1 /* GIO - GLib Input, Output and Streaming Library
3 * Copyright 2011 Red Hat, Inc.
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.
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.
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.
25 #include "gasyncresult.h"
26 #include "gcancellable.h"
30 * @short_description: Cancellable synchronous or asynchronous task and result
32 * @see_also: #GAsyncResult
35 * A #GTask represents and manages a cancellable "task".
38 * <title>Asynchronous operations</title>
40 * The most common usage of #GTask is as a #GAsyncResult, to
41 * manage data during an asynchronous operation. You call
42 * g_task_new() in the "start" method, followed by
43 * g_task_set_task_data() and the like if you need to keep some
44 * additional data associated with the task, and then pass the
45 * task object around through your asynchronous operation.
46 * Eventually, you will call a method such as
47 * g_task_return_pointer() or g_task_return_error(), which will
48 * save the value you give it and then invoke the task's callback
49 * function (waiting until the next next iteration of the main
50 * loop first, if necessary). The caller will pass the #GTask back
51 * to the operation's finish function (as a #GAsyncResult), and
52 * you can use g_task_propagate_pointer() or the like to extract
55 * <example id="gtask-async"><title>GTask as a GAsyncResult</title>
58 * CakeFrostingType frosting;
63 * decoration_data_free (DecorationData *decoration)
65 * g_free (decoration->message);
66 * g_slice_free (DecorationData, decoration);
70 * baked_cb (Cake *cake,
73 * GTask *task = user_data;
74 * DecorationData *decoration = g_task_get_task_data (task);
75 * GError *error = NULL;
79 * g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
80 * "Go to the supermarket");
81 * g_object_unref (task);
85 * if (!cake_decorate (cake, decoration->frosting, decoration->message, &error))
87 * g_object_unref (cake);
88 * /* g_task_return_error() takes ownership of error */
89 * g_task_return_error (task, error);
90 * g_object_unref (task);
94 * g_task_return_pointer (result, cake, g_object_unref);
95 * g_object_unref (task);
99 * baker_bake_cake_async (Baker *self,
102 * CakeFrostingType frosting,
103 * const char *message,
104 * GCancellable *cancellable,
105 * GAsyncReadyCallback callback,
106 * gpointer user_data)
109 * DecorationData *decoration;
112 * task = g_task_new (self, cancellable, callback, user_data);
115 * g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_TOO_SMALL,
116 * "%ucm radius cakes are silly",
118 * g_object_unref (task);
122 * cake = _baker_get_cached_cake (self, radius, flavor, frosting, message);
125 * /* _baker_get_cached_cake() returns a reffed cake */
126 * g_task_return_pointer (task, cake, g_object_unref);
127 * g_object_unref (task);
131 * decoration = g_slice_new (DecorationData);
132 * decoration->frosting = frosting;
133 * decoration->message = g_strdup (message);
134 * g_task_set_task_data (task, decoration, (GDestroyNotify) decoration_data_free);
136 * _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
140 * baker_bake_cake_finish (Baker *self,
141 * GAsyncResult *result,
144 * g_return_val_if_fail (g_task_is_valid (result, self), NULL);
146 * return g_task_propagate_pointer (G_TASK (result), error);
152 * <title>Chained asynchronous operations</title>
154 * #GTask also tries to simplify asynchronous operations that
155 * internally chain together several smaller asynchronous
156 * operations. g_task_get_cancellable(), g_task_get_context(), and
157 * g_task_get_priority() allow you to get back the task's
158 * #GCancellable, #GMainContext, and <link
159 * linkend="io-priority">I/O priority</link> when starting a new
160 * subtask, so you don't have to keep track of them yourself.
161 * g_task_attach_source() simplifies the case of waiting for a
162 * source to fire (automatically using the correct #GMainContext
165 * <example id="gtask-chained"><title>Chained asynchronous operations</title>
169 * CakeFrostingType frosting;
174 * decoration_data_free (BakingData *bd)
177 * g_object_unref (bd->cake);
178 * g_free (bd->message);
179 * g_slice_free (BakingData, bd);
183 * decorated_cb (Cake *cake,
184 * GAsyncResult *result,
185 * gpointer user_data)
187 * GTask *task = user_data;
188 * GError *error = NULL;
190 * if (!cake_decorate_finish (cake, result, &error))
192 * g_object_unref (cake);
193 * g_task_return_error (task, error);
194 * g_object_unref (task);
198 * /* baking_data_free() will drop its ref on the cake, so
199 * * we have to take another here to give to the caller.
201 * g_task_return_pointer (result, g_object_ref (cake), g_object_unref);
202 * g_object_unref (task);
206 * decorator_ready (gpointer user_data)
208 * GTask *task = user_data;
209 * BakingData *bd = g_task_get_task_data (task);
211 * cake_decorate_async (bd->cake, bd->frosting, bd->message,
212 * g_task_get_cancellable (task),
213 * decorated_cb, task);
217 * baked_cb (Cake *cake,
218 * gpointer user_data)
220 * GTask *task = user_data;
221 * BakingData *bd = g_task_get_task_data (task);
222 * GError *error = NULL;
226 * g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
227 * "Go to the supermarket");
228 * g_object_unref (task);
234 * /* Bail out now if the user has already cancelled */
235 * if (g_task_return_error_if_cancelled (g_task_get_cancellable (task)))
237 * g_object_unref (task);
241 * if (cake_decorator_available (cake))
242 * decorator_ready (task);
247 * source = cake_decorator_wait_source_new (cake);
248 * /* Attach @source to @task's GMainContext and have it call
249 * * decorator_ready() when it is ready.
251 * g_task_attach_source (task, source,
252 * G_CALLBACK (decorator_ready));
253 * g_source_unref (source);
258 * baker_bake_cake_async (Baker *self,
261 * CakeFrostingType frosting,
262 * const char *message,
264 * GCancellable *cancellable,
265 * GAsyncReadyCallback callback,
266 * gpointer user_data)
271 * task = g_task_new (self, cancellable, callback, user_data);
272 * g_task_set_priority (task, priority);
274 * bd = g_slice_new0 (BakingData);
275 * bd->frosting = frosting;
276 * bd->message = g_strdup (message);
277 * g_task_set_task_data (task, bd, (GDestroyNotify) baking_data_free);
279 * _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
283 * baker_bake_cake_finish (Baker *self,
284 * GAsyncResult *result,
287 * g_return_val_if_fail (g_task_is_valid (result, self), NULL);
289 * return g_task_propagate_pointer (G_TASK (result), error);
295 * <title>Asynchronous operations from synchronous ones</title>
297 * You can use g_task_run_in_thread() to turn a synchronous
298 * operation into an asynchronous one, by running it in a thread
299 * which will then dispatch the result back to the caller's
300 * #GMainContext when it completes.
302 * <example id="gtask-run-in-thread"><title>g_task_run_in_thread()</title>
307 * CakeFrostingType frosting;
312 * cake_data_free (CakeData *cake_data)
314 * g_free (cake_data->message);
315 * g_slice_free (CakeData, cake_data);
319 * bake_cake_thread (GTask *task,
320 * gpointer source_object,
321 * gpointer task_data,
322 * GCancellable *cancellable)
324 * Baker *self = source_object;
325 * CakeData *cake_data = task_data;
327 * GError *error = NULL;
329 * cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
330 * cake_data->frosting, cake_data->message,
331 * cancellable, &error);
333 * g_task_return_pointer (task, cake, g_object_unref);
335 * g_task_return_error (task, error);
339 * baker_bake_cake_async (Baker *self,
342 * CakeFrostingType frosting,
343 * const char *message,
344 * GCancellable *cancellable,
345 * GAsyncReadyCallback callback,
346 * gpointer user_data)
348 * CakeData *cake_data;
351 * cake_data = g_slice_new (CakeData);
352 * cake_data->radius = radius;
353 * cake_data->flavor = flavor;
354 * cake_data->frosting = frosting;
355 * cake_data->message = g_strdup (message);
356 * task = g_task_new (self, cancellable, callback, user_data);
357 * g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
358 * g_task_run_in_thread (task, bake_cake_thread);
362 * baker_bake_cake_finish (Baker *self,
363 * GAsyncResult *result,
366 * g_return_val_if_fail (g_task_is_valid (result, self), NULL);
368 * return g_task_propagate_pointer (G_TASK (result), error);
374 * <title>Adding cancellability to uncancellable tasks</title>
376 * Finally, g_task_run_in_thread() and g_task_run_in_thread_sync()
377 * can be used to turn an uncancellable operation into a
378 * cancellable one. If you call g_task_set_return_on_cancel(),
379 * passing %TRUE, then if the task's #GCancellable is cancelled,
380 * it will return control back to the caller immediately, while
381 * allowing the task thread to continue running in the background
382 * (and simply discarding its result when it finally does finish).
383 * Provided that the task thread is careful about how it uses
384 * locks and other externally-visible resources, this allows you
385 * to make "GLib-friendly" asynchronous and cancellable
386 * synchronous variants of blocking APIs.
388 * <example id="gtask-cancellable"><title>g_task_set_return_on_cancel()</title>
391 * bake_cake_thread (GTask *task,
392 * gpointer source_object,
393 * gpointer task_data,
394 * GCancellable *cancellable)
396 * Baker *self = source_object;
397 * CakeData *cake_data = task_data;
399 * GError *error = NULL;
401 * cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
402 * cake_data->frosting, cake_data->message,
406 * g_task_return_error (task, error);
410 * /* If the task has already been cancelled, then we don't
411 * * want to add the cake to the cake cache. Likewise, we don't
412 * * want to have the task get cancelled in the middle of
413 * * updating the cache. g_task_set_return_on_cancel() will
414 * * return %TRUE here if it managed to disable return-on-cancel,
415 * * or %FALSE if the task was cancelled before it could.
417 * if (g_task_set_return_on_cancel (task, FALSE))
419 * /* If the caller cancels at this point, their
420 * * GAsyncReadyCallback won't be invoked until we return,
421 * * so we don't have to worry that this code will run at
422 * * the same time as that code does. But if there were
423 * * other functions that might look at the cake cache,
424 * * then we'd probably need a GMutex here as well.
426 * baker_add_cake_to_cache (baker, cake);
427 * g_task_return_pointer (task, cake, g_object_unref);
432 * baker_bake_cake_async (Baker *self,
435 * CakeFrostingType frosting,
436 * const char *message,
437 * GCancellable *cancellable,
438 * GAsyncReadyCallback callback,
439 * gpointer user_data)
441 * CakeData *cake_data;
444 * cake_data = g_slice_new (CakeData);
447 * task = g_task_new (self, cancellable, callback, user_data);
448 * g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
449 * g_task_set_return_on_cancel (task, TRUE);
450 * g_task_run_in_thread (task, bake_cake_thread);
454 * baker_bake_cake_sync (Baker *self,
457 * CakeFrostingType frosting,
458 * const char *message,
459 * GCancellable *cancellable,
462 * CakeData *cake_data;
466 * cake_data = g_slice_new (CakeData);
469 * task = g_task_new (self, cancellable, NULL, NULL);
470 * g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
471 * g_task_set_return_on_cancel (task, TRUE);
472 * g_task_run_in_thread_sync (task, bake_cake_thread);
474 * cake = g_task_propagate_pointer (task, error);
475 * g_object_unref (task);
482 * <title>Porting from <literal>GSimpleAsyncResult</literal></title>
484 * #GTask's API attempts to be simpler than #GSimpleAsyncResult's
489 * You can save task-specific data with g_task_set_task_data(), and
490 * retrieve it later with g_task_get_task_data(). This replaces the
491 * abuse of g_simple_async_result_set_op_res_gpointer() for the same
492 * purpose with #GSimpleAsyncResult.
495 * In addition to the task data, #GTask also keeps track of the
496 * <link linkend="io-priority">priority</link>, #GCancellable, and
497 * #GMainContext associated with the task, so tasks that consist of
498 * a chain of simpler asynchronous operations will have easy access
499 * to those values when starting each sub-task.
502 * g_task_return_error_if_cancelled() provides simplified
503 * handling for cancellation. In addition, cancellation
504 * overrides any other #GTask return value by default, like
505 * #GSimpleAsyncResult does when
506 * g_simple_async_result_set_check_cancellable() is called.
507 * (You can use g_task_set_check_cancellable() to turn off that
508 * behavior.) On the other hand, g_task_run_in_thread()
509 * guarantees that it will always run your
510 * <literal>task_func</literal>, even if the task's #GCancellable
511 * is already cancelled before the task gets a chance to run;
512 * you can start your <literal>task_func</literal> with a
513 * g_task_return_error_if_cancelled() check if you need the
517 * The "return" methods (eg, g_task_return_pointer())
518 * automatically cause the task to be "completed" as well, and
519 * there is no need to worry about the "complete" vs "complete
520 * in idle" distinction. (#GTask automatically figures out
521 * whether the task's callback can be invoked directly, or
522 * if it needs to be sent to another #GMainContext, or delayed
523 * until the next iteration of the current #GMainContext.)
526 * The "finish" functions for #GTask-based operations are generally
527 * much simpler than #GSimpleAsyncResult ones, normally consisting
528 * of only a single call to g_task_propagate_pointer() or the like.
529 * Since g_task_propagate_pointer() "steals" the return value from
530 * the #GTask, it is not necessary to juggle pointers around to
531 * prevent it from being freed twice.
534 * With #GSimpleAsyncResult, it was common to call
535 * g_simple_async_result_propagate_error() from the
536 * <literal>_finish()</literal> wrapper function, and have
537 * virtual method implementations only deal with successful
538 * returns. This behavior is deprecated, because it makes it
539 * difficult for a subclass to chain to a parent class's async
540 * methods. Instead, the wrapper function should just be a
541 * simple wrapper, and the virtual method should call an
542 * appropriate <literal>g_task_propagate_</literal> function.
543 * Note that wrapper methods can now use
544 * g_async_result_legacy_propagate_error() to do old-style
545 * #GSimpleAsyncResult error-returning behavior, and
546 * g_async_result_is_tagged() to check if a result is tagged as
547 * having come from the <literal>_async()</literal> wrapper
548 * function (for "short-circuit" results, such as when passing
549 * 0 to g_input_stream_read_async()).
558 * The opaque object representing a synchronous or asynchronous task
563 GObject parent_instance;
565 gpointer source_object;
569 GDestroyNotify task_data_destroy;
571 GMainContext *context;
572 guint64 creation_time;
574 GCancellable *cancellable;
575 gboolean check_cancellable;
577 GAsyncReadyCallback callback;
578 gpointer callback_data;
580 GTaskThreadFunc task_func;
583 gboolean return_on_cancel;
584 gboolean thread_cancelled;
585 gboolean synchronous;
586 gboolean thread_complete;
594 GDestroyNotify result_destroy;
598 #define G_TASK_IS_THREADED(task) ((task)->task_func != NULL)
602 GObjectClass parent_class;
605 static void g_task_thread_pool_resort (void);
607 static void g_task_async_result_iface_init (GAsyncResultIface *iface);
608 static void g_task_thread_pool_init (void);
610 G_DEFINE_TYPE_WITH_CODE (GTask, g_task, G_TYPE_OBJECT,
611 G_IMPLEMENT_INTERFACE (G_TYPE_ASYNC_RESULT,
612 g_task_async_result_iface_init);
613 g_task_thread_pool_init ();)
615 static GThreadPool *task_pool;
618 g_task_init (GTask *task)
620 task->check_cancellable = TRUE;
624 g_task_finalize (GObject *object)
626 GTask *task = G_TASK (object);
628 g_clear_object (&task->source_object);
629 g_clear_object (&task->cancellable);
632 g_main_context_unref (task->context);
634 if (task->task_data_destroy)
635 task->task_data_destroy (task->task_data);
637 if (task->result_destroy && task->result.pointer)
638 task->result_destroy (task->result.pointer);
640 if (G_TASK_IS_THREADED (task))
642 g_mutex_clear (&task->lock);
643 g_cond_clear (&task->cond);
646 G_OBJECT_CLASS (g_task_parent_class)->finalize (object);
651 * @source_object: (allow-none): the #GObject that owns this task, or %NULL.
652 * @cancellable: (allow-none): optional #GCancellable object, %NULL to ignore.
653 * @callback: (scope async): a #GAsyncReadyCallback.
654 * @callback_data: (closure): user data passed to @callback.
656 * Creates a #GTask acting on @source_object, which will eventually be
657 * used to invoke @callback in the current <link
658 * linkend="g-main-context-push-thread-default">thread-default main
661 * Call this in the "start" method of your asynchronous method, and
662 * pass the #GTask around throughout the asynchronous operation. You
663 * can use g_task_set_task_data() to attach task-specific data to the
664 * object, which you can retrieve later via g_task_get_task_data().
666 * By default, if @cancellable is cancelled, then the return value of
667 * the task will always be %G_IO_ERROR_CANCELLED, even if the task had
668 * already completed before the cancellation. This allows for
669 * simplified handling in cases where cancellation may imply that
670 * other objects that the task depends on have been destroyed. If you
671 * do not want this behavior, you can use
672 * g_task_set_check_cancellable() to change it.
679 g_task_new (gpointer source_object,
680 GCancellable *cancellable,
681 GAsyncReadyCallback callback,
682 gpointer callback_data)
687 task = g_object_new (G_TYPE_TASK, NULL);
688 task->source_object = source_object ? g_object_ref (source_object) : NULL;
689 task->cancellable = cancellable ? g_object_ref (cancellable) : NULL;
690 task->callback = callback;
691 task->callback_data = callback_data;
692 task->context = g_main_context_ref_thread_default ();
694 source = g_main_current_source ();
696 task->creation_time = g_source_get_time (source);
702 * g_task_report_error:
703 * @source_object: (allow-none): the #GObject that owns this task, or %NULL.
704 * @callback: (scope async): a #GAsyncReadyCallback.
705 * @callback_data: (closure): user data passed to @callback.
706 * @source_tag: an opaque pointer indicating the source of this task
707 * @error: (transfer full): error to report
709 * Creates a #GTask and then immediately calls g_task_return_error()
710 * on it. Use this in the wrapper function of an asynchronous method
711 * when you want to avoid even calling the virtual method. You can
712 * then use g_async_result_is_tagged() in the finish method wrapper to
713 * check if the result there is tagged as having been created by the
714 * wrapper method, and deal with it appropriately if so.
716 * See also g_task_report_new_error().
721 g_task_report_error (gpointer source_object,
722 GAsyncReadyCallback callback,
723 gpointer callback_data,
729 task = g_task_new (source_object, NULL, callback, callback_data);
730 g_task_set_source_tag (task, source_tag);
731 g_task_return_error (task, error);
732 g_object_unref (task);
736 * g_task_report_new_error:
737 * @source_object: (allow-none): the #GObject that owns this task, or %NULL.
738 * @callback: (scope async): a #GAsyncReadyCallback.
739 * @callback_data: (closure): user data passed to @callback.
740 * @source_tag: an opaque pointer indicating the source of this task
741 * @domain: a #GQuark.
742 * @code: an error code.
743 * @format: a string with format characters.
744 * @...: a list of values to insert into @format.
746 * Creates a #GTask and then immediately calls
747 * g_task_return_new_error() on it. Use this in the wrapper function
748 * of an asynchronous method when you want to avoid even calling the
749 * virtual method. You can then use g_async_result_is_tagged() in the
750 * finish method wrapper to check if the result there is tagged as
751 * having been created by the wrapper method, and deal with it
752 * appropriately if so.
754 * See also g_task_report_error().
759 g_task_report_new_error (gpointer source_object,
760 GAsyncReadyCallback callback,
761 gpointer callback_data,
771 va_start (ap, format);
772 error = g_error_new_valist (domain, code, format, ap);
775 g_task_report_error (source_object, callback, callback_data,
780 * g_task_set_task_data:
782 * @task_data: (allow-none): task-specific data
783 * @task_data_destroy: (allow-none): #GDestroyNotify for @task_data
785 * Sets @task's task data (freeing the existing task data, if any).
790 g_task_set_task_data (GTask *task,
792 GDestroyNotify task_data_destroy)
794 if (task->task_data_destroy)
795 task->task_data_destroy (task->task_data);
797 task->task_data = task_data;
798 task->task_data_destroy = task_data_destroy;
802 * g_task_set_priority:
804 * @priority: the <link linkend="io-priority">priority</link>
807 * Sets @task's priority. If you do not call this, it will default to
808 * %G_PRIORITY_DEFAULT.
810 * This will affect the priority of #GSources created with
811 * g_task_attach_source() and the scheduling of tasks run in threads,
812 * and can also be explicitly retrieved later via
813 * g_task_get_priority().
818 g_task_set_priority (GTask *task,
821 task->priority = priority;
825 * g_task_set_check_cancellable:
827 * @check_cancellable: whether #GTask will check the state of
828 * its #GCancellable for you.
830 * Sets or clears @task's check-cancellable flag. If this is %TRUE
831 * (the default), then g_task_propagate_pointer(), etc, and
832 * g_task_had_error() will check the task's #GCancellable first, and
833 * if it has been cancelled, then they will consider the task to have
834 * returned an "Operation was cancelled" error
835 * (%G_IO_ERROR_CANCELLED), regardless of any other error or return
836 * value the task may have had.
838 * If @check_cancellable is %FALSE, then the #GTask will not check the
839 * cancellable itself, and it is up to @task's owner to do this (eg,
840 * via g_task_return_error_if_cancelled()).
842 * If you are using g_task_set_return_on_cancel() as well, then
843 * you must leave check-cancellable set %TRUE.
848 g_task_set_check_cancellable (GTask *task,
849 gboolean check_cancellable)
851 g_return_if_fail (check_cancellable || !task->return_on_cancel);
853 task->check_cancellable = check_cancellable;
856 static void g_task_thread_complete (GTask *task);
859 * g_task_set_return_on_cancel:
861 * @return_on_cancel: whether the task returns automatically when
864 * Sets or clears @task's return-on-cancel flag. This is only
865 * meaningful for tasks run via g_task_run_in_thread() or
866 * g_task_run_in_thread_sync().
868 * If @return_on_cancel is %TRUE, then cancelling @task's
869 * #GCancellable will immediately cause it to return, as though the
870 * task's #GTaskThreadFunc had called
871 * g_task_return_error_if_cancelled() and then returned.
873 * This allows you to create a cancellable wrapper around an
874 * uninterruptable function. The #GTaskThreadFunc just needs to be
875 * careful that it does not modify any externally-visible state after
876 * it has been cancelled. To do that, the thread should call
877 * g_task_set_return_on_cancel() again to (atomically) set
878 * return-on-cancel %FALSE before making externally-visible changes;
879 * if the task gets cancelled before the return-on-cancel flag could
880 * be changed, g_task_set_return_on_cancel() will indicate this by
883 * You can disable and re-enable this flag multiple times if you wish.
884 * If the task's #GCancellable is cancelled while return-on-cancel is
885 * %FALSE, then calling g_task_set_return_on_cancel() to set it %TRUE
886 * again will cause the task to be cancelled at that point.
888 * If the task's #GCancellable is already cancelled before you call
889 * g_task_run_in_thread()/g_task_run_in_thread_sync(), then the
890 * #GTaskThreadFunc will still be run (for consistency), but the task
891 * will also be completed right away.
893 * Returns: %TRUE if @task's return-on-cancel flag was changed to
894 * match @return_on_cancel. %FALSE if @task has already been
900 g_task_set_return_on_cancel (GTask *task,
901 gboolean return_on_cancel)
903 g_return_val_if_fail (task->check_cancellable || !return_on_cancel, FALSE);
905 if (!G_TASK_IS_THREADED (task))
907 task->return_on_cancel = return_on_cancel;
911 g_mutex_lock (&task->lock);
912 if (task->thread_cancelled)
914 if (return_on_cancel && !task->return_on_cancel)
916 g_mutex_unlock (&task->lock);
917 g_task_thread_complete (task);
920 g_mutex_unlock (&task->lock);
923 task->return_on_cancel = return_on_cancel;
924 g_mutex_unlock (&task->lock);
930 * g_task_set_source_tag:
932 * @source_tag: an opaque pointer indicating the source of this task
934 * Sets @task's source tag. You can use this to tag a task return
935 * value with a particular pointer (usually a pointer to the function
936 * doing the tagging) and then later check it using
937 * g_task_get_source_tag() (or g_async_result_is_tagged()) in the
938 * task's "finish" function, to figure out if the response came from a
944 g_task_set_source_tag (GTask *task,
947 task->source_tag = source_tag;
951 * g_task_get_source_object:
954 * Gets the source object from @task. Like
955 * g_async_result_get_source_object(), but does not ref the object.
957 * Returns: (transfer none): @task's source object, or %NULL
962 g_task_get_source_object (GTask *task)
964 return task->source_object;
968 g_task_ref_source_object (GAsyncResult *res)
970 GTask *task = G_TASK (res);
972 if (task->source_object)
973 return g_object_ref (task->source_object);
979 * g_task_get_task_data:
982 * Gets @task's <literal>task_data</literal>.
984 * Returns: (transfer none): @task's <literal>task_data</literal>.
989 g_task_get_task_data (GTask *task)
991 return task->task_data;
995 * g_task_get_priority:
998 * Gets @task's priority
1000 * Returns: @task's priority
1005 g_task_get_priority (GTask *task)
1007 return task->priority;
1011 * g_task_get_context:
1014 * Gets the #GMainContext that @task will return its result in (that
1015 * is, the context that was the <link
1016 * linkend="g-main-context-push-thread-default">thread-default main
1017 * context</link> at the point when @task was created).
1019 * This will always return a non-%NULL value, even if the task's
1020 * context is the default #GMainContext.
1022 * Returns: (transfer none): @task's #GMainContext
1027 g_task_get_context (GTask *task)
1029 return task->context;
1033 * g_task_get_cancellable:
1036 * Gets @task's #GCancellable
1038 * Returns: (transfer none): @task's #GCancellable
1043 g_task_get_cancellable (GTask *task)
1045 return task->cancellable;
1049 * g_task_get_check_cancellable:
1052 * Gets @task's check-cancellable flag. See
1053 * g_task_set_check_cancellable() for more details.
1058 g_task_get_check_cancellable (GTask *task)
1060 return task->check_cancellable;
1064 * g_task_get_return_on_cancel:
1067 * Gets @task's return-on-cancel flag. See
1068 * g_task_set_return_on_cancel() for more details.
1073 g_task_get_return_on_cancel (GTask *task)
1075 return task->return_on_cancel;
1079 * g_task_get_source_tag:
1082 * Gets @task's source tag. See g_task_set_source_tag().
1084 * Return value: (transfer none): @task's source tag
1089 g_task_get_source_tag (GTask *task)
1091 return task->source_tag;
1096 g_task_return_now (GTask *task)
1098 g_main_context_push_thread_default (task->context);
1099 task->callback (task->source_object,
1100 G_ASYNC_RESULT (task),
1101 task->callback_data);
1102 g_main_context_pop_thread_default (task->context);
1106 complete_in_idle_cb (gpointer task)
1108 g_task_return_now (task);
1109 g_object_unref (task);
1114 G_TASK_RETURN_SUCCESS,
1115 G_TASK_RETURN_ERROR,
1116 G_TASK_RETURN_FROM_THREAD
1120 g_task_return (GTask *task,
1121 GTaskReturnType type)
1125 if (type == G_TASK_RETURN_SUCCESS)
1126 task->result_set = TRUE;
1128 if (task->synchronous || !task->callback)
1131 /* Normally we want to invoke the task's callback when its return
1132 * value is set. But if the task is running in a thread, then we
1133 * want to wait until after the task_func returns, to simplify
1134 * locking/refcounting/etc.
1136 if (G_TASK_IS_THREADED (task) && type != G_TASK_RETURN_FROM_THREAD)
1139 g_object_ref (task);
1141 /* See if we can complete the task immediately. First, we have to be
1142 * running inside the task's thread/GMainContext.
1144 source = g_main_current_source ();
1145 if (source && g_source_get_context (source) == task->context)
1147 /* Second, we can only complete immediately if this is not the
1148 * same iteration of the main loop that the task was created in.
1150 if (g_source_get_time (source) > task->creation_time)
1152 g_task_return_now (task);
1153 g_object_unref (task);
1158 /* Otherwise, complete in the next iteration */
1159 source = g_idle_source_new ();
1160 g_task_attach_source (task, source, complete_in_idle_cb);
1161 g_source_unref (source);
1168 * @source_object: @task's source object
1169 * @task_data: @task's task data
1170 * @cancellable: @task's #GCancellable, or %NULL
1172 * The prototype for a task function to be run in a thread via
1173 * g_task_run_in_thread() or g_task_run_in_thread_sync().
1175 * If the return-on-cancel flag is set on @task, and @cancellable gets
1176 * cancelled, then the #GTask will be completed immediately (as though
1177 * g_task_return_error_if_cancelled() had been called), without
1178 * waiting for the task function to complete. However, the task
1179 * function will continue running in its thread in the background. The
1180 * function therefore needs to be careful about how it uses
1181 * externally-visible state in this case. See
1182 * g_task_set_return_on_cancel() for more details.
1184 * Other than in that case, @task will be completed when the
1185 * #GTaskThreadFunc returns, <emphasis>not</emphasis> when it calls
1186 * a <literal>g_task_return_</literal> function.
1191 static void task_thread_cancelled (GCancellable *cancellable,
1192 gpointer user_data);
1195 g_task_thread_complete (GTask *task)
1197 g_mutex_lock (&task->lock);
1198 if (task->thread_complete)
1200 /* The task belatedly completed after having been cancelled
1201 * (or was cancelled in the midst of being completed).
1203 g_mutex_unlock (&task->lock);
1207 task->thread_complete = TRUE;
1208 g_mutex_unlock (&task->lock);
1210 if (task->cancellable)
1211 g_signal_handlers_disconnect_by_func (task->cancellable, task_thread_cancelled, task);
1213 if (task->synchronous)
1214 g_cond_signal (&task->cond);
1216 g_task_return (task, G_TASK_RETURN_FROM_THREAD);
1220 g_task_thread_pool_thread (gpointer thread_data,
1223 GTask *task = thread_data;
1225 task->task_func (task, task->source_object, task->task_data,
1227 g_task_thread_complete (task);
1228 g_object_unref (task);
1232 task_thread_cancelled (GCancellable *cancellable,
1235 GTask *task = user_data;
1237 g_task_thread_pool_resort ();
1239 g_mutex_lock (&task->lock);
1240 task->thread_cancelled = TRUE;
1242 if (!task->return_on_cancel)
1244 g_mutex_unlock (&task->lock);
1248 /* We don't actually set task->error; g_task_return_error() doesn't
1249 * use a lock, and g_task_propagate_error() will call
1250 * g_cancellable_set_error_if_cancelled() anyway.
1252 g_mutex_unlock (&task->lock);
1253 g_task_thread_complete (task);
1257 task_thread_cancelled_disconnect_notify (gpointer task,
1260 g_object_unref (task);
1264 g_task_start_task_thread (GTask *task,
1265 GTaskThreadFunc task_func)
1267 g_mutex_init (&task->lock);
1268 g_cond_init (&task->cond);
1270 g_mutex_lock (&task->lock);
1272 task->task_func = task_func;
1274 if (task->cancellable)
1276 if (task->return_on_cancel &&
1277 g_cancellable_set_error_if_cancelled (task->cancellable,
1280 task->thread_cancelled = task->thread_complete = TRUE;
1281 g_thread_pool_push (task_pool, g_object_ref (task), NULL);
1285 g_signal_connect_data (task->cancellable, "cancelled",
1286 G_CALLBACK (task_thread_cancelled),
1287 g_object_ref (task),
1288 task_thread_cancelled_disconnect_notify, 0);
1291 g_thread_pool_push (task_pool, g_object_ref (task), &task->error);
1293 task->thread_complete = TRUE;
1297 * g_task_run_in_thread:
1299 * @task_func: a #GTaskThreadFunc
1301 * Runs @task_func in another thread. When @task_func returns, @task's
1302 * #GAsyncReadyCallback will be invoked in @task's #GMainContext.
1304 * This takes a ref on @task until the task completes.
1306 * See #GTaskThreadFunc for more details about how @task_func is handled.
1311 g_task_run_in_thread (GTask *task,
1312 GTaskThreadFunc task_func)
1314 g_return_if_fail (G_IS_TASK (task));
1316 g_object_ref (task);
1317 g_task_start_task_thread (task, task_func);
1319 /* The task may already be cancelled, or g_thread_pool_push() may
1322 if (task->thread_complete)
1324 g_mutex_unlock (&task->lock);
1325 g_task_return (task, G_TASK_RETURN_FROM_THREAD);
1328 g_mutex_unlock (&task->lock);
1330 g_object_unref (task);
1334 * g_task_run_in_thread_sync:
1336 * @task_func: a #GTaskThreadFunc
1338 * Runs @task_func in another thread, and waits for it to return or be
1339 * cancelled. You can use g_task_propagate_pointer(), etc, afterward
1340 * to get the result of @task_func.
1342 * See #GTaskThreadFunc for more details about how @task_func is handled.
1344 * Normally this is used with tasks created with a %NULL
1345 * <literal>callback</literal>, but note that even if the task does
1346 * have a callback, it will not be invoked when @task_func returns.
1351 g_task_run_in_thread_sync (GTask *task,
1352 GTaskThreadFunc task_func)
1354 g_return_if_fail (G_IS_TASK (task));
1356 g_object_ref (task);
1358 task->synchronous = TRUE;
1359 g_task_start_task_thread (task, task_func);
1361 while (!task->thread_complete)
1362 g_cond_wait (&task->cond, &task->lock);
1364 g_mutex_unlock (&task->lock);
1365 g_object_unref (task);
1369 * g_task_attach_source:
1371 * @source: the source to attach
1372 * @callback: the callback to invoke when @source triggers
1374 * A utility function for dealing with async operations where you need
1375 * to wait for a #GSource to trigger. Attaches @source to @task's
1376 * #GMainContext with @task's <link
1377 * linkend="io-priority">priority</link>, and sets @source's callback
1378 * to @callback, with @task as the callback's
1379 * <literal>user_data</literal>.
1381 * This takes a reference on @task until @source is destroyed.
1386 g_task_attach_source (GTask *task,
1388 GSourceFunc callback)
1390 g_source_set_callback (source, callback,
1391 g_object_ref (task), g_object_unref);
1392 g_source_set_priority (source, task->priority);
1393 g_source_attach (source, task->context);
1398 g_task_propagate_error (GTask *task,
1401 if (task->check_cancellable &&
1402 g_cancellable_set_error_if_cancelled (task->cancellable, error))
1404 else if (task->error)
1406 g_propagate_error (error, task->error);
1415 * g_task_return_pointer:
1417 * @result: (allow-none) (transfer full): the pointer result of a task
1419 * @result_destroy: (allow-none): a #GDestroyNotify function.
1421 * Sets @task's result to @result and completes the task. If @result
1422 * is not %NULL, then @result_destroy will be used to free @result if
1423 * the caller does not take ownership of it with
1424 * g_task_propagate_pointer().
1426 * "Completes the task" means that for an ordinary asynchronous task
1427 * it will either invoke the task's callback, or else queue that
1428 * callback to be invoked in the proper #GMainContext, or in the next
1429 * iteration of the current #GMainContext. For a task run via
1430 * g_task_run_in_thread() or g_task_run_in_thread_sync(), calling this
1431 * method will save @result to be returned to the caller later, but
1432 * the task will not actually be completed until the #GTaskThreadFunc
1435 * Note that since the task may be completed before returning from
1436 * g_task_return_pointer(), you cannot assume that @result is still
1437 * valid after calling this, unless you are still holding another
1443 g_task_return_pointer (GTask *task,
1445 GDestroyNotify result_destroy)
1447 g_return_if_fail (task->result_set == FALSE);
1449 task->result.pointer = result;
1450 task->result_destroy = result_destroy;
1452 g_task_return (task, G_TASK_RETURN_SUCCESS);
1456 * g_task_propagate_pointer:
1458 * @error: return location for a #GError
1460 * Gets the result of @task as a pointer, and transfers ownership
1461 * of that value to the caller.
1463 * If the task resulted in an error, or was cancelled, then this will
1464 * instead return %NULL and set @error.
1466 * Since this method transfers ownership of the return value (or
1467 * error) to the caller, you may only call it once.
1469 * Returns: (transfer full): the task result, or %NULL on error
1474 g_task_propagate_pointer (GTask *task,
1477 if (g_task_propagate_error (task, error))
1480 g_return_val_if_fail (task->result_set == TRUE, NULL);
1482 task->result_destroy = NULL;
1483 task->result_set = FALSE;
1484 return task->result.pointer;
1488 * g_task_return_int:
1490 * @result: the integer (#gssize) result of a task function.
1492 * Sets @task's result to @result and completes the task (see
1493 * g_task_return_pointer() for more discussion of exactly what this
1499 g_task_return_int (GTask *task,
1502 g_return_if_fail (task->result_set == FALSE);
1504 task->result.size = result;
1506 g_task_return (task, G_TASK_RETURN_SUCCESS);
1510 * g_task_propagate_int:
1512 * @error: return location for a #GError
1514 * Gets the result of @task as an integer (#gssize).
1516 * If the task resulted in an error, or was cancelled, then this will
1517 * instead return -1 and set @error.
1519 * Since this method transfers ownership of the return value (or
1520 * error) to the caller, you may only call it once.
1522 * Returns: the task result, or -1 on error
1527 g_task_propagate_int (GTask *task,
1530 if (g_task_propagate_error (task, error))
1533 g_return_val_if_fail (task->result_set == TRUE, -1);
1535 task->result_set = FALSE;
1536 return task->result.size;
1540 * g_task_return_boolean:
1542 * @result: the #gboolean result of a task function.
1544 * Sets @task's result to @result and completes the task (see
1545 * g_task_return_pointer() for more discussion of exactly what this
1551 g_task_return_boolean (GTask *task,
1554 g_return_if_fail (task->result_set == FALSE);
1556 task->result.boolean = result;
1558 g_task_return (task, G_TASK_RETURN_SUCCESS);
1562 * g_task_propagate_boolean:
1564 * @error: return location for a #GError
1566 * Gets the result of @task as a #gboolean.
1568 * If the task resulted in an error, or was cancelled, then this will
1569 * instead return %FALSE and set @error.
1571 * Since this method transfers ownership of the return value (or
1572 * error) to the caller, you may only call it once.
1574 * Returns: the task result, or %FALSE on error
1579 g_task_propagate_boolean (GTask *task,
1582 if (g_task_propagate_error (task, error))
1585 g_return_val_if_fail (task->result_set == TRUE, FALSE);
1587 task->result_set = FALSE;
1588 return task->result.boolean;
1592 * g_task_return_error:
1594 * @error: (transfer full): the #GError result of a task function.
1596 * Sets @task's result to @error (which @task assumes ownership of)
1597 * and completes the task (see g_task_return_pointer() for more
1598 * discussion of exactly what this means).
1600 * Note that since the task takes ownership of @error, and since the
1601 * task may be completed before returning from g_task_return_error(),
1602 * you cannot assume that @error is still valid after calling this.
1603 * Call g_error_copy() on the error if you need to keep a local copy
1606 * See also g_task_return_new_error().
1611 g_task_return_error (GTask *task,
1614 g_return_if_fail (task->result_set == FALSE);
1615 g_return_if_fail (error != NULL);
1617 task->error = error;
1619 g_task_return (task, G_TASK_RETURN_ERROR);
1623 * g_task_return_new_error:
1625 * @domain: a #GQuark.
1626 * @code: an error code.
1627 * @format: a string with format characters.
1628 * @...: a list of values to insert into @format.
1630 * Sets @task's result to a new #GError created from @domain, @code,
1631 * @format, and the remaining arguments, and completes the task (see
1632 * g_task_return_pointer() for more discussion of exactly what this
1635 * See also g_task_return_error().
1640 g_task_return_new_error (GTask *task,
1649 va_start (args, format);
1650 error = g_error_new_valist (domain, code, format, args);
1653 g_task_return_error (task, error);
1657 * g_task_return_error_if_cancelled:
1660 * Checks if @task's #GCancellable has been cancelled, and if so, sets
1661 * @task's error accordingly and completes the task (see
1662 * g_task_return_pointer() for more discussion of exactly what this
1665 * Return value: %TRUE if @task has been cancelled, %FALSE if not
1670 g_task_return_error_if_cancelled (GTask *task)
1672 GError *error = NULL;
1674 g_return_val_if_fail (task->result_set == FALSE, FALSE);
1676 if (g_cancellable_set_error_if_cancelled (task->cancellable, &error))
1678 /* We explicitly set task->error so this works even when
1679 * check-cancellable is not set.
1681 g_clear_error (&task->error);
1682 task->error = error;
1684 g_task_return (task, G_TASK_RETURN_ERROR);
1695 * Tests if @task resulted in an error.
1697 * Returns: %TRUE if the task resulted in an error, %FALSE otherwise.
1702 g_task_had_error (GTask *task)
1704 if (task->error != NULL)
1707 if (task->check_cancellable && g_cancellable_is_cancelled (task->cancellable))
1715 * @result: (type Gio.AsyncResult): A #GAsyncResult
1716 * @source_object: (allow-none): the source object expected to be
1717 * associated with the task
1719 * Checks that @result is a #GTask, and that @source_object is its
1720 * source object (or that @source_object is %NULL and @result has no
1721 * source object). This can be used in g_return_if_fail() checks.
1723 * Return value: %TRUE if @result and @source_object are valid, %FALSE
1729 g_task_is_valid (gpointer result,
1730 gpointer source_object)
1732 if (!G_IS_TASK (result))
1735 return G_TASK (result)->source_object == source_object;
1739 g_task_compare_priority (gconstpointer a,
1743 const GTask *ta = a;
1744 const GTask *tb = b;
1745 gboolean a_cancelled, b_cancelled;
1747 a_cancelled = (ta->check_cancellable &&
1748 g_cancellable_is_cancelled (ta->cancellable));
1749 b_cancelled = (tb->check_cancellable &&
1750 g_cancellable_is_cancelled (tb->cancellable));
1752 /* Let already-cancelled tasks finish right away */
1753 if (a_cancelled && !b_cancelled)
1755 else if (b_cancelled && !a_cancelled)
1758 /* Lower priority == run sooner == negative return value */
1759 return ta->priority - tb->priority;
1763 g_task_thread_pool_init (void)
1765 task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
1767 g_assert (task_pool != NULL);
1769 g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
1773 g_task_thread_pool_resort (void)
1775 g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
1779 g_task_class_init (GTaskClass *klass)
1781 GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
1783 gobject_class->finalize = g_task_finalize;
1787 g_task_get_user_data (GAsyncResult *res)
1789 return G_TASK (res)->callback_data;
1793 g_task_is_tagged (GAsyncResult *res,
1794 gpointer source_tag)
1796 return G_TASK (res)->source_tag == source_tag;
1800 g_task_async_result_iface_init (GAsyncResultIface *iface)
1802 iface->get_user_data = g_task_get_user_data;
1803 iface->get_source_object = g_task_ref_source_object;
1804 iface->is_tagged = g_task_is_tagged;