[unix-history] / usr / src / usr.bin / window / wwiomux.c

/*
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#ifndef lint
static char sccsid[] = "@(#)wwiomux.c   3.22 (Berkeley) %G%";
#endif /* not lint */

#include "ww.h"
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>

/*
* Multiple window output handler.
* The idea is to copy window outputs to the terminal, via the
* display package.  We try to give wwcurwin highest priority.
* The only return conditions are when there is keyboard input
* and when a child process dies, which are serviced by signal
* catchers (wwrint() and wwchild()).
* When there's nothing to do, we sleep in a select().
* This can be done better with interrupt driven io.  But that's
* not supported on ptys, yet.
* The history of this routine is interesting.
*/
wwiomux()
{
       register struct ww *w;
       fd_set imask;
       register n;
       register char *p;
       char c;
       struct timeval tv;
       char noblock = 0;

       for (;;) {
               if (wwinterrupt()) {
                       wwclrintr();
                       return;
               }

               FD_ZERO(&imask);
               for (w = wwhead.ww_forw; w != &wwhead; w = w->ww_forw) {
                       if (w->ww_pty < 0)
                               continue;
                       if (w->ww_obq < w->ww_obe)
                               FD_SET(w->ww_pty, &imask);
                       if (w->ww_obq > w->ww_obp && !w->ww_stopped)
                               noblock = 1;
               }

               if (!noblock) {
                       if (wwcurwin != 0)
                               wwcurtowin(wwcurwin);
                       wwupdate();
                       wwflush();
                       (void) setjmp(wwjmpbuf);
                       wwsetjmp = 1;
                       if (wwinterrupt()) {
                               wwsetjmp = 0;
                               wwclrintr();
                               return;
                       }
                       /*
                        * Defensive code.  If somebody else (for example,
                        * wall) clears the ASYNC flag on us, we will block
                        * forever.  So we need a finite timeout and set
                        * the flag again.  Anything more clever will probably
                        * need even more system calls.  (This is a bug
                        * in the kernel.)
                        * I don't like this one bit.
                        */
                       (void) fcntl(0, F_SETFL, wwnewtty.ww_fflags);
                       tv.tv_sec = 30;
                       tv.tv_usec = 0;
               } else {
                       tv.tv_sec = 0;
                       tv.tv_usec = 10000;
               }
               wwnselect++;
               n = select(wwdtablesize, &imask, (fd_set *)0, (fd_set *)0, &tv);
               wwsetjmp = 0;
               noblock = 0;

               if (n < 0)
                       wwnselecte++;
               else if (n == 0)
                       wwnselectz++;
               else
                       for (w = wwhead.ww_forw; w != &wwhead; w = w->ww_forw) {
                               if (w->ww_pty < 0 ||
                                   !FD_ISSET(w->ww_pty, &imask))
                                       continue;
                               wwnwread++;
                               p = w->ww_obq;
                               if (w->ww_ispty) {
                                       if (p == w->ww_ob) {
                                               w->ww_obp++;
                                               w->ww_obq++;
                                       } else
                                               p--;
                                       c = *p;
                               }
                               n = read(w->ww_pty, p, w->ww_obe - p);
                               if (n < 0) {
                                       wwnwreade++;
                                       (void) close(w->ww_pty);
                                       w->ww_pty = -1;
                               } else if (n == 0) {
                                       wwnwreadz++;
                                       (void) close(w->ww_pty);
                                       w->ww_pty = -1;
                               } else if (!w->ww_ispty) {
                                       wwnwreadd++;
                                       wwnwreadc += n;
                                       w->ww_obq += n;
                               } else if (*p == TIOCPKT_DATA) {
                                       n--;
                                       wwnwreadd++;
                                       wwnwreadc += n;
                                       w->ww_obq += n;
                               } else {
                                       wwnwreadp++;
                                       if (*p & TIOCPKT_STOP)
                                               w->ww_stopped = 1;
                                       if (*p & TIOCPKT_START)
                                               w->ww_stopped = 0;
                                       if (*p & TIOCPKT_FLUSHWRITE) {
                                               w->ww_stopped = 0;
                                               w->ww_obq = w->ww_obp =
                                                       w->ww_ob;
                                       }
                               }
                               if (w->ww_ispty)
                                       *p = c;
                       }
               /*
                * Try the current window first, if there is output
                * then process it and go back to the top to try again.
                * This can lead to starvation of the other windows,
                * but presumably that what we want.
                * Update will eventually happen when output from wwcurwin
                * dies down.
                */
               if ((w = wwcurwin) != 0 && w->ww_pty >= 0 &&
                   w->ww_obq > w->ww_obp && !w->ww_stopped) {
                       n = wwwrite(w, w->ww_obp, w->ww_obq - w->ww_obp);
                       if ((w->ww_obp += n) == w->ww_obq)
                               w->ww_obq = w->ww_obp = w->ww_ob;
                       noblock = 1;
                       continue;
               }
               for (w = wwhead.ww_forw; w != &wwhead; w = w->ww_forw)
                       if (w->ww_pty >= 0 && w->ww_obq > w->ww_obp &&
                           !w->ww_stopped) {
                               n = wwwrite(w, w->ww_obp,
                                       w->ww_obq - w->ww_obp);
                               if ((w->ww_obp += n) == w->ww_obq)
                                       w->ww_obq = w->ww_obp = w->ww_ob;
                               if (wwinterrupt())
                                       break;
                       }
       }
}