gio/gdbusnamewatching.c

   1 /* GDBus - GLib D-Bus Library
   2  *
   3  * Copyright (C) 2008-2009 Red Hat, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Author: David Zeuthen <davidz@redhat.com>
  21  */
  22
  23 #include "config.h"
  24
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include "gdbusutils.h"
  29 #include "gdbusnamewatching.h"
  30 #include "gdbuserror.h"
  31 #include "gdbusprivate.h"
  32 #include "gdbusconnection.h"
  33
  34 #include "glibintl.h"
  35
  36 /**
  37  * SECTION:gdbusnamewatching
  38  * @title: Watching Bus Names
  39  * @short_description: Simple API for watching bus names
  40  * @include: gio/gio.h
  41  *
  42  * Convenience API for watching bus names.
  43  *
  44  * <example id="gdbus-watching-names"><title>Simple application watching a name</title><programlisting><xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="text" href="../../../../gio/tests/gdbus-example-watch-name.c"><xi:fallback>FIXME: MISSING XINCLUDE CONTENT</xi:fallback></xi:include></programlisting></example>
  45  */
  46
  47 G_LOCK_DEFINE_STATIC (lock);
  48
  49 /* ---------------------------------------------------------------------------------------------------- */
  50
  51 typedef enum
  52 {
  53   PREVIOUS_CALL_NONE = 0,
  54   PREVIOUS_CALL_APPEARED,
  55   PREVIOUS_CALL_VANISHED,
  56 } PreviousCall;
  57
  58 typedef struct
  59 {
  60   volatile gint             ref_count;
  61   guint                     id;
  62   gchar                    *name;
  63   GBusNameWatcherFlags      flags;
  64   gchar                    *name_owner;
  65   GBusNameAppearedCallback  name_appeared_handler;
  66   GBusNameVanishedCallback  name_vanished_handler;
  67   gpointer                  user_data;
  68   GDestroyNotify            user_data_free_func;
  69   GMainContext             *main_context;
  70
  71   GDBusConnection          *connection;
  72   gulong                    disconnected_signal_handler_id;
  73   guint                     name_owner_changed_subscription_id;
  74
  75   PreviousCall              previous_call;
  76
  77   gboolean                  cancelled;
  78   gboolean                  initialized;
  79 } Client;
  80
  81 static guint next_global_id = 1;
  82 static GHashTable *map_id_to_client = NULL;
  83
  84 static Client *
  85 client_ref (Client *client)
  86 {
  87   g_atomic_int_inc (&client->ref_count);
  88   return client;
  89 }
  90
  91 static void
  92 client_unref (Client *client)
  93 {
  94   if (g_atomic_int_dec_and_test (&client->ref_count))
  95     {
  96       if (client->connection != NULL)
  97         {
  98           if (client->name_owner_changed_subscription_id > 0)
  99             g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 100           if (client->disconnected_signal_handler_id > 0)
 101             g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 102           g_object_unref (client->connection);
 103         }
 104       g_free (client->name);
 105       g_free (client->name_owner);
 106       if (client->main_context != NULL)
 107         g_main_context_unref (client->main_context);
 108       if (client->user_data_free_func != NULL)
 109         client->user_data_free_func (client->user_data);
 110       g_free (client);
 111     }
 112 }
 113
 114 /* ---------------------------------------------------------------------------------------------------- */
 115
 116 typedef enum
 117 {
 118   CALL_TYPE_NAME_APPEARED,
 119   CALL_TYPE_NAME_VANISHED
 120 } CallType;
 121
 122 typedef struct
 123 {
 124   Client *client;
 125
 126   /* keep this separate because client->connection may
 127    * be set to NULL after scheduling the call
 128    */
 129   GDBusConnection *connection;
 130
 131   /* ditto */
 132   gchar *name_owner;
 133
 134   CallType call_type;
 135 } CallHandlerData;
 136
 137 static void
 138 call_handler_data_free (CallHandlerData *data)
 139 {
 140   if (data->connection != NULL)
 141     g_object_unref (data->connection);
 142   g_free (data->name_owner);
 143   client_unref (data->client);
 144   g_free (data);
 145 }
 146
 147 static void
 148 actually_do_call (Client *client, GDBusConnection *connection, const gchar *name_owner, CallType call_type)
 149 {
 150   switch (call_type)
 151     {
 152     case CALL_TYPE_NAME_APPEARED:
 153       if (client->name_appeared_handler != NULL)
 154         {
 155           client->name_appeared_handler (connection,
 156                                          client->name,
 157                                          name_owner,
 158                                          client->user_data);
 159         }
 160       break;
 161
 162     case CALL_TYPE_NAME_VANISHED:
 163       if (client->name_vanished_handler != NULL)
 164         {
 165           client->name_vanished_handler (connection,
 166                                          client->name,
 167                                          client->user_data);
 168         }
 169       break;
 170
 171     default:
 172       g_assert_not_reached ();
 173       break;
 174     }
 175 }
 176
 177 static gboolean
 178 call_in_idle_cb (gpointer _data)
 179 {
 180   CallHandlerData *data = _data;
 181   actually_do_call (data->client, data->connection, data->name_owner, data->call_type);
 182   return FALSE;
 183 }
 184
 185 static void
 186 schedule_call_in_idle (Client *client, CallType call_type)
 187 {
 188   CallHandlerData *data;
 189   GSource *idle_source;
 190
 191   data = g_new0 (CallHandlerData, 1);
 192   data->client = client_ref (client);
 193   data->connection = client->connection != NULL ? g_object_ref (client->connection) : NULL;
 194   data->name_owner = g_strdup (client->name_owner);
 195   data->call_type = call_type;
 196
 197   idle_source = g_idle_source_new ();
 198   g_source_set_priority (idle_source, G_PRIORITY_HIGH);
 199   g_source_set_callback (idle_source,
 200                          call_in_idle_cb,
 201                          data,
 202                          (GDestroyNotify) call_handler_data_free);
 203   g_source_attach (idle_source, client->main_context);
 204   g_source_unref (idle_source);
 205 }
 206
 207 static void
 208 do_call (Client *client, CallType call_type)
 209 {
 210   /* only schedule in idle if we're not in the right thread */
 211   if (g_main_context_get_thread_default () != client->main_context)
 212     schedule_call_in_idle (client, call_type);
 213   else
 214     actually_do_call (client, client->connection, client->name_owner, call_type);
 215 }
 216
 217 static void
 218 call_appeared_handler (Client *client)
 219 {
 220   if (client->previous_call != PREVIOUS_CALL_APPEARED)
 221     {
 222       client->previous_call = PREVIOUS_CALL_APPEARED;
 223       if (!client->cancelled && client->name_appeared_handler != NULL)
 224         {
 225           do_call (client, CALL_TYPE_NAME_APPEARED);
 226         }
 227     }
 228 }
 229
 230 static void
 231 call_vanished_handler (Client  *client,
 232                        gboolean ignore_cancelled)
 233 {
 234   if (client->previous_call != PREVIOUS_CALL_VANISHED)
 235     {
 236       client->previous_call = PREVIOUS_CALL_VANISHED;
 237       if (((!client->cancelled) || ignore_cancelled) && client->name_vanished_handler != NULL)
 238         {
 239           do_call (client, CALL_TYPE_NAME_VANISHED);
 240         }
 241     }
 242 }
 243
 244 /* ---------------------------------------------------------------------------------------------------- */
 245
 246 static void
 247 on_connection_disconnected (GDBusConnection *connection,
 248                             gboolean         remote_peer_vanished,
 249                             GError          *error,
 250                             gpointer         user_data)
 251 {
 252   Client *client = user_data;
 253
 254   if (client->name_owner_changed_subscription_id > 0)
 255     g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 256   if (client->disconnected_signal_handler_id > 0)
 257     g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 258   g_object_unref (client->connection);
 259   client->disconnected_signal_handler_id = 0;
 260   client->name_owner_changed_subscription_id = 0;
 261   client->connection = NULL;
 262
 263   call_vanished_handler (client, FALSE);
 264 }
 265
 266 /* ---------------------------------------------------------------------------------------------------- */
 267
 268 static void
 269 on_name_owner_changed (GDBusConnection *connection,
 270                        const gchar      *sender_name,
 271                        const gchar      *object_path,
 272                        const gchar      *interface_name,
 273                        const gchar      *signal_name,
 274                        GVariant         *parameters,
 275                        gpointer          user_data)
 276 {
 277   Client *client = user_data;
 278   const gchar *name;
 279   const gchar *old_owner;
 280   const gchar *new_owner;
 281
 282   if (!client->initialized)
 283     goto out;
 284
 285   if (g_strcmp0 (object_path, "/org/freedesktop/DBus") != 0 ||
 286       g_strcmp0 (interface_name, "org.freedesktop.DBus") != 0 ||
 287       g_strcmp0 (sender_name, "org.freedesktop.DBus") != 0)
 288     goto out;
 289
 290   g_variant_get (parameters,
 291                  "(sss)",
 292                  &name,
 293                  &old_owner,
 294                  &new_owner);
 295
 296   /* we only care about a specific name */
 297   if (g_strcmp0 (name, client->name) != 0)
 298     goto out;
 299
 300   if ((old_owner != NULL && strlen (old_owner) > 0) && client->name_owner != NULL)
 301     {
 302       g_free (client->name_owner);
 303       client->name_owner = NULL;
 304       call_vanished_handler (client, FALSE);
 305     }
 306
 307   if (new_owner != NULL && strlen (new_owner) > 0)
 308     {
 309       g_warn_if_fail (client->name_owner == NULL);
 310       g_free (client->name_owner);
 311       client->name_owner = g_strdup (new_owner);
 312       call_appeared_handler (client);
 313     }
 314
 315  out:
 316   ;
 317 }
 318
 319 /* ---------------------------------------------------------------------------------------------------- */
 320
 321 static void
 322 get_name_owner_cb (GObject      *source_object,
 323                    GAsyncResult *res,
 324                    gpointer      user_data)
 325 {
 326   Client *client = user_data;
 327   GVariant *result;
 328   const char *name_owner;
 329
 330   name_owner = NULL;
 331   result = NULL;
 332
 333   result = g_dbus_connection_invoke_method_finish (client->connection,
 334                                                    res,
 335                                                    NULL);
 336   if (result != NULL)
 337     {
 338       g_variant_get (result, "(s)", &name_owner);
 339     }
 340
 341   if (name_owner != NULL)
 342     {
 343       g_warn_if_fail (client->name_owner == NULL);
 344       client->name_owner = g_strdup (name_owner);
 345       call_appeared_handler (client);
 346     }
 347   else
 348     {
 349       call_vanished_handler (client, FALSE);
 350     }
 351
 352   client->initialized = TRUE;
 353
 354   if (result != NULL)
 355     g_variant_unref (result);
 356   client_unref (client);
 357 }
 358
 359 /* ---------------------------------------------------------------------------------------------------- */
 360
 361 static void
 362 invoke_get_name_owner (Client *client)
 363 {
 364   g_dbus_connection_invoke_method (client->connection,
 365                                    "org.freedesktop.DBus",  /* bus name */
 366                                    "/org/freedesktop/DBus", /* object path */
 367                                    "org.freedesktop.DBus",  /* interface name */
 368                                    "GetNameOwner",          /* method name */
 369                                    g_variant_new ("(s)", client->name),
 370                                    G_DBUS_INVOKE_METHOD_FLAGS_NONE,
 371                                    -1,
 372                                    NULL,
 373                                    (GAsyncReadyCallback) get_name_owner_cb,
 374                                    client_ref (client));
 375 }
 376
 377 /* ---------------------------------------------------------------------------------------------------- */
 378
 379 static void
 380 start_service_by_name_cb (GObject      *source_object,
 381                           GAsyncResult *res,
 382                           gpointer      user_data)
 383 {
 384   Client *client = user_data;
 385   GVariant *result;
 386
 387   result = NULL;
 388
 389   result = g_dbus_connection_invoke_method_finish (client->connection,
 390                                                    res,
 391                                                    NULL);
 392   if (result != NULL)
 393     {
 394       guint32 start_service_result;
 395       g_variant_get (result, "(u)", &start_service_result);
 396
 397       if (start_service_result == 1) /* DBUS_START_REPLY_SUCCESS */
 398         {
 399           invoke_get_name_owner (client);
 400         }
 401       else if (start_service_result == 2) /* DBUS_START_REPLY_ALREADY_RUNNING */
 402         {
 403           invoke_get_name_owner (client);
 404         }
 405       else
 406         {
 407           g_warning ("Unexpected reply %d from StartServiceByName() method", start_service_result);
 408           call_vanished_handler (client, FALSE);
 409           client->initialized = TRUE;
 410         }
 411     }
 412   else
 413     {
 414       /* Errors are not unexpected; the bus will reply e.g.
 415        *
 416        *   org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Epiphany2
 417        *   was not provided by any .service files
 418        *
 419        * so just report vanished.
 420        */
 421       call_vanished_handler (client, FALSE);
 422       client->initialized = TRUE;
 423     }
 424
 425   if (result != NULL)
 426     g_variant_unref (result);
 427   client_unref (client);
 428 }
 429
 430 /* ---------------------------------------------------------------------------------------------------- */
 431
 432 static void
 433 has_connection (Client *client)
 434 {
 435   /* listen for disconnection */
 436   client->disconnected_signal_handler_id = g_signal_connect (client->connection,
 437                                                              "closed",
 438                                                              G_CALLBACK (on_connection_disconnected),
 439                                                              client);
 440
 441   /* start listening to NameOwnerChanged messages immediately */
 442   client->name_owner_changed_subscription_id = g_dbus_connection_signal_subscribe (client->connection,
 443                                                                                    "org.freedesktop.DBus",  /* name */
 444                                                                                    "org.freedesktop.DBus",  /* if */
 445                                                                                    "NameOwnerChanged",      /* signal */
 446                                                                                    "/org/freedesktop/DBus", /* path */
 447                                                                                    client->name,
 448                                                                                    on_name_owner_changed,
 449                                                                                    client,
 450                                                                                    NULL);
 451
 452   if (client->flags & G_BUS_NAME_WATCHER_FLAGS_AUTO_START)
 453     {
 454       g_dbus_connection_invoke_method (client->connection,
 455                                        "org.freedesktop.DBus",  /* bus name */
 456                                        "/org/freedesktop/DBus", /* object path */
 457                                        "org.freedesktop.DBus",  /* interface name */
 458                                        "StartServiceByName",    /* method name */
 459                                        g_variant_new ("(su)", client->name, 0),
 460                                        G_DBUS_INVOKE_METHOD_FLAGS_NONE,
 461                                        -1,
 462                                        NULL,
 463                                        (GAsyncReadyCallback) start_service_by_name_cb,
 464                                        client_ref (client));
 465     }
 466   else
 467     {
 468       /* check owner */
 469       invoke_get_name_owner (client);
 470     }
 471 }
 472
 473
 474 static void
 475 connection_get_cb (GObject      *source_object,
 476                    GAsyncResult *res,
 477                    gpointer      user_data)
 478 {
 479   Client *client = user_data;
 480
 481   client->connection = g_bus_get_finish (res, NULL);
 482   if (client->connection == NULL)
 483     {
 484       call_vanished_handler (client, FALSE);
 485       goto out;
 486     }
 487
 488   has_connection (client);
 489
 490  out:
 491   client_unref (client);
 492 }
 493
 494 /* ---------------------------------------------------------------------------------------------------- */
 495
 496 /**
 497  * g_bus_watch_name:
 498  * @bus_type: The type of bus to watch a name on.
 499  * @name: The name (well-known or unique) to watch.
 500  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 501  * @name_appeared_handler: Handler to invoke when @name is known to exist or %NULL.
 502  * @name_vanished_handler: Handler to invoke when @name is known to not exist or %NULL.
 503  * @user_data: User data to pass to handlers.
 504  * @user_data_free_func: Function for freeing @user_data or %NULL.
 505  *
 506  * Starts watching @name on the bus specified by @bus_type and calls
 507  * @name_appeared_handler and @name_vanished_handler when the name is
 508  * known to have a owner respectively known to lose its
 509  * owner. Callbacks will be invoked in the <link
 510  * linkend="g-main-context-push-thread-default">thread-default main
 511  * loop</link> of the thread you are calling this function from.
 512  *
 513  * You are guaranteed that one of the handlers will be invoked after
 514  * calling this function. When you are done watching the name, just
 515  * call g_bus_unwatch_name() with the watcher id this function
 516  * returns.
 517  *
 518  * If the name vanishes or appears (for example the application owning
 519  * the name could restart), the handlers are also invoked. If the
 520  * #GDBusConnection that is used for watching the name disconnects, then
 521  * @name_vanished_handler is invoked since it is no longer
 522  * possible to access the name.
 523  *
 524  * Another guarantee is that invocations of @name_appeared_handler
 525  * and @name_vanished_handler are guaranteed to alternate; that
 526  * is, if @name_appeared_handler is invoked then you are
 527  * guaranteed that the next time one of the handlers is invoked, it
 528  * will be @name_vanished_handler. The reverse is also true.
 529  *
 530  * This behavior makes it very simple to write applications that wants
 531  * to take action when a certain name exists, see <xref
 532  * linkend="gdbus-watching-names"/>. Basically, the application
 533  * should create object proxies in @name_appeared_handler and destroy
 534  * them again (if any) in @name_vanished_handler.
 535  *
 536  * Returns: An identifier (never 0) that an be used with
 537  * g_bus_unwatch_name() to stop watching the name.
 538  *
 539  * Since: 2.26
 540  */
 541 guint
 542 g_bus_watch_name (GBusType                  bus_type,
 543                   const gchar              *name,
 544                   GBusNameWatcherFlags      flags,
 545                   GBusNameAppearedCallback  name_appeared_handler,
 546                   GBusNameVanishedCallback  name_vanished_handler,
 547                   gpointer                  user_data,
 548                   GDestroyNotify            user_data_free_func)
 549 {
 550   Client *client;
 551
 552   g_return_val_if_fail (bus_type != G_BUS_TYPE_NONE, 0);
 553   g_return_val_if_fail (g_dbus_is_name (name), 0);
 554
 555   G_LOCK (lock);
 556
 557   client = g_new0 (Client, 1);
 558   client->ref_count = 1;
 559   client->id = next_global_id++; /* TODO: uh oh, handle overflow */
 560   client->name = g_strdup (name);
 561   client->flags = flags;
 562   client->name_appeared_handler = name_appeared_handler;
 563   client->name_vanished_handler = name_vanished_handler;
 564   client->user_data = user_data;
 565   client->user_data_free_func = user_data_free_func;
 566   client->main_context = g_main_context_get_thread_default ();
 567   if (client->main_context != NULL)
 568     g_main_context_ref (client->main_context);
 569
 570   if (map_id_to_client == NULL)
 571     {
 572       map_id_to_client = g_hash_table_new (g_direct_hash, g_direct_equal);
 573     }
 574   g_hash_table_insert (map_id_to_client,
 575                        GUINT_TO_POINTER (client->id),
 576                        client);
 577
 578   g_bus_get (bus_type,
 579              NULL,
 580              connection_get_cb,
 581              client_ref (client));
 582
 583   G_UNLOCK (lock);
 584
 585   return client->id;
 586 }
 587
 588 /**
 589  * g_bus_unwatch_name:
 590  * @watcher_id: An identifier obtained from g_bus_watch_name()
 591  *
 592  * Stops watching a name.
 593  *
 594  * Since: 2.26
 595  */
 596 void
 597 g_bus_unwatch_name (guint watcher_id)
 598 {
 599   Client *client;
 600
 601   g_return_if_fail (watcher_id > 0);
 602
 603   client = NULL;
 604
 605   G_LOCK (lock);
 606   if (watcher_id == 0 ||
 607       map_id_to_client == NULL ||
 608       (client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id))) == NULL)
 609     {
 610       g_warning ("Invalid id %d passed to g_bus_unwatch_name()", watcher_id);
 611       goto out;
 612     }
 613
 614   client->cancelled = TRUE;
 615   g_warn_if_fail (g_hash_table_remove (map_id_to_client, GUINT_TO_POINTER (watcher_id)));
 616
 617  out:
 618   G_UNLOCK (lock);
 619
 620   /* do callback without holding lock */
 621   if (client != NULL)
 622     {
 623       client_unref (client);
 624     }
 625 }