/* GIO - GLib Input, Output and Streaming Library
*
* Copyright 2011 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "config.h"
#include "gtask.h"
#include "gasyncresult.h"
#include "gcancellable.h"
/**
* SECTION:gtask
* @short_description: Cancellable synchronous or asynchronous task
* and result
* @include: gio/gio.h
* @see_also: #GAsyncResult
*
*
* A #GTask represents and manages a cancellable "task".
*
*
* Asynchronous operations
*
* The most common usage of #GTask is as a #GAsyncResult, to
* manage data during an asynchronous operation. You call
* g_task_new() in the "start" method, followed by
* g_task_set_task_data() and the like if you need to keep some
* additional data associated with the task, and then pass the
* task object around through your asynchronous operation.
* Eventually, you will call a method such as
* g_task_return_pointer() or g_task_return_error(), which will
* save the value you give it and then invoke the task's callback
* function (waiting until the next iteration of the main
* loop first, if necessary). The caller will pass the #GTask back
* to the operation's finish function (as a #GAsyncResult), and
* you can use g_task_propagate_pointer() or the like to extract
* the return value.
*
* GTask as a GAsyncResult
*
* typedef struct {
* CakeFrostingType frosting;
* char *message;
* } DecorationData;
*
* static void
* decoration_data_free (DecorationData *decoration)
* {
* g_free (decoration->message);
* g_slice_free (DecorationData, decoration);
* }
*
* static void
* baked_cb (Cake *cake,
* gpointer user_data)
* {
* GTask *task = user_data;
* DecorationData *decoration = g_task_get_task_data (task);
* GError *error = NULL;
*
* if (cake == NULL)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
* "Go to the supermarket");
* g_object_unref (task);
* return;
* }
*
* if (!cake_decorate (cake, decoration->frosting, decoration->message, &error))
* {
* g_object_unref (cake);
* /* g_task_return_error() takes ownership of error */
* g_task_return_error (task, error);
* g_object_unref (task);
* return;
* }
*
* g_task_return_pointer (task, cake, g_object_unref);
* g_object_unref (task);
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* GTask *task;
* DecorationData *decoration;
* Cake *cake;
*
* task = g_task_new (self, cancellable, callback, user_data);
* if (radius < 3)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_TOO_SMALL,
* "%ucm radius cakes are silly",
* radius);
* g_object_unref (task);
* return;
* }
*
* cake = _baker_get_cached_cake (self, radius, flavor, frosting, message);
* if (cake != NULL)
* {
* /* _baker_get_cached_cake() returns a reffed cake */
* g_task_return_pointer (task, cake, g_object_unref);
* g_object_unref (task);
* return;
* }
*
* decoration = g_slice_new (DecorationData);
* decoration->frosting = frosting;
* decoration->message = g_strdup (message);
* g_task_set_task_data (task, decoration, (GDestroyNotify) decoration_data_free);
*
* _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
*
*
*
*
* Chained asynchronous operations
*
* #GTask also tries to simplify asynchronous operations that
* internally chain together several smaller asynchronous
* operations. g_task_get_cancellable(), g_task_get_context(), and
* g_task_get_priority() allow you to get back the task's
* #GCancellable, #GMainContext, and I/O priority when starting a new
* subtask, so you don't have to keep track of them yourself.
* g_task_attach_source() simplifies the case of waiting for a
* source to fire (automatically using the correct #GMainContext
* and priority).
*
* Chained asynchronous operations
*
* typedef struct {
* Cake *cake;
* CakeFrostingType frosting;
* char *message;
* } BakingData;
*
* static void
* decoration_data_free (BakingData *bd)
* {
* if (bd->cake)
* g_object_unref (bd->cake);
* g_free (bd->message);
* g_slice_free (BakingData, bd);
* }
*
* static void
* decorated_cb (Cake *cake,
* GAsyncResult *result,
* gpointer user_data)
* {
* GTask *task = user_data;
* GError *error = NULL;
*
* if (!cake_decorate_finish (cake, result, &error))
* {
* g_object_unref (cake);
* g_task_return_error (task, error);
* g_object_unref (task);
* return;
* }
*
* /* baking_data_free() will drop its ref on the cake, so
* * we have to take another here to give to the caller.
* */
* g_task_return_pointer (result, g_object_ref (cake), g_object_unref);
* g_object_unref (task);
* }
*
* static void
* decorator_ready (gpointer user_data)
* {
* GTask *task = user_data;
* BakingData *bd = g_task_get_task_data (task);
*
* cake_decorate_async (bd->cake, bd->frosting, bd->message,
* g_task_get_cancellable (task),
* decorated_cb, task);
* }
*
* static void
* baked_cb (Cake *cake,
* gpointer user_data)
* {
* GTask *task = user_data;
* BakingData *bd = g_task_get_task_data (task);
* GError *error = NULL;
*
* if (cake == NULL)
* {
* g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
* "Go to the supermarket");
* g_object_unref (task);
* return;
* }
*
* bd->cake = cake;
*
* /* Bail out now if the user has already cancelled */
* if (g_task_return_error_if_cancelled (task))
* {
* g_object_unref (task);
* return;
* }
*
* if (cake_decorator_available (cake))
* decorator_ready (task);
* else
* {
* GSource *source;
*
* source = cake_decorator_wait_source_new (cake);
* /* Attach @source to @task's GMainContext and have it call
* * decorator_ready() when it is ready.
* */
* g_task_attach_source (task, source,
* G_CALLBACK (decorator_ready));
* g_source_unref (source);
* }
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* gint priority,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* GTask *task;
* BakingData *bd;
*
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_priority (task, priority);
*
* bd = g_slice_new0 (BakingData);
* bd->frosting = frosting;
* bd->message = g_strdup (message);
* g_task_set_task_data (task, bd, (GDestroyNotify) baking_data_free);
*
* _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
*
*
*
*
* Asynchronous operations from synchronous ones
*
* You can use g_task_run_in_thread() to turn a synchronous
* operation into an asynchronous one, by running it in a thread
* which will then dispatch the result back to the caller's
* #GMainContext when it completes.
*
* g_task_run_in_thread()
*
* typedef struct {
* guint radius;
* CakeFlavor flavor;
* CakeFrostingType frosting;
* char *message;
* } CakeData;
*
* static void
* cake_data_free (CakeData *cake_data)
* {
* g_free (cake_data->message);
* g_slice_free (CakeData, cake_data);
* }
*
* static void
* bake_cake_thread (GTask *task,
* gpointer source_object,
* gpointer task_data,
* GCancellable *cancellable)
* {
* Baker *self = source_object;
* CakeData *cake_data = task_data;
* Cake *cake;
* GError *error = NULL;
*
* cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
* cake_data->frosting, cake_data->message,
* cancellable, &error);
* if (cake)
* g_task_return_pointer (task, cake, g_object_unref);
* else
* g_task_return_error (task, error);
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* CakeData *cake_data;
* GTask *task;
*
* cake_data = g_slice_new (CakeData);
* cake_data->radius = radius;
* cake_data->flavor = flavor;
* cake_data->frosting = frosting;
* cake_data->message = g_strdup (message);
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_run_in_thread (task, bake_cake_thread);
* }
*
* Cake *
* baker_bake_cake_finish (Baker *self,
* GAsyncResult *result,
* GError **error)
* {
* g_return_val_if_fail (g_task_is_valid (result, self), NULL);
*
* return g_task_propagate_pointer (G_TASK (result), error);
* }
*
*
*
*
* Adding cancellability to uncancellable tasks
*
* Finally, g_task_run_in_thread() and g_task_run_in_thread_sync()
* can be used to turn an uncancellable operation into a
* cancellable one. If you call g_task_set_return_on_cancel(),
* passing %TRUE, then if the task's #GCancellable is cancelled,
* it will return control back to the caller immediately, while
* allowing the task thread to continue running in the background
* (and simply discarding its result when it finally does finish).
* Provided that the task thread is careful about how it uses
* locks and other externally-visible resources, this allows you
* to make "GLib-friendly" asynchronous and cancellable
* synchronous variants of blocking APIs.
*
* g_task_set_return_on_cancel()
*
* static void
* bake_cake_thread (GTask *task,
* gpointer source_object,
* gpointer task_data,
* GCancellable *cancellable)
* {
* Baker *self = source_object;
* CakeData *cake_data = task_data;
* Cake *cake;
* GError *error = NULL;
*
* cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
* cake_data->frosting, cake_data->message,
* &error);
* if (error)
* {
* g_task_return_error (task, error);
* return;
* }
*
* /* If the task has already been cancelled, then we don't
* * want to add the cake to the cake cache. Likewise, we don't
* * want to have the task get cancelled in the middle of
* * updating the cache. g_task_set_return_on_cancel() will
* * return %TRUE here if it managed to disable return-on-cancel,
* * or %FALSE if the task was cancelled before it could.
* */
* if (g_task_set_return_on_cancel (task, FALSE))
* {
* /* If the caller cancels at this point, their
* * GAsyncReadyCallback won't be invoked until we return,
* * so we don't have to worry that this code will run at
* * the same time as that code does. But if there were
* * other functions that might look at the cake cache,
* * then we'd probably need a GMutex here as well.
* */
* baker_add_cake_to_cache (baker, cake);
* g_task_return_pointer (task, cake, g_object_unref);
* }
* }
*
* void
* baker_bake_cake_async (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GAsyncReadyCallback callback,
* gpointer user_data)
* {
* CakeData *cake_data;
* GTask *task;
*
* cake_data = g_slice_new (CakeData);
* /* ... */
*
* task = g_task_new (self, cancellable, callback, user_data);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_set_return_on_cancel (task, TRUE);
* g_task_run_in_thread (task, bake_cake_thread);
* }
*
* Cake *
* baker_bake_cake_sync (Baker *self,
* guint radius,
* CakeFlavor flavor,
* CakeFrostingType frosting,
* const char *message,
* GCancellable *cancellable,
* GError **error)
* {
* CakeData *cake_data;
* GTask *task;
* Cake *cake;
*
* cake_data = g_slice_new (CakeData);
* /* ... */
*
* task = g_task_new (self, cancellable, NULL, NULL);
* g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
* g_task_set_return_on_cancel (task, TRUE);
* g_task_run_in_thread_sync (task, bake_cake_thread);
*
* cake = g_task_propagate_pointer (task, error);
* g_object_unref (task);
* return cake;
* }
*
*
*
*
* Porting from <literal>GSimpleAsyncResult</literal>
*
* #GTask's API attempts to be simpler than #GSimpleAsyncResult's
* in several ways:
*
*
*
* You can save task-specific data with g_task_set_task_data(), and
* retrieve it later with g_task_get_task_data(). This replaces the
* abuse of g_simple_async_result_set_op_res_gpointer() for the same
* purpose with #GSimpleAsyncResult.
*
*
* In addition to the task data, #GTask also keeps track of the
* priority, #GCancellable, and
* #GMainContext associated with the task, so tasks that consist of
* a chain of simpler asynchronous operations will have easy access
* to those values when starting each sub-task.
*
*
* g_task_return_error_if_cancelled() provides simplified
* handling for cancellation. In addition, cancellation
* overrides any other #GTask return value by default, like
* #GSimpleAsyncResult does when
* g_simple_async_result_set_check_cancellable() is called.
* (You can use g_task_set_check_cancellable() to turn off that
* behavior.) On the other hand, g_task_run_in_thread()
* guarantees that it will always run your
* task_func, even if the task's #GCancellable
* is already cancelled before the task gets a chance to run;
* you can start your task_func with a
* g_task_return_error_if_cancelled() check if you need the
* old behavior.
*
*
* The "return" methods (eg, g_task_return_pointer())
* automatically cause the task to be "completed" as well, and
* there is no need to worry about the "complete" vs "complete
* in idle" distinction. (#GTask automatically figures out
* whether the task's callback can be invoked directly, or
* if it needs to be sent to another #GMainContext, or delayed
* until the next iteration of the current #GMainContext.)
*
*
* The "finish" functions for #GTask-based operations are generally
* much simpler than #GSimpleAsyncResult ones, normally consisting
* of only a single call to g_task_propagate_pointer() or the like.
* Since g_task_propagate_pointer() "steals" the return value from
* the #GTask, it is not necessary to juggle pointers around to
* prevent it from being freed twice.
*
*
* With #GSimpleAsyncResult, it was common to call
* g_simple_async_result_propagate_error() from the
* _finish() wrapper function, and have
* virtual method implementations only deal with successful
* returns. This behavior is deprecated, because it makes it
* difficult for a subclass to chain to a parent class's async
* methods. Instead, the wrapper function should just be a
* simple wrapper, and the virtual method should call an
* appropriate g_task_propagate_ function.
* Note that wrapper methods can now use
* g_async_result_legacy_propagate_error() to do old-style
* #GSimpleAsyncResult error-returning behavior, and
* g_async_result_is_tagged() to check if a result is tagged as
* having come from the _async() wrapper
* function (for "short-circuit" results, such as when passing
* 0 to g_input_stream_read_async()).
*
*
*
*/
/**
* GTask:
*
* The opaque object representing a synchronous or asynchronous task
* and its result.
*/
struct _GTask {
GObject parent_instance;
gpointer source_object;
gpointer source_tag;
gpointer task_data;
GDestroyNotify task_data_destroy;
GMainContext *context;
guint64 creation_time;
gint priority;
GCancellable *cancellable;
gboolean check_cancellable;
GAsyncReadyCallback callback;
gpointer callback_data;
GTaskThreadFunc task_func;
GMutex lock;
GCond cond;
gboolean return_on_cancel;
gboolean thread_cancelled;
gboolean synchronous;
gboolean thread_complete;
gboolean blocking_other_task;
GError *error;
union {
gpointer pointer;
gssize size;
gboolean boolean;
} result;
GDestroyNotify result_destroy;
gboolean result_set;
};
#define G_TASK_IS_THREADED(task) ((task)->task_func != NULL)
struct _GTaskClass
{
GObjectClass parent_class;
};
static void g_task_thread_pool_resort (void);
static void g_task_async_result_iface_init (GAsyncResultIface *iface);
static void g_task_thread_pool_init (void);
G_DEFINE_TYPE_WITH_CODE (GTask, g_task, G_TYPE_OBJECT,
G_IMPLEMENT_INTERFACE (G_TYPE_ASYNC_RESULT,
g_task_async_result_iface_init);
g_task_thread_pool_init ();)
static GThreadPool *task_pool;
static GMutex task_pool_mutex;
static GPrivate task_private = G_PRIVATE_INIT (NULL);
static void
g_task_init (GTask *task)
{
task->check_cancellable = TRUE;
}
static void
g_task_finalize (GObject *object)
{
GTask *task = G_TASK (object);
g_clear_object (&task->source_object);
g_clear_object (&task->cancellable);
if (task->context)
g_main_context_unref (task->context);
if (task->task_data_destroy)
task->task_data_destroy (task->task_data);
if (task->result_destroy && task->result.pointer)
task->result_destroy (task->result.pointer);
if (task->error)
g_error_free (task->error);
if (G_TASK_IS_THREADED (task))
{
g_mutex_clear (&task->lock);
g_cond_clear (&task->cond);
}
G_OBJECT_CLASS (g_task_parent_class)->finalize (object);
}
/**
* g_task_new:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @cancellable: (allow-none): optional #GCancellable object, %NULL to ignore.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
*
* Creates a #GTask acting on @source_object, which will eventually be
* used to invoke @callback in the current thread-default main
* context.
*
* Call this in the "start" method of your asynchronous method, and
* pass the #GTask around throughout the asynchronous operation. You
* can use g_task_set_task_data() to attach task-specific data to the
* object, which you can retrieve later via g_task_get_task_data().
*
* By default, if @cancellable is cancelled, then the return value of
* the task will always be %G_IO_ERROR_CANCELLED, even if the task had
* already completed before the cancellation. This allows for
* simplified handling in cases where cancellation may imply that
* other objects that the task depends on have been destroyed. If you
* do not want this behavior, you can use
* g_task_set_check_cancellable() to change it.
*
* Returns: a #GTask.
*
* Since: 2.36
*/
GTask *
g_task_new (gpointer source_object,
GCancellable *cancellable,
GAsyncReadyCallback callback,
gpointer callback_data)
{
GTask *task;
GSource *source;
task = g_object_new (G_TYPE_TASK, NULL);
task->source_object = source_object ? g_object_ref (source_object) : NULL;
task->cancellable = cancellable ? g_object_ref (cancellable) : NULL;
task->callback = callback;
task->callback_data = callback_data;
task->context = g_main_context_ref_thread_default ();
source = g_main_current_source ();
if (source)
task->creation_time = g_source_get_time (source);
return task;
}
/**
* g_task_report_error:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
* @source_tag: an opaque pointer indicating the source of this task
* @error: (transfer full): error to report
*
* Creates a #GTask and then immediately calls g_task_return_error()
* on it. Use this in the wrapper function of an asynchronous method
* when you want to avoid even calling the virtual method. You can
* then use g_async_result_is_tagged() in the finish method wrapper to
* check if the result there is tagged as having been created by the
* wrapper method, and deal with it appropriately if so.
*
* See also g_task_report_new_error().
*
* Since: 2.36
*/
void
g_task_report_error (gpointer source_object,
GAsyncReadyCallback callback,
gpointer callback_data,
gpointer source_tag,
GError *error)
{
GTask *task;
task = g_task_new (source_object, NULL, callback, callback_data);
g_task_set_source_tag (task, source_tag);
g_task_return_error (task, error);
g_object_unref (task);
}
/**
* g_task_report_new_error:
* @source_object: (allow-none) (type GObject): the #GObject that owns
* this task, or %NULL.
* @callback: (scope async): a #GAsyncReadyCallback.
* @callback_data: (closure): user data passed to @callback.
* @source_tag: an opaque pointer indicating the source of this task
* @domain: a #GQuark.
* @code: an error code.
* @format: a string with format characters.
* @...: a list of values to insert into @format.
*
* Creates a #GTask and then immediately calls
* g_task_return_new_error() on it. Use this in the wrapper function
* of an asynchronous method when you want to avoid even calling the
* virtual method. You can then use g_async_result_is_tagged() in the
* finish method wrapper to check if the result there is tagged as
* having been created by the wrapper method, and deal with it
* appropriately if so.
*
* See also g_task_report_error().
*
* Since: 2.36
*/
void
g_task_report_new_error (gpointer source_object,
GAsyncReadyCallback callback,
gpointer callback_data,
gpointer source_tag,
GQuark domain,
gint code,
const char *format,
...)
{
GError *error;
va_list ap;
va_start (ap, format);
error = g_error_new_valist (domain, code, format, ap);
va_end (ap);
g_task_report_error (source_object, callback, callback_data,
source_tag, error);
}
/**
* g_task_set_task_data:
* @task: the #GTask
* @task_data: (allow-none): task-specific data
* @task_data_destroy: (allow-none): #GDestroyNotify for @task_data
*
* Sets @task's task data (freeing the existing task data, if any).
*
* Since: 2.36
*/
void
g_task_set_task_data (GTask *task,
gpointer task_data,
GDestroyNotify task_data_destroy)
{
if (task->task_data_destroy)
task->task_data_destroy (task->task_data);
task->task_data = task_data;
task->task_data_destroy = task_data_destroy;
}
/**
* g_task_set_priority:
* @task: the #GTask
* @priority: the priority
* of the request.
*
* Sets @task's priority. If you do not call this, it will default to
* %G_PRIORITY_DEFAULT.
*
* This will affect the priority of #GSources created with
* g_task_attach_source() and the scheduling of tasks run in threads,
* and can also be explicitly retrieved later via
* g_task_get_priority().
*
* Since: 2.36
*/
void
g_task_set_priority (GTask *task,
gint priority)
{
task->priority = priority;
}
/**
* g_task_set_check_cancellable:
* @task: the #GTask
* @check_cancellable: whether #GTask will check the state of
* its #GCancellable for you.
*
* Sets or clears @task's check-cancellable flag. If this is %TRUE
* (the default), then g_task_propagate_pointer(), etc, and
* g_task_had_error() will check the task's #GCancellable first, and
* if it has been cancelled, then they will consider the task to have
* returned an "Operation was cancelled" error
* (%G_IO_ERROR_CANCELLED), regardless of any other error or return
* value the task may have had.
*
* If @check_cancellable is %FALSE, then the #GTask will not check the
* cancellable itself, and it is up to @task's owner to do this (eg,
* via g_task_return_error_if_cancelled()).
*
* If you are using g_task_set_return_on_cancel() as well, then
* you must leave check-cancellable set %TRUE.
*
* Since: 2.36
*/
void
g_task_set_check_cancellable (GTask *task,
gboolean check_cancellable)
{
g_return_if_fail (check_cancellable || !task->return_on_cancel);
task->check_cancellable = check_cancellable;
}
static void g_task_thread_complete (GTask *task);
/**
* g_task_set_return_on_cancel:
* @task: the #GTask
* @return_on_cancel: whether the task returns automatically when
* it is cancelled.
*
* Sets or clears @task's return-on-cancel flag. This is only
* meaningful for tasks run via g_task_run_in_thread() or
* g_task_run_in_thread_sync().
*
* If @return_on_cancel is %TRUE, then cancelling @task's
* #GCancellable will immediately cause it to return, as though the
* task's #GTaskThreadFunc had called
* g_task_return_error_if_cancelled() and then returned.
*
* This allows you to create a cancellable wrapper around an
* uninterruptable function. The #GTaskThreadFunc just needs to be
* careful that it does not modify any externally-visible state after
* it has been cancelled. To do that, the thread should call
* g_task_set_return_on_cancel() again to (atomically) set
* return-on-cancel %FALSE before making externally-visible changes;
* if the task gets cancelled before the return-on-cancel flag could
* be changed, g_task_set_return_on_cancel() will indicate this by
* returning %FALSE.
*
* You can disable and re-enable this flag multiple times if you wish.
* If the task's #GCancellable is cancelled while return-on-cancel is
* %FALSE, then calling g_task_set_return_on_cancel() to set it %TRUE
* again will cause the task to be cancelled at that point.
*
* If the task's #GCancellable is already cancelled before you call
* g_task_run_in_thread()/g_task_run_in_thread_sync(), then the
* #GTaskThreadFunc will still be run (for consistency), but the task
* will also be completed right away.
*
* Returns: %TRUE if @task's return-on-cancel flag was changed to
* match @return_on_cancel. %FALSE if @task has already been
* cancelled.
*
* Since: 2.36
*/
gboolean
g_task_set_return_on_cancel (GTask *task,
gboolean return_on_cancel)
{
g_return_val_if_fail (task->check_cancellable || !return_on_cancel, FALSE);
if (!G_TASK_IS_THREADED (task))
{
task->return_on_cancel = return_on_cancel;
return TRUE;
}
g_mutex_lock (&task->lock);
if (task->thread_cancelled)
{
if (return_on_cancel && !task->return_on_cancel)
{
g_mutex_unlock (&task->lock);
g_task_thread_complete (task);
}
else
g_mutex_unlock (&task->lock);
return FALSE;
}
task->return_on_cancel = return_on_cancel;
g_mutex_unlock (&task->lock);
return TRUE;
}
/**
* g_task_set_source_tag:
* @task: the #GTask
* @source_tag: an opaque pointer indicating the source of this task
*
* Sets @task's source tag. You can use this to tag a task return
* value with a particular pointer (usually a pointer to the function
* doing the tagging) and then later check it using
* g_task_get_source_tag() (or g_async_result_is_tagged()) in the
* task's "finish" function, to figure out if the response came from a
* particular place.
*
* Since: 2.36
*/
void
g_task_set_source_tag (GTask *task,
gpointer source_tag)
{
task->source_tag = source_tag;
}
/**
* g_task_get_source_object:
* @task: a #GTask
*
* Gets the source object from @task. Like
* g_async_result_get_source_object(), but does not ref the object.
*
* Returns: (transfer none) (type GObject): @task's source object, or %NULL
*
* Since: 2.36
*/
gpointer
g_task_get_source_object (GTask *task)
{
return task->source_object;
}
static GObject *
g_task_ref_source_object (GAsyncResult *res)
{
GTask *task = G_TASK (res);
if (task->source_object)
return g_object_ref (task->source_object);
else
return NULL;
}
/**
* g_task_get_task_data:
* @task: a #GTask
*
* Gets @task's task_data.
*
* Returns: (transfer none): @task's task_data.
*
* Since: 2.36
*/
gpointer
g_task_get_task_data (GTask *task)
{
return task->task_data;
}
/**
* g_task_get_priority:
* @task: a #GTask
*
* Gets @task's priority
*
* Returns: @task's priority
*
* Since: 2.36
*/
gint
g_task_get_priority (GTask *task)
{
return task->priority;
}
/**
* g_task_get_context:
* @task: a #GTask
*
* Gets the #GMainContext that @task will return its result in (that
* is, the context that was the thread-default main
* context at the point when @task was created).
*
* This will always return a non-%NULL value, even if the task's
* context is the default #GMainContext.
*
* Returns: (transfer none): @task's #GMainContext
*
* Since: 2.36
*/
GMainContext *
g_task_get_context (GTask *task)
{
return task->context;
}
/**
* g_task_get_cancellable:
* @task: a #GTask
*
* Gets @task's #GCancellable
*
* Returns: (transfer none): @task's #GCancellable
*
* Since: 2.36
*/
GCancellable *
g_task_get_cancellable (GTask *task)
{
return task->cancellable;
}
/**
* g_task_get_check_cancellable:
* @task: the #GTask
*
* Gets @task's check-cancellable flag. See
* g_task_set_check_cancellable() for more details.
*
* Since: 2.36
*/
gboolean
g_task_get_check_cancellable (GTask *task)
{
return task->check_cancellable;
}
/**
* g_task_get_return_on_cancel:
* @task: the #GTask
*
* Gets @task's return-on-cancel flag. See
* g_task_set_return_on_cancel() for more details.
*
* Since: 2.36
*/
gboolean
g_task_get_return_on_cancel (GTask *task)
{
return task->return_on_cancel;
}
/**
* g_task_get_source_tag:
* @task: a #GTask
*
* Gets @task's source tag. See g_task_set_source_tag().
*
* Return value: (transfer none): @task's source tag
*
* Since: 2.36
*/
gpointer
g_task_get_source_tag (GTask *task)
{
return task->source_tag;
}
static void
g_task_return_now (GTask *task)
{
g_main_context_push_thread_default (task->context);
task->callback (task->source_object,
G_ASYNC_RESULT (task),
task->callback_data);
g_main_context_pop_thread_default (task->context);
}
static gboolean
complete_in_idle_cb (gpointer task)
{
g_task_return_now (task);
g_object_unref (task);
return FALSE;
}
typedef enum {
G_TASK_RETURN_SUCCESS,
G_TASK_RETURN_ERROR,
G_TASK_RETURN_FROM_THREAD
} GTaskReturnType;
static void
g_task_return (GTask *task,
GTaskReturnType type)
{
GSource *source;
if (type == G_TASK_RETURN_SUCCESS)
task->result_set = TRUE;
if (task->synchronous || !task->callback)
return;
/* Normally we want to invoke the task's callback when its return
* value is set. But if the task is running in a thread, then we
* want to wait until after the task_func returns, to simplify
* locking/refcounting/etc.
*/
if (G_TASK_IS_THREADED (task) && type != G_TASK_RETURN_FROM_THREAD)
return;
g_object_ref (task);
/* See if we can complete the task immediately. First, we have to be
* running inside the task's thread/GMainContext.
*/
source = g_main_current_source ();
if (source && g_source_get_context (source) == task->context)
{
/* Second, we can only complete immediately if this is not the
* same iteration of the main loop that the task was created in.
*/
if (g_source_get_time (source) > task->creation_time)
{
g_task_return_now (task);
g_object_unref (task);
return;
}
}
/* Otherwise, complete in the next iteration */
source = g_idle_source_new ();
g_task_attach_source (task, source, complete_in_idle_cb);
g_source_unref (source);
}
/**
* GTaskThreadFunc:
* @task: the #GTask
* @source_object: (type GObject): @task's source object
* @task_data: @task's task data
* @cancellable: @task's #GCancellable, or %NULL
*
* The prototype for a task function to be run in a thread via
* g_task_run_in_thread() or g_task_run_in_thread_sync().
*
* If the return-on-cancel flag is set on @task, and @cancellable gets
* cancelled, then the #GTask will be completed immediately (as though
* g_task_return_error_if_cancelled() had been called), without
* waiting for the task function to complete. However, the task
* function will continue running in its thread in the background. The
* function therefore needs to be careful about how it uses
* externally-visible state in this case. See
* g_task_set_return_on_cancel() for more details.
*
* Other than in that case, @task will be completed when the
* #GTaskThreadFunc returns, not when it calls
* a g_task_return_ function.
*
* Since: 2.36
*/
static void task_thread_cancelled (GCancellable *cancellable,
gpointer user_data);
static void
g_task_thread_complete (GTask *task)
{
g_mutex_lock (&task->lock);
if (task->thread_complete)
{
/* The task belatedly completed after having been cancelled
* (or was cancelled in the midst of being completed).
*/
g_mutex_unlock (&task->lock);
return;
}
task->thread_complete = TRUE;
if (task->blocking_other_task)
{
g_mutex_lock (&task_pool_mutex);
g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) - 1,
NULL);
g_mutex_unlock (&task_pool_mutex);
}
g_mutex_unlock (&task->lock);
if (task->cancellable)
g_signal_handlers_disconnect_by_func (task->cancellable, task_thread_cancelled, task);
if (task->synchronous)
g_cond_signal (&task->cond);
else
g_task_return (task, G_TASK_RETURN_FROM_THREAD);
}
static void
g_task_thread_pool_thread (gpointer thread_data,
gpointer pool_data)
{
GTask *task = thread_data;
g_private_set (&task_private, task);
task->task_func (task, task->source_object, task->task_data,
task->cancellable);
g_task_thread_complete (task);
g_private_set (&task_private, NULL);
g_object_unref (task);
}
static void
task_thread_cancelled (GCancellable *cancellable,
gpointer user_data)
{
GTask *task = user_data;
g_task_thread_pool_resort ();
g_mutex_lock (&task->lock);
task->thread_cancelled = TRUE;
if (!task->return_on_cancel)
{
g_mutex_unlock (&task->lock);
return;
}
/* We don't actually set task->error; g_task_return_error() doesn't
* use a lock, and g_task_propagate_error() will call
* g_cancellable_set_error_if_cancelled() anyway.
*/
g_mutex_unlock (&task->lock);
g_task_thread_complete (task);
}
static void
task_thread_cancelled_disconnect_notify (gpointer task,
GClosure *closure)
{
g_object_unref (task);
}
static void
g_task_start_task_thread (GTask *task,
GTaskThreadFunc task_func)
{
g_mutex_init (&task->lock);
g_cond_init (&task->cond);
g_mutex_lock (&task->lock);
task->task_func = task_func;
if (task->cancellable)
{
if (task->return_on_cancel &&
g_cancellable_set_error_if_cancelled (task->cancellable,
&task->error))
{
task->thread_cancelled = task->thread_complete = TRUE;
g_thread_pool_push (task_pool, g_object_ref (task), NULL);
return;
}
g_signal_connect_data (task->cancellable, "cancelled",
G_CALLBACK (task_thread_cancelled),
g_object_ref (task),
task_thread_cancelled_disconnect_notify, 0);
}
g_thread_pool_push (task_pool, g_object_ref (task), &task->error);
if (task->error)
task->thread_complete = TRUE;
else if (g_private_get (&task_private))
{
/* This thread is being spawned from another GTask thread, so
* bump up max-threads so we don't starve.
*/
g_mutex_lock (&task_pool_mutex);
if (g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) + 1,
NULL))
task->blocking_other_task = TRUE;
g_mutex_unlock (&task_pool_mutex);
}
}
/**
* g_task_run_in_thread:
* @task: a #GTask
* @task_func: a #GTaskThreadFunc
*
* Runs @task_func in another thread. When @task_func returns, @task's
* #GAsyncReadyCallback will be invoked in @task's #GMainContext.
*
* This takes a ref on @task until the task completes.
*
* See #GTaskThreadFunc for more details about how @task_func is handled.
*
* Since: 2.36
*/
void
g_task_run_in_thread (GTask *task,
GTaskThreadFunc task_func)
{
g_return_if_fail (G_IS_TASK (task));
g_object_ref (task);
g_task_start_task_thread (task, task_func);
/* The task may already be cancelled, or g_thread_pool_push() may
* have failed.
*/
if (task->thread_complete)
{
g_mutex_unlock (&task->lock);
g_task_return (task, G_TASK_RETURN_FROM_THREAD);
}
else
g_mutex_unlock (&task->lock);
g_object_unref (task);
}
/**
* g_task_run_in_thread_sync:
* @task: a #GTask
* @task_func: a #GTaskThreadFunc
*
* Runs @task_func in another thread, and waits for it to return or be
* cancelled. You can use g_task_propagate_pointer(), etc, afterward
* to get the result of @task_func.
*
* See #GTaskThreadFunc for more details about how @task_func is handled.
*
* Normally this is used with tasks created with a %NULL
* callback, but note that even if the task does
* have a callback, it will not be invoked when @task_func returns.
*
* Since: 2.36
*/
void
g_task_run_in_thread_sync (GTask *task,
GTaskThreadFunc task_func)
{
g_return_if_fail (G_IS_TASK (task));
g_object_ref (task);
task->synchronous = TRUE;
g_task_start_task_thread (task, task_func);
while (!task->thread_complete)
g_cond_wait (&task->cond, &task->lock);
g_mutex_unlock (&task->lock);
g_object_unref (task);
}
/**
* g_task_attach_source:
* @task: a #GTask
* @source: the source to attach
* @callback: the callback to invoke when @source triggers
*
* A utility function for dealing with async operations where you need
* to wait for a #GSource to trigger. Attaches @source to @task's
* #GMainContext with @task's priority, and sets @source's callback
* to @callback, with @task as the callback's
* user_data.
*
* This takes a reference on @task until @source is destroyed.
*
* Since: 2.36
*/
void
g_task_attach_source (GTask *task,
GSource *source,
GSourceFunc callback)
{
g_source_set_callback (source, callback,
g_object_ref (task), g_object_unref);
g_source_set_priority (source, task->priority);
g_source_attach (source, task->context);
}
static gboolean
g_task_propagate_error (GTask *task,
GError **error)
{
if (task->check_cancellable &&
g_cancellable_set_error_if_cancelled (task->cancellable, error))
return TRUE;
else if (task->error)
{
g_propagate_error (error, task->error);
task->error = NULL;
return TRUE;
}
else
return FALSE;
}
/**
* g_task_return_pointer:
* @task: a #GTask
* @result: (allow-none) (transfer full): the pointer result of a task
* function
* @result_destroy: (allow-none): a #GDestroyNotify function.
*
* Sets @task's result to @result and completes the task. If @result
* is not %NULL, then @result_destroy will be used to free @result if
* the caller does not take ownership of it with
* g_task_propagate_pointer().
*
* "Completes the task" means that for an ordinary asynchronous task
* it will either invoke the task's callback, or else queue that
* callback to be invoked in the proper #GMainContext, or in the next
* iteration of the current #GMainContext. For a task run via
* g_task_run_in_thread() or g_task_run_in_thread_sync(), calling this
* method will save @result to be returned to the caller later, but
* the task will not actually be completed until the #GTaskThreadFunc
* exits.
*
* Note that since the task may be completed before returning from
* g_task_return_pointer(), you cannot assume that @result is still
* valid after calling this, unless you are still holding another
* reference on it.
*
* Since: 2.36
*/
void
g_task_return_pointer (GTask *task,
gpointer result,
GDestroyNotify result_destroy)
{
g_return_if_fail (task->result_set == FALSE);
task->result.pointer = result;
task->result_destroy = result_destroy;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_pointer:
* @task: a #GTask
* @error: return location for a #GError
*
* Gets the result of @task as a pointer, and transfers ownership
* of that value to the caller.
*
* If the task resulted in an error, or was cancelled, then this will
* instead return %NULL and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: (transfer full): the task result, or %NULL on error
*
* Since: 2.36
*/
gpointer
g_task_propagate_pointer (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return NULL;
g_return_val_if_fail (task->result_set == TRUE, NULL);
task->result_destroy = NULL;
task->result_set = FALSE;
return task->result.pointer;
}
/**
* g_task_return_int:
* @task: a #GTask.
* @result: the integer (#gssize) result of a task function.
*
* Sets @task's result to @result and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Since: 2.36
*/
void
g_task_return_int (GTask *task,
gssize result)
{
g_return_if_fail (task->result_set == FALSE);
task->result.size = result;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_int:
* @task: a #GTask.
* @error: return location for a #GError
*
* Gets the result of @task as an integer (#gssize).
*
* If the task resulted in an error, or was cancelled, then this will
* instead return -1 and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: the task result, or -1 on error
*
* Since: 2.36
*/
gssize
g_task_propagate_int (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return -1;
g_return_val_if_fail (task->result_set == TRUE, -1);
task->result_set = FALSE;
return task->result.size;
}
/**
* g_task_return_boolean:
* @task: a #GTask.
* @result: the #gboolean result of a task function.
*
* Sets @task's result to @result and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Since: 2.36
*/
void
g_task_return_boolean (GTask *task,
gboolean result)
{
g_return_if_fail (task->result_set == FALSE);
task->result.boolean = result;
g_task_return (task, G_TASK_RETURN_SUCCESS);
}
/**
* g_task_propagate_boolean:
* @task: a #GTask.
* @error: return location for a #GError
*
* Gets the result of @task as a #gboolean.
*
* If the task resulted in an error, or was cancelled, then this will
* instead return %FALSE and set @error.
*
* Since this method transfers ownership of the return value (or
* error) to the caller, you may only call it once.
*
* Returns: the task result, or %FALSE on error
*
* Since: 2.36
*/
gboolean
g_task_propagate_boolean (GTask *task,
GError **error)
{
if (g_task_propagate_error (task, error))
return FALSE;
g_return_val_if_fail (task->result_set == TRUE, FALSE);
task->result_set = FALSE;
return task->result.boolean;
}
/**
* g_task_return_error:
* @task: a #GTask.
* @error: (transfer full): the #GError result of a task function.
*
* Sets @task's result to @error (which @task assumes ownership of)
* and completes the task (see g_task_return_pointer() for more
* discussion of exactly what this means).
*
* Note that since the task takes ownership of @error, and since the
* task may be completed before returning from g_task_return_error(),
* you cannot assume that @error is still valid after calling this.
* Call g_error_copy() on the error if you need to keep a local copy
* as well.
*
* See also g_task_return_new_error().
*
* Since: 2.36
*/
void
g_task_return_error (GTask *task,
GError *error)
{
g_return_if_fail (task->result_set == FALSE);
g_return_if_fail (error != NULL);
task->error = error;
g_task_return (task, G_TASK_RETURN_ERROR);
}
/**
* g_task_return_new_error:
* @task: a #GTask.
* @domain: a #GQuark.
* @code: an error code.
* @format: a string with format characters.
* @...: a list of values to insert into @format.
*
* Sets @task's result to a new #GError created from @domain, @code,
* @format, and the remaining arguments, and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* See also g_task_return_error().
*
* Since: 2.36
*/
void
g_task_return_new_error (GTask *task,
GQuark domain,
gint code,
const char *format,
...)
{
GError *error;
va_list args;
va_start (args, format);
error = g_error_new_valist (domain, code, format, args);
va_end (args);
g_task_return_error (task, error);
}
/**
* g_task_return_error_if_cancelled:
* @task: a #GTask
*
* Checks if @task's #GCancellable has been cancelled, and if so, sets
* @task's error accordingly and completes the task (see
* g_task_return_pointer() for more discussion of exactly what this
* means).
*
* Return value: %TRUE if @task has been cancelled, %FALSE if not
*
* Since: 2.36
*/
gboolean
g_task_return_error_if_cancelled (GTask *task)
{
GError *error = NULL;
g_return_val_if_fail (task->result_set == FALSE, FALSE);
if (g_cancellable_set_error_if_cancelled (task->cancellable, &error))
{
/* We explicitly set task->error so this works even when
* check-cancellable is not set.
*/
g_clear_error (&task->error);
task->error = error;
g_task_return (task, G_TASK_RETURN_ERROR);
return TRUE;
}
else
return FALSE;
}
/**
* g_task_had_error:
* @task: a #GTask.
*
* Tests if @task resulted in an error.
*
* Returns: %TRUE if the task resulted in an error, %FALSE otherwise.
*
* Since: 2.36
*/
gboolean
g_task_had_error (GTask *task)
{
if (task->error != NULL)
return TRUE;
if (task->check_cancellable && g_cancellable_is_cancelled (task->cancellable))
return TRUE;
return FALSE;
}
/**
* g_task_is_valid:
* @result: (type Gio.AsyncResult): A #GAsyncResult
* @source_object: (allow-none) (type GObject): the source object
* expected to be associated with the task
*
* Checks that @result is a #GTask, and that @source_object is its
* source object (or that @source_object is %NULL and @result has no
* source object). This can be used in g_return_if_fail() checks.
*
* Return value: %TRUE if @result and @source_object are valid, %FALSE
* if not
*
* Since: 2.36
*/
gboolean
g_task_is_valid (gpointer result,
gpointer source_object)
{
if (!G_IS_TASK (result))
return FALSE;
return G_TASK (result)->source_object == source_object;
}
static gint
g_task_compare_priority (gconstpointer a,
gconstpointer b,
gpointer user_data)
{
const GTask *ta = a;
const GTask *tb = b;
gboolean a_cancelled, b_cancelled;
/* Tasks that are causing other tasks to block have higher
* priority.
*/
if (ta->blocking_other_task && !tb->blocking_other_task)
return -1;
else if (tb->blocking_other_task && !ta->blocking_other_task)
return 1;
/* Let already-cancelled tasks finish right away */
a_cancelled = (ta->check_cancellable &&
g_cancellable_is_cancelled (ta->cancellable));
b_cancelled = (tb->check_cancellable &&
g_cancellable_is_cancelled (tb->cancellable));
if (a_cancelled && !b_cancelled)
return -1;
else if (b_cancelled && !a_cancelled)
return 1;
/* Lower priority == run sooner == negative return value */
return ta->priority - tb->priority;
}
static void
g_task_thread_pool_init (void)
{
task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
10, FALSE, NULL);
g_assert (task_pool != NULL);
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}
static void
g_task_thread_pool_resort (void)
{
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}
static void
g_task_class_init (GTaskClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->finalize = g_task_finalize;
}
static gpointer
g_task_get_user_data (GAsyncResult *res)
{
return G_TASK (res)->callback_data;
}
static gboolean
g_task_is_tagged (GAsyncResult *res,
gpointer source_tag)
{
return G_TASK (res)->source_tag == source_tag;
}
static void
g_task_async_result_iface_init (GAsyncResultIface *iface)
{
iface->get_user_data = g_task_get_user_data;
iface->get_source_object = g_task_ref_source_object;
iface->is_tagged = g_task_is_tagged;
}