/* blockinput.h - interface to blocking complicated interrupt-driven input. Copyright (C) 1989, 1993 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 2, 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; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #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 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) #define TOTALLY_UNBLOCK_INPUT (interrupt_input_blocked = 0) #define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT /* 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 */