xemacs-21.4 / src / event-unixoid.c

/* Code shared between all event loops that use select() and have a
   different input descriptor for each device.
   Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   Copyright (C) 1995 Board of Trustees, University of Illinois.
   Copyright (C) 1995 Sun Microsystems, Inc.
   Copyright (C) 1995, 1996 Ben Wing.

This file is part of XEmacs.

XEmacs is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

XEmacs is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with XEmacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Synched up with: Not in FSF. */

/* This file has been Mule-ized. */

#include <config.h>
#include "lisp.h"

#include "console-stream.h"
#include "console-tty.h"
#include "device.h"
#include "events.h"
#include "process.h"

#include "sysdep.h"
#include "sysproc.h"		/* select stuff */
#include "systime.h"

/* Mask of bits indicating the descriptors that we wait for input on.
   These work as follows:

   input_wait_mask == mask of all file descriptors we select() on,
                      including TTY/stream console descriptors,
		      process descriptors, and the signal event pipe.
		      Only used in event-tty.c; event-Xt.c uses
		      XtAppAddInput(), and the call to select() is down in
		      the guts of Xt.

   non_fake_input_wait_mask == same as input_wait_mask but minus the
                               signal event pipe.  Also only used in
			       event-tty.c.

   process_only_mask == only the process descriptors.

   tty_only_mask == only the TTY/stream console descriptors.
   */
SELECT_TYPE input_wait_mask, non_fake_input_wait_mask;
SELECT_TYPE process_only_mask, tty_only_mask;

/* This is used to terminate the select(), when an event came in
   through a signal (e.g. window-change or C-g on controlling TTY). */
int signal_event_pipe[2];

static int signal_event_pipe_initialized;

int fake_event_occurred;

int
read_event_from_tty_or_stream_desc (struct Lisp_Event *event,
				    struct console *con, int fd)
{
  unsigned char ch;
  int nread;
  Lisp_Object console = Qnil;

  XSETCONSOLE (console, con);

  nread = read (fd, &ch, 1);
  if (nread <= 0)
    {
      /* deleting the console might not be safe right now ... */
      enqueue_magic_eval_event (io_error_delete_console, console);
      /* but we definitely need to unselect it to avoid infinite
	 loops reading EOF's */
      Fconsole_disable_input (console);
    }
  else
    {
      character_to_event (ch, event, con, 1);
      event->channel = console;
      return 1;
    }
  return 0;
}

void
signal_fake_event (void)
{
  char byte = 0;
  /* We do the write always.  Formerly I tried to "optimize" this
     by setting a flag indicating whether we're blocking and only
     doing the write in that case, but there is a race condition
     if the signal occurs after we've checked for the signal
     occurrence (which could occur in many places throughout
     an iteration of the command loop, e.g. in status_notify()),
     but before we set the blocking flag.

     This should be OK as long as write() is reentrant, which
     I'm fairly sure it is since it's a system call. */

  if (signal_event_pipe_initialized)
    /* In case a signal comes through while we're dumping */
    {
      int old_errno = errno;
      write (signal_event_pipe[1], &byte, 1);
      errno = old_errno;
    }
}

void
drain_signal_event_pipe (void)
{
  char chars[128];
  /* The input end of the pipe has been set to non-blocking. */
  while (read (signal_event_pipe[0], chars, sizeof (chars)) > 0)
    ;
}

int
event_stream_unixoid_select_console (struct console *con)
{
  int infd;

  if (CONSOLE_STREAM_P (con))
    infd = fileno (CONSOLE_STREAM_DATA (con)->infd);
  else
    {
      assert (CONSOLE_TTY_P (con));
      infd = CONSOLE_TTY_DATA (con)->infd;
    }

  assert (infd >= 0);

  FD_SET (infd, &input_wait_mask);
  FD_SET (infd, &non_fake_input_wait_mask);
  FD_SET (infd, &tty_only_mask);
  return infd;
}

int
event_stream_unixoid_unselect_console (struct console *con)
{
  int infd;

  if (CONSOLE_STREAM_P (con))
    infd = fileno (CONSOLE_STREAM_DATA (con)->infd);
  else
    {
      assert (CONSOLE_TTY_P (con));
      infd = CONSOLE_TTY_DATA (con)->infd;
    }

  assert (infd >= 0);

  FD_CLR (infd, &input_wait_mask);
  FD_CLR (infd, &non_fake_input_wait_mask);
  FD_CLR (infd, &tty_only_mask);
  return infd;
}

int
event_stream_unixoid_select_process (struct Lisp_Process *proc)
{
  int infd, outfd;

  get_process_file_descriptors (proc, &infd, &outfd);
  assert (infd >= 0);

  FD_SET (infd, &input_wait_mask);
  FD_SET (infd, &non_fake_input_wait_mask);
  FD_SET (infd, &process_only_mask);
  return infd;
}

int
event_stream_unixoid_unselect_process (struct Lisp_Process *proc)
{
  int infd, outfd;

  get_process_file_descriptors (proc, &infd, &outfd);
  assert (infd >= 0);

  FD_CLR (infd, &input_wait_mask);
  FD_CLR (infd, &non_fake_input_wait_mask);
  FD_CLR (infd, &process_only_mask);
  return infd;
}

int
poll_fds_for_input (SELECT_TYPE mask)
{
  EMACS_TIME sometime;
  EMACS_SELECT_TIME select_time;
  SELECT_TYPE temp_mask;
  int retval;

  while (1)
    {
      EMACS_SET_SECS_USECS (sometime, 0, 0);
      EMACS_TIME_TO_SELECT_TIME (sometime, select_time);
      temp_mask = mask;
      /* To effect a poll, tell select() to block for zero seconds. */
      retval = select (MAXDESC, &temp_mask, 0, 0, &select_time);
      if (retval >= 0)
	return retval;
      if (errno != EINTR)
	{
	  /* Something went seriously wrong; don't abort since maybe
	     the TTY just died at the wrong time. */
	  fprintf (stderr, "xemacs: select failed: errno = %d\n", errno);
	  return 0;
	}
      /* else, we got interrupted by a signal, so try again. */
    }

  RETURN_NOT_REACHED(0) /* not reached */
}


void
init_event_unixoid (void)
{
  /* Do this first; the init_event_*_late() functions
     pay attention to it. */
  if (pipe (signal_event_pipe) < 0)
    {
      perror ("XEmacs: can't open pipe");
      exit (-1);
    }
  signal_event_pipe_initialized = 1;
  
  /* Set it non-blocking so we can drain its output. */
  set_descriptor_non_blocking (signal_event_pipe[0]);
  
  /* Also set the write descriptor non-blocking so we don't
     hang in case a long time passes between times when
     we drain the pipe. */
  set_descriptor_non_blocking (signal_event_pipe[1]);
  
  /* WARNING: In order for the signal-event pipe to work correctly
     and not cause lockups, the following need to be followed:
     
     1) event_pending_p() must ignore input on the signal-event pipe.
     2) As soon as next_event() notices input on the signal-event
     pipe, it must drain it. */
  FD_ZERO (&input_wait_mask);
  FD_ZERO (&non_fake_input_wait_mask);
  FD_ZERO (&process_only_mask);
  FD_ZERO (&tty_only_mask);
  
  FD_SET (signal_event_pipe[0], &input_wait_mask);
}
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