1 /* blockinput.h - interface to blocking complicated interrupt-driven input.
2 Copyright (C) 1989, 1993, 2001, 2002, 2003, 2004,
3 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
5 This file is part of GNU Emacs.
7 GNU Emacs is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 GNU Emacs is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
20 #ifndef EMACS_BLOCKINPUT_H
21 #define EMACS_BLOCKINPUT_H
25 /* When Emacs is using signal-driven input, the processing of those
26 input signals can get pretty hairy. For example, when Emacs is
27 running under X windows, handling an input signal can entail
28 retrieving events from the X event queue, or making other X calls.
30 If an input signal occurs while Emacs is in the midst of some
31 non-reentrant code, and the signal processing invokes that same
32 code, we lose. For example, malloc and the Xlib functions aren't
33 usually re-entrant, and both are used by the X input signal handler
34 - if we try to process an input signal in the midst of executing
35 any of these functions, we'll lose.
37 To avoid this, we make the following requirements:
39 * Everyone must evaluate BLOCK_INPUT before entering these functions,
40 and then call UNBLOCK_INPUT after performing them. Calls
41 BLOCK_INPUT and UNBLOCK_INPUT may be nested.
43 * Any complicated interrupt handling code should test
44 interrupt_input_blocked, and put off its work until later.
46 * If the interrupt handling code wishes, it may set
47 interrupt_input_pending to a non-zero value. If that flag is set
48 when input becomes unblocked, UNBLOCK_INPUT will send a new SIGIO. */
50 extern volatile int interrupt_input_blocked
;
52 /* Nonzero means an input interrupt has arrived
53 during the current critical section. */
54 extern int interrupt_input_pending
;
57 /* Non-zero means asynchronous timers should be run when input is
60 extern int pending_atimers
;
62 #if defined HAVE_NS && !defined COCOA_EXPERIMENTAL_CTRL_G
63 /* NS does not use interrupt-driven input processing (yet), so this is
64 unneeded and moreover was causing problems. */
67 #define TOTALLY_UNBLOCK_INPUT
68 #define UNBLOCK_INPUT_TO(LEVEL)
72 /* Begin critical section. */
73 #define BLOCK_INPUT (interrupt_input_blocked++)
75 /* End critical section.
77 If doing signal-driven input, and a signal came in when input was
78 blocked, reinvoke the signal handler now to deal with it.
80 We used to have two possible definitions of this macro - one for
81 when SIGIO was #defined, and one for when it wasn't; when SIGIO
82 wasn't #defined, we wouldn't bother to check if we should re-invoke
83 the signal handler. But that doesn't work very well; some of the
84 files which use this macro don't #include the right files to get
87 So, we always test interrupt_input_pending now; that's not too
88 expensive, and it'll never get set if we don't need to resignal. */
90 #define UNBLOCK_INPUT \
93 --interrupt_input_blocked; \
94 if (interrupt_input_blocked == 0) \
96 if (interrupt_input_pending) \
97 reinvoke_input_signal (); \
98 if (pending_atimers) \
99 do_pending_atimers (); \
101 else if (interrupt_input_blocked < 0) \
106 /* Undo any number of BLOCK_INPUT calls,
107 and also reinvoke any pending signal. */
109 #define TOTALLY_UNBLOCK_INPUT \
110 do if (interrupt_input_blocked != 0) \
112 interrupt_input_blocked = 1; \
117 /* Undo any number of BLOCK_INPUT calls down to level LEVEL,
118 and also (if the level is now 0) reinvoke any pending signal. */
120 #define UNBLOCK_INPUT_TO(LEVEL) \
123 interrupt_input_blocked = (LEVEL) + 1; \
128 #endif /* defined HAVE_NS && !defined COCOA_EXPERIMENTAL_CTRL_G */
130 #define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT
132 /* In critical section ? */
133 #define INPUT_BLOCKED_P (interrupt_input_blocked > 0)
135 /* Defined in keyboard.c */
136 /* Don't use a prototype here; it causes trouble in some files. */
137 extern void reinvoke_input_signal ();
139 #endif /* EMACS_BLOCKINPUT_H */
141 /* arch-tag: 51a9ec86-945a-4966-8f04-2d1341250e03
142 (do not change this comment) */