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| -rw-r--r-- | gdb/ChangeLog | 4 | ||||
| -rw-r--r-- | gdb/observer.c | 194 | ||||
| -rw-r--r-- | gdb/observer.h | 35 |
3 files changed, 233 insertions, 0 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 020c3ff..b9b5047 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2003-02-27 J. Brobecker <brobecker@gnat.com> + + * observer.h, observer.c: New file. + 2003-02-27 Andrew Cagney <cagney@redhat.com> * arm-tdep.c (gdb_print_insn_arm): Rename _bfd to just bfd. diff --git a/gdb/observer.c b/gdb/observer.c new file mode 100644 index 0000000..c331112 --- /dev/null +++ b/gdb/observer.c @@ -0,0 +1,194 @@ +/* GDB Notifications to Observers. + Copyright 2003 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 2 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, write to the Free Software + Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +/* 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" + +/* 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 = XMALLOC (struct observer_list); + node->observer = XMALLOC (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 represented by its list + of observers LIST. 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 list of observers that need + to be notified by the subject represented by its LIST of observers. + 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 a subject represented by + its LIST of observers. 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; + } +} + +/* normal_stop notifications. */ + +static struct observer_list *normal_stop_subject = NULL; + +static void +observer_normal_stop_notification_stub (const void *data, + const void *unused_args) +{ + observer_normal_stop_ftype *notify = (observer_normal_stop_ftype *) data; + (*notify) (); +} + +struct observer * +observer_attach_normal_stop (observer_normal_stop_ftype *f) +{ + return generic_observer_attach (&normal_stop_subject, + &observer_normal_stop_notification_stub, + (void *) f); +} + +void +observer_detach_normal_stop (struct observer *observer) +{ + generic_observer_detach (&normal_stop_subject, observer); +} + +void +observer_notify_normal_stop (void) +{ + generic_observer_notify (normal_stop_subject, NULL); +} diff --git a/gdb/observer.h b/gdb/observer.h new file mode 100644 index 0000000..8b9a6db --- /dev/null +++ b/gdb/observer.h @@ -0,0 +1,35 @@ +/* GDB Notifications to Observers. + Copyright 2003 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 2 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, write to the Free Software + Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#ifndef OBSERVER_H +#define OBSERVER_H + +struct observer; + +/* normal_stop notifications. */ + +typedef void (observer_normal_stop_ftype) (void); + +extern struct observer * + observer_attach_normal_stop (observer_normal_stop_ftype *f); +extern void observer_detach_normal_stop (struct observer *observer); +extern void observer_notify_normal_stop (void); + +#endif /* OBSERVER_H */ |