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GSimpleAsyncResult

GSimpleAsyncResult — Simple asynchronous results implementation

Types and Values

Object Hierarchy

    GObject
    ╰── GSimpleAsyncResult

Implemented Interfaces

GSimpleAsyncResult implements GAsyncResult.

Includes

#include <gio/gio.h>

Description

As of GLib 2.46, GSimpleAsyncResult is deprecated in favor of GTask, which provides a simpler API.

GSimpleAsyncResult implements GAsyncResult.

GSimpleAsyncResult handles GAsyncReadyCallbacks, error reporting, operation cancellation and the final state of an operation, completely transparent to the application. Results can be returned as a pointer e.g. for functions that return data that is collected asynchronously, a boolean value for checking the success or failure of an operation, or a gssize for operations which return the number of bytes modified by the operation; all of the simple return cases are covered.

Most of the time, an application will not need to know of the details of this API; it is handled transparently, and any necessary operations are handled by GAsyncResult's interface. However, if implementing a new GIO module, for writing language bindings, or for complex applications that need better control of how asynchronous operations are completed, it is important to understand this functionality.

GSimpleAsyncResults are tagged with the calling function to ensure that asynchronous functions and their finishing functions are used together correctly.

To create a new GSimpleAsyncResult, call g_simple_async_result_new(). If the result needs to be created for a GError, use g_simple_async_result_new_from_error() or g_simple_async_result_new_take_error(). If a GError is not available (e.g. the asynchronous operation's doesn't take a GError argument), but the result still needs to be created for an error condition, use g_simple_async_result_new_error() (or g_simple_async_result_set_error_va() if your application or binding requires passing a variable argument list directly), and the error can then be propagated through the use of g_simple_async_result_propagate_error().

An asynchronous operation can be made to ignore a cancellation event by calling g_simple_async_result_set_handle_cancellation() with a GSimpleAsyncResult for the operation and FALSE. This is useful for operations that are dangerous to cancel, such as close (which would cause a leak if cancelled before being run).

GSimpleAsyncResult can integrate into GLib's event loop, GMainLoop, or it can use GThreads. g_simple_async_result_complete() will finish an I/O task directly from the point where it is called. g_simple_async_result_complete_in_idle() will finish it from an idle handler in the thread-default main context . g_simple_async_result_run_in_thread() will run the job in a separate thread and then deliver the result to the thread-default main context.

To set the results of an asynchronous function, g_simple_async_result_set_op_res_gpointer(), g_simple_async_result_set_op_res_gboolean(), and g_simple_async_result_set_op_res_gssize() are provided, setting the operation's result to a gpointer, gboolean, or gssize, respectively.

Likewise, to get the result of an asynchronous function, g_simple_async_result_get_op_res_gpointer(), g_simple_async_result_get_op_res_gboolean(), and g_simple_async_result_get_op_res_gssize() are provided, getting the operation's result as a gpointer, gboolean, and gssize, respectively.

For the details of the requirements implementations must respect, see GAsyncResult. A typical implementation of an asynchronous operation using GSimpleAsyncResult looks something like this:

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static void
baked_cb (Cake    *cake,
          gpointer user_data)
{
  // In this example, this callback is not given a reference to the cake,
  // so the GSimpleAsyncResult has to take a reference to it.
  GSimpleAsyncResult *result = user_data;

  if (cake == NULL)
    g_simple_async_result_set_error (result,
                                     BAKER_ERRORS,
                                     BAKER_ERROR_NO_FLOUR,
                                     "Go to the supermarket");
  else
    g_simple_async_result_set_op_res_gpointer (result,
                                               g_object_ref (cake),
                                               g_object_unref);


  // In this example, we assume that baked_cb is called as a callback from
  // the mainloop, so it's safe to complete the operation synchronously here.
  // If, however, _baker_prepare_cake () might call its callback without
  // first returning to the mainloop — inadvisable, but some APIs do so —
  // we would need to use g_simple_async_result_complete_in_idle().
  g_simple_async_result_complete (result);
  g_object_unref (result);
}

void
baker_bake_cake_async (Baker              *self,
                       guint               radius,
                       GAsyncReadyCallback callback,
                       gpointer            user_data)
{
  GSimpleAsyncResult *simple;
  Cake               *cake;

  if (radius < 3)
    {
      g_simple_async_report_error_in_idle (G_OBJECT (self),
                                           callback,
                                           user_data,
                                           BAKER_ERRORS,
                                           BAKER_ERROR_TOO_SMALL,
                                           "%ucm radius cakes are silly",
                                           radius);
      return;
    }

  simple = g_simple_async_result_new (G_OBJECT (self),
                                      callback,
                                      user_data,
                                      baker_bake_cake_async);
  cake = _baker_get_cached_cake (self, radius);

  if (cake != NULL)
    {
      g_simple_async_result_set_op_res_gpointer (simple,
                                                 g_object_ref (cake),
                                                 g_object_unref);
      g_simple_async_result_complete_in_idle (simple);
      g_object_unref (simple);
      // Drop the reference returned by _baker_get_cached_cake();
      // the GSimpleAsyncResult has taken its own reference.
      g_object_unref (cake);
      return;
    }

  _baker_prepare_cake (self, radius, baked_cb, simple);
}

Cake *
baker_bake_cake_finish (Baker        *self,
                        GAsyncResult *result,
                        GError      **error)
{
  GSimpleAsyncResult *simple;
  Cake               *cake;

  g_return_val_if_fail (g_simple_async_result_is_valid (result,
                                                        G_OBJECT (self),
                                                        baker_bake_cake_async),
                        NULL);

  simple = (GSimpleAsyncResult *) result;

  if (g_simple_async_result_propagate_error (simple, error))
    return NULL;

  cake = CAKE (g_simple_async_result_get_op_res_gpointer (simple));
  return g_object_ref (cake);
}

Functions

GSimpleAsyncThreadFunc ()

void
(*GSimpleAsyncThreadFunc) (GSimpleAsyncResult *res,
                           GObject *object,
                           GCancellable *cancellable);

Simple thread function that runs an asynchronous operation and checks for cancellation.

Parameters

res

a GSimpleAsyncResult.

 

object

a GObject.

 

cancellable

optional GCancellable object, NULL to ignore.

 

g_simple_async_result_new ()

GSimpleAsyncResult *
g_simple_async_result_new (GObject *source_object,
                           GAsyncReadyCallback callback,
                           gpointer user_data,
                           gpointer source_tag);

g_simple_async_result_new has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_new() instead.

Creates a GSimpleAsyncResult.

The common convention is to create the GSimpleAsyncResult in the function that starts the asynchronous operation and use that same function as the source_tag .

If your operation supports cancellation with GCancellable (which it probably should) then you should provide the user's cancellable to g_simple_async_result_set_check_cancellable() immediately after this function returns.

Parameters

source_object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

source_tag

the asynchronous function.

 

Returns

a GSimpleAsyncResult.


g_simple_async_result_new_error ()

GSimpleAsyncResult *
g_simple_async_result_new_error (GObject *source_object,
                                 GAsyncReadyCallback callback,
                                 gpointer user_data,
                                 GQuark domain,
                                 gint code,
                                 const char *format,
                                 ...);

g_simple_async_result_new_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_new() and g_task_return_new_error() instead.

Creates a new GSimpleAsyncResult with a set error.

Parameters

source_object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

domain

a GQuark.

 

code

an error code.

 

format

a string with format characters.

 

...

a list of values to insert into format .

 

Returns

a GSimpleAsyncResult.


g_simple_async_result_new_from_error ()

GSimpleAsyncResult *
g_simple_async_result_new_from_error (GObject *source_object,
                                      GAsyncReadyCallback callback,
                                      gpointer user_data,
                                      const GError *error);

g_simple_async_result_new_from_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_new() and g_task_return_error() instead.

Creates a GSimpleAsyncResult from an error condition.

Parameters

source_object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

error

a GError

 

Returns

a GSimpleAsyncResult.


g_simple_async_result_new_take_error ()

GSimpleAsyncResult *
g_simple_async_result_new_take_error (GObject *source_object,
                                      GAsyncReadyCallback callback,
                                      gpointer user_data,
                                      GError *error);

g_simple_async_result_new_take_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_new() and g_task_return_error() instead.

Creates a GSimpleAsyncResult from an error condition, and takes over the caller's ownership of error , so the caller does not need to free it anymore.

[skip]

Parameters

source_object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

error

a GError

 

Returns

a GSimpleAsyncResult

Since: 2.28


g_simple_async_result_set_check_cancellable ()

void
g_simple_async_result_set_check_cancellable
                               (GSimpleAsyncResult *simple,
                                GCancellable *check_cancellable);

g_simple_async_result_set_check_cancellable has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask instead.

Sets a GCancellable to check before dispatching results.

This function has one very specific purpose: the provided cancellable is checked at the time of g_simple_async_result_propagate_error() If it is cancelled, these functions will return an "Operation was cancelled" error (G_IO_ERROR_CANCELLED).

Implementors of cancellable asynchronous functions should use this in order to provide a guarantee to their callers that cancelling an async operation will reliably result in an error being returned for that operation (even if a positive result for the operation has already been sent as an idle to the main context to be dispatched).

The checking described above is done regardless of any call to the unrelated g_simple_async_result_set_handle_cancellation() function.

Parameters

simple

a GSimpleAsyncResult

 

check_cancellable

a GCancellable to check, or NULL to unset.

[nullable]

Since: 2.32


g_simple_async_result_set_op_res_gpointer ()

void
g_simple_async_result_set_op_res_gpointer
                               (GSimpleAsyncResult *simple,
                                gpointer op_res,
                                GDestroyNotify destroy_op_res);

g_simple_async_result_set_op_res_gpointer has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_pointer() instead.

Sets the operation result within the asynchronous result to a pointer.

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

op_res

a pointer result from an asynchronous function.

 

destroy_op_res

a GDestroyNotify function.

 

g_simple_async_result_get_op_res_gpointer ()

gpointer
g_simple_async_result_get_op_res_gpointer
                               (GSimpleAsyncResult *simple);

g_simple_async_result_get_op_res_gpointer has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_propagate_pointer() instead.

Gets a pointer result as returned by the asynchronous function.

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

Returns

a pointer from the result.


g_simple_async_result_set_op_res_gssize ()

void
g_simple_async_result_set_op_res_gssize
                               (GSimpleAsyncResult *simple,
                                gssize op_res);

g_simple_async_result_set_op_res_gssize has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_int() instead.

Sets the operation result within the asynchronous result to the given op_res .

Parameters

simple

a GSimpleAsyncResult.

 

op_res

a gssize.

 

g_simple_async_result_get_op_res_gssize ()

gssize
g_simple_async_result_get_op_res_gssize
                               (GSimpleAsyncResult *simple);

g_simple_async_result_get_op_res_gssize has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_propagate_int() instead.

Gets a gssize from the asynchronous result.

Parameters

simple

a GSimpleAsyncResult.

 

Returns

a gssize returned from the asynchronous function.


g_simple_async_result_set_op_res_gboolean ()

void
g_simple_async_result_set_op_res_gboolean
                               (GSimpleAsyncResult *simple,
                                gboolean op_res);

g_simple_async_result_set_op_res_gboolean has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_boolean() instead.

Sets the operation result to a boolean within the asynchronous result.

Parameters

simple

a GSimpleAsyncResult.

 

op_res

a gboolean.

 

g_simple_async_result_get_op_res_gboolean ()

gboolean
g_simple_async_result_get_op_res_gboolean
                               (GSimpleAsyncResult *simple);

g_simple_async_result_get_op_res_gboolean has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_propagate_boolean() instead.

Gets the operation result boolean from within the asynchronous result.

Parameters

simple

a GSimpleAsyncResult.

 

Returns

TRUE if the operation's result was TRUE, FALSE if the operation's result was FALSE.


g_simple_async_result_get_source_tag ()

gpointer
g_simple_async_result_get_source_tag (GSimpleAsyncResult *simple);

g_simple_async_result_get_source_tag has been deprecated since version 2.46. and should not be used in newly-written code.

Use GTask and g_task_get_source_tag() instead.

Gets the source tag for the GSimpleAsyncResult.

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

Returns

a gpointer to the source object for the GSimpleAsyncResult.


g_simple_async_result_is_valid ()

gboolean
g_simple_async_result_is_valid (GAsyncResult *result,
                                GObject *source,
                                gpointer source_tag);

g_simple_async_result_is_valid has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_is_valid() instead.

Ensures that the data passed to the _finish function of an async operation is consistent. Three checks are performed.

First, result is checked to ensure that it is really a GSimpleAsyncResult. Second, source is checked to ensure that it matches the source object of result . Third, source_tag is checked to ensure that it is equal to the source_tag argument given to g_simple_async_result_new() (which, by convention, is a pointer to the _async function corresponding to the _finish function from which this function is called). (Alternatively, if either source_tag or result 's source tag is NULL, then the source tag check is skipped.)

Parameters

result

the GAsyncResult passed to the _finish function.

 

source

the GObject passed to the _finish function.

[nullable]

source_tag

the asynchronous function.

[nullable]

Returns

TRUE if all checks passed or FALSE if any failed.

Since: 2.20


g_simple_async_result_set_handle_cancellation ()

void
g_simple_async_result_set_handle_cancellation
                               (GSimpleAsyncResult *simple,
                                gboolean handle_cancellation);

g_simple_async_result_set_handle_cancellation has been deprecated since version 2.46 and should not be used in newly-written code.

Sets whether to handle cancellation within the asynchronous operation.

This function has nothing to do with g_simple_async_result_set_check_cancellable(). It only refers to the GCancellable passed to g_simple_async_result_run_in_thread().

Parameters

simple

a GSimpleAsyncResult.

 

handle_cancellation

a gboolean.

 

g_simple_async_result_complete ()

void
g_simple_async_result_complete (GSimpleAsyncResult *simple);

g_simple_async_result_complete has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask instead.

Completes an asynchronous I/O job immediately. Must be called in the thread where the asynchronous result was to be delivered, as it invokes the callback directly. If you are in a different thread use g_simple_async_result_complete_in_idle().

Calling this function takes a reference to simple for as long as is needed to complete the call.

Parameters

simple

a GSimpleAsyncResult.

 

g_simple_async_result_complete_in_idle ()

void
g_simple_async_result_complete_in_idle
                               (GSimpleAsyncResult *simple);

g_simple_async_result_complete_in_idle has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask instead.

Completes an asynchronous function in an idle handler in the thread-default main context of the thread that simple was initially created in (and re-pushes that context around the invocation of the callback).

Calling this function takes a reference to simple for as long as is needed to complete the call.

Parameters

simple

a GSimpleAsyncResult.

 

g_simple_async_result_run_in_thread ()

void
g_simple_async_result_run_in_thread (GSimpleAsyncResult *simple,
                                     GSimpleAsyncThreadFunc func,
                                     int io_priority,
                                     GCancellable *cancellable);

g_simple_async_result_run_in_thread has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_run_in_thread() instead.

Runs the asynchronous job in a separate thread and then calls g_simple_async_result_complete_in_idle() on simple to return the result to the appropriate main loop.

Calling this function takes a reference to simple for as long as is needed to run the job and report its completion.

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

func

a GSimpleAsyncThreadFunc.

 

io_priority

the io priority of the request.

 

cancellable

optional GCancellable object, NULL to ignore.

[nullable]

g_simple_async_result_set_from_error ()

void
g_simple_async_result_set_from_error (GSimpleAsyncResult *simple,
                                      const GError *error);

g_simple_async_result_set_from_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_error() instead.

Sets the result from a GError.

Parameters

simple

a GSimpleAsyncResult.

 

error

GError.

 

g_simple_async_result_take_error ()

void
g_simple_async_result_take_error (GSimpleAsyncResult *simple,
                                  GError *error);

g_simple_async_result_take_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_error() instead.

Sets the result from error , and takes over the caller's ownership of error , so the caller does not need to free it any more.

[skip]

Parameters

simple

a GSimpleAsyncResult

 

error

a GError

 

Since: 2.28


g_simple_async_result_propagate_error ()

gboolean
g_simple_async_result_propagate_error (GSimpleAsyncResult *simple,
                                       GError **dest);

g_simple_async_result_propagate_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask instead.

Propagates an error from within the simple asynchronous result to a given destination.

If the GCancellable given to a prior call to g_simple_async_result_set_check_cancellable() is cancelled then this function will return TRUE with dest set appropriately.

Parameters

simple

a GSimpleAsyncResult.

 

dest

a location to propagate the error to.

[out]

Returns

TRUE if the error was propagated to dest . FALSE otherwise.


g_simple_async_result_set_error ()

void
g_simple_async_result_set_error (GSimpleAsyncResult *simple,
                                 GQuark domain,
                                 gint code,
                                 const char *format,
                                 ...);

g_simple_async_result_set_error has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_new_error() instead.

Sets an error within the asynchronous result without a GError.

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

domain

a GQuark (usually G_IO_ERROR).

 

code

an error code.

 

format

a formatted error reporting string.

 

...

a list of variables to fill in format .

 

g_simple_async_result_set_error_va ()

void
g_simple_async_result_set_error_va (GSimpleAsyncResult *simple,
                                    GQuark domain,
                                    gint code,
                                    const char *format,
                                    va_list args);

g_simple_async_result_set_error_va has been deprecated since version 2.46 and should not be used in newly-written code.

Use GTask and g_task_return_error() instead.

Sets an error within the asynchronous result without a GError. Unless writing a binding, see g_simple_async_result_set_error().

[skip]

Parameters

simple

a GSimpleAsyncResult.

 

domain

a GQuark (usually G_IO_ERROR).

 

code

an error code.

 

format

a formatted error reporting string.

 

args

va_list of arguments.

 

g_simple_async_report_error_in_idle ()

void
g_simple_async_report_error_in_idle (GObject *object,
                                     GAsyncReadyCallback callback,
                                     gpointer user_data,
                                     GQuark domain,
                                     gint code,
                                     const char *format,
                                     ...);

g_simple_async_report_error_in_idle has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_report_error().

Reports an error in an asynchronous function in an idle function by directly setting the contents of the GAsyncResult with the given error information.

[skip]

Parameters

object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

 

user_data

user data passed to callback .

 

domain

a GQuark containing the error domain (usually G_IO_ERROR).

 

code

a specific error code.

 

format

a formatted error reporting string.

 

...

a list of variables to fill in format .

 

g_simple_async_report_gerror_in_idle ()

void
g_simple_async_report_gerror_in_idle (GObject *object,
                                      GAsyncReadyCallback callback,
                                      gpointer user_data,
                                      const GError *error);

g_simple_async_report_gerror_in_idle has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_report_error().

Reports an error in an idle function. Similar to g_simple_async_report_error_in_idle(), but takes a GError rather than building a new one.

Parameters

object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

[scope async]

user_data

user data passed to callback .

[closure]

error

the GError to report

 

g_simple_async_report_take_gerror_in_idle ()

void
g_simple_async_report_take_gerror_in_idle
                               (GObject *object,
                                GAsyncReadyCallback callback,
                                gpointer user_data,
                                GError *error);

g_simple_async_report_take_gerror_in_idle has been deprecated since version 2.46 and should not be used in newly-written code.

Use g_task_report_error().

Reports an error in an idle function. Similar to g_simple_async_report_gerror_in_idle(), but takes over the caller's ownership of error , so the caller does not have to free it any more.

[skip]

Parameters

object

a GObject, or NULL.

[nullable]

callback

a GAsyncReadyCallback.

 

user_data

user data passed to callback .

 

error

the GError to report

 

Since: 2.28

Types and Values

GSimpleAsyncResult

typedef struct _GSimpleAsyncResult GSimpleAsyncResult;

A simple implementation of GAsyncResult.

See Also

GAsyncResult, GTask

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