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105 lines
3.7 KiB
C
105 lines
3.7 KiB
C
/* blockinput.h - interface to blocking complicated interrupt-driven input.
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Copyright (C) 1989, 1993 Free Software Foundation, Inc.
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This file is part of GNU Emacs.
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GNU Emacs is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Emacs is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Emacs; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef EMACS_BLOCKINPUT_H
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#define EMACS_BLOCKINPUT_H
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#include "atimer.h"
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/* When Emacs is using signal-driven input, the processing of those
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input signals can get pretty hairy. For example, when Emacs is
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running under X windows, handling an input signal can entail
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retrieving events from the X event queue, or making other X calls.
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If an input signal occurs while Emacs is in the midst of some
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non-reentrant code, and the signal processing invokes that same
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code, we lose. For example, malloc and the Xlib functions aren't
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usually re-entrant, and both are used by the X input signal handler
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- if we try to process an input signal in the midst of executing
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any of these functions, we'll lose.
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To avoid this, we make the following requirements:
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* Everyone must evaluate BLOCK_INPUT before entering these functions,
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and then call UNBLOCK_INPUT after performing them. Calls
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BLOCK_INPUT and UNBLOCK_INPUT may be nested.
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* Any complicated interrupt handling code should test
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interrupt_input_blocked, and put off its work until later.
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* If the interrupt handling code wishes, it may set
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interrupt_input_pending to a non-zero value. If that flag is set
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when input becomes unblocked, UNBLOCK_INPUT will send a new SIGIO. */
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extern int interrupt_input_blocked;
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/* Nonzero means an input interrupt has arrived
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during the current critical section. */
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extern int interrupt_input_pending;
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/* Non-zero means asynchronous timers should be run when input is
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unblocked. */
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extern int pending_atimers;
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/* Begin critical section. */
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#define BLOCK_INPUT (interrupt_input_blocked++)
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/* End critical section.
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If doing signal-driven input, and a signal came in when input was
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blocked, reinvoke the signal handler now to deal with it.
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We used to have two possible definitions of this macro - one for
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when SIGIO was #defined, and one for when it wasn't; when SIGIO
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wasn't #defined, we wouldn't bother to check if we should re-invoke
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the signal handler. But that doesn't work very well; some of the
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files which use this macro don't #include the right files to get
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SIGIO.
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So, we always test interrupt_input_pending now; that's not too
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expensive, and it'll never get set if we don't need to resignal. */
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#define UNBLOCK_INPUT \
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do \
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{ \
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--interrupt_input_blocked; \
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if (interrupt_input_blocked == 0) \
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{ \
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if (interrupt_input_pending) \
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reinvoke_input_signal (); \
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if (pending_atimers) \
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do_pending_atimers (); \
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} \
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else if (interrupt_input_blocked < 0) \
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abort (); \
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} \
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while (0)
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#define TOTALLY_UNBLOCK_INPUT (interrupt_input_blocked = 0)
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#define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT
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/* Defined in keyboard.c */
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/* Don't use a prototype here; it causes trouble in some files. */
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extern void reinvoke_input_signal ();
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#endif /* EMACS_BLOCKINPUT_H */
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