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| -rw-r--r-- | src/blockinput.h | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/src/blockinput.h b/src/blockinput.h new file mode 100644 index 00000000000..c4c4979bcf4 --- /dev/null +++ b/src/blockinput.h @@ -0,0 +1,72 @@ +/* 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, 675 Mass Ave, Cambridge, MA 02139, USA. */ + + +/* 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 unsigned int interrupt_input_blocked; + +/* Nonzero means an input interrupt has arrived + during the current critical section. */ +extern int interrupt_input_pending; + +/* Begin critical section. */ +#define BLOCK_INPUT (interrupt_input_blocked++) + +/* End critical section. */ +#ifdef SIGIO +/* If doing interrupt input, and an interrupt came in when input was blocked, + reinvoke the interrupt handler now to deal with it. */ +#define UNBLOCK_INPUT \ + (interrupt_input_blocked--, \ + (interrupt_input_blocked < 0 ? (abort (), 0) : 0), \ + ((interrupt_input_blocked == 0 && interupt_input_pending != 0) \ + ? (kill (0, SIGIO), 0) \ + : 0)) +#else +#define UNBLOCK_INPUT \ + (interrupt_input_blocked--, \ + (interrupt_input_blocked < 0 ? (abort (), 0) : 0)) +#endif + +#define TOTALLY_UNBLOCK_INPUT (interrupt_input_blocked = 0) +#define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT |