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[emacs.git] / src / blockinput.h
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1 /* blockinput.h - interface to blocking complicated interrupt-driven input.
2 Copyright (C) 1989, 1993, 2004 Free Software Foundation, Inc.
4 This file is part of GNU Emacs.
6 GNU Emacs is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
11 GNU Emacs is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU Emacs; see the file COPYING. If not, write to
18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 #ifndef EMACS_BLOCKINPUT_H
22 #define EMACS_BLOCKINPUT_H
24 #include "atimer.h"
26 /* When Emacs is using signal-driven input, the processing of those
27 input signals can get pretty hairy. For example, when Emacs is
28 running under X windows, handling an input signal can entail
29 retrieving events from the X event queue, or making other X calls.
31 If an input signal occurs while Emacs is in the midst of some
32 non-reentrant code, and the signal processing invokes that same
33 code, we lose. For example, malloc and the Xlib functions aren't
34 usually re-entrant, and both are used by the X input signal handler
35 - if we try to process an input signal in the midst of executing
36 any of these functions, we'll lose.
38 To avoid this, we make the following requirements:
40 * Everyone must evaluate BLOCK_INPUT before entering these functions,
41 and then call UNBLOCK_INPUT after performing them. Calls
42 BLOCK_INPUT and UNBLOCK_INPUT may be nested.
44 * Any complicated interrupt handling code should test
45 interrupt_input_blocked, and put off its work until later.
47 * If the interrupt handling code wishes, it may set
48 interrupt_input_pending to a non-zero value. If that flag is set
49 when input becomes unblocked, UNBLOCK_INPUT will send a new SIGIO. */
51 extern int interrupt_input_blocked;
53 /* Nonzero means an input interrupt has arrived
54 during the current critical section. */
55 extern int interrupt_input_pending;
58 /* Non-zero means asynchronous timers should be run when input is
59 unblocked. */
61 extern int pending_atimers;
63 /* Begin critical section. */
64 #define BLOCK_INPUT (interrupt_input_blocked++)
66 /* End critical section.
68 If doing signal-driven input, and a signal came in when input was
69 blocked, reinvoke the signal handler now to deal with it.
71 We used to have two possible definitions of this macro - one for
72 when SIGIO was #defined, and one for when it wasn't; when SIGIO
73 wasn't #defined, we wouldn't bother to check if we should re-invoke
74 the signal handler. But that doesn't work very well; some of the
75 files which use this macro don't #include the right files to get
76 SIGIO.
78 So, we always test interrupt_input_pending now; that's not too
79 expensive, and it'll never get set if we don't need to resignal. */
81 #define UNBLOCK_INPUT \
82 do \
83 { \
84 --interrupt_input_blocked; \
85 if (interrupt_input_blocked == 0) \
86 { \
87 if (interrupt_input_pending) \
88 reinvoke_input_signal (); \
89 if (pending_atimers) \
90 do_pending_atimers (); \
91 } \
92 else if (interrupt_input_blocked < 0) \
93 abort (); \
94 } \
95 while (0)
97 #define TOTALLY_UNBLOCK_INPUT (interrupt_input_blocked = 0)
98 #define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT
100 /* In critical section ? */
101 #define INPUT_BLOCKED_P (interrupt_input_blocked > 0)
103 /* Defined in keyboard.c */
104 /* Don't use a prototype here; it causes trouble in some files. */
105 extern void reinvoke_input_signal ();
107 #endif /* EMACS_BLOCKINPUT_H */
109 /* arch-tag: 51a9ec86-945a-4966-8f04-2d1341250e03
110 (do not change this comment) */