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
  27 #include <glib/gi18n.h>
  28
  29 #include "gdbusutils.h"
  30 #include "gdbusnamewatching.h"
  31 #include "gdbuserror.h"
  32 #include "gdbusprivate.h"
  33 #include "gdbusconnection.h"
  34
  35 /**
  36  * SECTION:gdbusnamewatching
  37  * @title: Watching Bus Names
  38  * @short_description: Simple API for watching bus names
  39  * @include: gio/gio.h
  40  *
  41  * Convenience API for watching bus names.
  42  *
  43  * <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>
  44  */
  45
  46 G_LOCK_DEFINE_STATIC (lock);
  47
  48 /* ---------------------------------------------------------------------------------------------------- */
  49
  50 typedef enum
  51 {
  52   PREVIOUS_CALL_NONE = 0,
  53   PREVIOUS_CALL_APPEARED,
  54   PREVIOUS_CALL_VANISHED,
  55 } PreviousCall;
  56
  57 typedef struct
  58 {
  59   volatile gint             ref_count;
  60   guint                     id;
  61   gchar                    *name;
  62   GBusNameWatcherFlags      flags;
  63   gchar                    *name_owner;
  64   GBusNameAppearedCallback  name_appeared_handler;
  65   GBusNameVanishedCallback  name_vanished_handler;
  66   gpointer                  user_data;
  67   GDestroyNotify            user_data_free_func;
  68   GMainContext             *main_context;
  69
  70   GDBusConnection          *connection;
  71   gulong                    disconnected_signal_handler_id;
  72   guint                     name_owner_changed_subscription_id;
  73
  74   PreviousCall              previous_call;
  75
  76   gboolean                  cancelled;
  77   gboolean                  initialized;
  78 } Client;
  79
  80 static guint next_global_id = 1;
  81 static GHashTable *map_id_to_client = NULL;
  82
  83 static Client *
  84 client_ref (Client *client)
  85 {
  86   g_atomic_int_inc (&client->ref_count);
  87   return client;
  88 }
  89
  90 static void
  91 client_unref (Client *client)
  92 {
  93   if (g_atomic_int_dec_and_test (&client->ref_count))
  94     {
  95       if (client->connection != NULL)
  96         {
  97           if (client->name_owner_changed_subscription_id > 0)
  98             g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
  99           if (client->disconnected_signal_handler_id > 0)
 100             g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 101           g_object_unref (client->connection);
 102         }
 103       g_free (client->name);
 104       g_free (client->name_owner);
 105       if (client->main_context != NULL)
 106         g_main_context_unref (client->main_context);
 107       if (client->user_data_free_func != NULL)
 108         client->user_data_free_func (client->user_data);
 109       g_free (client);
 110     }
 111 }
 112
 113 /* ---------------------------------------------------------------------------------------------------- */
 114
 115 typedef enum
 116 {
 117   CALL_TYPE_NAME_APPEARED,
 118   CALL_TYPE_NAME_VANISHED
 119 } CallType;
 120
 121 typedef struct
 122 {
 123   Client *client;
 124
 125   /* keep this separate because client->connection may
 126    * be set to NULL after scheduling the call
 127    */
 128   GDBusConnection *connection;
 129
 130   /* ditto */
 131   gchar *name_owner;
 132
 133   CallType call_type;
 134 } CallHandlerData;
 135
 136 static void
 137 call_handler_data_free (CallHandlerData *data)
 138 {
 139   if (data->connection != NULL)
 140     g_object_unref (data->connection);
 141   g_free (data->name_owner);
 142   client_unref (data->client);
 143   g_free (data);
 144 }
 145
 146 static void
 147 actually_do_call (Client *client, GDBusConnection *connection, const gchar *name_owner, CallType call_type)
 148 {
 149   switch (call_type)
 150     {
 151     case CALL_TYPE_NAME_APPEARED:
 152       if (client->name_appeared_handler != NULL)
 153         {
 154           client->name_appeared_handler (connection,
 155                                          client->name,
 156                                          name_owner,
 157                                          client->user_data);
 158         }
 159       break;
 160
 161     case CALL_TYPE_NAME_VANISHED:
 162       if (client->name_vanished_handler != NULL)
 163         {
 164           client->name_vanished_handler (connection,
 165                                          client->name,
 166                                          client->user_data);
 167         }
 168       break;
 169
 170     default:
 171       g_assert_not_reached ();
 172       break;
 173     }
 174 }
 175
 176 static gboolean
 177 call_in_idle_cb (gpointer _data)
 178 {
 179   CallHandlerData *data = _data;
 180   actually_do_call (data->client, data->connection, data->name_owner, data->call_type);
 181   return FALSE;
 182 }
 183
 184 static void
 185 schedule_call_in_idle (Client *client, CallType call_type)
 186 {
 187   CallHandlerData *data;
 188   GSource *idle_source;
 189
 190   data = g_new0 (CallHandlerData, 1);
 191   data->client = client_ref (client);
 192   data->connection = client->connection != NULL ? g_object_ref (client->connection) : NULL;
 193   data->name_owner = g_strdup (client->name_owner);
 194   data->call_type = call_type;
 195
 196   idle_source = g_idle_source_new ();
 197   g_source_set_priority (idle_source, G_PRIORITY_HIGH);
 198   g_source_set_callback (idle_source,
 199                          call_in_idle_cb,
 200                          data,
 201                          (GDestroyNotify) call_handler_data_free);
 202   g_source_attach (idle_source, client->main_context);
 203   g_source_unref (idle_source);
 204 }
 205
 206 static void
 207 do_call (Client *client, CallType call_type)
 208 {
 209   /* only schedule in idle if we're not in the right thread */
 210   if (g_main_context_get_thread_default () != client->main_context)
 211     schedule_call_in_idle (client, call_type);
 212   else
 213     actually_do_call (client, client->connection, client->name_owner, call_type);
 214 }
 215
 216 static void
 217 call_appeared_handler (Client *client)
 218 {
 219   if (client->previous_call != PREVIOUS_CALL_APPEARED)
 220     {
 221       client->previous_call = PREVIOUS_CALL_APPEARED;
 222       if (!client->cancelled && client->name_appeared_handler != NULL)
 223         {
 224           do_call (client, CALL_TYPE_NAME_APPEARED);
 225         }
 226     }
 227 }
 228
 229 static void
 230 call_vanished_handler (Client  *client,
 231                        gboolean ignore_cancelled)
 232 {
 233   if (client->previous_call != PREVIOUS_CALL_VANISHED)
 234     {
 235       client->previous_call = PREVIOUS_CALL_VANISHED;
 236       if (((!client->cancelled) || ignore_cancelled) && client->name_vanished_handler != NULL)
 237         {
 238           do_call (client, CALL_TYPE_NAME_VANISHED);
 239         }
 240     }
 241 }
 242
 243 /* ---------------------------------------------------------------------------------------------------- */
 244
 245 static void
 246 on_connection_disconnected (GDBusConnection *connection,
 247                             gboolean         remote_peer_vanished,
 248                             GError          *error,
 249                             gpointer         user_data)
 250 {
 251   Client *client = user_data;
 252
 253   if (client->name_owner_changed_subscription_id > 0)
 254     g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
 255   if (client->disconnected_signal_handler_id > 0)
 256     g_signal_handler_disconnect (client->connection, client->disconnected_signal_handler_id);
 257   g_object_unref (client->connection);
 258   client->disconnected_signal_handler_id = 0;
 259   client->name_owner_changed_subscription_id = 0;
 260   client->connection = NULL;
 261
 262   call_vanished_handler (client, FALSE);
 263 }
 264
 265 /* ---------------------------------------------------------------------------------------------------- */
 266
 267 static void
 268 on_name_owner_changed (GDBusConnection *connection,
 269                        const gchar      *sender_name,
 270                        const gchar      *object_path,
 271                        const gchar      *interface_name,
 272                        const gchar      *signal_name,
 273                        GVariant         *parameters,
 274                        gpointer          user_data)
 275 {
 276   Client *client = user_data;
 277   const gchar *name;
 278   const gchar *old_owner;
 279   const gchar *new_owner;
 280
 281   if (!client->initialized)
 282     goto out;
 283
 284   if (g_strcmp0 (object_path, "/org/freedesktop/DBus") != 0 ||
 285       g_strcmp0 (interface_name, "org.freedesktop.DBus") != 0 ||
 286       g_strcmp0 (sender_name, "org.freedesktop.DBus") != 0)
 287     goto out;
 288
 289   g_variant_get (parameters,
 290                  "(sss)",
 291                  &name,
 292                  &old_owner,
 293                  &new_owner);
 294
 295   /* we only care about a specific name */
 296   if (g_strcmp0 (name, client->name) != 0)
 297     goto out;
 298
 299   if ((old_owner != NULL && strlen (old_owner) > 0) && client->name_owner != NULL)
 300     {
 301       g_free (client->name_owner);
 302       client->name_owner = NULL;
 303       call_vanished_handler (client, FALSE);
 304     }
 305
 306   if (new_owner != NULL && strlen (new_owner) > 0)
 307     {
 308       g_warn_if_fail (client->name_owner == NULL);
 309       g_free (client->name_owner);
 310       client->name_owner = g_strdup (new_owner);
 311       call_appeared_handler (client);
 312     }
 313
 314  out:
 315   ;
 316 }
 317
 318 /* ---------------------------------------------------------------------------------------------------- */
 319
 320 static void
 321 get_name_owner_cb (GObject      *source_object,
 322                    GAsyncResult *res,
 323                    gpointer      user_data)
 324 {
 325   Client *client = user_data;
 326   GVariant *result;
 327   const char *name_owner;
 328
 329   name_owner = NULL;
 330   result = NULL;
 331
 332   result = g_dbus_connection_invoke_method_finish (client->connection,
 333                                                    res,
 334                                                    NULL);
 335   if (result != NULL)
 336     {
 337       g_variant_get (result, "(s)", &name_owner);
 338     }
 339
 340   if (name_owner != NULL)
 341     {
 342       g_warn_if_fail (client->name_owner == NULL);
 343       client->name_owner = g_strdup (name_owner);
 344       call_appeared_handler (client);
 345     }
 346   else
 347     {
 348       call_vanished_handler (client, FALSE);
 349     }
 350
 351   client->initialized = TRUE;
 352
 353   if (result != NULL)
 354     g_variant_unref (result);
 355   client_unref (client);
 356 }
 357
 358 /* ---------------------------------------------------------------------------------------------------- */
 359
 360 static void
 361 invoke_get_name_owner (Client *client)
 362 {
 363   g_dbus_connection_invoke_method (client->connection,
 364                                    "org.freedesktop.DBus",  /* bus name */
 365                                    "/org/freedesktop/DBus", /* object path */
 366                                    "org.freedesktop.DBus",  /* interface name */
 367                                    "GetNameOwner",          /* method name */
 368                                    g_variant_new ("(s)", client->name),
 369                                    G_DBUS_INVOKE_METHOD_FLAGS_NONE,
 370                                    -1,
 371                                    NULL,
 372                                    (GAsyncReadyCallback) get_name_owner_cb,
 373                                    client_ref (client));
 374 }
 375
 376 /* ---------------------------------------------------------------------------------------------------- */
 377
 378 static void
 379 start_service_by_name_cb (GObject      *source_object,
 380                           GAsyncResult *res,
 381                           gpointer      user_data)
 382 {
 383   Client *client = user_data;
 384   GVariant *result;
 385
 386   result = NULL;
 387
 388   result = g_dbus_connection_invoke_method_finish (client->connection,
 389                                                    res,
 390                                                    NULL);
 391   if (result != NULL)
 392     {
 393       guint32 start_service_result;
 394       g_variant_get (result, "(u)", &start_service_result);
 395
 396       if (start_service_result == 1) /* DBUS_START_REPLY_SUCCESS */
 397         {
 398           invoke_get_name_owner (client);
 399         }
 400       else if (start_service_result == 2) /* DBUS_START_REPLY_ALREADY_RUNNING */
 401         {
 402           invoke_get_name_owner (client);
 403         }
 404       else
 405         {
 406           g_warning ("Unexpected reply %d from StartServiceByName() method", start_service_result);
 407           call_vanished_handler (client, FALSE);
 408           client->initialized = TRUE;
 409         }
 410     }
 411   else
 412     {
 413       /* Errors are not unexpected; the bus will reply e.g.
 414        *
 415        *   org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.Epiphany2
 416        *   was not provided by any .service files
 417        *
 418        * so just report vanished.
 419        */
 420       call_vanished_handler (client, FALSE);
 421       client->initialized = TRUE;
 422     }
 423
 424   if (result != NULL)
 425     g_variant_unref (result);
 426   client_unref (client);
 427 }
 428
 429 /* ---------------------------------------------------------------------------------------------------- */
 430
 431 static void
 432 has_connection (Client *client)
 433 {
 434   /* listen for disconnection */
 435   client->disconnected_signal_handler_id = g_signal_connect (client->connection,
 436                                                              "closed",
 437                                                              G_CALLBACK (on_connection_disconnected),
 438                                                              client);
 439
 440   /* start listening to NameOwnerChanged messages immediately */
 441   client->name_owner_changed_subscription_id = g_dbus_connection_signal_subscribe (client->connection,
 442                                                                                    "org.freedesktop.DBus",  /* name */
 443                                                                                    "org.freedesktop.DBus",  /* if */
 444                                                                                    "NameOwnerChanged",      /* signal */
 445                                                                                    "/org/freedesktop/DBus", /* path */
 446                                                                                    client->name,
 447                                                                                    on_name_owner_changed,
 448                                                                                    client,
 449                                                                                    NULL);
 450
 451   if (client->flags & G_BUS_NAME_WATCHER_FLAGS_AUTO_START)
 452     {
 453       g_dbus_connection_invoke_method (client->connection,
 454                                        "org.freedesktop.DBus",  /* bus name */
 455                                        "/org/freedesktop/DBus", /* object path */
 456                                        "org.freedesktop.DBus",  /* interface name */
 457                                        "StartServiceByName",    /* method name */
 458                                        g_variant_new ("(su)", client->name, 0),
 459                                        G_DBUS_INVOKE_METHOD_FLAGS_NONE,
 460                                        -1,
 461                                        NULL,
 462                                        (GAsyncReadyCallback) start_service_by_name_cb,
 463                                        client_ref (client));
 464     }
 465   else
 466     {
 467       /* check owner */
 468       invoke_get_name_owner (client);
 469     }
 470 }
 471
 472
 473 static void
 474 connection_get_cb (GObject      *source_object,
 475                    GAsyncResult *res,
 476                    gpointer      user_data)
 477 {
 478   Client *client = user_data;
 479
 480   client->connection = g_bus_get_finish (res, NULL);
 481   if (client->connection == NULL)
 482     {
 483       call_vanished_handler (client, FALSE);
 484       goto out;
 485     }
 486
 487   has_connection (client);
 488
 489  out:
 490   client_unref (client);
 491 }
 492
 493 /* ---------------------------------------------------------------------------------------------------- */
 494
 495 /**
 496  * g_bus_watch_name:
 497  * @bus_type: The type of bus to watch a name on.
 498  * @name: The name (well-known or unique) to watch.
 499  * @flags: Flags from the #GBusNameWatcherFlags enumeration.
 500  * @name_appeared_handler: Handler to invoke when @name is known to exist or %NULL.
 501  * @name_vanished_handler: Handler to invoke when @name is known to not exist or %NULL.
 502  * @user_data: User data to pass to handlers.
 503  * @user_data_free_func: Function for freeing @user_data or %NULL.
 504  *
 505  * Starts watching @name on the bus specified by @bus_type and calls
 506  * @name_appeared_handler and @name_vanished_handler when the name is
 507  * known to have a owner respectively known to lose its
 508  * owner. Callbacks will be invoked in the <link
 509  * linkend="g-main-context-push-thread-default">thread-default main
 510  * loop</link> of the thread you are calling this function from.
 511  *
 512  * You are guaranteed that one of the handlers will be invoked after
 513  * calling this function. When you are done watching the name, just
 514  * call g_bus_unwatch_name() with the watcher id this function
 515  * returns.
 516  *
 517  * If the name vanishes or appears (for example the application owning
 518  * the name could restart), the handlers are also invoked. If the
 519  * #GDBusConnection that is used for watching the name disconnects, then
 520  * @name_vanished_handler is invoked since it is no longer
 521  * possible to access the name.
 522  *
 523  * Another guarantee is that invocations of @name_appeared_handler
 524  * and @name_vanished_handler are guaranteed to alternate; that
 525  * is, if @name_appeared_handler is invoked then you are
 526  * guaranteed that the next time one of the handlers is invoked, it
 527  * will be @name_vanished_handler. The reverse is also true.
 528  *
 529  * This behavior makes it very simple to write applications that wants
 530  * to take action when a certain name exists, see <xref
 531  * linkend="gdbus-watching-names"/>. Basically, the application
 532  * should create object proxies in @name_appeared_handler and destroy
 533  * them again (if any) in @name_vanished_handler.
 534  *
 535  * Returns: An identifier (never 0) that an be used with
 536  * g_bus_unwatch_name() to stop watching the name.
 537  *
 538  * Since: 2.26
 539  */
 540 guint
 541 g_bus_watch_name (GBusType                  bus_type,
 542                   const gchar              *name,
 543                   GBusNameWatcherFlags      flags,
 544                   GBusNameAppearedCallback  name_appeared_handler,
 545                   GBusNameVanishedCallback  name_vanished_handler,
 546                   gpointer                  user_data,
 547                   GDestroyNotify            user_data_free_func)
 548 {
 549   Client *client;
 550
 551   g_return_val_if_fail (bus_type != G_BUS_TYPE_NONE, 0);
 552   g_return_val_if_fail (g_dbus_is_name (name), 0);
 553
 554   G_LOCK (lock);
 555
 556   client = g_new0 (Client, 1);
 557   client->ref_count = 1;
 558   client->id = next_global_id++; /* TODO: uh oh, handle overflow */
 559   client->name = g_strdup (name);
 560   client->flags = flags;
 561   client->name_appeared_handler = name_appeared_handler;
 562   client->name_vanished_handler = name_vanished_handler;
 563   client->user_data = user_data;
 564   client->user_data_free_func = user_data_free_func;
 565   client->main_context = g_main_context_get_thread_default ();
 566   if (client->main_context != NULL)
 567     g_main_context_ref (client->main_context);
 568
 569   if (map_id_to_client == NULL)
 570     {
 571       map_id_to_client = g_hash_table_new (g_direct_hash, g_direct_equal);
 572     }
 573   g_hash_table_insert (map_id_to_client,
 574                        GUINT_TO_POINTER (client->id),
 575                        client);
 576
 577   g_bus_get (bus_type,
 578              NULL,
 579              connection_get_cb,
 580              client_ref (client));
 581
 582   G_UNLOCK (lock);
 583
 584   return client->id;
 585 }
 586
 587 /**
 588  * g_bus_unwatch_name:
 589  * @watcher_id: An identifier obtained from g_bus_watch_name()
 590  *
 591  * Stops watching a name.
 592  *
 593  * Since: 2.26
 594  */
 595 void
 596 g_bus_unwatch_name (guint watcher_id)
 597 {
 598   Client *client;
 599
 600   g_return_if_fail (watcher_id > 0);
 601
 602   client = NULL;
 603
 604   G_LOCK (lock);
 605   if (watcher_id == 0 ||
 606       map_id_to_client == NULL ||
 607       (client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id))) == NULL)
 608     {
 609       g_warning ("Invalid id %d passed to g_bus_unwatch_name()", watcher_id);
 610       goto out;
 611     }
 612
 613   client->cancelled = TRUE;
 614   g_warn_if_fail (g_hash_table_remove (map_id_to_client, GUINT_TO_POINTER (watcher_id)));
 615
 616  out:
 617   G_UNLOCK (lock);
 618
 619   /* do callback without holding lock */
 620   if (client != NULL)
 621     {
 622       client_unref (client);
 623     }
 624 }