218 lines
6.6 KiB
C
218 lines
6.6 KiB
C
/* GDB Notifications to Observers.
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Copyright (C) 2003-2004, 2007-2012 Free Software Foundation, Inc.
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This file is part of GDB.
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This program 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 3 of the License, or
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(at your option) any later version.
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This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */
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/* An observer is an entity who is interested in being notified when GDB
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reaches certain states, or certain events occur in GDB. The entity being
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observed is called the Subject. To receive notifications, the observer
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attaches a callback to the subject. One subject can have several
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observers.
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This file implements an internal generic low-level event notification
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mechanism based on the Observer paradigm described in the book "Design
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Patterns". This generic event notification mechansim is then re-used
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to implement the exported high-level notification management routines
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for all possible notifications.
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The current implementation of the generic observer provides support
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for contextual data. This contextual data is given to the subject
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when attaching the callback. In return, the subject will provide
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this contextual data back to the observer as a parameter of the
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callback.
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FIXME: The current support for the contextual data is only partial,
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as it lacks a mechanism that would deallocate this data when the
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callback is detached. This is not a problem so far, as this contextual
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data is only used internally to hold a function pointer. Later on,
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if a certain observer needs to provide support for user-level
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contextual data, then the generic notification mechanism will need
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need to be enhanced to allow the observer to provide a routine to
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deallocate the data when attaching the callback.
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This file is currently maintained by hand, but the long term plan
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if the number of different notifications starts growing is to create
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a new script (observer.sh) that would generate this file, and the
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associated documentation. */
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#include "defs.h"
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#include "observer.h"
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#include "command.h"
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#include "gdbcmd.h"
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static int observer_debug;
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static void
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show_observer_debug (struct ui_file *file, int from_tty,
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struct cmd_list_element *c, const char *value)
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{
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fprintf_filtered (file, _("Observer debugging is %s.\n"), value);
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}
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/* The internal generic observer. */
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typedef void (generic_observer_notification_ftype) (const void *data,
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const void *args);
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struct observer
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{
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generic_observer_notification_ftype *notify;
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/* No memory management needed for the following field for now. */
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void *data;
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};
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/* A list of observers, maintained by the subject. A subject is
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actually represented by its list of observers. */
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struct observer_list
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{
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struct observer_list *next;
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struct observer *observer;
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};
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/* Allocate a struct observer_list, intended to be used as a node
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in the list of observers maintained by a subject. */
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static struct observer_list *
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xalloc_observer_list_node (void)
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{
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struct observer_list *node = XMALLOC (struct observer_list);
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node->observer = XMALLOC (struct observer);
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return node;
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}
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/* The opposite of xalloc_observer_list_node, frees the memory for
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the given node. */
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static void
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xfree_observer_list_node (struct observer_list *node)
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{
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xfree (node->observer);
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xfree (node);
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}
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/* Attach the callback NOTIFY to a SUBJECT. The DATA is also stored,
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in order for the subject to provide it back to the observer during
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a notification. */
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static struct observer *
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generic_observer_attach (struct observer_list **subject,
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generic_observer_notification_ftype * notify,
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void *data)
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{
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struct observer_list *observer_list = xalloc_observer_list_node ();
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observer_list->next = *subject;
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observer_list->observer->notify = notify;
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observer_list->observer->data = data;
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*subject = observer_list;
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return observer_list->observer;
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}
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/* Remove the given OBSERVER from the SUBJECT. Once detached, OBSERVER
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should no longer be used, as it is no longer valid. */
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static void
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generic_observer_detach (struct observer_list **subject,
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const struct observer *observer)
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{
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struct observer_list *previous_node = NULL;
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struct observer_list *current_node = *subject;
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while (current_node != NULL)
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{
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if (current_node->observer == observer)
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{
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if (previous_node != NULL)
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previous_node->next = current_node->next;
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else
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*subject = current_node->next;
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xfree_observer_list_node (current_node);
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return;
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}
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previous_node = current_node;
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current_node = current_node->next;
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}
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/* We should never reach this point. However, this should not be
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a very serious error, so simply report a warning to the user. */
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warning (_("Failed to detach observer"));
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}
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/* Send a notification to all the observers of SUBJECT. ARGS is passed to
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all observers as an argument to the notification callback. */
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static void
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generic_observer_notify (struct observer_list *subject, const void *args)
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{
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struct observer_list *current_node = subject;
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while (current_node != NULL)
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{
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(*current_node->observer->notify) (current_node->observer->data, args);
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current_node = current_node->next;
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}
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}
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/* The following code is only used to unit-test the observers from our
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testsuite. DO NOT USE IT within observer.c (or anywhere else for
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that matter)! */
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/* If we define these variables and functions as `static', the
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compiler will optimize them out. */
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int observer_test_first_observer = 0;
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int observer_test_second_observer = 0;
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int observer_test_third_observer = 0;
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void
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observer_test_first_notification_function (int arg)
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{
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observer_test_first_observer++;
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}
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void
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observer_test_second_notification_function (int arg)
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{
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observer_test_second_observer++;
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}
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void
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observer_test_third_notification_function (int arg)
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{
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observer_test_third_observer++;
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}
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extern initialize_file_ftype _initialize_observer; /* -Wmissing-prototypes */
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void
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_initialize_observer (void)
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{
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add_setshow_zinteger_cmd ("observer", class_maintenance,
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&observer_debug, _("\
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Set observer debugging."), _("\
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Show observer debugging."), _("\
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When non-zero, observer debugging is enabled."),
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NULL,
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show_observer_debug,
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&setdebuglist, &showdebuglist);
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}
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#include "observer.inc"
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