223 lines
6.9 KiB
C
223 lines
6.9 KiB
C
/* GDB Notifications to Observers.
|
|
|
|
Copyright (C) 2003-2015 Free Software Foundation, Inc.
|
|
|
|
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/>. */
|
|
|
|
/* An observer is an entity who is interested in being notified when GDB
|
|
reaches certain states, or certain events occur in GDB. The entity being
|
|
observed is called the Subject. To receive notifications, the observer
|
|
attaches a callback to the subject. One subject can have several
|
|
observers.
|
|
|
|
This file implements an internal generic low-level event notification
|
|
mechanism based on the Observer paradigm described in the book "Design
|
|
Patterns". This generic event notification mechansim is then re-used
|
|
to implement the exported high-level notification management routines
|
|
for all possible notifications.
|
|
|
|
The current implementation of the generic observer provides support
|
|
for contextual data. This contextual data is given to the subject
|
|
when attaching the callback. In return, the subject will provide
|
|
this contextual data back to the observer as a parameter of the
|
|
callback.
|
|
|
|
FIXME: The current support for the contextual data is only partial,
|
|
as it lacks a mechanism that would deallocate this data when the
|
|
callback is detached. This is not a problem so far, as this contextual
|
|
data is only used internally to hold a function pointer. Later on,
|
|
if a certain observer needs to provide support for user-level
|
|
contextual data, then the generic notification mechanism will need
|
|
need to be enhanced to allow the observer to provide a routine to
|
|
deallocate the data when attaching the callback.
|
|
|
|
This file is currently maintained by hand, but the long term plan
|
|
if the number of different notifications starts growing is to create
|
|
a new script (observer.sh) that would generate this file, and the
|
|
associated documentation. */
|
|
|
|
#include "defs.h"
|
|
#include "observer.h"
|
|
#include "command.h"
|
|
#include "gdbcmd.h"
|
|
|
|
static unsigned int observer_debug;
|
|
static void
|
|
show_observer_debug (struct ui_file *file, int from_tty,
|
|
struct cmd_list_element *c, const char *value)
|
|
{
|
|
fprintf_filtered (file, _("Observer debugging is %s.\n"), value);
|
|
}
|
|
|
|
/* The internal generic observer. */
|
|
|
|
typedef void (generic_observer_notification_ftype) (const void *data,
|
|
const void *args);
|
|
|
|
struct observer
|
|
{
|
|
generic_observer_notification_ftype *notify;
|
|
/* No memory management needed for the following field for now. */
|
|
void *data;
|
|
};
|
|
|
|
/* A list of observers, maintained by the subject. A subject is
|
|
actually represented by its list of observers. */
|
|
|
|
struct observer_list
|
|
{
|
|
struct observer_list *next;
|
|
struct observer *observer;
|
|
};
|
|
|
|
/* Allocate a struct observer_list, intended to be used as a node
|
|
in the list of observers maintained by a subject. */
|
|
|
|
static struct observer_list *
|
|
xalloc_observer_list_node (void)
|
|
{
|
|
struct observer_list *node = XNEW (struct observer_list);
|
|
|
|
node->observer = XNEW (struct observer);
|
|
return node;
|
|
}
|
|
|
|
/* The opposite of xalloc_observer_list_node, frees the memory for
|
|
the given node. */
|
|
|
|
static void
|
|
xfree_observer_list_node (struct observer_list *node)
|
|
{
|
|
xfree (node->observer);
|
|
xfree (node);
|
|
}
|
|
|
|
/* Attach the callback NOTIFY to a SUBJECT. The DATA is also stored,
|
|
in order for the subject to provide it back to the observer during
|
|
a notification. */
|
|
|
|
static struct observer *
|
|
generic_observer_attach (struct observer_list **subject,
|
|
generic_observer_notification_ftype * notify,
|
|
void *data)
|
|
{
|
|
struct observer_list *observer_list = xalloc_observer_list_node ();
|
|
|
|
observer_list->next = *subject;
|
|
observer_list->observer->notify = notify;
|
|
observer_list->observer->data = data;
|
|
*subject = observer_list;
|
|
|
|
return observer_list->observer;
|
|
}
|
|
|
|
/* Remove the given OBSERVER from the SUBJECT. Once detached, OBSERVER
|
|
should no longer be used, as it is no longer valid. */
|
|
|
|
static void
|
|
generic_observer_detach (struct observer_list **subject,
|
|
const struct observer *observer)
|
|
{
|
|
struct observer_list *previous_node = NULL;
|
|
struct observer_list *current_node = *subject;
|
|
|
|
while (current_node != NULL)
|
|
{
|
|
if (current_node->observer == observer)
|
|
{
|
|
if (previous_node != NULL)
|
|
previous_node->next = current_node->next;
|
|
else
|
|
*subject = current_node->next;
|
|
xfree_observer_list_node (current_node);
|
|
return;
|
|
}
|
|
previous_node = current_node;
|
|
current_node = current_node->next;
|
|
}
|
|
|
|
/* We should never reach this point. However, this should not be
|
|
a very serious error, so simply report a warning to the user. */
|
|
warning (_("Failed to detach observer"));
|
|
}
|
|
|
|
/* Send a notification to all the observers of SUBJECT. ARGS is passed to
|
|
all observers as an argument to the notification callback. */
|
|
|
|
static void
|
|
generic_observer_notify (struct observer_list *subject, const void *args)
|
|
{
|
|
struct observer_list *current_node = subject;
|
|
|
|
while (current_node != NULL)
|
|
{
|
|
(*current_node->observer->notify) (current_node->observer->data, args);
|
|
current_node = current_node->next;
|
|
}
|
|
}
|
|
|
|
|
|
/* The following code is only used to unit-test the observers from our
|
|
testsuite. DO NOT USE IT within observer.c (or anywhere else for
|
|
that matter)! */
|
|
|
|
/* If we define these variables and functions as `static', the
|
|
compiler will optimize them out. */
|
|
|
|
int observer_test_first_observer = 0;
|
|
int observer_test_second_observer = 0;
|
|
int observer_test_third_observer = 0;
|
|
|
|
/* Provide prototypes to silence -Wmissing-prototypes. */
|
|
extern void observer_test_first_notification_function (int arg);
|
|
extern void observer_test_second_notification_function (int arg);
|
|
extern void observer_test_third_notification_function (int arg);
|
|
|
|
void
|
|
observer_test_first_notification_function (int arg)
|
|
{
|
|
observer_test_first_observer++;
|
|
}
|
|
|
|
void
|
|
observer_test_second_notification_function (int arg)
|
|
{
|
|
observer_test_second_observer++;
|
|
}
|
|
|
|
void
|
|
observer_test_third_notification_function (int arg)
|
|
{
|
|
observer_test_third_observer++;
|
|
}
|
|
|
|
extern initialize_file_ftype _initialize_observer; /* -Wmissing-prototypes */
|
|
|
|
void
|
|
_initialize_observer (void)
|
|
{
|
|
add_setshow_zuinteger_cmd ("observer", class_maintenance,
|
|
&observer_debug, _("\
|
|
Set observer debugging."), _("\
|
|
Show observer debugging."), _("\
|
|
When non-zero, observer debugging is enabled."),
|
|
NULL,
|
|
show_observer_debug,
|
|
&setdebuglist, &showdebuglist);
|
|
}
|
|
|
|
#include "observer.inc"
|