/* 
 * tclUnixChan.c
 *
 *	Common channel driver for Unix channels based on files, command
 *	pipes and TCP sockets.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 * Copyright (c) 1998-1999 by Scriptics Corporation.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclUnixChan.c,v 1.1 2000/08/14 19:44:24 jgdavidson Exp $
 */

#include	"tclInt.h"	/* Internal definitions for Tcl. */
#include	"tclPort.h"	/* Portability features for Tcl. */

/*
 * sys/ioctl.h has already been included by tclPort.h.  Including termios.h
 * or termio.h causes a bunch of warning messages because some duplicate
 * (but not contradictory) #defines exist in termios.h and/or termio.h
 */
#undef NL0
#undef NL1
#undef CR0
#undef CR1
#undef CR2
#undef CR3
#undef TAB0
#undef TAB1
#undef TAB2
#undef XTABS
#undef BS0
#undef BS1
#undef FF0
#undef FF1
#undef ECHO
#undef NOFLSH
#undef TOSTOP
#undef FLUSHO
#undef PENDIN

#define SUPPORTS_TTY

#ifdef USE_TERMIOS
#   include <termios.h>
#   define IOSTATE			struct termios
#   define GETIOSTATE(fd, statePtr)	tcgetattr((fd), (statePtr))
#   define SETIOSTATE(fd, statePtr)	tcsetattr((fd), TCSADRAIN, (statePtr))
#else	/* !USE_TERMIOS */
#ifdef USE_TERMIO
#   include <termio.h>
#   define IOSTATE			struct termio
#   define GETIOSTATE(fd, statePtr)	ioctl((fd), TCGETA, (statePtr))
#   define SETIOSTATE(fd, statePtr)	ioctl((fd), TCSETAW, (statePtr))
#else	/* !USE_TERMIO */
#ifdef USE_SGTTY
#   include <sgtty.h>
#   define IOSTATE			struct sgttyb
#   define GETIOSTATE(fd, statePtr)	ioctl((fd), TIOCGETP, (statePtr))
#   define SETIOSTATE(fd, statePtr)	ioctl((fd), TIOCSETP, (statePtr))
#else	/* !USE_SGTTY */
#   undef SUPPORTS_TTY
#endif	/* !USE_SGTTY */
#endif	/* !USE_TERMIO */
#endif	/* !USE_TERMIOS */

/*
 * This structure describes per-instance state of a file based channel.
 */

typedef struct FileState {
    Tcl_Channel channel;	/* Channel associated with this file. */
    int fd;			/* File handle. */
    int validMask;		/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which operations are valid on the file. */
    struct FileState *nextPtr;	/* Pointer to next file in list of all
				 * file channels. */
} FileState;

#ifdef SUPPORTS_TTY

/*
 * The following structure describes per-instance state of a tty-based
 * channel.
 */

typedef struct TtyState {
    FileState fs;		/* Per-instance state of the file
				 * descriptor.  Must be the first field. */
    IOSTATE savedState;		/* Initial state of device.  Used to reset
				 * state when device closed. */
} TtyState;

/*
 * The following structure is used to set or get the serial port
 * attributes in a platform-independant manner.
 */
 
typedef struct TtyAttrs {
    int baud;
    int parity;
    int data;
    int stop;
} TtyAttrs;

#endif	/* !SUPPORTS_TTY */

typedef struct ThreadSpecificData {
    /*
     * List of all file channels currently open.  This is per thread and is
     * used to match up fd's to channels, which rarely occurs.
     */
    
    FileState *firstFilePtr;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;

/*
 * This structure describes per-instance state of a tcp based channel.
 */

typedef struct TcpState {
    Tcl_Channel channel;	/* Channel associated with this file. */
    int fd;			/* The socket itself. */
    int flags;			/* ORed combination of the bitfields
				 * defined below. */
    Tcl_TcpAcceptProc *acceptProc;
				/* Proc to call on accept. */
    ClientData acceptProcData;	/* The data for the accept proc. */
} TcpState;

/*
 * These bits may be ORed together into the "flags" field of a TcpState
 * structure.
 */

#define TCP_ASYNC_SOCKET	(1<<0)	/* Asynchronous socket. */
#define TCP_ASYNC_CONNECT	(1<<1)	/* Async connect in progress. */

/*
 * The following defines the maximum length of the listen queue. This is
 * the number of outstanding yet-to-be-serviced requests for a connection
 * on a server socket, more than this number of outstanding requests and
 * the connection request will fail.
 */

#ifndef	SOMAXCONN
#define SOMAXCONN	100
#endif

#if	(SOMAXCONN < 100)
#undef	SOMAXCONN
#define	SOMAXCONN	100
#endif

/*
 * The following defines how much buffer space the kernel should maintain
 * for a socket.
 */

#define SOCKET_BUFSIZE	4096

/*
 * Static routines for this file:
 */

static TcpState *	CreateSocket _ANSI_ARGS_((Tcl_Interp *interp,
			    int port, char *host, int server,
			    char *myaddr, int myport, int async));
static int		CreateSocketAddress _ANSI_ARGS_(
			    (struct sockaddr_in *sockaddrPtr,
			    char *host, int port));
static int		FileBlockModeProc _ANSI_ARGS_((
    			    ClientData instanceData, int mode));
static int		FileCloseProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp));
static int		FileGetHandleProc _ANSI_ARGS_((ClientData instanceData,
		            int direction, ClientData *handlePtr));
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		FileWatchProc _ANSI_ARGS_((ClientData instanceData,
		            int mask));
static void		TcpAccept _ANSI_ARGS_((ClientData data, int mask));
static int		TcpBlockModeProc _ANSI_ARGS_((ClientData data,
        		    int mode));
static int		TcpCloseProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp));
static int		TcpGetHandleProc _ANSI_ARGS_((ClientData instanceData,
		            int direction, ClientData *handlePtr));
static int		TcpGetOptionProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp, char *optionName,
			    Tcl_DString *dsPtr));
static int		TcpInputProc _ANSI_ARGS_((ClientData instanceData,
		            char *buf, int toRead,  int *errorCode));
static int		TcpOutputProc _ANSI_ARGS_((ClientData instanceData,
		            char *buf, int toWrite, int *errorCode));
static void		TcpWatchProc _ANSI_ARGS_((ClientData instanceData,
		            int mask));
#ifdef SUPPORTS_TTY
static int		TtyCloseProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp));
static void		TtyGetAttributes _ANSI_ARGS_((int fd,
			    TtyAttrs *ttyPtr));
static int		TtyGetOptionProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp, char *optionName,
			    Tcl_DString *dsPtr));
static FileState *	TtyInit _ANSI_ARGS_((int fd));
static int		TtyParseMode _ANSI_ARGS_((Tcl_Interp *interp,
			    CONST char *mode, int *speedPtr, int *parityPtr,
			    int *dataPtr, int *stopPtr));
static void		TtySetAttributes _ANSI_ARGS_((int fd,
			    TtyAttrs *ttyPtr));
static int		TtySetOptionProc _ANSI_ARGS_((ClientData instanceData,
			    Tcl_Interp *interp, char *optionName, 
			    char *value));
#endif	/* SUPPORTS_TTY */
static int		WaitForConnect _ANSI_ARGS_((TcpState *statePtr,
		            int *errorCodePtr));

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

static Tcl_ChannelType fileChannelType = {
    "file",				/* Type name. */
    FileBlockModeProc,			/* Set blocking/nonblocking mode.*/
    FileCloseProc,			/* Close proc. */
    FileInputProc,			/* Input proc. */
    FileOutputProc,			/* Output proc. */
    FileSeekProc,			/* Seek proc. */
    NULL,				/* Set option proc. */
    NULL,				/* Get option proc. */
    FileWatchProc,			/* Initialize notifier. */
    FileGetHandleProc,			/* Get OS handles out of channel. */
};

#ifdef SUPPORTS_TTY
/*
 * This structure describes the channel type structure for serial IO.
 * Note that this type is a subclass of the "file" type.
 */

static Tcl_ChannelType ttyChannelType = {
    "tty",				/* Type name. */
    FileBlockModeProc,			/* Set blocking/nonblocking mode.*/
    TtyCloseProc,			/* Close proc. */
    FileInputProc,			/* Input proc. */
    FileOutputProc,			/* Output proc. */
    NULL,				/* Seek proc. */
    TtySetOptionProc,			/* Set option proc. */
    TtyGetOptionProc,			/* Get option proc. */
    FileWatchProc,			/* Initialize notifier. */
    FileGetHandleProc,			/* Get OS handles out of channel. */
};
#endif	/* SUPPORTS_TTY */

/*
 * This structure describes the channel type structure for TCP socket
 * based IO:
 */

static Tcl_ChannelType tcpChannelType = {
    "tcp",				/* Type name. */
    TcpBlockModeProc,			/* Set blocking/nonblocking mode.*/
    TcpCloseProc,			/* Close proc. */
    TcpInputProc,			/* Input proc. */
    TcpOutputProc,			/* Output proc. */
    NULL,				/* Seek proc. */
    NULL,				/* Set option proc. */
    TcpGetOptionProc,			/* Get option proc. */
    TcpWatchProc,			/* Initialize notifier. */
    TcpGetHandleProc,			/* Get OS handles out of channel. */
};


/*
 *----------------------------------------------------------------------
 *
 * FileBlockModeProc --
 *
 *	Helper procedure to set blocking and nonblocking modes on a
 *	file based channel. Invoked by generic IO level code.
 *
 * Results:
 *	0 if successful, errno when failed.
 *
 * Side effects:
 *	Sets the device into blocking or non-blocking mode.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static int
FileBlockModeProc(instanceData, mode)
    ClientData instanceData;		/* File state. */
    int mode;				/* The mode to set. Can be one of
                                         * TCL_MODE_BLOCKING or
                                         * TCL_MODE_NONBLOCKING. */
{
    FileState *fsPtr = (FileState *) instanceData;
    int curStatus;

#ifndef USE_FIONBIO
    curStatus = fcntl(fsPtr->fd, F_GETFL);
    if (mode == TCL_MODE_BLOCKING) {
	curStatus &= (~(O_NONBLOCK));
    } else {
	curStatus |= O_NONBLOCK;
    }
    if (fcntl(fsPtr->fd, F_SETFL, curStatus) < 0) {
	return errno;
    }
    curStatus = fcntl(fsPtr->fd, F_GETFL);
#else
    if (mode == TCL_MODE_BLOCKING) {
	curStatus = 0;
    } else {
	curStatus = 1;
    }
    if (ioctl(fsPtr->fd, (int) FIONBIO, &curStatus) < 0) {
	return errno;
    }
#endif
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * FileInputProc --
 *
 *	This procedure is invoked from the generic IO level to read
 *	input from a file based channel.
 *
 * Results:
 *	The number of bytes read is returned or -1 on error. An output
 *	argument contains a POSIX error code if an error occurs, or zero.
 *
 * Side effects:
 *	Reads input from the input device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
FileInputProc(instanceData, buf, toRead, errorCodePtr)
    ClientData instanceData;		/* File state. */
    char *buf;				/* Where to store data read. */
    int toRead;				/* How much space is available
                                         * in the buffer? */
    int *errorCodePtr;			/* Where to store error code. */
{
    FileState *fsPtr = (FileState *) instanceData;
    int bytesRead;			/* How many bytes were actually
                                         * read from the input device? */

    *errorCodePtr = 0;
    
    /*
     * Assume there is always enough input available. This will block
     * appropriately, and read will unblock as soon as a short read is
     * possible, if the channel is in blocking mode. If the channel is
     * nonblocking, the read will never block.
     */

    bytesRead = read(fsPtr->fd, buf, (size_t) toRead);
    if (bytesRead > -1) {
        return bytesRead;
    }
    *errorCodePtr = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileOutputProc--
 *
 *	This procedure is invoked from the generic IO level to write
 *	output to a file channel.
 *
 * Results:
 *	The number of bytes written is returned or -1 on error. An
 *	output argument	contains a POSIX error code if an error occurred,
 *	or zero.
 *
 * Side effects:
 *	Writes output on the output device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
FileOutputProc(instanceData, buf, toWrite, errorCodePtr)
    ClientData instanceData;		/* File state. */
    char *buf;				/* The data buffer. */
    int toWrite;			/* How many bytes to write? */
    int *errorCodePtr;			/* Where to store error code. */
{
    FileState *fsPtr = (FileState *) instanceData;
    int written;

    *errorCodePtr = 0;
    written = write(fsPtr->fd, buf, (size_t) toWrite);
    if (written > -1) {
        return written;
    }
    *errorCodePtr = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * FileCloseProc --
 *
 *	This procedure is called from the generic IO level to perform
 *	channel-type-specific cleanup when a file based channel is closed.
 *
 * Results:
 *	0 if successful, errno if failed.
 *
 * Side effects:
 *	Closes the device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
FileCloseProc(instanceData, interp)
    ClientData instanceData;	/* File state. */
    Tcl_Interp *interp;		/* For error reporting - unused. */
{
    FileState *fsPtr = (FileState *) instanceData;
    FileState **nextPtrPtr;
    int errorCode = 0;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    Tcl_DeleteFileHandler(fsPtr->fd);

    /*
     * Do not close standard channels while in thread-exit.
     */

    if (!TclInExit()
	    || ((fsPtr->fd != 0) && (fsPtr->fd != 1) && (fsPtr->fd != 2))) {
	if (close(fsPtr->fd) < 0) {
	    errorCode = errno;
	}
    }
    for (nextPtrPtr = &(tsdPtr->firstFilePtr); (*nextPtrPtr) != NULL;
	 nextPtrPtr = &((*nextPtrPtr)->nextPtr)) {
	if ((*nextPtrPtr) == fsPtr) {
	    (*nextPtrPtr) = fsPtr->nextPtr;
	    break;
	}
    }
    ckfree((char *) fsPtr);
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * FileSeekProc --
 *
 *	This procedure is called by the generic IO level to move the
 *	access point in a file based channel.
 *
 * Results:
 *	-1 if failed, the new position if successful. An output
 *	argument contains the POSIX error code if an error occurred,
 *	or zero.
 *
 * 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? Can be
                                                 * one of SEEK_START,
                                                 * SEEK_SET or SEEK_END. */
    int *errorCodePtr;				/* To store error code. */
{
    FileState *fsPtr = (FileState *) instanceData;
    int newLoc;

    newLoc = lseek(fsPtr->fd, (off_t) offset, mode);

    *errorCodePtr = (newLoc == -1) ? errno : 0;
    return newLoc;
}

/*
 *----------------------------------------------------------------------
 *
 * FileWatchProc --
 *
 *	Initialize the notifier to watch the fd from this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets up the notifier so that a future event on the channel will
 *	be seen by Tcl.
 *
 *----------------------------------------------------------------------
 */

static void
FileWatchProc(instanceData, mask)
    ClientData instanceData;		/* The file state. */
    int mask;				/* Events of interest; an OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    FileState *fsPtr = (FileState *) instanceData;

    /*
     * Make sure we only register for events that are valid on this file.
     * Note that we are passing Tcl_NotifyChannel directly to
     * Tcl_CreateFileHandler with the channel pointer as the client data.
     */

    mask &= fsPtr->validMask;
    if (mask) {
	Tcl_CreateFileHandler(fsPtr->fd, mask,
		(Tcl_FileProc *) Tcl_NotifyChannel,
		(ClientData) fsPtr->channel);
    } else {
	Tcl_DeleteFileHandler(fsPtr->fd);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FileGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle 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.  */
{
    FileState *fsPtr = (FileState *) instanceData;

    if (direction & fsPtr->validMask) {
	*handlePtr = (ClientData) fsPtr->fd;
	return TCL_OK;
    } else {
	return TCL_ERROR;
    }
}

#ifdef SUPPORTS_TTY 

/*
 *----------------------------------------------------------------------
 *
 * TtyCloseProc --
 *
 *	This procedure is called from the generic IO level to perform
 *	channel-type-specific cleanup when a tty based channel is closed.
 *
 * Results:
 *	0 if successful, errno if failed.
 *
 * Side effects:
 *	Restores the settings and closes the device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
TtyCloseProc(instanceData, interp)
    ClientData instanceData;	/* Tty state. */
    Tcl_Interp *interp;		/* For error reporting - unused. */
{
    TtyState *ttyPtr;

    ttyPtr = (TtyState *) instanceData;
    SETIOSTATE(ttyPtr->fs.fd, &ttyPtr->savedState);
    return FileCloseProc(instanceData, interp);
}

/*
 *----------------------------------------------------------------------
 *
 * TtySetOptionProc --
 *
 *	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.
 *      Sets Error message if needed (by calling Tcl_BadChannelOption).
 *
 *----------------------------------------------------------------------
 */

static int		
TtySetOptionProc(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. */
{
    FileState *fsPtr = (FileState *) instanceData;
    unsigned int len;
    TtyAttrs tty;

    len = strlen(optionName);
    if ((len > 1) && (strncmp(optionName, "-mode", len) == 0)) {
	if (TtyParseMode(interp, value, &tty.baud, &tty.parity, &tty.data,
		&tty.stop) != TCL_OK) {
	    return TCL_ERROR;
	}
	/*
	 * system calls results should be checked there. -- dl
	 */

	TtySetAttributes(fsPtr->fd, &tty);
	return TCL_OK;
    } else {
	return Tcl_BadChannelOption(interp, optionName, "mode");
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TtyGetOptionProc --
 *
 *	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.
 *      Sets Error message if needed (by calling Tcl_BadChannelOption).
 *
 *----------------------------------------------------------------------
 */

static int		
TtyGetOptionProc(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). */
{
    FileState *fsPtr = (FileState *) instanceData;
    unsigned int len;
    char buf[3 * TCL_INTEGER_SPACE + 16];
    TtyAttrs tty;

    if (optionName == NULL) {
	Tcl_DStringAppendElement(dsPtr, "-mode");
	len = 0;
    } else {
	len = strlen(optionName);
    }
    if ((len == 0) || 
	    ((len > 1) && (strncmp(optionName, "-mode", len) == 0))) {
	TtyGetAttributes(fsPtr->fd, &tty);
	sprintf(buf, "%d,%c,%d,%d", tty.baud, tty.parity, tty.data, tty.stop);
	Tcl_DStringAppendElement(dsPtr, buf);
	return TCL_OK;
    } else {
	return Tcl_BadChannelOption(interp, optionName, "mode");
    }
}

#undef DIRECT_BAUD
#ifdef B4800
#   if (B4800 == 4800)
#	define DIRECT_BAUD
#   endif
#endif

#ifdef DIRECT_BAUD
#   define TtyGetSpeed(baud)   ((unsigned) (baud))
#   define TtyGetBaud(speed)   ((int) (speed))
#else

static struct {int baud; unsigned long speed;} speeds[] = {
#ifdef B0
    {0, B0},
#endif
#ifdef B50
    {50, B50},
#endif
#ifdef B75
    {75, B75},
#endif
#ifdef B110
    {110, B110},
#endif
#ifdef B134
    {134, B134},
#endif
#ifdef B150
    {150, B150},
#endif
#ifdef B200
    {200, B200},
#endif
#ifdef B300
    {300, B300},
#endif
#ifdef B600
    {600, B600},
#endif
#ifdef B1200
    {1200, B1200},
#endif
#ifdef B1800
    {1800, B1800},
#endif
#ifdef B2400
    {2400, B2400},
#endif
#ifdef B4800
    {4800, B4800},
#endif
#ifdef B9600
    {9600, B9600},
#endif
#ifdef B14400
    {14400, B14400},
#endif
#ifdef B19200
    {19200, B19200},
#endif
#ifdef EXTA
    {19200, EXTA},
#endif
#ifdef B28800
    {28800, B28800},
#endif
#ifdef B38400
    {38400, B38400},
#endif
#ifdef EXTB
    {38400, EXTB},
#endif
#ifdef B57600
    {57600, B57600},
#endif
#ifdef _B57600
    {57600, _B57600},
#endif
#ifdef B76800
    {76800, B76800},
#endif
#ifdef B115200
    {115200, B115200},
#endif
#ifdef _B115200
    {115200, _B115200},
#endif
#ifdef B153600
    {153600, B153600},
#endif
#ifdef B230400
    {230400, B230400},
#endif
#ifdef B307200
    {307200, B307200},
#endif
#ifdef B460800
    {460800, B460800},
#endif
    {-1, 0}
};

/*
 *---------------------------------------------------------------------------
 *
 * TtyGetSpeed --
 *
 *	Given a baud rate, get the mask value that should be stored in
 *	the termios, termio, or sgttyb structure in order to select that
 *	baud rate.
 *
 * Results:
 *	As above.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static unsigned long
TtyGetSpeed(baud)
    int baud;			/* The baud rate to look up. */
{
    int bestIdx, bestDiff, i, diff;
    
    bestIdx = 0;
    bestDiff = 1000000;
    
    /*
     * If the baud rate does not correspond to one of the known mask values,
     * choose the mask value whose baud rate is closest to the specified
     * baud rate.
     */

    for (i = 0; speeds[i].baud >= 0; i++) {
	diff = speeds[i].baud - baud;
	if (diff < 0) {
	    diff = -diff;
	}
	if (diff < bestDiff) {
	    bestIdx = i;
	    bestDiff = diff;
	}
    }
    return speeds[bestIdx].speed;
}

/*
 *---------------------------------------------------------------------------
 *
 * TtyGetBaud --
 *
 *	Given a speed mask value from a termios, termio, or sgttyb
 *	structure, get the baus rate that corresponds to that mask value.
 *
 * Results:
 *	As above.  If the mask value was not recognized, 0 is returned.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
TtyGetBaud(speed)
    unsigned long speed;	/* Speed mask value to look up. */
{
    int i;
    
    for (i = 0; speeds[i].baud >= 0; i++) {
	if (speeds[i].speed == speed) {
	    return speeds[i].baud;
	}
    }
    return 0;
}

#endif	/* !DIRECT_BAUD */


/*
 *---------------------------------------------------------------------------
 *
 * TtyGetAttributes --
 *
 *	Get the current attributes of the specified serial device.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */
 
static void
TtyGetAttributes(fd, ttyPtr)
    int fd;			/* Open file descriptor for serial port to
				 * be queried. */
    TtyAttrs *ttyPtr;		/* Buffer filled with serial port
				 * attributes. */
{
    IOSTATE iostate;
    int baud, parity, data, stop;

    GETIOSTATE(fd, &iostate);

#ifdef USE_TERMIOS
    baud = TtyGetBaud(cfgetospeed(&iostate));
    
    parity = 'n';
#ifdef PAREXT
    switch ((int) (iostate.c_cflag & (PARENB | PARODD | PAREXT))) {
	case PARENB		      : parity = 'e'; break;
	case PARENB | PARODD	      :	parity = 'o'; break;
	case PARENB |	       PAREXT : parity = 's'; break;
	case PARENB | PARODD | PAREXT :	parity = 'm'; break;
    }
#else	/* !PAREXT */
    switch ((int) (iostate.c_cflag & (PARENB | PARODD))) {
	case PARENB		      : parity = 'e'; break;
	case PARENB | PARODD	      :	parity = 'o'; break;
    }
#endif	/* !PAREXT */

    data = iostate.c_cflag & CSIZE;
    data = (data == CS5) ? 5 : (data == CS6) ? 6 : (data == CS7) ? 7 : 8;

    stop = (iostate.c_cflag & CSTOPB) ? 2 : 1;
#endif	/* USE_TERMIOS */

#ifdef USE_TERMIO
    baud = TtyGetBaud(iostate.c_cflag & CBAUD);

    parity = 'n';
    switch (iostate.c_cflag & (PARENB | PARODD | PAREXT)) {
	case PARENB		      : parity = 'e'; break;
	case PARENB | PARODD	      :	parity = 'o'; break;
	case PARENB |	       PAREXT : parity = 's'; break;
	case PARENB | PARODD | PAREXT :	parity = 'm'; break;
    }

    data = iostate.c_cflag & CSIZE;
    data = (data == CS5) ? 5 : (data == CS6) ? 6 : (data == CS7) ? 7 : 8;

    stop = (iostate.c_cflag & CSTOPB) ? 2 : 1;
#endif	/* USE_TERMIO */

#ifdef USE_SGTTY
    baud = TtyGetBaud(iostate.sg_ospeed);

    parity = 'n';
    if (iostate.sg_flags & EVENP) {
	parity = 'e';
    } else if (iostate.sg_flags & ODDP) {
	parity = 'o';
    }

    data = (iostate.sg_flags & (EVENP | ODDP)) ? 7 : 8;

    stop = 1;
#endif	/* USE_SGTTY */

    ttyPtr->baud    = baud;
    ttyPtr->parity  = parity;
    ttyPtr->data    = data;
    ttyPtr->stop    = stop;
}

/*
 *---------------------------------------------------------------------------
 *
 * TtySetAttributes --
 *
 *	Set the current attributes of the specified serial device. 
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */
 
static void
TtySetAttributes(fd, ttyPtr)
    int fd;			/* Open file descriptor for serial port to
				 * be modified. */
    TtyAttrs *ttyPtr;		/* Buffer containing new attributes for
				 * serial port. */
{
    IOSTATE iostate;

#ifdef USE_TERMIOS
    int parity, data, flag;

    GETIOSTATE(fd, &iostate);
    cfsetospeed(&iostate, TtyGetSpeed(ttyPtr->baud));
    cfsetispeed(&iostate, TtyGetSpeed(ttyPtr->baud));

    flag = 0;
    parity = ttyPtr->parity;
    if (parity != 'n') {
	flag |= PARENB;
#ifdef PAREXT
	iostate.c_cflag &= ~PAREXT;
	if ((parity == 'm') || (parity == 's')) {
	    flag |= PAREXT;
	}
#endif
	if ((parity == 'm') || (parity == 'o')) {
	    flag |= PARODD;
	}
    }
    data = ttyPtr->data;
    flag |= (data == 5) ? CS5 : (data == 6) ? CS6 : (data == 7) ? CS7 : CS8;
    if (ttyPtr->stop == 2) {
	flag |= CSTOPB;
    }

    iostate.c_cflag &= ~(PARENB | PARODD | CSIZE | CSTOPB);
    iostate.c_cflag |= flag;

#endif	/* USE_TERMIOS */

#ifdef USE_TERMIO
    int parity, data, flag;

    GETIOSTATE(fd, &iostate);
    iostate.c_cflag &= ~CBAUD;
    iostate.c_cflag |= TtyGetSpeed(ttyPtr->baud);

    flag = 0;
    parity = ttyPtr->parity;
    if (parity != 'n') {
	flag |= PARENB;
	if ((parity == 'm') || (parity == 's')) {
	    flag |= PAREXT;
	}
	if ((parity == 'm') || (parity == 'o')) {
	    flag |= PARODD;
	}
    }
    data = ttyPtr->data;
    flag |= (data == 5) ? CS5 : (data == 6) ? CS6 : (data == 7) ? CS7 : CS8;
    if (ttyPtr->stop == 2) {
	flag |= CSTOPB;
    }

    iostate.c_cflag &= ~(PARENB | PARODD | PAREXT | CSIZE | CSTOPB);
    iostate.c_cflag |= flag;

#endif	/* USE_TERMIO */

#ifdef USE_SGTTY
    int parity;

    GETIOSTATE(fd, &iostate);
    iostate.sg_ospeed = TtyGetSpeed(ttyPtr->baud);
    iostate.sg_ispeed = TtyGetSpeed(ttyPtr->baud);

    parity = ttyPtr->parity;
    if (parity == 'e') {
	iostate.sg_flags &= ~ODDP;
	iostate.sg_flags |= EVENP;
    } else if (parity == 'o') {
	iostate.sg_flags &= ~EVENP;
	iostate.sg_flags |= ODDP;
    }
#endif	/* USE_SGTTY */

    SETIOSTATE(fd, &iostate);
}

/*
 *---------------------------------------------------------------------------
 *
 * TtyParseMode --
 *
 *	Parse the "-mode" argument to the fconfigure command.  The argument
 *	is of the form baud,parity,data,stop.
 *
 * Results:
 *	The return value is TCL_OK if the argument was successfully
 *	parsed, TCL_ERROR otherwise.  If TCL_ERROR is returned, an
 *	error message is left in the interp's result (if interp is non-NULL).
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */
 
static int
TtyParseMode(interp, mode, speedPtr, parityPtr, dataPtr, stopPtr)
    Tcl_Interp *interp;		/* If non-NULL, interp for error return. */
    CONST char *mode;		/* Mode string to be parsed. */
    int *speedPtr;		/* Filled with baud rate from mode string. */
    int *parityPtr;		/* Filled with parity from mode string. */
    int *dataPtr;		/* Filled with data bits from mode string. */
    int *stopPtr;		/* Filled with stop bits from mode string. */
{
    int i, end;
    char parity;
    static char *bad = "bad value for -mode";

    i = sscanf(mode, "%d,%c,%d,%d%n", speedPtr, &parity, dataPtr,
	    stopPtr, &end);
    if ((i != 4) || (mode[end] != '\0')) {
	if (interp != NULL) {
	    Tcl_AppendResult(interp, bad, ": should be baud,parity,data,stop",
		    NULL);
	}
	return TCL_ERROR;
    }
    /*
     * Only allow setting mark/space parity on platforms that support it
     * Make sure to allow for the case where strchr is a macro.
     * [Bug: 5089]
     */
    if (
#if defined(PAREXT) || defined(USE_TERMIO)
	strchr("noems", parity) == NULL
#else
	strchr("noe", parity) == NULL
#endif
	) {
	if (interp != NULL) {
	    Tcl_AppendResult(interp, bad,
#if defined(PAREXT) || defined(USE_TERMIO)
		    " parity: should be n, o, e, m, or s",
#else
		    " parity: should be n, o, or e",
#endif
		    NULL);
	}
	return TCL_ERROR;
    }
    *parityPtr = parity;
    if ((*dataPtr < 5) || (*dataPtr > 8)) {
	if (interp != NULL) {
	    Tcl_AppendResult(interp, bad, " data: should be 5, 6, 7, or 8",
		    NULL);
	}
	return TCL_ERROR;
    }
    if ((*stopPtr < 0) || (*stopPtr > 2)) {
	if (interp != NULL) {
	    Tcl_AppendResult(interp, bad, " stop: should be 1 or 2", NULL);
	}
	return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * TtyInit --
 *
 *	Given file descriptor that refers to a serial port, 
 *	initialize the serial port to a set of sane values so that
 *	Tcl can talk to a device located on the serial port.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Serial device initialized to non-blocking raw mode, similar to
 *	sockets.  All other modes can be simulated on top of this in Tcl.
 *
 *---------------------------------------------------------------------------
 */

static FileState *
TtyInit(fd)
    int fd;			/* Open file descriptor for serial port to
				 * be initialized. */
{
    IOSTATE iostate;
    TtyState *ttyPtr;

    ttyPtr = (TtyState *) ckalloc((unsigned) sizeof(TtyState));
    GETIOSTATE(fd, &ttyPtr->savedState);

    iostate = ttyPtr->savedState;

#ifdef USE_TERMIOS
    iostate.c_iflag = IGNBRK;
    iostate.c_oflag = 0;
    iostate.c_lflag = 0;
    iostate.c_cflag |= CREAD;
    iostate.c_cc[VMIN] = 1;
    iostate.c_cc[VTIME] = 0;
#endif	/* USE_TERMIOS */

#ifdef USE_TERMIO
    iostate.c_iflag = IGNBRK;
    iostate.c_oflag = 0;
    iostate.c_lflag = 0;
    iostate.c_cflag |= CREAD;
    iostate.c_cc[VMIN] = 1;
    iostate.c_cc[VTIME] = 0;
#endif	/* USE_TERMIO */

#ifdef USE_SGTTY
    iostate.sg_flags &= (EVENP | ODDP);
    iostate.sg_flags |= RAW;
#endif	/* USE_SGTTY */

    SETIOSTATE(fd, &iostate);

    return &ttyPtr->fs;
}
#endif	/* SUPPORTS_TTY */

/*
 *----------------------------------------------------------------------
 *
 * 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 and an error message is
 *	left in the interp's result if interp is not NULL.
 *
 * 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? */
{
    int fd, seekFlag, mode, channelPermissions;
    FileState *fsPtr;
    char *native, *translation;
    char channelName[16 + TCL_INTEGER_SPACE];
    Tcl_DString ds, buffer;
    Tcl_ChannelType *channelTypePtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    mode = TclGetOpenMode(interp, modeString, &seekFlag);
    if (mode == -1) {
        return NULL;
    }
    switch (mode & (O_RDONLY | O_WRONLY | O_RDWR)) {
	case O_RDONLY:
	    channelPermissions = TCL_READABLE;
	    break;
	case O_WRONLY:
	    channelPermissions = TCL_WRITABLE;
	    break;
	case O_RDWR:
	    channelPermissions = (TCL_READABLE | TCL_WRITABLE);
	    break;
	default:
            /*
             * This may occurr if modeString was "", for example.
             */
	    panic("TclpOpenFileChannel: invalid mode value");
	    return NULL;
    }

    native = Tcl_TranslateFileName(interp, fileName, &buffer);
    if (native == NULL) {
	return NULL;
    }
    native = Tcl_UtfToExternalDString(NULL, native, -1, &ds);
    fd = open(native, mode, permissions);		/* INTL: Native. */
    Tcl_DStringFree(&ds);    
    Tcl_DStringFree(&buffer);

    if (fd < 0) {
        if (interp != (Tcl_Interp *) NULL) {
            Tcl_AppendResult(interp, "couldn't open \"", fileName, "\": ",
                    Tcl_PosixError(interp), (char *) NULL);
        }
        return NULL;
    }

    /*
     * Set close-on-exec flag on the fd so that child processes will not
     * inherit this fd.
     */
  
    fcntl(fd, F_SETFD, FD_CLOEXEC);
    
    sprintf(channelName, "file%d", fd);
    
#ifdef SUPPORTS_TTY
    if (isatty(fd)) {
	/*
	 * Initialize the serial port to a set of sane parameters.
	 * Especially important if the remote device is set to echo and
	 * the serial port driver was also set to echo -- as soon as a char
	 * were sent to the serial port, the remote device would echo it,
	 * then the serial driver would echo it back to the device, etc.
	 */
	 
	translation = "auto crlf";
	channelTypePtr = &ttyChannelType;
	fsPtr = TtyInit(fd);
    } else 
#endif	/* SUPPORTS_TTY */
    {
	translation = NULL;
	channelTypePtr = &fileChannelType;
	fsPtr = (FileState *) ckalloc((unsigned) sizeof(FileState));
    }

    fsPtr->nextPtr = tsdPtr->firstFilePtr;
    tsdPtr->firstFilePtr = fsPtr;
    fsPtr->validMask = channelPermissions | TCL_EXCEPTION;
    fsPtr->fd = fd;
    
    fsPtr->channel = Tcl_CreateChannel(channelTypePtr, channelName,
	    (ClientData) fsPtr, channelPermissions);

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

    if (translation != NULL) {
	/*
	 * Gotcha.  Most modems need a "\r" at the end of the command
	 * sequence.  If you just send "at\n", the modem will not respond
	 * with "OK" because it never got a "\r" to actually invoke the
	 * command.  So, by default, newlines are translated to "\r\n" on
	 * output to avoid "bug" reports that the serial port isn't working.
	 */
	 
	if (Tcl_SetChannelOption(interp, fsPtr->channel, "-translation",
		translation) != TCL_OK) {
	    Tcl_Close(NULL, fsPtr->channel);
	    return NULL;
	}
    }

    return fsPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeFileChannel --
 *
 *	Makes a Tcl_Channel from an existing OS level file handle.
 *
 * Results:
 *	The Tcl_Channel created around the preexisting OS level file handle.
 *
 * 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. */
{
    FileState *fsPtr;
    char channelName[16 + TCL_INTEGER_SPACE];
    int fd = (int) handle;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

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

    sprintf(channelName, "file%d", fd);

    /*
     * Look to see if a channel with this fd and the same mode already exists.
     * If the fd is used, but the mode doesn't match, return NULL.
     */
    
    for (fsPtr = tsdPtr->firstFilePtr; fsPtr != NULL; fsPtr = fsPtr->nextPtr) {
	if (fsPtr->fd == fd) {
	    return ((mode|TCL_EXCEPTION) == fsPtr->validMask) ?
		    fsPtr->channel : NULL;
	}
    }

    fsPtr = (FileState *) ckalloc((unsigned) sizeof(FileState));
    fsPtr->nextPtr = tsdPtr->firstFilePtr;
    tsdPtr->firstFilePtr = fsPtr;

    fsPtr->fd = fd;
    fsPtr->validMask = mode | TCL_EXCEPTION;
    fsPtr->channel = Tcl_CreateChannel(&fileChannelType, channelName,
            (ClientData) fsPtr, mode);
    
    return fsPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpBlockModeProc --
 *
 *	This procedure is invoked by the generic IO level to set blocking
 *	and nonblocking mode on a TCP socket based channel.
 *
 * Results:
 *	0 if successful, errno when failed.
 *
 * Side effects:
 *	Sets the device into blocking or nonblocking mode.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static int
TcpBlockModeProc(instanceData, mode)
    ClientData instanceData;		/* Socket state. */
    int mode;				/* The mode to set. Can be one of
                                         * TCL_MODE_BLOCKING or
                                         * TCL_MODE_NONBLOCKING. */
{
    TcpState *statePtr = (TcpState *) instanceData;
    int setting;
    
#ifndef	USE_FIONBIO
    setting = fcntl(statePtr->fd, F_GETFL);
    if (mode == TCL_MODE_BLOCKING) {
        statePtr->flags &= (~(TCP_ASYNC_SOCKET));
        setting &= (~(O_NONBLOCK));
    } else {
        statePtr->flags |= TCP_ASYNC_SOCKET;
        setting |= O_NONBLOCK;
    }
    if (fcntl(statePtr->fd, F_SETFL, setting) < 0) {
        return errno;
    }
#endif

#ifdef	USE_FIONBIO
    if (mode == TCL_MODE_BLOCKING) {
        statePtr->flags &= (~(TCP_ASYNC_SOCKET));
        setting = 0;
        if (ioctl(statePtr->fd, (int) FIONBIO, &setting) == -1) {
            return errno;
        }
    } else {
        statePtr->flags |= TCP_ASYNC_SOCKET;
        setting = 1;
        if (ioctl(statePtr->fd, (int) FIONBIO, &setting) == -1) {
            return errno;
        }
    }
#endif

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * WaitForConnect --
 *
 *	Waits for a connection on an asynchronously opened socket to
 *	be completed.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The socket is connected after this function returns.
 *
 *----------------------------------------------------------------------
 */

static int
WaitForConnect(statePtr, errorCodePtr)
    TcpState *statePtr;		/* State of the socket. */
    int *errorCodePtr;		/* Where to store errors? */
{
    int timeOut;		/* How long to wait. */
    int state;			/* Of calling TclWaitForFile. */
    int flags;			/* fcntl flags for the socket. */

    /*
     * If an asynchronous connect is in progress, attempt to wait for it
     * to complete before reading.
     */
    
    if (statePtr->flags & TCP_ASYNC_CONNECT) {
        if (statePtr->flags & TCP_ASYNC_SOCKET) {
            timeOut = 0;
        } else {
            timeOut = -1;
        }
        errno = 0;
        state = TclUnixWaitForFile(statePtr->fd,
		TCL_WRITABLE | TCL_EXCEPTION, timeOut);
        if (!(statePtr->flags & TCP_ASYNC_SOCKET)) {
#ifndef	USE_FIONBIO
            flags = fcntl(statePtr->fd, F_GETFL);
            flags &= (~(O_NONBLOCK));
            (void) fcntl(statePtr->fd, F_SETFL, flags);
#endif

#ifdef	USE_FIONBIO
            flags = 0;
            (void) ioctl(statePtr->fd, FIONBIO, &flags);
#endif
        }
        if (state & TCL_EXCEPTION) {
            return -1;
        }
        if (state & TCL_WRITABLE) {
            statePtr->flags &= (~(TCP_ASYNC_CONNECT));
        } else if (timeOut == 0) {
            *errorCodePtr = errno = EWOULDBLOCK;
            return -1;
        }
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpInputProc --
 *
 *	This procedure is invoked by the generic IO level to read input
 *	from a TCP socket based channel.
 *
 *	NOTE: We cannot share code with FilePipeInputProc because here
 *	we must use recv to obtain the input from the channel, not read.
 *
 * Results:
 *	The number of bytes read is returned or -1 on error. An output
 *	argument contains the POSIX error code on error, or zero if no
 *	error occurred.
 *
 * Side effects:
 *	Reads input from the input device of the channel.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static int
TcpInputProc(instanceData, buf, bufSize, errorCodePtr)
    ClientData instanceData;		/* Socket state. */
    char *buf;				/* Where to store data read. */
    int bufSize;			/* How much space is available
                                         * in the buffer? */
    int *errorCodePtr;			/* Where to store error code. */
{
    TcpState *statePtr = (TcpState *) instanceData;
    int bytesRead, state;

    *errorCodePtr = 0;
    state = WaitForConnect(statePtr, errorCodePtr);
    if (state != 0) {
        return -1;
    }
    bytesRead = recv(statePtr->fd, buf, (size_t) bufSize, 0);
    if (bytesRead > -1) {
        return bytesRead;
    }
    if (errno == ECONNRESET) {

        /*
         * Turn ECONNRESET into a soft EOF condition.
         */
        
        return 0;
    }
    *errorCodePtr = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpOutputProc --
 *
 *	This procedure is invoked by the generic IO level to write output
 *	to a TCP socket based channel.
 *
 *	NOTE: We cannot share code with FilePipeOutputProc because here
 *	we must use send, not write, to get reliable error reporting.
 *
 * Results:
 *	The number of bytes written is returned. An output argument is
 *	set to a POSIX error code if an error occurred, or zero.
 *
 * Side effects:
 *	Writes output on the output device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
TcpOutputProc(instanceData, buf, toWrite, errorCodePtr)
    ClientData instanceData;		/* Socket state. */
    char *buf;				/* The data buffer. */
    int toWrite;			/* How many bytes to write? */
    int *errorCodePtr;			/* Where to store error code. */
{
    TcpState *statePtr = (TcpState *) instanceData;
    int written;
    int state;				/* Of waiting for connection. */

    *errorCodePtr = 0;
    state = WaitForConnect(statePtr, errorCodePtr);
    if (state != 0) {
        return -1;
    }
    written = send(statePtr->fd, buf, (size_t) toWrite, 0);
    if (written > -1) {
        return written;
    }
    *errorCodePtr = errno;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpCloseProc --
 *
 *	This procedure is invoked by the generic IO level to perform
 *	channel-type-specific cleanup when a TCP socket based channel
 *	is closed.
 *
 * Results:
 *	0 if successful, the value of errno if failed.
 *
 * Side effects:
 *	Closes the socket of the channel.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static int
TcpCloseProc(instanceData, interp)
    ClientData instanceData;	/* The socket to close. */
    Tcl_Interp *interp;		/* For error reporting - unused. */
{
    TcpState *statePtr = (TcpState *) instanceData;
    int errorCode = 0;

    /*
     * Delete a file handler that may be active for this socket if this
     * is a server socket - the file handler was created automatically
     * by Tcl as part of the mechanism to accept new client connections.
     * Channel handlers are already deleted in the generic IO channel
     * closing code that called this function, so we do not have to
     * delete them here.
     */

    Tcl_DeleteFileHandler(statePtr->fd);

    if (close(statePtr->fd) < 0) {
	errorCode = errno;
    }
    ckfree((char *) statePtr);

    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpGetOptionProc --
 *
 *	Computes an option value for a TCP socket based channel, or a
 *	list of all options and their values.
 *
 *	Note: This code is based on code contributed by John Haxby.
 *
 * Results:
 *	A standard Tcl result. The value of the specified option or a
 *	list of all options and	their values is returned in the
 *	supplied DString. Sets Error message if needed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
TcpGetOptionProc(instanceData, interp, optionName, dsPtr)
    ClientData instanceData;     /* Socket state. */
    Tcl_Interp *interp;          /* For error reporting - can be NULL. */
    char *optionName;	         /* Name of the option to
				  * retrieve the value for, or
				  * NULL to get all options and
				  * their values. */
    Tcl_DString *dsPtr;	         /* Where to store the computed
				  * value; initialized by caller. */
{
    TcpState *statePtr = (TcpState *) instanceData;
    struct sockaddr_in sockname;
    struct sockaddr_in peername;
    struct hostent *hostEntPtr;
    int size = sizeof(struct sockaddr_in);
    size_t len = 0;
    char buf[TCL_INTEGER_SPACE];

    if (optionName != (char *) NULL) {
        len = strlen(optionName);
    }

    if ((len > 1) && (optionName[1] == 'e') &&
	    (strncmp(optionName, "-error", len) == 0)) {
	int optlen;
	int err, ret;
    
	optlen = sizeof(int);
	ret = getsockopt(statePtr->fd, SOL_SOCKET, SO_ERROR,
		(char *)&err, &optlen);
	if (ret < 0) {
	    err = errno;
	}
	if (err != 0) {
	    Tcl_DStringAppend(dsPtr, Tcl_ErrnoMsg(err), -1);
	}
       return TCL_OK;
    }

    if ((len == 0) ||
            ((len > 1) && (optionName[1] == 'p') &&
                    (strncmp(optionName, "-peername", len) == 0))) {
        if (getpeername(statePtr->fd, (struct sockaddr *) &peername,
		&size) >= 0) {
            if (len == 0) {
                Tcl_DStringAppendElement(dsPtr, "-peername");
                Tcl_DStringStartSublist(dsPtr);
            }
            Tcl_DStringAppendElement(dsPtr, inet_ntoa(peername.sin_addr));
            hostEntPtr = gethostbyaddr(			/* INTL: Native. */
		    (char *) &peername.sin_addr,
		    sizeof(peername.sin_addr), AF_INET);
            if (hostEntPtr != NULL) {
		Tcl_DString ds;

		Tcl_ExternalToUtfDString(NULL, hostEntPtr->h_name, -1, &ds);
                Tcl_DStringAppendElement(dsPtr, Tcl_DStringValue(&ds));
            } else {
                Tcl_DStringAppendElement(dsPtr, inet_ntoa(peername.sin_addr));
            }
            TclFormatInt(buf, ntohs(peername.sin_port));
            Tcl_DStringAppendElement(dsPtr, buf);
            if (len == 0) {
                Tcl_DStringEndSublist(dsPtr);
            } else {
                return TCL_OK;
            }
        } else {
            /*
             * getpeername failed - but if we were asked for all the options
             * (len==0), don't flag an error at that point because it could
             * be an fconfigure request on a server socket. (which have
             * no peer). same must be done on win&mac.
             */

            if (len) {
                if (interp) {
                    Tcl_AppendResult(interp, "can't get peername: ",
                                     Tcl_PosixError(interp),
                                     (char *) NULL);
                }
                return TCL_ERROR;
            }
        }
    }

    if ((len == 0) ||
            ((len > 1) && (optionName[1] == 's') &&
                    (strncmp(optionName, "-sockname", len) == 0))) {
        if (getsockname(statePtr->fd, (struct sockaddr *) &sockname, &size)
		>= 0) {
            if (len == 0) {
                Tcl_DStringAppendElement(dsPtr, "-sockname");
                Tcl_DStringStartSublist(dsPtr);
            }
            Tcl_DStringAppendElement(dsPtr, inet_ntoa(sockname.sin_addr));
            hostEntPtr = gethostbyaddr(			/* INTL: Native. */
		    (char *) &sockname.sin_addr,
                    sizeof(sockname.sin_addr), AF_INET);
            if (hostEntPtr != (struct hostent *) NULL) {
		Tcl_DString ds;

		Tcl_ExternalToUtfDString(NULL, hostEntPtr->h_name, -1, &ds);
                Tcl_DStringAppendElement(dsPtr, Tcl_DStringValue(&ds));
            } else {
                Tcl_DStringAppendElement(dsPtr, inet_ntoa(sockname.sin_addr));
            }
            TclFormatInt(buf, ntohs(sockname.sin_port));
            Tcl_DStringAppendElement(dsPtr, buf);
            if (len == 0) {
                Tcl_DStringEndSublist(dsPtr);
            } else {
                return TCL_OK;
            }
        } else {
	    if (interp) {
		Tcl_AppendResult(interp, "can't get sockname: ",
				 Tcl_PosixError(interp),
				 (char *) NULL);
	    }
	    return TCL_ERROR;
	}
    }

    if (len > 0) {
        return Tcl_BadChannelOption(interp, optionName, "peername sockname");
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpWatchProc --
 *
 *	Initialize the notifier to watch the fd from this channel.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Sets up the notifier so that a future event on the channel will
 *	be seen by Tcl.
 *
 *----------------------------------------------------------------------
 */

static void
TcpWatchProc(instanceData, mask)
    ClientData instanceData;		/* The socket state. */
    int mask;				/* Events of interest; an OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    TcpState *statePtr = (TcpState *) instanceData;

    /*
     * Make sure we don't mess with server sockets since they will never
     * be readable or writable at the Tcl level.  This keeps Tcl scripts
     * from interfering with the -accept behavior.
     */

    if (!statePtr->acceptProc) {
	if (mask) {
	    Tcl_CreateFileHandler(statePtr->fd, mask,
		    (Tcl_FileProc *) Tcl_NotifyChannel,
		    (ClientData) statePtr->channel);
	} else {
	    Tcl_DeleteFileHandler(statePtr->fd);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TcpGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle to retrieve OS handles from inside
 *	a TCP socket 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.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static int
TcpGetHandleProc(instanceData, direction, handlePtr)
    ClientData instanceData;	/* The socket state. */
    int direction;		/* Not used. */
    ClientData *handlePtr;	/* Where to store the handle.  */
{
    TcpState *statePtr = (TcpState *) instanceData;

    *handlePtr = (ClientData)statePtr->fd;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * CreateSocket --
 *
 *	This function opens a new socket in client or server mode
 *	and initializes the TcpState structure.
 *
 * Results:
 *	Returns a new TcpState, or NULL with an error in the interp's
 *	result, if interp is not NULL.
 *
 * Side effects:
 *	Opens a socket.
 *
 *----------------------------------------------------------------------
 */

static TcpState *
CreateSocket(interp, port, host, server, myaddr, myport, async)
    Tcl_Interp *interp;		/* For error reporting; can be NULL. */
    int port;			/* Port number to open. */
    char *host;			/* Name of host on which to open port.
				 * NULL implies INADDR_ANY */
    int server;			/* 1 if socket should be a server socket,
				 * else 0 for a client socket. */
    char *myaddr;		/* Optional client-side address */
    int myport;			/* Optional client-side port */
    int async;			/* If nonzero and creating a client socket,
                                 * attempt to do an async connect. Otherwise
                                 * do a synchronous connect or bind. */
{
    int status, sock, asyncConnect, curState, origState;
    struct sockaddr_in sockaddr;	/* socket address */
    struct sockaddr_in mysockaddr;	/* Socket address for client */
    TcpState *statePtr;

    sock = -1;
    origState = 0;
    if (! CreateSocketAddress(&sockaddr, host, port)) {
	goto addressError;
    }
    if ((myaddr != NULL || myport != 0) &&
	    ! CreateSocketAddress(&mysockaddr, myaddr, myport)) {
	goto addressError;
    }

    sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
	goto addressError;
    }

    /*
     * Set the close-on-exec flag so that the socket will not get
     * inherited by child processes.
     */

    fcntl(sock, F_SETFD, FD_CLOEXEC);
    
    /*
     * Set kernel space buffering
     */

    TclSockMinimumBuffers(sock, SOCKET_BUFSIZE);

    asyncConnect = 0;
    status = 0;
    if (server) {

	/*
	 * Set up to reuse server addresses automatically and bind to the
	 * specified port.
	 */
    
	status = 1;
	(void) setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (char *) &status,
		sizeof(status));
	status = bind(sock, (struct sockaddr *) &sockaddr,
                sizeof(struct sockaddr));
	if (status != -1) {
	    status = listen(sock, SOMAXCONN);
	} 
    } else {
	if (myaddr != NULL || myport != 0) { 
	    curState = 1;
	    (void) setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
                    (char *) &curState, sizeof(curState));
	    status = bind(sock, (struct sockaddr *) &mysockaddr,
		    sizeof(struct sockaddr));
	    if (status < 0) {
		goto bindError;
	    }
	}

	/*
	 * Attempt to connect. The connect may fail at present with an
	 * EINPROGRESS but at a later time it will complete. The caller
	 * will set up a file handler on the socket if she is interested in
	 * being informed when the connect completes.
	 */

        if (async) {
#ifndef	USE_FIONBIO
            origState = fcntl(sock, F_GETFL);
            curState = origState | O_NONBLOCK;
            status = fcntl(sock, F_SETFL, curState);
#endif

#ifdef	USE_FIONBIO
            curState = 1;
            status = ioctl(sock, FIONBIO, &curState);
#endif            
        } else {
            status = 0;
        }
        if (status > -1) {
            status = connect(sock, (struct sockaddr *) &sockaddr,
                    sizeof(sockaddr));
            if (status < 0) {
                if (errno == EINPROGRESS) {
                    asyncConnect = 1;
                    status = 0;
                }
	    } else {
		/*
		 * Here we are if the connect succeeds. In case of an
		 * asynchronous connect we have to reset the channel to
		 * blocking mode.  This appears to happen not very often,
		 * but e.g. on a HP 9000/800 under HP-UX B.11.00 we enter
		 * this stage. [Bug: 4388]
		 */
		if (async) {
#ifndef USE_FIONBIO
		    origState = fcntl(sock, F_GETFL);
		    curState = origState & ~(O_NONBLOCK);
		    status = fcntl(sock, F_SETFL, curState);
#endif

#ifdef  USE_FIONBIO
		    curState = 0;
		    status = ioctl(sock, FIONBIO, &curState);
#endif
		}
	    }
        }
    }

bindError:
    if (status < 0) {
        if (interp != NULL) {
            Tcl_AppendResult(interp, "couldn't open socket: ",
                    Tcl_PosixError(interp), (char *) NULL);
        }
        if (sock != -1) {
            close(sock);
        }
        return NULL;
    }

    /*
     * Allocate a new TcpState for this socket.
     */

    statePtr = (TcpState *) ckalloc((unsigned) sizeof(TcpState));
    statePtr->flags = 0;
    if (asyncConnect) {
        statePtr->flags = TCP_ASYNC_CONNECT;
    }
    statePtr->fd = sock;

    return statePtr;

addressError:
    if (sock != -1) {
        close(sock);
    }
    if (interp != NULL) {
	Tcl_AppendResult(interp, "couldn't open socket: ",
		Tcl_PosixError(interp), (char *) NULL);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CreateSocketAddress --
 *
 *	This function initializes a sockaddr structure for a host and port.
 *
 * Results:
 *	1 if the host was valid, 0 if the host could not be converted to
 *	an IP address.
 *
 * Side effects:
 *	Fills in the *sockaddrPtr structure.
 *
 *----------------------------------------------------------------------
 */

static int
CreateSocketAddress(sockaddrPtr, host, port)
    struct sockaddr_in *sockaddrPtr;	/* Socket address */
    char *host;				/* Host.  NULL implies INADDR_ANY */
    int port;				/* Port number */
{
    struct hostent *hostent;		/* Host database entry */
    struct in_addr addr;		/* For 64/32 bit madness */

    (void) memset((VOID *) sockaddrPtr, '\0', sizeof(struct sockaddr_in));
    sockaddrPtr->sin_family = AF_INET;
    sockaddrPtr->sin_port = htons((unsigned short) (port & 0xFFFF));
    if (host == NULL) {
	addr.s_addr = INADDR_ANY;
    } else {
	Tcl_DString ds;
	CONST char *native;

	if (host == NULL) {
	    native = NULL;
	} else {
	    native = Tcl_UtfToExternalDString(NULL, host, -1, &ds);
	}
        addr.s_addr = inet_addr(native);		/* INTL: Native. */
	/*
	 * This is 0xFFFFFFFF to ensure that it compares as a 32bit -1
	 * on either 32 or 64 bits systems.
	 */
        if (addr.s_addr == 0xFFFFFFFF) {
            hostent = gethostbyname(native);		/* INTL: Native. */
            if (hostent != NULL) {
                memcpy((VOID *) &addr,
                        (VOID *) hostent->h_addr_list[0],
                        (size_t) hostent->h_length);
            } else {
#ifdef	EHOSTUNREACH
                errno = EHOSTUNREACH;
#else
#ifdef ENXIO
                errno = ENXIO;
#endif
#endif
		if (native != NULL) {
		    Tcl_DStringFree(&ds);
		}
                return 0;	/* error */
            }
        }
	if (native != NULL) {
	    Tcl_DStringFree(&ds);
	}
    }
        
    /*
     * NOTE: On 64 bit machines the assignment below is rumored to not
     * do the right thing. Please report errors related to this if you
     * observe incorrect behavior on 64 bit machines such as DEC Alphas.
     * Should we modify this code to do an explicit memcpy?
     */

    sockaddrPtr->sin_addr.s_addr = addr.s_addr;
    return 1;	/* Success. */
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_OpenTcpClient --
 *
 *	Opens a TCP client socket and creates a channel around it.
 *
 * Results:
 *	The channel or NULL if failed.  An error message is returned
 *	in the interpreter on failure.
 *
 * Side effects:
 *	Opens a client socket and creates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_OpenTcpClient(interp, port, host, myaddr, myport, async)
    Tcl_Interp *interp;			/* For error reporting; can be NULL. */
    int port;				/* Port number to open. */
    char *host;				/* Host on which to open port. */
    char *myaddr;			/* Client-side address */
    int myport;				/* Client-side port */
    int async;				/* If nonzero, attempt to do an
                                         * asynchronous connect. Otherwise
                                         * we do a blocking connect. */
{
    TcpState *statePtr;
    char channelName[16 + TCL_INTEGER_SPACE];

    /*
     * Create a new client socket and wrap it in a channel.
     */

    statePtr = CreateSocket(interp, port, host, 0, myaddr, myport, async);
    if (statePtr == NULL) {
	return NULL;
    }

    statePtr->acceptProc = NULL;
    statePtr->acceptProcData = (ClientData) NULL;

    sprintf(channelName, "sock%d", statePtr->fd);

    statePtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) statePtr, (TCL_READABLE | TCL_WRITABLE));
    if (Tcl_SetChannelOption(interp, statePtr->channel, "-translation",
	    "auto crlf") == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, statePtr->channel);
        return NULL;
    }
    return statePtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeTcpClientChannel --
 *
 *	Creates a Tcl_Channel from an existing client TCP socket.
 *
 * Results:
 *	The Tcl_Channel wrapped around the preexisting TCP socket.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_MakeTcpClientChannel(sock)
    ClientData sock;		/* The socket to wrap up into a channel. */
{
    TcpState *statePtr;
    char channelName[16 + TCL_INTEGER_SPACE];

    statePtr = (TcpState *) ckalloc((unsigned) sizeof(TcpState));
    statePtr->fd = (int) sock;
    statePtr->acceptProc = NULL;
    statePtr->acceptProcData = (ClientData) NULL;

    sprintf(channelName, "sock%d", statePtr->fd);
    
    statePtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) statePtr, (TCL_READABLE | TCL_WRITABLE));
    if (Tcl_SetChannelOption((Tcl_Interp *) NULL, statePtr->channel,
	    "-translation", "auto crlf") == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, statePtr->channel);
        return NULL;
    }
    return statePtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_OpenTcpServer --
 *
 *	Opens a TCP server socket and creates a channel around it.
 *
 * Results:
 *	The channel or NULL if failed. If an error occurred, an
 *	error message is left in the interp's result if interp is
 *	not NULL.
 *
 * Side effects:
 *	Opens a server socket and creates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_OpenTcpServer(interp, port, myHost, acceptProc, acceptProcData)
    Tcl_Interp *interp;			/* For error reporting - may be
                                         * NULL. */
    int port;				/* Port number to open. */
    char *myHost;			/* Name of local host. */
    Tcl_TcpAcceptProc *acceptProc;	/* Callback for accepting connections
                                         * from new clients. */
    ClientData acceptProcData;		/* Data for the callback. */
{
    TcpState *statePtr;
    char channelName[16 + TCL_INTEGER_SPACE];

    /*
     * Create a new client socket and wrap it in a channel.
     */

    statePtr = CreateSocket(interp, port, myHost, 1, NULL, 0, 0);
    if (statePtr == NULL) {
	return NULL;
    }

    statePtr->acceptProc = acceptProc;
    statePtr->acceptProcData = acceptProcData;

    /*
     * Set up the callback mechanism for accepting connections
     * from new clients.
     */

    Tcl_CreateFileHandler(statePtr->fd, TCL_READABLE, TcpAccept,
            (ClientData) statePtr);
    sprintf(channelName, "sock%d", statePtr->fd);
    statePtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) statePtr, 0);
    return statePtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpAccept --
 *	Accept a TCP socket connection.  This is called by the event loop.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Creates a new connection socket. Calls the registered callback
 *	for the connection acceptance mechanism.
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static void
TcpAccept(data, mask)
    ClientData data;			/* Callback token. */
    int mask;				/* Not used. */
{
    TcpState *sockState;		/* Client data of server socket. */
    int newsock;			/* The new client socket */
    TcpState *newSockState;		/* State for new socket. */
    struct sockaddr_in addr;		/* The remote address */
    int len;				/* For accept interface */
    char channelName[16 + TCL_INTEGER_SPACE];

    sockState = (TcpState *) data;

    len = sizeof(struct sockaddr_in);
    newsock = accept(sockState->fd, (struct sockaddr *) &addr, &len);
    if (newsock < 0) {
        return;
    }

    /*
     * Set close-on-exec flag to prevent the newly accepted socket from
     * being inherited by child processes.
     */

    (void) fcntl(newsock, F_SETFD, FD_CLOEXEC);
    
    newSockState = (TcpState *) ckalloc((unsigned) sizeof(TcpState));

    newSockState->flags = 0;
    newSockState->fd = newsock;
    newSockState->acceptProc = NULL;
    newSockState->acceptProcData = NULL;
        
    sprintf(channelName, "sock%d", newsock);
    newSockState->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
	    (ClientData) newSockState, (TCL_READABLE | TCL_WRITABLE));

    Tcl_SetChannelOption(NULL, newSockState->channel, "-translation",
	    "auto crlf");

    if (sockState->acceptProc != NULL) {
	(*sockState->acceptProc)(sockState->acceptProcData,
		newSockState->channel, inet_ntoa(addr.sin_addr),
		ntohs(addr.sin_port));
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpGetDefaultStdChannel --
 *
 *	Creates channels for standard input, standard output or standard
 *	error output if they do not already exist.
 *
 * 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
TclpGetDefaultStdChannel(type)
    int type;			/* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR. */
{
    Tcl_Channel channel = NULL;
    int fd = 0;			/* Initializations needed to prevent */
    int mode = 0;		/* compiler warning (used before set). */
    char *bufMode = NULL;

    switch (type) {
        case TCL_STDIN:
            if ((lseek(0, (off_t) 0, SEEK_CUR) == -1) &&
                    (errno == EBADF)) {
                return (Tcl_Channel) NULL;
            }
	    fd = 0;
	    mode = TCL_READABLE;
            bufMode = "line";
            break;
        case TCL_STDOUT:
            if ((lseek(1, (off_t) 0, SEEK_CUR) == -1) &&
                    (errno == EBADF)) {
                return (Tcl_Channel) NULL;
            }
	    fd = 1;
	    mode = TCL_WRITABLE;
            bufMode = "line";
            break;
        case TCL_STDERR:
            if ((lseek(2, (off_t) 0, SEEK_CUR) == -1) &&
                    (errno == EBADF)) {
                return (Tcl_Channel) NULL;
            }
	    fd = 2;
	    mode = TCL_WRITABLE;
	    bufMode = "none";
            break;
	default:
	    panic("TclGetDefaultStdChannel: Unexpected channel type");
	    break;
    }

    channel = Tcl_MakeFileChannel((ClientData) fd, mode);
    if (channel == NULL) {
	return NULL;
    }

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

    Tcl_SetChannelOption(NULL, channel, "-translation", "auto");
    Tcl_SetChannelOption(NULL, channel, "-buffering", bufMode);
    return channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetOpenFile --
 *
 *	Given a name of a channel registered in the given interpreter,
 *	returns a FILE * for it.
 *
 * Results:
 *	A standard Tcl result. If the channel is registered in the given
 *	interpreter and it is managed by the "file" channel driver, and
 *	it is open for the requested mode, then the output parameter
 *	filePtr is set to a FILE * for the underlying file. On error, the
 *	filePtr is not set, TCL_ERROR is returned and an error message is
 *	left in the interp's result.
 *
 * Side effects:
 *	May invoke fdopen to create the FILE * for the requested file.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_GetOpenFile(interp, string, forWriting, checkUsage, filePtr)
    Tcl_Interp *interp;		/* Interpreter in which to find file. */
    char *string;		/* String that identifies file. */
    int forWriting;		/* 1 means the file is going to be used
				 * for writing, 0 means for reading. */
    int checkUsage;		/* 1 means verify that the file was opened
				 * in a mode that allows the access specified
				 * by "forWriting". Ignored, we always
                                 * check that the channel is open for the
                                 * requested mode. */
    ClientData *filePtr;	/* Store pointer to FILE structure here. */
{
    Tcl_Channel chan;
    int chanMode;
    Tcl_ChannelType *chanTypePtr;
    ClientData data;
    int fd;
    FILE *f;
    
    chan = Tcl_GetChannel(interp, string, &chanMode);
    if (chan == (Tcl_Channel) NULL) {
        return TCL_ERROR;
    }
    if ((forWriting) && ((chanMode & TCL_WRITABLE) == 0)) {
        Tcl_AppendResult(interp,
                "\"", string, "\" wasn't opened for writing", (char *) NULL);
        return TCL_ERROR;
    } else if ((!(forWriting)) && ((chanMode & TCL_READABLE) == 0)) {
        Tcl_AppendResult(interp,
                "\"", string, "\" wasn't opened for reading", (char *) NULL);
        return TCL_ERROR;
    }

    /*
     * We allow creating a FILE * out of file based, pipe based and socket
     * based channels. We currently do not allow any other channel types,
     * because it is likely that stdio will not know what to do with them.
     */

    chanTypePtr = Tcl_GetChannelType(chan);
    if ((chanTypePtr == &fileChannelType)
#ifdef SUPPORTS_TTY
	    || (chanTypePtr == &ttyChannelType)
#endif	/* SUPPORTS_TTY */
	    || (chanTypePtr == &tcpChannelType)
	    || (strcmp(chanTypePtr->typeName, "pipe") == 0)) {
        if (Tcl_GetChannelHandle(chan,
		(forWriting ? TCL_WRITABLE : TCL_READABLE),
		(ClientData*) &data) == TCL_OK) {
	    fd = (int) data;

	    /*
	     * The call to fdopen below is probably dangerous, since it will
	     * truncate an existing file if the file is being opened
	     * for writing....
	     */
        
	    f = fdopen(fd, (forWriting ? "w" : "r"));
	    if (f == NULL) {
		Tcl_AppendResult(interp, "cannot get a FILE * for \"", string,
			"\"", (char *) NULL);
		return TCL_ERROR;
	    }
	    *filePtr = (ClientData) f;
	    return TCL_OK;
	}
    }

    Tcl_AppendResult(interp, "\"", string,
            "\" cannot be used to get a FILE *", (char *) NULL);
    return TCL_ERROR;        
}

/*
 *----------------------------------------------------------------------
 *
 * TclUnixWaitForFile --
 *
 *	This procedure waits synchronously for a file to become readable
 *	or writable, with an optional timeout.
 *
 * Results:
 *	The return value is an OR'ed combination of TCL_READABLE,
 *	TCL_WRITABLE, and TCL_EXCEPTION, indicating the conditions
 *	that are present on file at the time of the return.  This
 *	procedure will not return until either "timeout" milliseconds
 *	have elapsed or at least one of the conditions given by mask
 *	has occurred for file (a return value of 0 means that a timeout
 *	occurred).  No normal events will be serviced during the
 *	execution of this procedure.
 *
 * Side effects:
 *	Time passes.
 *
 *----------------------------------------------------------------------
 */

int
TclUnixWaitForFile(fd, mask, timeout)
    int fd;			/* Handle for file on which to wait. */
    int mask;			/* What to wait for: OR'ed combination of
				 * TCL_READABLE, TCL_WRITABLE, and
				 * TCL_EXCEPTION. */
    int timeout;		/* Maximum amount of time to wait for one
				 * of the conditions in mask to occur, in
				 * milliseconds.  A value of 0 means don't
				 * wait at all, and a value of -1 means
				 * wait forever. */
{
    Tcl_Time abortTime, now;
    struct timeval blockTime, *timeoutPtr;
    int index, bit, numFound, result = 0;
    fd_mask readyMasks[3*MASK_SIZE];
				/* This array reflects the readable/writable
				 * conditions that were found to exist by the
				 * last call to select. */

    /*
     * If there is a non-zero finite timeout, compute the time when
     * we give up.
     */

    if (timeout > 0) {
	TclpGetTime(&now);
	abortTime.sec = now.sec + timeout/1000;
	abortTime.usec = now.usec + (timeout%1000)*1000;
	if (abortTime.usec >= 1000000) {
	    abortTime.usec -= 1000000;
	    abortTime.sec += 1;
	}
	timeoutPtr = &blockTime;
    } else if (timeout == 0) {
	timeoutPtr = &blockTime;
	blockTime.tv_sec = 0;
	blockTime.tv_usec = 0;
    } else {
	timeoutPtr = NULL;
    }

    /*
     * Initialize the ready masks and compute the mask offsets.
     */

    if (fd >= FD_SETSIZE) {
	panic("TclWaitForFile can't handle file id %d", fd);
    }
    memset((VOID *) readyMasks, 0, 3*MASK_SIZE*sizeof(fd_mask));
    index = fd/(NBBY*sizeof(fd_mask));
    bit = 1 << (fd%(NBBY*sizeof(fd_mask)));
    
    /*
     * Loop in a mini-event loop of our own, waiting for either the
     * file to become ready or a timeout to occur.
     */

    while (1) {
	if (timeout > 0) {
	    blockTime.tv_sec = abortTime.sec - now.sec;
	    blockTime.tv_usec = abortTime.usec - now.usec;
	    if (blockTime.tv_usec < 0) {
		blockTime.tv_sec -= 1;
		blockTime.tv_usec += 1000000;
	    }
	    if (blockTime.tv_sec < 0) {
		blockTime.tv_sec = 0;
		blockTime.tv_usec = 0;
	    }
	}
	
	/*
	 * Set the appropriate bit in the ready masks for the fd.
	 */

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

	/*
	 * Wait for the event or a timeout.
	 */

	numFound = select(fd+1, (SELECT_MASK *) &readyMasks[0],
		(SELECT_MASK *) &readyMasks[MASK_SIZE],
		(SELECT_MASK *) &readyMasks[2*MASK_SIZE], timeoutPtr);
	if (numFound == 1) {
	    if (readyMasks[index] & bit) {
		result |= TCL_READABLE;
	    }
	    if ((readyMasks+MASK_SIZE)[index] & bit) {
		result |= TCL_WRITABLE;
	    }
	    if ((readyMasks+2*(MASK_SIZE))[index] & bit) {
		result |= TCL_EXCEPTION;
	    }
	    result &= mask;
	    if (result) {
		break;
	    }
	}
	if (timeout == 0) {
	    break;
	}

	/*
	 * The select returned early, so we need to recompute the timeout.
	 */

	TclpGetTime(&now);
	if ((abortTime.sec < now.sec)
		|| ((abortTime.sec == now.sec)
		&& (abortTime.usec <= now.usec))) {
	    break;
	}
    }
    return result;
}
