Move event-loop.[ch] to gdbsupport/

This moves event-loop.[ch] to gdbsupport/ and updates the uses in gdb.

gdb/ChangeLog
2020-04-13  Tom Tromey  <tom@tromey.com>

	* run-on-main-thread.c: Update include.
	* unittests/main-thread-selftests.c: Update include.
	* tui/tui-win.c: Update include.
	* tui/tui-io.c: Update include.
	* tui/tui-interp.c: Update include.
	* tui/tui-hooks.c: Update include.
	* top.h: Update include.
	* top.c: Update include.
	* ser-base.c: Update include.
	* remote.c: Update include.
	* remote-notif.c: Update include.
	* remote-fileio.c: Update include.
	* record-full.c: Update include.
	* record-btrace.c: Update include.
	* python/python.c: Update include.
	* posix-hdep.c: Update include.
	* mingw-hdep.c: Update include.
	* mi/mi-main.c: Update include.
	* mi/mi-interp.c: Update include.
	* main.c: Update include.
	* linux-nat.c: Update include.
	* interps.c: Update include.
	* infrun.c: Update include.
	* inf-loop.c: Update include.
	* event-top.c: Update include.
	* event-loop.c: Move to ../gdbsupport/.
	* event-loop.h: Move to ../gdbsupport/.
	* async-event.h: Update include.
	* Makefile.in (COMMON_SFILES, HFILES_NO_SRCDIR): Update.

gdbsupport/ChangeLog
2020-04-13  Tom Tromey  <tom@tromey.com>

	* event-loop.h: Move from ../gdb/.
	* event-loop.cc: Move from ../gdb/.

1 files changed, 102 insertions, 0 deletions

diff --git a/gdbsupport/event-loop.h b/gdbsupport/event-loop.h
new file mode 100644
index 00000000000..2eaaa0c8b60
--- /dev/null
+++ b/gdbsupport/event-loop.h
@@ -0,0 +1,102 @@
+/* Definitions used by the GDB event loop.
+   Copyright (C) 1999-2020 Free Software Foundation, Inc.
+   Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
+
+   This file is part of GDB.
+
+   This program 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.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef EVENT_LOOP_H
+#define EVENT_LOOP_H
+
+/* An event loop listens for events from multiple event sources.  When
+   an event arrives, it is queued and processed by calling the
+   appropriate event handler.  The event loop then continues to listen
+   for more events.  An event loop completes when there are no event
+   sources to listen on.  External event sources can be plugged into
+   the loop.
+
+   There are 4 main components:
+   - a list of file descriptors to be monitored, GDB_NOTIFIER.
+   - a list of asynchronous event sources to be monitored,
+     ASYNC_EVENT_HANDLER_LIST.
+   - a list of events that have occurred, EVENT_QUEUE.
+   - a list of signal handling functions, SIGHANDLER_LIST.
+
+   GDB_NOTIFIER keeps track of the file descriptor based event
+   sources.  ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous
+   event sources that are signalled by some component of gdb, usually
+   a target_ops instance.  Event sources for gdb are currently the UI
+   and the target.  Gdb communicates with the command line user
+   interface via the readline library and usually communicates with
+   remote targets via a serial port.  Serial ports are represented in
+   GDB as file descriptors and select/poll calls.  For native targets
+   instead, the communication varies across operating system debug
+   APIs, but usually consists of calls to ptrace and waits (via
+   signals) or calls to poll/select (via file descriptors).  In the
+   current gdb, the code handling events related to the target resides
+   in wait_for_inferior for synchronous targets; or, for asynchronous
+   capable targets, by having the target register either a target
+   controlled file descriptor and/or an asynchronous event source in
+   the event loop, with the fetch_inferior_event function as the event
+   callback.  In both the synchronous and asynchronous cases, usually
+   the target event is collected through the target_wait interface.
+   The target is free to install other event sources in the event loop
+   if it so requires.
+
+   EVENT_QUEUE keeps track of the events that have happened during the
+   last iteration of the event loop, and need to be processed.  An
+   event is represented by a procedure to be invoked in order to
+   process the event.  The queue is scanned head to tail.  If the
+   event of interest is a change of state in a file descriptor, then a
+   call to poll or select will be made to detect it.
+
+   If the events generate signals, they are also queued by special
+   functions that are invoked through traditional signal handlers.
+   The actions to be taken is response to such events will be executed
+   when the SIGHANDLER_LIST is scanned, the next time through the
+   infinite loop.
+
+   Corollary tasks are the creation and deletion of event sources.  */
+
+typedef void *gdb_client_data;
+typedef void (handler_func) (int, gdb_client_data);
+typedef void (timer_handler_func) (gdb_client_data);
+
+/* Exported functions from event-loop.c */
+
+extern int gdb_do_one_event (void);
+extern void delete_file_handler (int fd);
+extern void add_file_handler (int fd, handler_func *proc, 
+			      gdb_client_data client_data);
+extern int create_timer (int milliseconds, 
+			 timer_handler_func *proc, 
+			 gdb_client_data client_data);
+extern void delete_timer (int id);
+
+/* Must be defined by client.  */
+
+extern void handle_event_loop_exception (const gdb_exception &);
+
+/* Must be defined by client.  Returns true if any signal handler was
+   ready.  */
+
+extern int invoke_async_signal_handlers ();
+
+/* Must be defined by client.  Returns true if any event handler was
+   ready.  */
+
+extern int check_async_event_handlers ();
+
+#endif /* EVENT_LOOP_H */