/* GIO - GLib Input, Output and Streaming Library
*
* Copyright (C) 2006-2007 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 2.1 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, see <http://www.gnu.org/licenses/>.
*
* Author: Alexander Larsson <alexl@redhat.com>
*/
#include "config.h"
#include "gasyncresult.h"
#include "gsimpleasyncresult.h"
#include "glibintl.h"
/**
* SECTION:gasyncresult
* @short_description: Asynchronous Function Results
* @include: gio/gio.h
* @see_also: #GTask
*
* Provides a base class for implementing asynchronous function results.
*
* Asynchronous operations are broken up into two separate operations
* which are chained together by a #GAsyncReadyCallback. To begin
* an asynchronous operation, provide a #GAsyncReadyCallback to the
* asynchronous function. This callback will be triggered when the
* operation has completed, and must be run in a later iteration of
* the [thread-default main context][g-main-context-push-thread-default]
* from where the operation was initiated. It will be passed a
* #GAsyncResult instance filled with the details of the operation's
* success or failure, the object the asynchronous function was
* started for and any error codes returned. The asynchronous callback
* function is then expected to call the corresponding "_finish()"
* function, passing the object the function was called for, the
* #GAsyncResult instance, and (optionally) an @error to grab any
* error conditions that may have occurred.
*
* The "_finish()" function for an operation takes the generic result
* (of type #GAsyncResult) and returns the specific result that the
* operation in question yields (e.g. a #GFileEnumerator for a
* "enumerate children" operation). If the result or error status of the
* operation is not needed, there is no need to call the "_finish()"
* function; GIO will take care of cleaning up the result and error
* information after the #GAsyncReadyCallback returns. You can pass
* %NULL for the #GAsyncReadyCallback if you don't need to take any
* action at all after the operation completes. Applications may also
* take a reference to the #GAsyncResult and call "_finish()" later;
* however, the "_finish()" function may be called at most once.
*
* Example of a typical asynchronous operation flow:
* |[<!-- language="C" -->
* void _theoretical_frobnitz_async (Theoretical *t,
* GCancellable *c,
* GAsyncReadyCallback cb,
* gpointer u);
*
* gboolean _theoretical_frobnitz_finish (Theoretical *t,
* GAsyncResult *res,
* GError **e);
*
* static void
* frobnitz_result_func (GObject *source_object,
* GAsyncResult *res,
* gpointer user_data)
* {
* gboolean success = FALSE;
*
* success = _theoretical_frobnitz_finish (source_object, res, NULL);
*
* if (success)
* g_printf ("Hurray!\n");
* else
* g_printf ("Uh oh!\n");
*
* ...
*
* }
*
* int main (int argc, void *argv[])
* {
* ...
*
* _theoretical_frobnitz_async (theoretical_data,
* NULL,
* frobnitz_result_func,
* NULL);
*
* ...
* }
* ]|
*
* The callback for an asynchronous operation is called only once, and is
* always called, even in the case of a cancelled operation. On cancellation
* the result is a %G_IO_ERROR_CANCELLED error.
*
* ## I/O Priority # {#io-priority}
*
* Many I/O-related asynchronous operations have a priority parameter,
* which is used in certain cases to determine the order in which
* operations are executed. They are not used to determine system-wide
* I/O scheduling. Priorities are integers, with lower numbers indicating
* higher priority. It is recommended to choose priorities between
* %G_PRIORITY_LOW and %G_PRIORITY_HIGH, with %G_PRIORITY_DEFAULT
* as a default.
*/
typedef GAsyncResultIface GAsyncResultInterface;
G_DEFINE_INTERFACE (GAsyncResult, g_async_result, G_TYPE_OBJECT)
static void
g_async_result_default_init (GAsyncResultInterface *iface)
{
}
/**
* g_async_result_get_user_data:
* @res: a #GAsyncResult.
*
* Gets the user data from a #GAsyncResult.
*
* Returns: (transfer full): the user data for @res.
**/
gpointer
g_async_result_get_user_data (GAsyncResult *res)
{
GAsyncResultIface *iface;
g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
iface = G_ASYNC_RESULT_GET_IFACE (res);
return (* iface->get_user_data) (res);
}
/**
* g_async_result_get_source_object:
* @res: a #GAsyncResult
*
* Gets the source object from a #GAsyncResult.
*
* Returns: (transfer full) (nullable): a new reference to the source
* object for the @res, or %NULL if there is none.
*/
GObject *
g_async_result_get_source_object (GAsyncResult *res)
{
GAsyncResultIface *iface;
g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
iface = G_ASYNC_RESULT_GET_IFACE (res);
return (* iface->get_source_object) (res);
}
/**
* g_async_result_legacy_propagate_error:
* @res: a #GAsyncResult
* @error: (out): a location to propagate the error to.
*
* If @res is a #GSimpleAsyncResult, this is equivalent to
* g_simple_async_result_propagate_error(). Otherwise it returns
* %FALSE.
*
* This can be used for legacy error handling in async *_finish()
* wrapper functions that traditionally handled #GSimpleAsyncResult
* error returns themselves rather than calling into the virtual method.
* This should not be used in new code; #GAsyncResult errors that are
* set by virtual methods should also be extracted by virtual methods,
* to enable subclasses to chain up correctly.
*
* Returns: %TRUE if @error is has been filled in with an error from
* @res, %FALSE if not.
*
* Since: 2.34
**/
gboolean
g_async_result_legacy_propagate_error (GAsyncResult *res,
GError **error)
{
/* This doesn't use a vmethod, because it's only for code that used
* to use GSimpleAsyncResult. (But it's a GAsyncResult method so
* that callers don't need to worry about GSimpleAsyncResult
* deprecation warnings in the future.)
*/
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
if (G_IS_SIMPLE_ASYNC_RESULT (res))
{
return g_simple_async_result_propagate_error (G_SIMPLE_ASYNC_RESULT (res),
error);
}
else
return FALSE;
G_GNUC_END_IGNORE_DEPRECATIONS
}
/**
* g_async_result_is_tagged:
* @res: a #GAsyncResult
* @source_tag: an application-defined tag
*
* Checks if @res has the given @source_tag (generally a function
* pointer indicating the function @res was created by).
*
* Returns: %TRUE if @res has the indicated @source_tag, %FALSE if
* not.
*
* Since: 2.34
**/
gboolean
g_async_result_is_tagged (GAsyncResult *res,
gpointer source_tag)
{
GAsyncResultIface *iface;
g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
iface = G_ASYNC_RESULT_GET_IFACE (res);
if (!iface->is_tagged)
return FALSE;
return (* iface->is_tagged) (res, source_tag);
}