/*
 * Copyright (c) 1986 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *	@(#)tty.c	1.5 (2.11BSD GTE) 1997/5/4
 */

#include "param.h"
#include "user.h"
#include "ioctl.h"
#include "tty.h"
#include "proc.h"
#include "file.h"
#include "conf.h"
#include "dk.h"
#include "uio.h"
#include "kernel.h"
#include "systm.h"
#include "inode.h"
#include "syslog.h"

/*
 * These were moved here from tty.h so that they could be easily modified
 * and/or patched instead of recompiling the kernel.  There is only 1 other
 * place which references these - see tty_pty.c
 *
 * The block and unblock numbers may look low but certain devices (the DHV-11
 * for example) have poor silo handling and at high data rates (19200) the
 * raw queue overflows even though we've stopped the sending device.  At 192
 * characters for the 'block' point c-kermit would regularily see dropped data
 * during interactive mode at 19200.
 *
 * It would be nice to have a larger than 8kb clist area and raise these limits
 * but that would require 2 mapping registers and/or a rewrite of the entire
 * clist handling.
*/

	int	TTYHOG = 255;
	int	TTYBLOCK=128;
	int	TTYUNBLOCK=64;

/*
 * Table giving parity for characters and indicating
 * character classes to tty driver.  In particular,
 * if the low 6 bits are 0, then the character needs
 * no special processing on output.
 */

char partab[] = {
	0001,0201,0201,0001,0201,0001,0001,0201,
	0202,0004,0003,0201,0005,0206,0201,0001,
	0201,0001,0001,0201,0001,0201,0201,0001,
	0001,0201,0201,0001,0201,0001,0001,0201,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0000,0200,0200,0000,0200,0000,0000,0200,
	0000,0200,0200,0000,0200,0000,0000,0200,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0000,0200,0200,0000,0200,0000,0000,0200,
	0000,0200,0200,0000,0200,0000,0000,0200,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0000,0200,0200,0000,0200,0000,0000,0200,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0200,0000,0000,0200,0000,0200,0200,0000,
	0000,0200,0200,0000,0200,0000,0000,0201,

	/*
	 * 7 bit ascii ends with the last character above,
	 * but we contine through all 256 codes for the sake
	 * of the tty output routines which use special vax
	 * instructions which need a 256 character trt table.
	 */

	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007,
	0007,0007,0007,0007,0007,0007,0007,0007
};

short	tthiwat[16] =
   { 100,100,100,100,100,100,100,200,200,400,400,400,650,650,1300,2000 };
short	ttlowat[16] =
   {  30, 30, 30, 30, 30, 30, 30, 50, 50,120,120,120,125,125,125,125 };

struct	ttychars ttydefaults = {
	CERASE,	CKILL,	CINTR,	CQUIT,	CSTART,	CSTOP,	CEOF,
	CBRK,	CSUSP,	CDSUSP, CRPRNT, CFLUSH, CWERASE,CLNEXT
};

#define	SET(t,f)	(t) |= (f)
#define	CLR(t,f)	(t) &= ~(f)
#define	ISSET(t,f)	((t) & (f))

extern	char	*nextc();
extern	int	nldisp;
extern	int	wakeup();

ttychars(tp)
	struct tty *tp;
{

	tp->t_chars = ttydefaults;
}

/*
 * Wakeup processes waiting on output flow control (TS_ASLEEP).  Normally
 * called from driver start routine (dhvstart, etc) after a transmit done
 * interrupt.  If t_outq.c_cc <= t_lowat then do the wakeup.
*/
ttyowake(tp)
	register struct tty *tp;
	{

	if	(tp->t_outq.c_cc <= TTLOWAT(tp))
		{
		if	(ISSET(tp->t_state,TS_ASLEEP))
			{
			CLR(tp->t_state,TS_ASLEEP);
			wakeup((caddr_t)&tp->t_outq);
			}
		if	(tp->t_wsel)
			{
			selwakeup(tp->t_wsel, tp->t_state & TS_WCOLL);
			tp->t_wsel = 0;
			CLR(tp->t_state,TS_WCOLL);
			}
		}
	}

/*
 * Wait for output to drain, then flush input waiting.
 */
ttywflush(tp)
	register struct tty *tp;
{

	ttywait(tp);
	ttyflush(tp, FREAD);
}

ttywait(tp)
	register struct tty *tp;
{
	register int s = spltty();

	while ((tp->t_outq.c_cc || tp->t_state&TS_BUSY) &&
	    tp->t_state&TS_CARR_ON && tp->t_oproc) {
		(*tp->t_oproc)(tp);
/*
 * If the output routine drains the queue and the device is no longer busy
 * then don't wait for something that's already happened.
*/
		if	(tp->t_outq.c_cc == 0 && !ISSET(tp->t_state,TS_BUSY))
			break;
		tp->t_state |= TS_ASLEEP;
		sleep((caddr_t)&tp->t_outq, TTOPRI);
		splx(s);	/* drop priority, give interrupts a chance */
		s = spltty();
	}
	splx(s);
}

/*
 * Flush all TTY queues
 */
ttyflush(tp, rw)
	register struct tty *tp;
{
	register int s;

	s = spltty();
	if (rw & FREAD) {
		while (getc(&tp->t_canq) >= 0)
			;
		while (getc(&tp->t_rawq) >= 0)
			;
		tp->t_rocount = 0;
		tp->t_rocol = 0;
		tp->t_state &= ~TS_LOCAL;
		ttwakeup(tp);
	}
	if (rw & FWRITE) {
		tp->t_state &= ~TS_TTSTOP;
		(*cdevsw[major(tp->t_dev)].d_stop)(tp, rw);
		wakeup((caddr_t)&tp->t_outq);
		while (getc(&tp->t_outq) >= 0)
			;
		selwakeup(&tp->t_wsel, tp->t_state & TS_WCOLL);
		CLR(tp->t_state, TS_WCOLL);
		tp->t_wsel = 0;
	}
	if (rw & FREAD && ISSET(tp->t_state,TS_TBLOCK))
		ttyunblock(tp);
	splx(s);
}

static	int	rts = TIOCM_RTS;

/*
 * Send stop character on input overflow.
 */
ttyblock(tp)
	register struct tty *tp;
	{
	register int total;

	total = tp->t_rawq.c_cc + tp->t_canq.c_cc;
	/*
	 * Block further input iff:
	 * Current input > threshold AND input is available to user program
	 */
	if	(total >= TTYBLOCK && 
		 ((tp->t_flags & (RAW|CBREAK)) || (tp->t_canq.c_cc > 0)) &&
		 (tp->t_state&TS_TBLOCK) == 0)
		{
/*
 * TANDEM is the same as IXOFF for all intents and purposes.  Since we could
 * get called for either software or hardware flow control we need to check
 * the IXOFF bit.
*/
		if	(ISSET(tp->t_flags,TANDEM) && 
			 tp->t_stopc != _POSIX_VDISABLE && 
			 putc(tp->t_stopc, &tp->t_outq) == 0)
			{
			SET(tp->t_state, TS_TBLOCK);
			ttstart(tp);
			}
/*
 * If queue is full, drop RTS to tell modem to stop sending us stuff
*/
		if	(ISSET(tp->t_flags, RTSCTS) &&
			 (*cdevsw[major(tp->t_dev)].d_ioctl)(tp->t_dev,TIOCMBIC, &rts, 0) == 0)
			{
			SET(tp->t_state, TS_TBLOCK);
			}
		}
	}

ttyunblock(tp)
	register struct tty *tp;
	{
	register int s = spltty();

	if	(ISSET(tp->t_flags,TANDEM) &&
		 tp->t_startc != _POSIX_VDISABLE && 
		 putc(tp->t_startc, &tp->t_outq) == 0)
		{
		CLR(tp->t_state,TS_TBLOCK);
		ttstart(tp);
		}
	if	(ISSET(tp->t_flags, RTSCTS) && 
		 (*cdevsw[major(tp->t_dev)].d_ioctl)(tp->t_dev,TIOCMBIS,&rts,0) == 0)
		{
		CLR(tp->t_state, TS_TBLOCK);
		}
	}

/*
 * Restart typewriter output following a delay timeout.
 * The name of the routine is passed to the timeout
 * subroutine and it is called during a clock interrupt.
 */
ttrstrt(tp)
	register struct tty *tp;
{

	tp->t_state &= ~TS_TIMEOUT;
	ttstart(tp);
}

/*
 * Start output on the typewriter. It is used from the top half
 * after some characters have been put on the output queue,
 * from the interrupt routine to transmit the next
 * character, and after a timeout has finished.
 *
 * The spl calls were removed because the priority should already be spltty.
 */
ttstart(tp)
	register struct tty *tp;
	{

	if	(tp->t_oproc)		/* kludge for pty */
		(*tp->t_oproc)(tp);
	}

/*
 * Common code for tty ioctls.
 */
/*ARGSUSED*/
ttioctl(tp, com, data, flag)
	register struct tty *tp;
	u_int com;
	caddr_t data;
	int flag;
{
	int dev = tp->t_dev;
	int s;
	long newflags;

	/*
	 * If the ioctl involves modification,
	 * hang if in the background.
	 */
	switch (com) {

	case TIOCSETD:
	case TIOCSETP:
	case TIOCSETN:
	case TIOCFLUSH:
	case TIOCSETC:
	case TIOCSLTC:
	case TIOCSPGRP:
	case TIOCLBIS:
	case TIOCLBIC:
	case TIOCLSET:
	case TIOCSTI:
	case TIOCSWINSZ:
		while (tp->t_line == NTTYDISC &&
		   u.u_procp->p_pgrp != tp->t_pgrp && tp == u.u_ttyp &&
		   (u.u_procp->p_flag&SVFORK) == 0 &&
		   !(u.u_procp->p_sigignore & sigmask(SIGTTOU)) &&
		   !(u.u_procp->p_sigmask & sigmask(SIGTTOU))) {
			gsignal(u.u_procp->p_pgrp, SIGTTOU);
			sleep((caddr_t)&lbolt, TTOPRI);
		}
		break;
	}

	/*
	 * Process the ioctl.
	 */
	switch (com) {

	/* get discipline number */
	case TIOCGETD:
		*(int *)data = tp->t_line;
		break;

	/* set line discipline */
	case TIOCSETD: {
		register int t = *(int *)data;
		int error = 0;

		if ((unsigned) t >= nldisp)
			return (ENXIO);
		if (t != tp->t_line) {
			s = spltty();
			(*linesw[tp->t_line].l_close)(tp, flag);
			error = (*linesw[t].l_open)(dev, tp);
			if (error) {
				(void) (*linesw[tp->t_line].l_open)(dev, tp);
				splx(s);
				return (error);
			}
			tp->t_line = t;
			splx(s);
		}
		break;
	}

	/* prevent more opens on channel */
	case TIOCEXCL:
		tp->t_state |= TS_XCLUDE;
		break;

	case TIOCNXCL:
		tp->t_state &= ~TS_XCLUDE;
		break;

	/* hang up line on last close */
	case TIOCHPCL:
		tp->t_state |= TS_HUPCLS;
		break;

	case TIOCFLUSH: {
		register int flags = *(int *)data;

		if (flags == 0)
			flags = FREAD|FWRITE;
		else
			flags &= FREAD|FWRITE;
		ttyflush(tp, flags);
		break;
	}

	/* return number of characters immediately available */
	case FIONREAD:
		*(off_t *)data = ttnread(tp);
		break;

	case TIOCOUTQ:
		*(int *)data = tp->t_outq.c_cc;
		break;

	case TIOCSTOP:
		s = spltty();
		if ((tp->t_state&TS_TTSTOP) == 0) {
			tp->t_state |= TS_TTSTOP;
			(*cdevsw[major(tp->t_dev)].d_stop)(tp, 0);
		}
		splx(s);
		break;

	case TIOCSTART:
		s = spltty();
		if ((tp->t_state&TS_TTSTOP) || (tp->t_flags&FLUSHO)) {
			tp->t_state &= ~TS_TTSTOP;
			tp->t_flags &= ~FLUSHO;
			ttstart(tp);
		}
		splx(s);
		break;

	/*
	 * Simulate typing of a character at the terminal.
	 */
	case TIOCSTI:
		if (u.u_uid && (flag & FREAD) == 0)
			return (EPERM);
		if (u.u_uid && u.u_ttyp != tp)
			return (EACCES);
		(*linesw[tp->t_line].l_rint)(*(char *)data, tp);
		break;

	case TIOCSETP:
	case TIOCSETN: {
		register struct sgttyb *sg = (struct sgttyb *)data;

		tp->t_erase = sg->sg_erase;
		tp->t_kill = sg->sg_kill;
		tp->t_ispeed = sg->sg_ispeed;
		tp->t_ospeed = sg->sg_ospeed;
		newflags = (tp->t_flags&0xffff0000) | (sg->sg_flags&0xffffL);
		s = spltty();
		if (tp->t_flags&RAW || newflags&RAW || com == TIOCSETP) {
			ttywait(tp);
			ttyflush(tp, FREAD);
		} else if ((tp->t_flags&CBREAK) != (newflags&CBREAK)) {
			if (newflags&CBREAK) {
				struct clist tq;

				catq(&tp->t_rawq, &tp->t_canq);
				tq = tp->t_rawq;
				tp->t_rawq = tp->t_canq;
				tp->t_canq = tq;
			} else {
				tp->t_flags |= PENDIN;
				newflags |= PENDIN;
				ttwakeup(tp);
			}
		}
		tp->t_flags = newflags;
		if (tp->t_flags&RAW) {
			tp->t_state &= ~TS_TTSTOP;
			ttstart(tp);
		}
		splx(s);
		break;
	}

	/* send current parameters to user */
	case TIOCGETP: {
		register struct sgttyb *sg = (struct sgttyb *)data;

		sg->sg_ispeed = tp->t_ispeed;
		sg->sg_ospeed = tp->t_ospeed;
		sg->sg_erase = tp->t_erase;
		sg->sg_kill = tp->t_kill;
		sg->sg_flags = tp->t_flags;
		break;
	}

	case FIONBIO:
		break;	/* XXX remove */

	case FIOASYNC:
		if (*(int *)data)
			tp->t_state |= TS_ASYNC;
		else
			tp->t_state &= ~TS_ASYNC;
		break;

	case TIOCGETC:
		bcopy((caddr_t)&tp->t_intrc, data, sizeof (struct tchars));
		break;

	case TIOCSETC:
		bcopy(data, (caddr_t)&tp->t_intrc, sizeof (struct tchars));
		break;

	/* set/get local special characters */
	case TIOCSLTC:
		bcopy(data, (caddr_t)&tp->t_suspc, sizeof (struct ltchars));
		break;

	case TIOCGLTC:
		bcopy((caddr_t)&tp->t_suspc, data, sizeof (struct ltchars));
		break;

	/*
	 * Modify local mode word.
	 */
	case TIOCLBIS:
		tp->t_flags |= (long)*(u_int *)data << 16;
		break;

	case TIOCLBIC:
		tp->t_flags &= ~((long)*(u_int *)data << 16);
		break;

	case TIOCLSET:
		tp->t_flags &= 0xffffL;
		tp->t_flags |= (long)*(u_int *)data << 16;
		break;

	case TIOCLGET:
		*(int *)data = tp->t_flags >> 16;
		break;

	/*
	 * Allow SPGRP only if tty is open for reading.
	 * Quick check: if we can find a process in the new pgrp,
	 * this user must own that process.
	 * SHOULD VERIFY THAT PGRP IS IN USE AND IS THIS USER'S.
	 */
	case TIOCSPGRP: {
		struct proc *p;
		short pgrp = *(int *)data;

		if (u.u_uid && (flag & FREAD) == 0)
			return (EPERM);
		p = pfind(pgrp);
		if (p && p->p_pgrp == pgrp &&
		    p->p_uid != u.u_uid && u.u_uid && !inferior(p))
			return (EPERM);
		tp->t_pgrp = pgrp;
		break;
	}

	case TIOCGPGRP:
		*(int *)data = tp->t_pgrp;
		break;

	case TIOCSWINSZ:
		if (bcmp((caddr_t)&tp->t_winsize, data,
		    sizeof (struct winsize))) {
			tp->t_winsize = *(struct winsize *)data;
			gsignal(tp->t_pgrp, SIGWINCH);
		}
		break;

	case TIOCGWINSZ:
		*(struct winsize *)data = tp->t_winsize;
		break;

	default:
		return (-1);
	}
	return (0);
}

ttnread(tp)
	register struct tty *tp;
{
	register int nread = 0;

	if (tp->t_flags & PENDIN)
		ttypend(tp);
	nread = tp->t_canq.c_cc;
	if (tp->t_flags & (RAW|CBREAK))
		nread += tp->t_rawq.c_cc;
	return (nread);
}

/*
 * XXX - this cleans up the minor device number by stripping off the 
 * softcarrier bit.  Drives which use more bits of the minor device
 * MUST call their own select routine.  See dhv.c for an example.
 *
 * This routine will go away when all the drivers have been updated/converted
*/

ttselect(dev, rw)
	register dev_t dev;
	int rw;
	{
	struct tty *tp = &cdevsw[major(dev)].d_ttys[minor(dev)&0177];

	return(ttyselect(tp,rw));
	}

ttyselect(tp,rw)
	register struct tty *tp;
	int	rw;
	{
	int nread;
	register int s = spltty();

	switch (rw) {

	case FREAD:
		nread = ttnread(tp);
		if ((nread > 0) || ((tp->t_state & TS_CARR_ON) == 0))
			goto win;
		if (tp->t_rsel && tp->t_rsel->p_wchan == (caddr_t)&selwait)
			tp->t_state |= TS_RCOLL;
		else
			tp->t_rsel = u.u_procp;
		break;

	case FWRITE:
		if (tp->t_outq.c_cc <= TTLOWAT(tp))
			goto win;
		if (tp->t_wsel && tp->t_wsel->p_wchan == (caddr_t)&selwait)
			tp->t_state |= TS_WCOLL;
		else
			tp->t_wsel = u.u_procp;
		break;
	}
	splx(s);
	return (0);
win:
	splx(s);
	return (1);
}

/*
 * Initial open of tty, or (re)entry to line discipline.
 * Establish a process group for distribution of
 * quits and interrupts from the tty.
 */
ttyopen(dev, tp)
	dev_t dev;
	register struct tty *tp;
{
	register struct proc *pp;

	pp = u.u_procp;
	tp->t_dev = dev;
	if (pp->p_pgrp == 0) {
		u.u_ttyp = tp;
		u.u_ttyd = dev;
		if (tp->t_pgrp == 0)
			tp->t_pgrp = pp->p_pid;
		pp->p_pgrp = tp->t_pgrp;
	}
	tp->t_state &= ~TS_WOPEN;
	if ((tp->t_state & TS_ISOPEN) == 0) {
		tp->t_state |= TS_ISOPEN;
		bzero((caddr_t)&tp->t_winsize, sizeof(tp->t_winsize));
		if (tp->t_line != NTTYDISC)
			ttywflush(tp);
	}
	return (0);
}

/*
 * "close" a line discipline
 */
ttylclose(tp, flag)
	register struct tty *tp;
	int flag;
{

/*
 * 4.4 has IO_NDELAY but I think that is a mistake because the upper level
 * 'close' routines all pass 'fp->f_flags' down.  This was verified with a
 * printf here - the F* flags are received rather than the IO_* flags!
*/

	if (flag & FNDELAY)
		ttyflush(tp, FREAD|FWRITE);
	else
		ttywflush(tp);
	tp->t_line = 0;
}

/*
 * clean tp on last close
 */
ttyclose(tp)
	register struct tty *tp;
{

	ttyflush(tp, FREAD|FWRITE);
	tp->t_pgrp = 0;
	tp->t_state = 0;
}

/*
 * Handle modem control transition on a tty.
 * Flag indicates new state of carrier.
 * Returns 0 if the line should be turned off, otherwise 1.
 */
ttymodem(tp, flag)
	register struct tty *tp;
	int flag;
{

	if ((tp->t_state&TS_WOPEN) == 0 && (tp->t_flags & MDMBUF)) {
		/*
		 * MDMBUF: do flow control according to carrier flag
		 */
		if (flag) {
			tp->t_state &= ~TS_TTSTOP;
			ttstart(tp);
		} else if ((tp->t_state&TS_TTSTOP) == 0) {
			tp->t_state |= TS_TTSTOP;
			(*cdevsw[major(tp->t_dev)].d_stop)(tp, 0);
		}
	} else if (flag == 0) {
		/*
		 * Lost carrier.
		 */
		tp->t_state &= ~TS_CARR_ON;
		if (tp->t_state & TS_ISOPEN) {
			if ((tp->t_flags & NOHANG) == 0) {
				gsignal(tp->t_pgrp, SIGHUP);
				gsignal(tp->t_pgrp, SIGCONT);
				ttyflush(tp, FREAD|FWRITE);
				return (0);
			}
		}
	} else {
		/*
		 * Carrier now on.
		 */
		tp->t_state |= TS_CARR_ON;
		wakeup((caddr_t)&tp->t_rawq);
	}
	return (1);
}

/*
 * Default modem control routine (for other line disciplines).
 * Return argument flag, to turn off device on carrier drop.
 */
nullmodem(tp, flag)
	register struct tty *tp;
	int flag;
{
	
	if (flag)
		tp->t_state |= TS_CARR_ON;
	else
		tp->t_state &= ~TS_CARR_ON;
	return (flag);
}

/*
 * reinput pending characters after state switch
 * call at spltty().
 */
ttypend(tp)
	register struct tty *tp;
{
	struct clist tq;
	register int c;

	tp->t_flags &= ~PENDIN;
	tp->t_state |= TS_TYPEN;
	tq = tp->t_rawq;
	tp->t_rawq.c_cc = 0;
	tp->t_rawq.c_cf = tp->t_rawq.c_cl = 0;
	while ((c = getc(&tq)) >= 0)
		ttyinput(c, tp);
	tp->t_state &= ~TS_TYPEN;
}

/*
 * Place a character on raw TTY input queue,
 * putting in delimiters and waking up top
 * half as needed.  Also echo if required.
 * The arguments are the character and the
 * appropriate tty structure.
 */
ttyinput(c, tp)
	register int c;
	register struct tty *tp;
{
	long t_flags = tp->t_flags;
	int i;

	/*
	 * If input is pending take it first.
	 */
	if (t_flags&PENDIN)
		ttypend(tp);
#ifdef UCB_METER
	tk_nin++;
#endif
	c &= 0377;

	/*
	 * In tandem mode, check high water mark.
	 */
	if	(t_flags & (TANDEM|RTSCTS))
		ttyblock(tp);

	if (t_flags&RAW) {
		/*
		 * Raw mode, just put character
		 * in input q w/o interpretation.
		 */
		if (tp->t_rawq.c_cc > TTYHOG) 
			ttyflush(tp, FREAD|FWRITE);
		else {
			if (putc(c, &tp->t_rawq) == 0)
				ttwakeup(tp);
			ttyecho(c, tp);
		}
		goto endcase;
	}

	/*
	 * Ignore any high bit added during
	 * previous ttyinput processing.
	 */
	if ((tp->t_state&TS_TYPEN) == 0 && (t_flags&PASS8) == 0)
		c &= 0177;

	/*
	 * Check for literal nexting very first.  This is the _ONLY_ place
	 * left which ORs in 0200.  Handling literal nexting this way is
	 * what keeps the tty subsystem from being 8 bit clean.  The fix is
	 * horrendous though and is put off for now.  And to think that ALL
	 * of this is made necessary by ttyrubout() - it's the only place that
	 * actually _checks_ the 0200 bit and only for newline and tab chars
	 * at that!
	 *
	 * If we had 9 bit bytes life would be a lot simpler ;)
	 *
	 * The basic idea is to flag the character as "special" and also
	 * modify it so that the character does not match any of the special
	 * editing or control characters.  We could just as simply jump directly
	 * to the test for 'cbreak' below.
	 */
	if (tp->t_state&TS_LNCH) {
		c |= 0200;
		tp->t_state &= ~TS_LNCH;
	}

	/*
	 * Scan for special characters.  This code
	 * is really just a big case statement with
	 * non-constant cases.  The bottom of the
	 * case statement is labeled ``endcase'', so goto
	 * it after a case match, or similar.
	 */
	if (tp->t_line == NTTYDISC) {
		if (CCEQ(tp->t_lnextc,c)) {
			if (t_flags&ECHO)
				ttyout("^\b", tp);
			tp->t_state |= TS_LNCH;
			goto endcase;
		}
		if (CCEQ(tp->t_flushc,c)) {
			if (t_flags&FLUSHO)
				tp->t_flags &= ~FLUSHO;
			else {
				ttyflush(tp, FWRITE);
				ttyecho(c, tp);
				if (tp->t_rawq.c_cc + tp->t_canq.c_cc)
					ttyretype(tp);
				tp->t_flags |= FLUSHO;
			}
			goto startoutput;
		}
		if (CCEQ(tp->t_suspc,c)) {
			if ((t_flags&NOFLSH) == 0)
				ttyflush(tp, FREAD);
			ttyecho(c, tp);
			gsignal(tp->t_pgrp, SIGTSTP);
			goto endcase;
		}
	}

	/*
	 * Handle start/stop characters.
	 */
	if (CCEQ(tp->t_stopc,c)) {
		if ((tp->t_state&TS_TTSTOP) == 0) {
			tp->t_state |= TS_TTSTOP;
			(*cdevsw[major(tp->t_dev)].d_stop)(tp, 0);
			return;
		}
		if (CCEQ(tp->t_startc,c))
			return;
		goto endcase;
	}
	if (CCEQ(tp->t_startc,c))
		goto restartoutput;

	/*
	 * Look for interrupt/quit chars.
	 */
	if (CCEQ(tp->t_intrc,c) || CCEQ(tp->t_quitc,c)) {
		if ((t_flags&NOFLSH) == 0)
			ttyflush(tp, FREAD|FWRITE);
		ttyecho(c, tp);
		gsignal(tp->t_pgrp, CCEQ(tp->t_intrc,c) ? SIGINT : SIGQUIT);
		goto endcase;
	}

	/*
	 * Cbreak mode, don't process line editing
	 * characters; check high water mark for wakeup.
	 */
	if (t_flags&CBREAK) {
		if (tp->t_rawq.c_cc > TTYHOG) {
			if (tp->t_outq.c_cc < TTHIWAT(tp) &&
			    tp->t_line == NTTYDISC)
				(void) ttyoutput(CTRL(g), tp);
		} else if (putc(c, &tp->t_rawq) == 0) {
			ttwakeup(tp);
			ttyecho(c, tp);
		}
		goto endcase;
	}

	/*
	 * From here on down cooked mode character
	 * processing takes place.
	 */
	if (CCEQ(tp->t_erase,c)) {
		if (tp->t_rawq.c_cc)
			ttyrub(unputc(&tp->t_rawq), tp);
		goto endcase;
	}
	if (CCEQ(tp->t_kill,c)) {
		if (t_flags&CRTKIL &&
		    tp->t_rawq.c_cc == tp->t_rocount) {
			while (tp->t_rawq.c_cc)
				ttyrub(unputc(&tp->t_rawq), tp);
		} else {
			ttyecho(c, tp);
			ttyecho('\n', tp);
			while (getc(&tp->t_rawq) > 0)
				;
			tp->t_rocount = 0;
		}
		tp->t_state &= ~TS_LOCAL;
		goto endcase;
	}

	/*
	 * New line discipline,
	 * check word erase/reprint line.
	 */
	if (tp->t_line == NTTYDISC) {
		if (CCEQ(tp->t_werasc,c)) {
			if (tp->t_rawq.c_cc == 0)
				goto endcase;
			do {
				c = unputc(&tp->t_rawq);
				if (c != ' ' && c != '\t')
					goto erasenb;
				ttyrub(c, tp);
			} while (tp->t_rawq.c_cc);
			goto endcase;
	erasenb:
			do {
				ttyrub(c, tp);
				if (tp->t_rawq.c_cc == 0)
					goto endcase;
				c = unputc(&tp->t_rawq);
			} while (c != ' ' && c != '\t');
			(void) putc(c, &tp->t_rawq);
			goto endcase;
		}
		if (CCEQ(tp->t_rprntc,c)) {
			ttyretype(tp);
			goto endcase;
		}
	}

	/*
	 * Check for input buffer overflow
	 */
	if (tp->t_rawq.c_cc+tp->t_canq.c_cc >= TTYHOG) {
		if (tp->t_line == NTTYDISC)
			(void) ttyoutput(CTRL(g), tp);
		goto endcase;
	}

	/*
	 * Put data char in q for user and
	 * wakeup on seeing a line delimiter.
	 */
	if (putc(c, &tp->t_rawq) == 0) {
		if (ttbreakc(c, tp)) {
			tp->t_rocount = 0;
			catq(&tp->t_rawq, &tp->t_canq);
			ttwakeup(tp);
		} else if (tp->t_rocount++ == 0)
			tp->t_rocol = tp->t_col;
		if (tp->t_state&TS_ERASE) {
			tp->t_state &= ~TS_ERASE;
			(void) ttyoutput('/', tp);
		}
		i = tp->t_col;
		ttyecho(c, tp);
		if (CCEQ(tp->t_eofc,c) && t_flags&ECHO) {
			i = MIN(2, tp->t_col - i);
			while (i > 0) {
				(void) ttyoutput('\b', tp);
				i--;
			}
		}
	}
endcase:
	/*
	 * If DEC-style start/stop is enabled don't restart
	 * output until seeing the start character.
	 */
	if (t_flags&DECCTQ && tp->t_state&TS_TTSTOP &&
	    tp->t_startc != tp->t_stopc)
		return;
restartoutput:
	tp->t_state &= ~TS_TTSTOP;
	tp->t_flags &= ~FLUSHO;
startoutput:
	ttstart(tp);
}

/*
 * Put character on TTY output queue, adding delays,
 * expanding tabs, and handling the CR/NL bit.
 * This is called both from the top half for output,
 * and from interrupt level for echoing.
 * The arguments are the character and the tty structure.
 * Returns < 0 if putc succeeds, otherwise returns char to resend
 */
ttyoutput(c, tp)
	register int c;
	register struct tty *tp;
{
	register int col;

	if (tp->t_flags & (RAW|LITOUT)) {
		if (tp->t_flags&FLUSHO)
			return (-1);
		if (putc(c, &tp->t_outq))
			return(c);
#ifdef UCB_METER
		tk_nout++;
#endif
		return(-1);
	}

	c &= 0177;
#ifdef	whybother
	/*
	 * Ignore EOT in normal mode to avoid
	 * hanging up certain terminals.
	 */
	if (c == CEOT && (tp->t_flags&CBREAK) == 0)
		return(-1);
#endif
	/*
	 * Turn tabs to spaces as required
	 */
	if (c == '\t' && (tp->t_flags&XTABS)) {
		register int s;

		c = 8 - (tp->t_col&7);
		if ((tp->t_flags&FLUSHO) == 0) {
			s = spltty();		/* don't interrupt tabs */
			c -= b_to_q("        ", c, &tp->t_outq);
#ifdef UCB_METER
			tk_nout += c;
#endif
			splx(s);
		}
		tp->t_col += c;
		return (c ? -1 : '\t');
	}
#ifdef UCB_METER
	tk_nout++;
#endif
	/*
	 * turn <nl> to <cr><lf> if desired.
	 */
	if (c == '\n' && tp->t_flags&CRMOD)
		{
		if (putc('\r', &tp->t_outq))
			return(c);
#ifdef UCB_METER
		tk_nout++;
#endif
		}
	if ((tp->t_flags&FLUSHO) == 0 && putc(c, &tp->t_outq))
		return (c);

	col = tp->t_col;
	switch (partab[c]&077) {

	case ORDINARY:
		col++;
	case CONTROL:
		break;
	case BACKSPACE:
		if (col)
			col--;
		break;
	case NEWLINE:
	case RETURN:
		col = 0;
		break;
	case TAB:
		col = (col | 07) + 1;
		break;
	}
	tp->t_col = col;
	return(-1);
}

/*
 * Called from device's read routine after it has
 * calculated the tty-structure given as argument.
 */
ttread(tp, uio, flag)
	register struct tty *tp;
	struct uio *uio;
{
	register struct clist *qp;
	register int c;
	long t_flags;
	int s, first, error = 0, carrier;

loop:
	/*
	 * Take any pending input first.
	 */
	s = spltty();
	if (tp->t_flags&PENDIN)
		ttypend(tp);
	splx(s);

	/*
	 * Hang process if it's in the background.
	 */
	if (tp == u.u_ttyp && u.u_procp->p_pgrp != tp->t_pgrp) {
		if ((u.u_procp->p_sigignore & sigmask(SIGTTIN)) ||
		   (u.u_procp->p_sigmask & sigmask(SIGTTIN)) ||
		    u.u_procp->p_flag&SVFORK)
			return (EIO);
		gsignal(u.u_procp->p_pgrp, SIGTTIN);
		sleep((caddr_t)&lbolt, TTIPRI);
		goto loop;
	}
	t_flags = tp->t_flags;

	/*
	 * In raw mode take characters directly from the
	 * raw queue w/o processing.  Interlock against
	 * device interrupts when interrogating rawq.
	 */
	if (t_flags&RAW) {
		s = spltty();
		if (tp->t_rawq.c_cc <= 0) {
			carrier = ISSET(tp->t_state, TS_CARR_ON);
			if (!carrier && ISSET(tp->t_state, TS_ISOPEN))
				{
				splx(s);
				return(0);	/* EOF */
				}
			if (flag & IO_NDELAY)
				{
				splx(s);
				return(EWOULDBLOCK);
				}
			sleep((caddr_t)&tp->t_rawq, TTIPRI);
			splx(s);
			goto loop;
		}
		splx(s);
 		while (!error && tp->t_rawq.c_cc && uio->uio_resid)
 			error = ureadc(getc(&tp->t_rawq), uio);
		goto checktandem;
	}

	/*
	 * In cbreak mode use the rawq, otherwise
	 * take characters from the canonicalized q.
	 */
	qp = t_flags&CBREAK ? &tp->t_rawq : &tp->t_canq;

	/*
	 * No input, sleep on rawq awaiting hardware
	 * receipt and notification.
	 */
	s = spltty();
	if (qp->c_cc <= 0) {
		carrier = ISSET(tp->t_state, TS_CARR_ON);
		if (!carrier && ISSET(tp->t_state,TS_ISOPEN))
			{
			splx(s);
			return(0);	/* EOF */
			}
		if (flag & IO_NDELAY)
			{
			splx(s);
			return(EWOULDBLOCK);
			}
		sleep((caddr_t)&tp->t_rawq, TTIPRI);
		splx(s);
		goto loop;
	}
	splx(s);

	/*
	 * Input present, perform input mapping
	 * and processing (we're not in raw mode).
	 */
	first = 1;
	while ((c = getc(qp)) >= 0) {
		if (t_flags&CRMOD && c == '\r')
			c = '\n';
		/*
		 * Check for delayed suspend character.
		 */
		if (tp->t_line == NTTYDISC && CCEQ(tp->t_dsuspc,c)) {
			gsignal(tp->t_pgrp, SIGTSTP);
			if (first) {
				sleep((caddr_t)&lbolt, TTIPRI);
				goto loop;
			}
			break;
		}
		/*
		 * Interpret EOF only in cooked mode.
		 */
		if (CCEQ(tp->t_eofc,c) && (t_flags&CBREAK) == 0)
			break;
		/*
		 * Give user character.
		 */
 		error = ureadc(t_flags&PASS8 ? c : c & 0177, uio);
		if (error)
			break;
 		if (uio->uio_resid == 0)
			break;
		/*
		 * In cooked mode check for a "break character"
		 * marking the end of a "line of input".
		 */
		if ((t_flags&CBREAK) == 0 && ttbreakc(c, tp))
			break;
		first = 0;
	}

checktandem:
	/*
	 * Look to unblock output now that (presumably)
	 * the input queue has gone down.
	 */
	s = spltty();
	if	(ISSET(tp->t_state,TS_TBLOCK) && tp->t_rawq.c_cc < TTYUNBLOCK)
		ttyunblock(tp);
	splx(s);
	return(error);
}

/*
 * Check the output queue on tp for space for a kernel message
 * (from uprintf/tprintf).  Allow some space over the normal
 * hiwater mark so we don't lose messages due to normal flow
 * control, but don't let the tty run amok.
 * Sleeps here are not interruptible, but we return prematurely
 * if new signals come in.
 */
ttycheckoutq(tp, wait)
	register struct tty *tp;
	int wait;
{
	int hiwat, s, oldsig;

	hiwat = TTHIWAT(tp);
	s = spltty();
	oldsig = u.u_procp->p_sig;
	if (tp->t_outq.c_cc > hiwat + 200)
	    while (tp->t_outq.c_cc > hiwat) {
		ttstart(tp);
		if (wait == 0 || u.u_procp->p_sig != oldsig) {
			splx(s);
			return(0);
		}
		timeout(wakeup, (caddr_t)&tp->t_outq, hz);
		tp->t_state |= TS_ASLEEP;
		sleep((caddr_t)&tp->t_outq, PZERO - 1);
	}
	splx(s);
	return(1);
}

/*
 * Called from the device's write routine after it has
 * calculated the tty-structure given as argument.
 */
ttwrite(tp, uio, flag)
	register struct tty *tp;
	register struct uio *uio;
{
	char *cp;
	register int cc, ce, c;
	int i, hiwat, cnt, error, s;
	char obuf[OBUFSIZ];

	hiwat = TTHIWAT(tp);
	cnt = uio->uio_resid;
	error = 0;
	cc = 0;
loop:
	s = spltty();
	if (!(tp->t_state&TS_CARR_ON)) {
		if (tp->t_state & TS_ISOPEN) {
			splx(s);
			return(EIO);
		} else if (flag & IO_NDELAY) {
			splx(s);
			error = EWOULDBLOCK;
			goto out;
		} else {
			/* Sleep awaiting carrier. */
			sleep((caddr_t)&tp->t_rawq, TTIPRI);
			goto loop;
		}
	}
	splx(s);
	/*
	 * Hang the process if it's in the background.
	 */
	if (u.u_procp->p_pgrp != tp->t_pgrp && tp == u.u_ttyp &&
	    (tp->t_flags&TOSTOP) && (u.u_procp->p_flag&SVFORK)==0 &&
	    !(u.u_procp->p_sigignore & sigmask(SIGTTOU)) &&
	    !(u.u_procp->p_sigmask & sigmask(SIGTTOU))) {
		gsignal(u.u_procp->p_pgrp, SIGTTOU);
		sleep((caddr_t)&lbolt, TTIPRI);
		goto loop;
	}

	/*
	 * Process the user's data in at most OBUFSIZ
	 * chunks.  Perform lower case simulation and
	 * similar hacks.  Keep track of high water
	 * mark, sleep on overflow awaiting device aid
	 * in acquiring new space.
	 */
	while (uio->uio_resid || cc > 0) {
		if (tp->t_flags&FLUSHO) {
			uio->uio_resid = 0;
			return(0);
		}
		if (tp->t_outq.c_cc > hiwat)
			goto ovhiwat;
		/*
		 * Grab a hunk of data from the user, unless we have some
		 * leftover from last time.
		*/
		if (cc == 0) {
			cc = MIN(uio->uio_resid, OBUFSIZ);
			cp = obuf;
			error = uiomove(cp, cc, uio);
			if (error) {
				cc = 0;
				break;
			}
		}
		/*
		 * If nothing fancy need be done, grab those characters we
		 * can handle without any of ttyoutput's processing and
		 * just transfer them to the output q.  For those chars
		 * which require special processing (as indicated by the
		 * bits in partab), call ttyoutput.  After processing
		 * a hunk of data, look for FLUSHO so ^O's will take effect
		 * immediately.
		 */
		while (cc > 0) {
			if (tp->t_flags & (RAW|LITOUT))
				ce = cc;
			else {
				ce = cc - scanc((unsigned)cc, (caddr_t)cp,
				   (caddr_t)partab, 077);
				/*
				 * If ce is zero, then we're processing
				 * a special character through ttyoutput.
				 */
				if (ce == 0) {
					tp->t_rocount = 0;
					if (ttyoutput(*cp, tp) >= 0) {
					    /* no c-lists, wait a bit */
					    ttstart(tp);
					    sleep((caddr_t)&lbolt, TTOPRI);
					    goto loop;
					}
					cp++, cc--;
					if (tp->t_flags&FLUSHO ||
					    tp->t_outq.c_cc > hiwat)
						goto ovhiwat;
					continue;
				}
			}
			/*
			 * A bunch of normal characters have been found,
			 * transfer them en masse to the output queue and
			 * continue processing at the top of the loop.
			 * If there are any further characters in this
			 * <= OBUFSIZ chunk, the first should be a character
			 * requiring special handling by ttyoutput.
			 */
			tp->t_rocount = 0;
			i = b_to_q(cp, ce, &tp->t_outq);
			ce -= i;
			tp->t_col += ce;
			cp += ce, cc -= ce;
#ifdef UCB_METER
 			tk_nout += ce;
#endif
			if (i > 0) {
				/* out of c-lists, wait a bit */
				ttstart(tp);
				sleep((caddr_t)&lbolt, TTOPRI);
				goto loop;
			}
			if (tp->t_flags&FLUSHO || tp->t_outq.c_cc > hiwat)
				break;
		}	/* while (cc > 0) */
		ttstart(tp);
	}	/* while (uio->uio_resid || cc > 0) */
out:
	/*
	 * If cc is nonzero, we leave the uio structure inconsistent, as the
	 * offset and iov pointers have moved forward, but it doesn't matter
	 * (the call will either return short or restart with a new uio).
	*/
	uio->uio_resid += cc;
	return (error);

ovhiwat:
	s = spltty();
	/*
	 * This can only occur if FLUSHO is also set in t_flags,
	 * or if ttstart/oproc is synchronous (or very fast).
	 */
	if (tp->t_outq.c_cc <= hiwat) {
		splx(s);
		goto loop;
	}
	ttstart(tp);
	if (flag & IO_NDELAY) {
		splx(s);
		uio->uio_resid += cc;
		return (uio->uio_resid == cnt ? EWOULDBLOCK : 0);
	}
	tp->t_state |= TS_ASLEEP;
	sleep((caddr_t)&tp->t_outq, TTOPRI);
	splx(s);
	goto loop;
}

/*
 * Rubout one character from the rawq of tp
 * as cleanly as possible.
 */
ttyrub(c, tp)
	register int c;
	register struct tty *tp;
{
	register char *cp;
	int savecol;
	int s;

	if ((tp->t_flags&ECHO) == 0)
		return;
	tp->t_flags &= ~FLUSHO;
	c &= 0377;
	if (tp->t_flags&CRTBS) {
		if (tp->t_rocount == 0) {
			/*
			 * Screwed by ttwrite; retype
			 */
			ttyretype(tp);
			return;
		}
/*
 * Out of the ENTIRE tty subsystem would believe this is the ONLY place
 * that the "9th" bit (quoted chars) is tested?
*/
		if (c == ('\t'|0200) || c == ('\n'|0200))
			ttyrubo(tp, 2);
		else switch (partab[c&=0177]&0177) {

		case ORDINARY:
			ttyrubo(tp, 1);
			break;

		case VTAB:
		case BACKSPACE:
		case CONTROL:
		case RETURN:
			if (tp->t_flags&CTLECH)
				ttyrubo(tp, 2);
			break;

		case TAB:
			if (tp->t_rocount < tp->t_rawq.c_cc) {
				ttyretype(tp);
				return;
			}
			s = spltty();
			savecol = tp->t_col;
			tp->t_state |= TS_CNTTB;
			tp->t_flags |= FLUSHO;
			tp->t_col = tp->t_rocol;
			cp = tp->t_rawq.c_cf;
#ifdef UCB_CLIST
			{
			char store;

			if (cp)
				store = lookc(cp);
			for (; cp; cp = nextc(&tp->t_rawq, cp, &store))
				ttyecho(store, tp);
			}
#else
			for (; cp; cp = nextc(&tp->t_rawq, cp))
				ttyecho(*cp, tp);
#endif
			tp->t_flags &= ~FLUSHO;
			tp->t_state &= ~TS_CNTTB;
			splx(s);
			/*
			 * savecol will now be length of the tab
			 */
			savecol -= tp->t_col;
			tp->t_col += savecol;
			if (savecol > 8)
				savecol = 8;		/* overflow screw */
			while (--savecol >= 0)
				(void) ttyoutput('\b', tp);
			break;

		default:
			panic("ttyrub");
		}
	} else if (tp->t_flags&PRTERA) {
		if ((tp->t_state&TS_ERASE) == 0) {
			(void) ttyoutput('\\', tp);
			tp->t_state |= TS_ERASE;
		}
		ttyecho(c, tp);
	} else
		ttyecho(tp->t_erase, tp);
	tp->t_rocount--;
}

/*
 * Crt back over cnt chars perhaps
 * erasing them.
 */
ttyrubo(tp, cnt)
	register struct tty *tp;
	register int cnt;
{
	register char *rubostring = tp->t_flags&CRTERA ? "\b \b" : "\b";

	while	(--cnt >= 0)
		ttyout(rubostring, tp);
}

/*
 * Reprint the rawq line.
 * We assume c_cc has already been checked.
 */
ttyretype(tp)
	register struct tty *tp;
{
	register char *cp;
	int s;

	if (tp->t_rprntc != _POSIX_VDISABLE)
		ttyecho(tp->t_rprntc, tp);
	(void) ttyoutput('\n', tp);
	s = spltty();
#ifdef UCB_CLIST
	{
	char store;

	if (cp = tp->t_canq.c_cf)
		store = lookc(cp);
	for (; cp; cp = nextc(&tp->t_canq, cp, &store))
		ttyecho(store, tp);
	if (cp = tp->t_rawq.c_cf)
		store = lookc(cp);
	for (; cp; cp = nextc(&tp->t_rawq, cp, &store))
		ttyecho(store, tp);
	}
#else
	for (cp = tp->t_canq.c_cf; cp; cp = nextc(&tp->t_canq, cp))
		ttyecho(*cp, tp);
	for (cp = tp->t_rawq.c_cf; cp; cp = nextc(&tp->t_rawq, cp))
		ttyecho(*cp, tp);
#endif
	tp->t_state &= ~TS_ERASE;
	splx(s);
	tp->t_rocount = tp->t_rawq.c_cc;
	tp->t_rocol = 0;
}

/*
 * Echo a typed character to the terminal
 */
ttyecho(c, tp)
	register int c;
	register struct tty *tp;
{
	register int c7;

	if ((tp->t_state&TS_CNTTB) == 0)
		tp->t_flags &= ~FLUSHO;
	if ((tp->t_flags&ECHO) == 0)
		return;
	c &= 0377;

	if (tp->t_flags&RAW) {
		(void) ttyoutput(c, tp);
		return;
	}
	if (c == '\r' && tp->t_flags&CRMOD)
		c = '\n';
	c7 = c & 0177;
	if (tp->t_flags&CTLECH) {
		if (c7 <= 037 && c != '\t' && c != '\n' || c7 == 0177) {
			(void) ttyoutput('^', tp);
			if (c7 == 0177)
				c7 = '?';
			else
				c7 += 'A' - 1;
		}
	}
	(void) ttyoutput(c7, tp);
}

/*
 * Is c a break char for tp?
 */
ttbreakc(c, tp)
	register int c;
	register struct tty *tp;
{
	return (c == '\n' || CCEQ(tp->t_eofc,c) || CCEQ(tp->t_brkc,c) ||
		c == '\r' && (tp->t_flags&CRMOD));
}

/*
 * send string cp to tp
 */
ttyout(cp, tp)
	register char *cp;
	register struct tty *tp;
{
	register int c;

	while (c = *cp++)
		(void) ttyoutput(c, tp);
}

ttwakeup(tp)
	register struct tty *tp;
{

	if (tp->t_rsel) {
		selwakeup(tp->t_rsel, tp->t_state&TS_RCOLL);
		tp->t_state &= ~TS_RCOLL;
		tp->t_rsel = 0;
	}
	if (tp->t_state & TS_ASYNC)
		gsignal(tp->t_pgrp, SIGIO); 
	wakeup((caddr_t)&tp->t_rawq);
}