gio/gdbusnamewatching.c

   1 /* GDBus - GLib D-Bus Library
   2  *
   3  * Copyright (C) 2008-2010 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 #include "gioalias.h"
  36
  37 /**
  38  * SECTION:gdbusnamewatching
  39  * @title: Watching Bus Names
  40  * @short_description: Simple API for watching bus names
  41  * @include: gio/gio.h
  42  *
  43  * Convenience API for watching bus names.
  44  *
  45  * <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>
  46  */
  47
  48 G_LOCK_DEFINE_STATIC (lock);
  49
  50 /* ---------------------------------------------------------------------------------------------------- */
  51
  52 typedef enum
  53 {
  54   PREVIOUS_CALL_NONE = 0,
  55   PREVIOUS_CALL_APPEARED,
  56   PREVIOUS_CALL_VANISHED,
  57 } PreviousCall;
  58
  59 typedef struct
  60 {
  61   volatile gint             ref_count;
  62   guint                     id;
  63   gchar                    *name;
  64   GBusNameWatcherFlags      flags;
  65   gchar                    *name_owner;
  66   GBusNameAppearedCallback  name_appeared_handler;
  67   GBusNameVanishedCallback  name_vanished_handler;
  68   gpointer                  user_data;
  69   GDestroyNotify            user_data_free_func;
  70   GMainContext             *main_context;
  71
  72   GDBusConnection          *connection;
  73   gulong                    disconnected_signal_handler_id;
  74   guint                     name_owner_changed_subscription_id;
  75
  76   PreviousCall              previous_call;
  77
  78   gboolean                  cancelled;
  79   gboolean                  initialized;
  80 } Client;
  81
  82 static guint next_global_id = 1;
  83 static GHashTable *map_id_to_client = NULL;
  84
  85 static Client *
  86 client_ref (Client *client)
  87 {
  88   g_atomic_int_inc (&client->ref_count);
  89   return client;
  90 }
  91
  92 static void
  93 client_unref (Client *client)
  94 {
  95   if (g_atomic_int_dec_and_test (&client->ref_count))
  96     {
  97       if (client->connection != NULL)
  98         {
  99           if (client->name_owner_changed_subscription_id > 0)
 100             g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 101           if (client->disconnected_signal_handler_id > 0)
 102             g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 103           g_object_unref (client->connection);
 104         }
 105       g_free (client->name);
 106       g_free (client->name_owner);
 107       if (client->main_context != NULL)
 108         g_main_context_unref (client->main_context);
 109       if (client->user_data_free_func != NULL)
 110         client->user_data_free_func (client->user_data);
 111       g_free (client);
 112     }
 113 }
 114
 115 /* ---------------------------------------------------------------------------------------------------- */
 116
 117 typedef enum
 118 {
 119   CALL_TYPE_NAME_APPEARED,
 120   CALL_TYPE_NAME_VANISHED
 121 } CallType;
 122
 123 typedef struct
 124 {
 125   Client *client;
 126
 127   /* keep this separate because client->connection may
 128    * be set to NULL after scheduling the call
 129    */
 130   GDBusConnection *connection;
 131
 132   /* ditto */
 133   gchar *name_owner;
 134
 135   CallType call_type;
 136 } CallHandlerData;
 137
 138 static void
 139 call_handler_data_free (CallHandlerData *data)
 140 {
 141   if (data->connection != NULL)
 142     g_object_unref (data->connection);
 143   g_free (data->name_owner);
 144   client_unref (data->client);
 145   g_free (data);
 146 }
 147
 148 static void
 149 actually_do_call (Client *client, GDBusConnection *connection, const gchar *name_owner, CallType call_type)
 150 {
 151   switch (call_type)
 152     {
 153     case CALL_TYPE_NAME_APPEARED:
 154       if (client->name_appeared_handler != NULL)
 155         {
 156           client->name_appeared_handler (connection,
 157                                          client->name,
 158                                          name_owner,
 159                                          client->user_data);
 160         }
 161       break;
 162
 163     case CALL_TYPE_NAME_VANISHED:
 164       if (client->name_vanished_handler != NULL)
 165         {
 166           client->name_vanished_handler (connection,
 167                                          client->name,
 168                                          client->user_data);
 169         }
 170       break;
 171
 172     default:
 173       g_assert_not_reached ();
 174       break;
 175     }
 176 }
 177
 178 static gboolean
 179 call_in_idle_cb (gpointer _data)
 180 {
 181   CallHandlerData *data = _data;
 182   actually_do_call (data->client, data->connection, data->name_owner, data->call_type);
 183   return FALSE;
 184 }
 185
 186 static void
 187 schedule_call_in_idle (Client *client, CallType call_type)
 188 {
 189   CallHandlerData *data;
 190   GSource *idle_source;
 191
 192   data = g_new0 (CallHandlerData, 1);
 193   data->client = client_ref (client);
 194   data->connection = client->connection != NULL ? g_object_ref (client->connection) : NULL;
 195   data->name_owner = g_strdup (client->name_owner);
 196   data->call_type = call_type;
 197
 198   idle_source = g_idle_source_new ();
 199   g_source_set_priority (idle_source, G_PRIORITY_HIGH);
 200   g_source_set_callback (idle_source,
 201                          call_in_idle_cb,
 202                          data,
 203                          (GDestroyNotify) call_handler_data_free);
 204   g_source_attach (idle_source, client->main_context);
 205   g_source_unref (idle_source);
 206 }
 207
 208 static void
 209 do_call (Client *client, CallType call_type)
 210 {
 211   /* only schedule in idle if we're not in the right thread */
 212   if (g_main_context_get_thread_default () != client->main_context)
 213     schedule_call_in_idle (client, call_type);
 214   else
 215     actually_do_call (client, client->connection, client->name_owner, call_type);
 216 }
 217
 218 static void
 219 call_appeared_handler (Client *client)
 220 {
 221   if (client->previous_call != PREVIOUS_CALL_APPEARED)
 222     {
 223       client->previous_call = PREVIOUS_CALL_APPEARED;
 224       if (!client->cancelled && client->name_appeared_handler != NULL)
 225         {
 226           do_call (client, CALL_TYPE_NAME_APPEARED);
 227         }
 228     }
 229 }
 230
 231 static void
 232 call_vanished_handler (Client  *client,
 233                        gboolean ignore_cancelled)
 234 {
 235   if (client->previous_call != PREVIOUS_CALL_VANISHED)
 236     {
 237       client->previous_call = PREVIOUS_CALL_VANISHED;
 238       if (((!client->cancelled) || ignore_cancelled) && client->name_vanished_handler != NULL)
 239         {
 240           do_call (client, CALL_TYPE_NAME_VANISHED);
 241         }
 242     }
 243 }
 244
 245 /* ---------------------------------------------------------------------------------------------------- */
 246
 247 static void
 248 on_connection_disconnected (GDBusConnection *connection,
 249                             gboolean         remote_peer_vanished,
 250                             GError          *error,
 251                             gpointer         user_data)
 252 {
 253   Client *client = user_data;
 254
 255   if (client->name_owner_changed_subscription_id > 0)
 256     g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 257   if (client->disconnected_signal_handler_id > 0)
 258     g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 259   g_object_unref (client->connection);
 260   client->disconnected_signal_handler_id = 0;
 261   client->name_owner_changed_subscription_id = 0;
 262   client->connection = NULL;
 263
 264   call_vanished_handler (client, FALSE);
 265 }
 266
 267 /* ---------------------------------------------------------------------------------------------------- */
 268
 269 static void
 270 on_name_owner_changed (GDBusConnection *connection,
 271                        const gchar      *sender_name,
 272                        const gchar      *object_path,
 273                        const gchar      *interface_name,
 274                        const gchar      *signal_name,
 275                        GVariant         *parameters,
 276                        gpointer          user_data)
 277 {
 278   Client *client = user_data;
 279   const gchar *name;
 280   const gchar *old_owner;
 281   const gchar *new_owner;
 282
 283   if (!client->initialized)
 284     goto out;
 285
 286   if (g_strcmp0 (object_path, "/org/freedesktop/DBus") != 0 ||
 287       g_strcmp0 (interface_name, "org.freedesktop.DBus") != 0 ||
 288       g_strcmp0 (sender_name, "org.freedesktop.DBus") != 0)
 289     goto out;
 290
 291   g_variant_get (parameters,
 292                  "(sss)",
 293                  &name,
 294                  &old_owner,
 295                  &new_owner);
 296
 297   /* we only care about a specific name */
 298   if (g_strcmp0 (name, client->name) != 0)
 299     goto out;
 300
 301   if ((old_owner != NULL && strlen (old_owner) > 0) && client->name_owner != NULL)
 302     {
 303       g_free (client->name_owner);
 304       client->name_owner = NULL;
 305       call_vanished_handler (client, FALSE);
 306     }
 307
 308   if (new_owner != NULL && strlen (new_owner) > 0)
 309     {
 310       g_warn_if_fail (client->name_owner == NULL);
 311       g_free (client->name_owner);
 312       client->name_owner = g_strdup (new_owner);
 313       call_appeared_handler (client);
 314     }
 315
 316  out:
 317   ;
 318 }
 319
 320 /* ---------------------------------------------------------------------------------------------------- */
 321
 322 static void
 323 get_name_owner_cb (GObject      *source_object,
 324                    GAsyncResult *res,
 325                    gpointer      user_data)
 326 {
 327   Client *client = user_data;
 328   GVariant *result;
 329   const char *name_owner;
 330
 331   name_owner = NULL;
 332   result = NULL;
 333
 334   result = g_dbus_connection_call_finish (client->connection,
 335                                           res,
 336                                           NULL);
 337   if (result != NULL)
 338     {
 339       g_variant_get (result, "(s)", &name_owner);
 340     }
 341
 342   if (name_owner != NULL)
 343     {
 344       g_warn_if_fail (client->name_owner == NULL);
 345       client->name_owner = g_strdup (name_owner);
 346       call_appeared_handler (client);
 347     }
 348   else
 349     {
 350       call_vanished_handler (client, FALSE);
 351     }
 352
 353   client->initialized = TRUE;
 354
 355   if (result != NULL)
 356     g_variant_unref (result);
 357   client_unref (client);
 358 }
 359
 360 /* ---------------------------------------------------------------------------------------------------- */
 361
 362 static void
 363 invoke_get_name_owner (Client *client)
 364 {
 365   g_dbus_connection_call (client->connection,
 366                           "org.freedesktop.DBus",  /* bus name */
 367                           "/org/freedesktop/DBus", /* object path */
 368                           "org.freedesktop.DBus",  /* interface name */
 369                           "GetNameOwner",          /* method name */
 370                           g_variant_new ("(s)", client->name),
 371                           G_DBUS_CALL_FLAGS_NONE,
 372                           -1,
 373                           NULL,
 374                           (GAsyncReadyCallback) get_name_owner_cb,
 375                           client_ref (client));
 376 }
 377
 378 /* ---------------------------------------------------------------------------------------------------- */
 379
 380 static void
 381 start_service_by_name_cb (GObject      *source_object,
 382                           GAsyncResult *res,
 383                           gpointer      user_data)
 384 {
 385   Client *client = user_data;
 386   GVariant *result;
 387
 388   result = NULL;
 389
 390   result = g_dbus_connection_call_finish (client->connection,
 391                                           res,
 392                                           NULL);
 393   if (result != NULL)
 394     {
 395       guint32 start_service_result;
 396       g_variant_get (result, "(u)", &start_service_result);
 397
 398       if (start_service_result == 1) /* DBUS_START_REPLY_SUCCESS */
 399         {
 400           invoke_get_name_owner (client);
 401         }
 402       else if (start_service_result == 2) /* DBUS_START_REPLY_ALREADY_RUNNING */
 403         {
 404           invoke_get_name_owner (client);
 405         }
 406       else
 407         {
 408           g_warning ("Unexpected reply %d from StartServiceByName() method", start_service_result);
 409           call_vanished_handler (client, FALSE);
 410           client->initialized = TRUE;
 411         }
 412     }
 413   else
 414     {
 415       /* Errors are not unexpected; the bus will reply e.g.
 416        *
 417        *   org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Epiphany2
 418        *   was not provided by any .service files
 419        *
 420        * so just report vanished.
 421        */
 422       call_vanished_handler (client, FALSE);
 423       client->initialized = TRUE;
 424     }
 425
 426   if (result != NULL)
 427     g_variant_unref (result);
 428   client_unref (client);
 429 }
 430
 431 /* ---------------------------------------------------------------------------------------------------- */
 432
 433 static void
 434 has_connection (Client *client)
 435 {
 436   /* listen for disconnection */
 437   client->disconnected_signal_handler_id = g_signal_connect (client->connection,
 438                                                              "closed",
 439                                                              G_CALLBACK (on_connection_disconnected),
 440                                                              client);
 441
 442   /* start listening to NameOwnerChanged messages immediately */
 443   client->name_owner_changed_subscription_id = g_dbus_connection_signal_subscribe (client->connection,
 444                                                                                    "org.freedesktop.DBus",  /* name */
 445                                                                                    "org.freedesktop.DBus",  /* if */
 446                                                                                    "NameOwnerChanged",      /* signal */
 447                                                                                    "/org/freedesktop/DBus", /* path */
 448                                                                                    client->name,
 449                                                                                    on_name_owner_changed,
 450                                                                                    client,
 451                                                                                    NULL);
 452
 453   if (client->flags & G_BUS_NAME_WATCHER_FLAGS_AUTO_START)
 454     {
 455       g_dbus_connection_call (client->connection,
 456                               "org.freedesktop.DBus",  /* bus name */
 457                               "/org/freedesktop/DBus", /* object path */
 458                               "org.freedesktop.DBus",  /* interface name */
 459                               "StartServiceByName",    /* method name */
 460                               g_variant_new ("(su)", client->name, 0),
 461                               G_DBUS_CALL_FLAGS_NONE,
 462                               -1,
 463                               NULL,
 464                               (GAsyncReadyCallback) start_service_by_name_cb,
 465                               client_ref (client));
 466     }
 467   else
 468     {
 469       /* check owner */
 470       invoke_get_name_owner (client);
 471     }
 472 }
 473
 474
 475 static void
 476 connection_get_cb (GObject      *source_object,
 477                    GAsyncResult *res,
 478                    gpointer      user_data)
 479 {
 480   Client *client = user_data;
 481
 482   client->connection = g_bus_get_finish (res, NULL);
 483   if (client->connection == NULL)
 484     {
 485       call_vanished_handler (client, FALSE);
 486       goto out;
 487     }
 488
 489   has_connection (client);
 490
 491  out:
 492   client_unref (client);
 493 }
 494
 495 /* ---------------------------------------------------------------------------------------------------- */
 496
 497 /**
 498  * g_bus_watch_name:
 499  * @bus_type: The type of bus to watch a name on.
 500  * @name: The name (well-known or unique) to watch.
 501  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 502  * @name_appeared_handler: Handler to invoke when @name is known to exist or %NULL.
 503  * @name_vanished_handler: Handler to invoke when @name is known to not exist or %NULL.
 504  * @user_data: User data to pass to handlers.
 505  * @user_data_free_func: Function for freeing @user_data or %NULL.
 506  *
 507  * Starts watching @name on the bus specified by @bus_type and calls
 508  * @name_appeared_handler and @name_vanished_handler when the name is
 509  * known to have a owner respectively known to lose its
 510  * owner. Callbacks will be invoked in the <link
 511  * linkend="g-main-context-push-thread-default">thread-default main
 512  * loop</link> of the thread you are calling this function from.
 513  *
 514  * You are guaranteed that one of the handlers will be invoked after
 515  * calling this function. When you are done watching the name, just
 516  * call g_bus_unwatch_name() with the watcher id this function
 517  * returns.
 518  *
 519  * If the name vanishes or appears (for example the application owning
 520  * the name could restart), the handlers are also invoked. If the
 521  * #GDBusConnection that is used for watching the name disconnects, then
 522  * @name_vanished_handler is invoked since it is no longer
 523  * possible to access the name.
 524  *
 525  * Another guarantee is that invocations of @name_appeared_handler
 526  * and @name_vanished_handler are guaranteed to alternate; that
 527  * is, if @name_appeared_handler is invoked then you are
 528  * guaranteed that the next time one of the handlers is invoked, it
 529  * will be @name_vanished_handler. The reverse is also true.
 530  *
 531  * This behavior makes it very simple to write applications that wants
 532  * to take action when a certain name exists, see <xref
 533  * linkend="gdbus-watching-names"/>. Basically, the application
 534  * should create object proxies in @name_appeared_handler and destroy
 535  * them again (if any) in @name_vanished_handler.
 536  *
 537  * Returns: An identifier (never 0) that an be used with
 538  * g_bus_unwatch_name() to stop watching the name.
 539  *
 540  * Since: 2.26
 541  */
 542 guint
 543 g_bus_watch_name (GBusType                  bus_type,
 544                   const gchar              *name,
 545                   GBusNameWatcherFlags      flags,
 546                   GBusNameAppearedCallback  name_appeared_handler,
 547                   GBusNameVanishedCallback  name_vanished_handler,
 548                   gpointer                  user_data,
 549                   GDestroyNotify            user_data_free_func)
 550 {
 551   Client *client;
 552
 553   g_return_val_if_fail (bus_type != G_BUS_TYPE_NONE, 0);
 554   g_return_val_if_fail (g_dbus_is_name (name), 0);
 555
 556   G_LOCK (lock);
 557
 558   client = g_new0 (Client, 1);
 559   client->ref_count = 1;
 560   client->id = next_global_id++; /* TODO: uh oh, handle overflow */
 561   client->name = g_strdup (name);
 562   client->flags = flags;
 563   client->name_appeared_handler = name_appeared_handler;
 564   client->name_vanished_handler = name_vanished_handler;
 565   client->user_data = user_data;
 566   client->user_data_free_func = user_data_free_func;
 567   client->main_context = g_main_context_get_thread_default ();
 568   if (client->main_context != NULL)
 569     g_main_context_ref (client->main_context);
 570
 571   if (map_id_to_client == NULL)
 572     {
 573       map_id_to_client = g_hash_table_new (g_direct_hash, g_direct_equal);
 574     }
 575   g_hash_table_insert (map_id_to_client,
 576                        GUINT_TO_POINTER (client->id),
 577                        client);
 578
 579   g_bus_get (bus_type,
 580              NULL,
 581              connection_get_cb,
 582              client_ref (client));
 583
 584   G_UNLOCK (lock);
 585
 586   return client->id;
 587 }
 588
 589 /**
 590  * g_bus_unwatch_name:
 591  * @watcher_id: An identifier obtained from g_bus_watch_name()
 592  *
 593  * Stops watching a name.
 594  *
 595  * Since: 2.26
 596  */
 597 void
 598 g_bus_unwatch_name (guint watcher_id)
 599 {
 600   Client *client;
 601
 602   g_return_if_fail (watcher_id > 0);
 603
 604   client = NULL;
 605
 606   G_LOCK (lock);
 607   if (watcher_id == 0 ||
 608       map_id_to_client == NULL ||
 609       (client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id))) == NULL)
 610     {
 611       g_warning ("Invalid id %d passed to g_bus_unwatch_name()", watcher_id);
 612       goto out;
 613     }
 614
 615   client->cancelled = TRUE;
 616   g_warn_if_fail (g_hash_table_remove (map_id_to_client, GUINT_TO_POINTER (watcher_id)));
 617
 618  out:
 619   G_UNLOCK (lock);
 620
 621   /* do callback without holding lock */
 622   if (client != NULL)
 623     {
 624       client_unref (client);
 625     }
 626 }
 627
 628 #define __G_DBUS_NAME_WATCHING_C__
 629 #include "gioaliasdef.c"