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tclUnixChan.c

/* 
 * tclUnixChan.c
 *
 *    Common channel driver for Unix 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: tclUnixChan.c,v 1.7 1998/09/14 18:40:17 stanton 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

#ifdef USE_TERMIOS
#   include <termios.h>
#else /* !USE_TERMIOS */
#ifdef USE_TERMIO
#   include <termio.h>
#else /* !USE_TERMIO */
#ifdef USE_SGTTY
#   include <sgtty.h>
#endif      /* USE_SGTTY */
#endif      /* !USE_TERMIO */
#endif      /* !USE_TERMIOS */

/*
 * 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;

/*
 * 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;

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

static FileState *firstFilePtr = NULL;

/*
 * 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));
static int        TtyParseMode _ANSI_ARGS_((Tcl_Interp *interp,
                      CONST char *mode, int *speedPtr, int *parityPtr,
                      int *dataPtr, int *stopPtr));
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 void       TtyInit _ANSI_ARGS_((int fd));
static void       TtySetAttributes _ANSI_ARGS_((int fd,
                      TtyAttrs *ttyPtr));
static int        TtySetOptionProc _ANSI_ARGS_((ClientData instanceData,
                      Tcl_Interp *interp, char *optionName, 
                      char *value));
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. */
};

/*
 * 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.*/
    FileCloseProc,                  /* 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. */
};

/*
 * 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;

    Tcl_DeleteFileHandler(fsPtr->fd);
    if (!TclInExit()
          || ((fsPtr->fd != 0) && (fsPtr->fd != 1) && (fsPtr->fd != 2))) {
      if (close(fsPtr->fd) < 0) {
          errorCode = errno;
      }
    }
    for (nextPtrPtr = &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, 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_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.  */
{
    FileState *fsPtr = (FileState *) instanceData;

    if (direction & fsPtr->validMask) {
      *handlePtr = (ClientData) fsPtr->fd;
      return TCL_OK;
    } else {
      return TCL_ERROR;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TtySetOptionProc --
 *
 *    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.
 *      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[32];
    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 */


/*
 *---------------------------------------------------------------------------
 *
 * 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.
 *
 *---------------------------------------------------------------------------
 */

static void
TtyInit(fd)
    int fd;             /* Open file descriptor for serial port to
                         * be initialized. */
{
#ifdef USE_TERMIOS
    struct termios termios;

    tcgetattr(fd, &termios);
    termios.c_iflag = IGNBRK;
    termios.c_oflag = 0;
    termios.c_lflag = 0;
    termios.c_cflag |= CREAD;
    termios.c_cc[VMIN] = 60;
    termios.c_cc[VTIME] = 2;
    tcsetattr(fd, TCSANOW, &termios);
#else /* !USE_TERMIOS */
#ifdef USE_TERMIO
    struct termio termio;

    ioctl(fd, TCGETA, &termio);
    termio.c_iflag = IGNBRK;
    termio.c_oflag = 0;
    termio.c_lflag = 0;
    termio.c_cflag |= CREAD;
    termio.c_cc[VMIN] = 60;
    termio.c_cc[VTIME] = 2;
    ioctl(fd, TCSETAW, &termio);
#else /* !USE_TERMIO */
#ifdef USE_SGTTY
    struct sgttyb sgttyb;

    ioctl(fd, TIOCGETP, &sgttyb);
    sgttyb.sg_flags &= (EVENP | ODDP);
    sgttyb.sg_flags |= RAW;
    ioctl(fd, TIOCSETP, &sgttyb);
#endif      /* USE_SGTTY */
#endif      /* !USE_TERMIO */
#endif      /* !USE_TERMIOS */
}

/*
 *---------------------------------------------------------------------------
 *
 * 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. */
{
#ifdef USE_TERMIOS
    int parity, data;
    struct termios termios;

    tcgetattr(fd, &termios);
    ttyPtr->baud = TtyGetBaud(cfgetospeed(&termios));
    
    parity = 'n';
#ifdef PAREXT
    switch ((int) (termios.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) (termios.c_cflag & (PARENB | PARODD))) {
      case PARENB             : parity = 'e'; break;
      case PARENB | PARODD          :     parity = 'o'; break;
    }
#endif      /* !PAREXT */
    ttyPtr->parity = parity;

    data = termios.c_cflag & CSIZE;
    ttyPtr->data = (data == CS5) ? 5 : (data == CS6) ? 6 :
          (data == CS7) ? 7 : 8;

    ttyPtr->stop = (termios.c_cflag & CSTOPB) ? 2 : 1;
#else /* !USE_TERMIOS */
#ifdef USE_TERMIO
    int parity, data;
    struct termio termio;

    ioctl(fd, TCGETA, &termio);
    ttyPtr->baud = TtyGetBaud(termio.c_cflag & CBAUD);
    parity = 'n';
    switch (termio.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;
    }
    ttyPtr->parity = parity;

    data = termio.c_cflag & CSIZE;
    ttyPtr->data = (data == CS5) ? 5 : (data == CS6) ? 6 :
          (data == CS7) ? 7 : 8;

    ttyPtr->stop = (termio.c_cflag & CSTOPB) ? 2 : 1;
#else /* !USE_TERMIO */
#ifdef USE_SGTTY
    int parity;
    struct sgttyb sgttyb;

    ioctl(fd, TIOCGETP, &sgttyb);
    ttyPtr->baud = TtyGetBaud(sgttyb.sg_ospeed);
    parity = 'n';
    if (sgttyb.sg_flags & EVENP) {
      parity = 'e';
    } else if (sgttyb.sg_flags & ODDP) {
      parity = 'o';
    }
    ttyPtr->parity = parity;
    ttyPtr->data = (sgttyb.sg_flags & (EVENP | ODDP)) ? 7 : 8;
    ttyPtr->stop = 1;
#else /* !USE_SGTTY */
    ttyPtr->baud = 0;
    ttyPtr->parity = 'n';
    ttyPtr->data = 0;
    ttyPtr->stop = 0;
#endif      /* !USE_SGTTY */
#endif      /* !USE_TERMIO */
#endif      /* !USE_TERMIOS */
}

/*
 *---------------------------------------------------------------------------
 *
 * 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. */
{
#ifdef USE_TERMIOS
    int parity, data, flag;
    struct termios termios;

    tcgetattr(fd, &termios);
    cfsetospeed(&termios, TtyGetSpeed(ttyPtr->baud));
    cfsetispeed(&termios, TtyGetSpeed(ttyPtr->baud));

    flag = 0;
    parity = ttyPtr->parity;
    if (parity != 'n') {
      flag |= PARENB;
#ifdef PAREXT
      termios.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;
    }

    termios.c_cflag &= ~(PARENB | PARODD | CSIZE | CSTOPB);
    termios.c_cflag |= flag;
    tcsetattr(fd, TCSANOW, &termios);

#else /* !USE_TERMIOS */
#ifdef USE_TERMIO
    int parity, data, flag;
    struct termio termio;

    ioctl(fd, TCGETA, &termio);
    termio.c_cflag &= ~CBAUD;
    termio.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;
    }

    termio.c_cflag &= ~(PARENB | PARODD | PAREXT | CSIZE | CSTOPB);
    termio.c_cflag |= flag;
    ioctl(fd, TCSETAW, &termio);

#else /* !USE_TERMIO */
#ifdef USE_SGTTY
    int parity;
    struct sgttyb sgttyb;

    ioctl(fd, TIOCGETP, &sgttyb);
    sgttyb.sg_ospeed = TtyGetSpeed(ttyPtr->baud);
    sgttyb.sg_ispeed = TtyGetSpeed(ttyPtr->baud);

    parity = ttyPtr->parity;
    if (parity == 'e') {
      sgttyb.sg_flags &= ~ODDP;
      sgttyb.sg_flags |= EVENP;
    } else if (parity == 'o') {
      sgttyb.sg_flags &= ~EVENP;
      sgttyb.sg_flags |= ODDP;
    }
    ioctl(fd, TIOCSETP, &sgttyb);
#endif      /* USE_SGTTY */
#endif      /* !USE_TERMIO */
#endif      /* !USE_TERMIOS */
}

/*
 *---------------------------------------------------------------------------
 *
 * 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 interp->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;
    }
    if (strchr("noems", parity) == NULL) {
      if (interp != NULL) {
          Tcl_AppendResult(interp, bad,
                " parity: should be n, o, e, m, or s", 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;
}

/*
 *----------------------------------------------------------------------
 *
 * 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 interp->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 *nativeName, channelName[20];
    Tcl_DString buffer;
    Tcl_ChannelType *channelTypePtr;

    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;
    }

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

    /*
     * If nativeName is not NULL, the buffer is valid and we must free
     * the storage.
     */
    
    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);
    
    fsPtr = (FileState *) ckalloc((unsigned) sizeof(FileState));
    fsPtr->nextPtr = firstFilePtr;
    firstFilePtr = fsPtr;
    fsPtr->validMask = channelPermissions | TCL_EXCEPTION;
    fsPtr->fd = fd;
    
    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.
       */
       
      TtyInit(fd);
      channelTypePtr = &ttyChannelType;
    } else {
      channelTypePtr = &fileChannelType;
    }

    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 (channelTypePtr == &ttyChannelType) {
      /*
       * 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",
            "auto crlf") != 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[20];
#ifdef BUGFIX
    Tcl_ChannelType *channelTypePtr = &fileChannelType;
#endif /* BUGFIX */
    int fd = (int) handle;

    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 = firstFilePtr; fsPtr != NULL; fsPtr = fsPtr->nextPtr) {
      if (fsPtr->fd == fd) {
          return (mode == fsPtr->validMask) ? fsPtr->channel : NULL;
      }
    }

    fsPtr = (FileState *) ckalloc((unsigned) sizeof(FileState));
    fsPtr->nextPtr = firstFilePtr;
    firstFilePtr = fsPtr;
    fsPtr->fd = fd;
#ifdef BUGFIX
    if (isatty(fd)) {
        channelTypePtr = &ttyChannelType;
    }
#endif /* BUGFIX */
    fsPtr->validMask = mode | TCL_EXCEPTION;
#ifdef BUGFIX
    fsPtr->channel = Tcl_CreateChannel(channelTypePtr, channelName,
            (ClientData) fsPtr, mode);
#else
    fsPtr->channel = Tcl_CreateChannel(&fileChannelType, channelName,
            (ClientData) fsPtr, mode);
#endif /* BUGFIX */    
    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, 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, 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[128];

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

    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((char *) &(peername.sin_addr),
                    sizeof(peername.sin_addr), AF_INET);
            if (hostEntPtr != (struct hostent *) NULL) {
                Tcl_DStringAppendElement(dsPtr, hostEntPtr->h_name);
            } else {
                Tcl_DStringAppendElement(dsPtr, inet_ntoa(peername.sin_addr));
            }
            sprintf(buf, "%d", 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((char *) &(sockname.sin_addr),
                    sizeof(sockname.sin_addr), AF_INET);
            if (hostEntPtr != (struct hostent *) NULL) {
                Tcl_DStringAppendElement(dsPtr, hostEntPtr->h_name);
            } else {
                Tcl_DStringAppendElement(dsPtr, inet_ntoa(sockname.sin_addr));
            }
            sprintf(buf, "%d", 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_GetChannelFile 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 interp->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;
                }
            }
        }
    }

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 {
        addr.s_addr = inet_addr(host);
        if (addr.s_addr == -1) {
            hostent = gethostbyname(host);
            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
                return 0;     /* error */
            }
        }
    }
        
    /*
     * 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[20];

    /*
     * 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[20];

    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 interp->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[20];

    /*
     * 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[20];

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

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

    if (sockState->acceptProc != (Tcl_TcpAcceptProc *) NULL) {
      (sockState->acceptProc) (sockState->acceptProcData,
            newSockState->channel, inet_ntoa(addr.sin_addr),
            ntohs(addr.sin_port));
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetDefaultStdChannel --
 *
 *    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
TclGetDefaultStdChannel(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);

    /*
     * 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 interp->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) || (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;
    static 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;
}

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