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