 *
 * FileInputProc --
 *
 *	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
FileInputProc(instanceData, buf, bufSize, errorCode)
    ClientData instanceData;		/* File 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. */
{
    FileInfo *infoPtr;
    DWORD bytesRead;

    *errorCode = 0;
    infoPtr = (FileInfo *) instanceData;

    /*
     * Note that we will block on reads from a console buffer until a
     * full line has been entered.  The only way I know of to get
     * around this is to write a console driver.  We should probably
     * do this at some point, but for now, we just block.  The same
     * problem exists for files being read over the network.
     */

    if (ReadFile(infoPtr->handle, (LPVOID) buf, (DWORD) bufSize, &bytesRead,
            (LPOVERLAPPED) NULL) != FALSE) {
	return bytesRead;
    }
    
    TclWinConvertError(GetLastError());
    *errorCode = errno;
    if (errno == EPIPE) {
	return 0;
    }
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileOutputProc --
 *
 *	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
FileOutputProc(instanceData, buf, toWrite, errorCode)
    ClientData instanceData;		/* File state. */
    char *buf;				/* The data buffer. */
    int toWrite;			/* How many bytes to write? */
    int *errorCode;			/* Where to store error code. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    DWORD bytesWritten;
    
    *errorCode = 0;

    /*
     * If we are writing to a file that was opened with O_APPEND, we need to
     * seek to the end of the file before writing the current buffer.
     */

    if (infoPtr->flags & FILE_APPEND) {
        SetFilePointer(infoPtr->handle, 0, NULL, FILE_END);
    }

    if (WriteFile(infoPtr->handle, (LPVOID) buf, (DWORD) toWrite, &bytesWritten,
            (LPOVERLAPPED) NULL) == FALSE) {
        TclWinConvertError(GetLastError());
        *errorCode = errno;
        return -1;
    }
    FlushFileBuffers(infoPtr->handle);
    return bytesWritten;
}

/*
 *----------------------------------------------------------------------
 *
 * FileWatchProc --
 *
 *	Called by the notifier to set up to watch for events on this
 *	channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static void
FileWatchProc(instanceData, mask)
    ClientData instanceData;		/* File state. */
    int mask;				/* What events to watch for; OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;
    Tcl_Time blockTime = { 0, 0 };

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

    infoPtr->watchMask = mask & infoPtr->validMask;
    if (infoPtr->watchMask) {
	Tcl_SetMaxBlockTime(&blockTime);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileGetHandleProc --
 *
 *	Called from Tcl_GetChannelFile to retrieve OS handles from
 *	a file 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
FileGetHandleProc(instanceData, direction, handlePtr)
    ClientData instanceData;	/* The file state. */
    int direction;		/* TCL_READABLE or TCL_WRITABLE */
    ClientData *handlePtr;	/* Where to store the handle.  */
{
    FileInfo *infoPtr = (FileInfo *) instanceData;

    if (direction & infoPtr->validMask) {
	*handlePtr = (ClientData) infoPtr->handle;
	return TCL_OK;
    } else {
	return TCL_ERROR;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ComInputProc --
 *
 *	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
ComInputProc(instanceData, buf, bufSize, errorCode)
    ClientData instanceData;	/* File 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. */
{
    FileInfo *infoPtr;
    DWORD bytesRead;
    DWORD dw;
    COMSTAT cs;

    *errorCode = 0;
    infoPtr = (FileInfo *) instanceData;

    if (ClearCommError(infoPtr->handle, &dw, &cs)) {
	if (dw != 0) {
	    *errorCode = EIO;
	    return -1;
	}
	if (cs.cbInQue != 0) {
	    if ((DWORD) bufSize > cs.cbInQue) {
		bufSize = cs.cbInQue;
	    }
	} else {
	    if (infoPtr->flags & FILE_ASYNC) {
		errno = *errorCode = EAGAIN;
		return -1;
	    } else {
		bufSize = 1;
	    }
	}
    }
    
    if (ReadFile(infoPtr->handle, (LPVOID) buf, (DWORD) bufSize, &bytesRead,
            (LPOVERLAPPED) NULL) == FALSE) {
	TclWinConvertError(GetLastError());
	*errorCode = errno;
	return -1;
    }
    
    return bytesRead;
}

/*
 *----------------------------------------------------------------------
 *
 * ComSetOptionProc --
 *
 *	Sets an option on a channel.
 *
 * Results:
 *	A standard Tcl result. Also sets interp->result on error if
 *	interp is not NULL.
 *
 * Side effects:
 *	May modify an option on a device.
 *
 *----------------------------------------------------------------------
 */

static int		
ComSetOptionProc(instanceData, interp, optionName, value)
    ClientData instanceData;	/* File state. */
    Tcl_Interp *interp;		/* For error reporting - can be NULL. */
    char *optionName;		/* Which option to set? */
    char *value;		/* New value for option. */
{
    FileInfo *infoPtr;
    DCB dcb;
    int len;

    infoPtr = (FileInfo *) instanceData;

    len = strlen(optionName);
    if ((len > 1) && (strncmp(optionName, "-mode", len) == 0)) {
	if (GetCommState(infoPtr->handle, &dcb)) {
	    if ((BuildCommDCB(value, &dcb) == FALSE) ||
		    (SetCommState(infoPtr->handle, &dcb) == FALSE)) {
		/*
		 * one should separate the 2 errors... 
		 */
                if (interp) {
                    Tcl_AppendResult(interp, "bad value for -mode: should be ",
			    "baud,parity,data,stop", NULL);
		}
		return TCL_ERROR;
	    } else {
		return TCL_OK;
	    }
	} else {
	    if (interp) {
		Tcl_AppendResult(interp, "can't get comm state", NULL);
	    }
	    return TCL_ERROR;
	}
    } else {
	return Tcl_BadChannelOption(interp, optionName, "mode");
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ComGetOptionProc --
 *
 *	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		
ComGetOptionProc(instanceData, interp, optionName, dsPtr)
    ClientData instanceData;	/* File state. */
    Tcl_Interp *interp;          /* For error reporting - can be NULL. */
    char *optionName;		/* Option to get. */
    Tcl_DString *dsPtr;		/* Where to store value(s). */
{
    FileInfo *infoPtr;
    DCB dcb;
    int len;

    infoPtr = (FileInfo *) instanceData;

    if (optionName == NULL) {
	Tcl_DStringAppendElement(dsPtr, "-mode");
	len = 0;
    } else {
	len = strlen(optionName);
    }
    if ((len == 0) || 
	    ((len > 1) && (strncmp(optionName, "-mode", len) == 0))) {
	if (GetCommState(infoPtr->handle, &dcb) == 0) {
	    /*
	     * shouldn't we flag an error instead ? 
	     */
	    Tcl_DStringAppendElement(dsPtr, "");
	} else {
	    char parity;
	    char *stop;
	    char buf[32];

	    parity = 'n';
	    if (dcb.Parity < 4) {
		parity = "noems"[dcb.Parity];
	    }

	    stop = (dcb.StopBits == ONESTOPBIT) ? "1" : 
		    (dcb.StopBits == ONE5STOPBITS) ? "1.5" : "2";

	    wsprintf(buf, "%d,%c,%d,%s", dcb.BaudRate, parity, dcb.ByteSize,
		    stop);
	    Tcl_DStringAppendElement(dsPtr, buf);
	}
	return TCL_OK;
    } else {
	return Tcl_BadChannelOption(interp, optionName, "mode");
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpOpenFileChannel --
 *
 *	Open an File based channel on Unix systems.
 *
 * Results:
 *	The new channel or NULL. If NULL, the output argument
 *	errorCodePtr is set to a POSIX error.
 *
 * Side effects:
 *	May open the channel and may cause creation of a file on the
 *	file system.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpOpenFileChannel(interp, fileName, modeString, permissions)
    Tcl_Interp *interp;			/* Interpreter for error reporting;
                                         * can be NULL. */
    char *fileName;			/* Name of file to open. */
    char *modeString;			/* A list of POSIX open modes or
                                         * a string such as "rw". */
    int permissions;			/* If the open involves creating a
                                         * file, with what modes to create
                                         * it? */
{
    FileInfo *infoPtr;
    int seekFlag, mode, channelPermissions;
    DWORD accessMode, createMode, shareMode, flags;
    char *nativeName;
    Tcl_DString buffer;
    DCB dcb;
    Tcl_ChannelType *channelTypePtr;
    HANDLE handle;

    if (!initialized) {
	FileInit();
    }

    mode = TclGetOpenMode(interp, modeString, &seekFlag);
    if (mode == -1) {
        return NULL;
    }

    nativeName = Tcl_TranslateFileName(interp, fileName, &buffer);
    if (nativeName == NULL) {
	return NULL;
    }

    switch (mode & (O_RDONLY | O_WRONLY | O_RDWR)) {
	case O_RDONLY:
	    accessMode = GENERIC_READ;
	    channelPermissions = TCL_READABLE;
	    break;
	case O_WRONLY:
	    accessMode = GENERIC_WRITE;
	    channelPermissions = TCL_WRITABLE;
	    break;
	case O_RDWR:
	    accessMode = (GENERIC_READ | GENERIC_WRITE);
	    channelPermissions = (TCL_READABLE | TCL_WRITABLE);
	    break;
	default:
	    panic("TclpOpenFileChannel: invalid mode value");
	    break;
    }

    /*
     * Map the creation flags to the NT create mode.
     */

    switch (mode & (O_CREAT | O_EXCL | O_TRUNC)) {
	case (O_CREAT | O_EXCL):
	case (O_CREAT | O_EXCL | O_TRUNC):
	    createMode = CREATE_NEW;
	    break;
	case (O_CREAT | O_TRUNC):
	    createMode = CREATE_ALWAYS;
	    break;
	case O_CREAT:
	    createMode = OPEN_ALWAYS;
	    break;
	case O_TRUNC:
	case (O_TRUNC | O_EXCL):
	    createMode = TRUNCATE_EXISTING;
	    break;
	default:
	    createMode = OPEN_EXISTING;
	    break;
    }

    /*
     * If the file is being created, get the file attributes from the
     * permissions argument, else use the existing file attributes.
     */

    if (mode & O_CREAT) {
        if (permissions & S_IWRITE) {
            flags = FILE_ATTRIBUTE_NORMAL;
        } else {
            flags = FILE_ATTRIBUTE_READONLY;
        }
    } else {
	flags = GetFileAttributes(nativeName);
        if (flags == 0xFFFFFFFF) {
	    flags = 0;
	}
    }

    /*
     * Set up the file sharing mode.  We want to allow simultaneous access.
     */

    shareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;

    /*
     * Now we get to create the file.
     */

    handle = CreateFile(nativeName, accessMode, shareMode, NULL, createMode,
            flags, (HANDLE) NULL);

    if (handle == INVALID_HANDLE_VALUE) {
	DWORD err;

	openerr:
	err = GetLastError();
	if ((err & 0xffffL) == ERROR_OPEN_FAILED) {
	    err = (mode & O_CREAT) ? ERROR_FILE_EXISTS : ERROR_FILE_NOT_FOUND;
	}
        TclWinConvertError(err);
	if (interp != (Tcl_Interp *) NULL) {
            Tcl_AppendResult(interp, "couldn't open \"", fileName, "\": ",
                    Tcl_PosixError(interp), (char *) NULL);
        }
        Tcl_DStringFree(&buffer);
        return NULL;
    }

    if (GetFileType(handle) == FILE_TYPE_CHAR) {
	dcb.DCBlength = sizeof( DCB ) ;
	if (GetCommState(handle, &dcb)) {
	    /*
	     * This is a com port.  Reopen it with the correct modes. 
	     */

	    COMMTIMEOUTS cto;

	    CloseHandle(handle);
	    handle = CreateFile(nativeName, accessMode, 0, NULL, OPEN_EXISTING,
		    flags, NULL);
	    if (handle == INVALID_HANDLE_VALUE) {
		goto openerr;
	    }

	    /*
	     * FileInit the com port.
	     */

	    SetCommMask(handle, EV_RXCHAR);
	    SetupComm(handle, 4096, 4096);
	    PurgeComm(handle, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR
		    | PURGE_RXCLEAR);
	    cto.ReadIntervalTimeout = MAXDWORD;
	    cto.ReadTotalTimeoutMultiplier = 0;
	    cto.ReadTotalTimeoutConstant = 0;
	    cto.WriteTotalTimeoutMultiplier = 0;
	    cto.WriteTotalTimeoutConstant = 0;
	    SetCommTimeouts(handle, &cto);

	    GetCommState(handle, &dcb);
	    SetCommState(handle, &dcb);
	    channelTypePtr = &comChannelType;
	} else {
	    channelTypePtr = &fileChannelType;
	}
    } else {
	channelTypePtr = &fileChannelType;
    }
    Tcl_DStringFree(&buffer);

    infoPtr = (FileInfo *) ckalloc((unsigned) sizeof(FileInfo));
    infoPtr->nextPtr = firstFilePtr;
    firstFilePtr = infoPtr;
    infoPtr->validMask = channelPermissions;
    infoPtr->watchMask = 0;
    infoPtr->flags = (mode & O_APPEND) ? FILE_APPEND : 0;
    infoPtr->handle = handle;
   
    sprintf(channelName, "file%d", (int) handle);

    infoPtr->channel = Tcl_CreateChannel(channelTypePtr, channelName,
            (ClientData) infoPtr, channelPermissions);

    if (seekFlag) {
        if (Tcl_Seek(infoPtr->channel, 0, SEEK_END) < 0) {
            if (interp != (Tcl_Interp *) NULL) {
                Tcl_AppendResult(interp, "could not seek to end of file on \"",
                        channelName, "\": ", Tcl_PosixError(interp),
                        (char *) NULL);
            }
            Tcl_Close(NULL, infoPtr->channel);
            return NULL;
        }
    }

    /*
     * Files have default translation of AUTO and ^Z eof char, which
     * means that a ^Z will be appended to them at close.
     */
    
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeFileChannel --
 *
 *	Creates a Tcl_Channel from an existing platform specific file
 *	handle.
 *
 * Results:
 *	The Tcl_Channel created around the preexisting file.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_MakeFileChannel(handle, mode)
    ClientData handle;		/* OS level handle */
    int mode;			/* ORed combination of TCL_READABLE and
                                 * TCL_WRITABLE to indicate file mode. */
{
    char channelName[20];
    FileInfo *infoPtr;

    if (!initialized) {
	FileInit();
    }

    if (mode == 0) {
	return NULL;
    }

    sprintf(channelName, "file%d", (int) handle);

    /*
     * See if a channel with this handle already exists.
     */
    
    for (infoPtr = firstFilePtr; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
	if (infoPtr->handle == (HANDLE) handle) {
	    return (mode == infoPtr->validMask) ? infoPtr->channel : NULL;
	}
    }

    infoPtr = (FileInfo *) ckalloc((unsigned) sizeof(FileInfo));
    infoPtr->nextPtr = firstFilePtr;
    firstFilePtr = infoPtr;
    infoPtr->validMask = mode;
    infoPtr->watchMask = 0;
    infoPtr->flags = 0;
    infoPtr->handle = (HANDLE) handle;
    infoPtr->channel = Tcl_CreateChannel(&fileChannelType, channelName,
            (ClientData) infoPtr, mode);

    /*
     * Windows files have AUTO translation mode and ^Z eof char on input.
     */
    
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "\032 {}");
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetDefaultStdChannel --
 *
 *	Constructs a channel for the specified standard OS handle.
 *
 * Results:
 *	Returns the specified default standard channel, or NULL.
 *
 * Side effects:
 *	May cause the creation of a standard channel and the underlying
 *	file.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclGetDefaultStdChannel(type)
    int type;			/* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR. */
{
    Tcl_Channel channel;
    HANDLE handle;
    int mode;
    char *bufMode;
    DWORD handleId;		/* Standard handle to retrieve. */

    switch (type) {
	case TCL_STDIN:
	    handleId = STD_INPUT_HANDLE;
	    mode = TCL_READABLE;
	    bufMode = "line";
	    break;
	case TCL_STDOUT:
	    handleId = STD_OUTPUT_HANDLE;
	    mode = TCL_WRITABLE;
	    bufMode = "line";
	    break;
	case TCL_STDERR:
	    handleId = STD_ERROR_HANDLE;
	    mode = TCL_WRITABLE;
	    bufMode = "none";
	    break;
	default:
	    panic("TclGetDefaultStdChannel: Unexpected channel type");
	    break;
    }
    handle = GetStdHandle(handleId);

    /*
     * Note that we need to check for 0 because Windows will return 0 if this
     * is not a console mode application, even though this is not a valid
     * handle. 
     */

    if ((handle == INVALID_HANDLE_VALUE) || (handle == 0)) {
	return NULL;
    }

    channel = Tcl_MakeFileChannel(handle, mode);

    /*
     * Set up the normal channel options for stdio handles.
     */

    if ((Tcl_SetChannelOption((Tcl_Interp *) NULL, channel, "-translation",
            "auto") == TCL_ERROR)
	    || (Tcl_SetChannelOption((Tcl_Interp *) NULL, channel, "-eofchar",
		    "\032 {}") == TCL_ERROR)
	    || (Tcl_SetChannelOption((Tcl_Interp *) NULL, channel,
		    "-buffering", bufMode) == TCL_ERROR)) {
        Tcl_Close((Tcl_Interp *) NULL, channel);
        return (Tcl_Channel) NULL;
    }
    return channel;
}