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/* blockinput.h - interface to blocking complicated interrupt-driven input.
Copyright (C) 1989, 1993, 2001-2023 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 <https://www.gnu.org/licenses/>. */
#ifndef EMACS_BLOCKINPUT_H
#define EMACS_BLOCKINPUT_H
INLINE_HEADER_BEGIN
/* Emacs should avoid doing anything hairy in a signal handler, because
so many system functions are non-reentrant. For example, malloc
and the Xlib functions aren't usually re-entrant, so if they were
used by the SIGIO handler, we'd lose.
To avoid this, we make the following requirements:
* Everyone must evaluate BLOCK_INPUT before performing actions that
might conflict with a signal handler, and then call UNBLOCK_INPUT
after performing them. Calls BLOCK_INPUT and UNBLOCK_INPUT may be
nested.
* Any complicated interrupt handling code should test
INPUT_BLOCKED_P, and put off its work until later.
* If the interrupt handling code wishes, it may set
pending_signals to a non-zero value. If that flag is set
when input becomes unblocked, UNBLOCK_INPUT will then read
input and process timers.
Historically, Emacs signal handlers did much more than they do now,
and this caused many BLOCK_INPUT calls to be sprinkled around the code.
FIXME: Remove calls that aren't needed now. */
extern volatile int interrupt_input_blocked;
/* Begin critical section. */
INLINE void
block_input (void)
{
interrupt_input_blocked++;
}
extern void unblock_input (void);
extern void totally_unblock_input (void);
extern void unblock_input_to (int);
/* In critical section? */
INLINE bool
input_blocked_p (void)
{
return interrupt_input_blocked > 0;
}
INLINE_HEADER_END
#endif /* EMACS_BLOCKINPUT_H */
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