/* blockinput.h - interface to blocking complicated interrupt-driven input.
   Copyright (C) 1989, 1993, 2001, 2002, 2003, 2004,
                 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012  Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 3 of the License, or
(at your option) any later version.

GNU Emacs 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 GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef EMACS_BLOCKINPUT_H
#define EMACS_BLOCKINPUT_H

#include "atimer.h"

/* When Emacs is using signal-driven input, the processing of those
   input signals can get pretty hairy.  For example, when Emacs is
   running under X windows, handling an input signal can entail
   retrieving events from the X event queue, or making other X calls.

   If an input signal occurs while Emacs is in the midst of some
   non-reentrant code, and the signal processing invokes that same
   code, we lose.  For example, malloc and the Xlib functions aren't
   usually re-entrant, and both are used by the X input signal handler
   - if we try to process an input signal in the midst of executing
   any of these functions, we'll lose.

   To avoid this, we make the following requirements:

   * Everyone must evaluate BLOCK_INPUT before entering these functions,
   and then call UNBLOCK_INPUT after performing them.  Calls
   BLOCK_INPUT and UNBLOCK_INPUT may be nested.

   * Any complicated interrupt handling code should test
   interrupt_input_blocked, and put off its work until later.

   * If the interrupt handling code wishes, it may set
   interrupt_input_pending to a non-zero value.  If that flag is set
   when input becomes unblocked, UNBLOCK_INPUT will send a new SIGIO.  */

extern volatile int interrupt_input_blocked;

/* Nonzero means an input interrupt has arrived
   during the current critical section.  */
extern int interrupt_input_pending;


/* Non-zero means asynchronous timers should be run when input is
   unblocked.  */

extern int pending_atimers;


/* Begin critical section. */
#define BLOCK_INPUT (interrupt_input_blocked++)

/* End critical section.

   If doing signal-driven input, and a signal came in when input was
   blocked, reinvoke the signal handler now to deal with it.

   We used to have two possible definitions of this macro - one for
   when SIGIO was #defined, and one for when it wasn't; when SIGIO
   wasn't #defined, we wouldn't bother to check if we should re-invoke
   the signal handler.  But that doesn't work very well; some of the
   files which use this macro don't #include the right files to get
   SIGIO.

   So, we always test interrupt_input_pending now; that's not too
   expensive, and it'll never get set if we don't need to resignal.  */

#define UNBLOCK_INPUT 				\
  do						\
    {						\
      --interrupt_input_blocked;		\
      if (interrupt_input_blocked == 0)		\
	{					\
	  if (interrupt_input_pending)		\
	    reinvoke_input_signal ();		\
	  if (pending_atimers)			\
	    do_pending_atimers ();		\
	}					\
      else if (interrupt_input_blocked < 0)	\
	abort ();				\
    }						\
  while (0)

/* Undo any number of BLOCK_INPUT calls,
   and also reinvoke any pending signal.  */

#define TOTALLY_UNBLOCK_INPUT			\
  do if (interrupt_input_blocked != 0)		\
    {						\
      interrupt_input_blocked = 1;		\
      UNBLOCK_INPUT;				\
    }						\
  while (0)

/* Undo any number of BLOCK_INPUT calls down to level LEVEL,
   and also (if the level is now 0) reinvoke any pending signal.  */

#define UNBLOCK_INPUT_TO(LEVEL)				\
  do							\
    {							\
      interrupt_input_blocked = (LEVEL) + 1;		\
      UNBLOCK_INPUT;					\
    }							\
  while (0)

#define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT

/* In critical section ? */
#define INPUT_BLOCKED_P (interrupt_input_blocked > 0)

/* Defined in keyboard.c */
/* Don't use a prototype here; it causes trouble in some files.  */
extern void reinvoke_input_signal ();

#endif /* EMACS_BLOCKINPUT_H */

/* arch-tag: 51a9ec86-945a-4966-8f04-2d1341250e03
   (do not change this comment) */
