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      1 /* GIO - GLib Input, Output and Streaming Library
      2  *
      3  * Copyright (C) 2006-2007 Red Hat, Inc.
      4  *
      5  * This library is free software; you can redistribute it and/or
      6  * modify it under the terms of the GNU Lesser General Public
      7  * License as published by the Free Software Foundation; either
      8  * version 2 of the License, or (at your option) any later version.
      9  *
     10  * This library is distributed in the hope that it will be useful,
     11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13  * Lesser General Public License for more details.
     14  *
     15  * You should have received a copy of the GNU Lesser General
     16  * Public License along with this library; if not, write to the
     17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
     18  * Boston, MA 02111-1307, USA.
     19  *
     20  * Author: Alexander Larsson <alexl (at) redhat.com>
     21  */
     22 
     23 #include "config.h"
     24 #include "gasyncresult.h"
     25 #include "glibintl.h"
     26 
     27 #include "gioalias.h"
     28 
     29 /**
     30  * SECTION:gasyncresult
     31  * @short_description: Asynchronous Function Results
     32  * @include: gio/gio.h
     33  * @see_also: #GSimpleAsyncResult
     34  *
     35  * Provides a base class for implementing asynchronous function results.
     36  *
     37  * Asynchronous operations are broken up into two separate operations
     38  * which are chained together by a #GAsyncReadyCallback. To begin
     39  * an asynchronous operation, provide a #GAsyncReadyCallback to the
     40  * asynchronous function. This callback will be triggered when the
     41  * operation has completed, and will be passed a #GAsyncResult instance
     42  * filled with the details of the operation's success or failure, the
     43  * object the asynchronous function was started for and any error codes
     44  * returned. The asynchronous callback function is then expected to call
     45  * the corresponding "_finish()" function with the object the function
     46  * was called for, and the #GAsyncResult instance, and optionally,
     47  * an @error to grab any error conditions that may have occurred.
     48  *
     49  * The purpose of the "_finish()" function is to take the generic
     50  * result of type #GAsyncResult and return the specific result
     51  * that the operation in question yields (e.g. a #GFileEnumerator for
     52  * a "enumerate children" operation). If the result or error status
     53  * of the operation is not needed, there is no need to call the
     54  * "_finish()" function, GIO will take care of cleaning up the
     55  * result and error information after the #GAsyncReadyCallback
     56  * returns. It is also allowed to take a reference to the #GAsyncResult and
     57  * call "_finish()" later.
     58  *
     59  * Example of a typical asynchronous operation flow:
     60  * |[
     61  * void _theoretical_frobnitz_async (Theoretical         *t,
     62  *                                   GCancellable        *c,
     63  *                                   GAsyncReadyCallback *cb,
     64  *                                   gpointer             u);
     65  *
     66  * gboolean _theoretical_frobnitz_finish (Theoretical   *t,
     67  *                                        GAsyncResult  *res,
     68  *                                        GError       **e);
     69  *
     70  * static void
     71  * frobnitz_result_func (GObject      *source_object,
     72  *			 GAsyncResult *res,
     73  *			 gpointer      user_data)
     74  * {
     75  *   gboolean success = FALSE;
     76  *
     77  *   success = _theoretical_frobnitz_finish (source_object, res, NULL);
     78  *
     79  *   if (success)
     80  *     g_printf ("Hurray!\n");
     81  *   else
     82  *     g_printf ("Uh oh!\n");
     83  *
     84  *   /<!-- -->* ... *<!-- -->/
     85  *
     86  * }
     87  *
     88  * int main (int argc, void *argv[])
     89  * {
     90  *    /<!-- -->* ... *<!-- -->/
     91  *
     92  *    _theoretical_frobnitz_async (theoretical_data,
     93  *                                 NULL,
     94  *                                 frobnitz_result_func,
     95  *                                 NULL);
     96  *
     97  *    /<!-- -->* ... *<!-- -->/
     98  * }
     99  * ]|
    100  *
    101  * The callback for an asynchronous operation is called only once, and is
    102  * always called, even in the case of a cancelled operation. On cancellation
    103  * the result is a %G_IO_ERROR_CANCELLED error.
    104  *
    105  * Some ascynchronous operations are implemented using synchronous calls. These
    106  * are run in a separate thread, if #GThread has been initialized, but otherwise they
    107  * are sent to the Main Event Loop and processed in an idle function. So, if you
    108  * truly need asynchronous operations, make sure to initialize #GThread.
    109  **/
    110 
    111 static void g_async_result_base_init (gpointer g_class);
    112 static void g_async_result_class_init (gpointer g_class,
    113 				       gpointer class_data);
    114 
    115 GType
    116 g_async_result_get_type (void)
    117 {
    118   static volatile gsize g_define_type_id__volatile = 0;
    119 
    120   if (g_once_init_enter (&g_define_type_id__volatile))
    121     {
    122       const GTypeInfo async_result_info =
    123       {
    124         sizeof (GAsyncResultIface), /* class_size */
    125 	g_async_result_base_init,   /* base_init */
    126 	NULL,		            /* base_finalize */
    127 	g_async_result_class_init,
    128 	NULL,		/* class_finalize */
    129 	NULL,		/* class_data */
    130 	0,
    131 	0,              /* n_preallocs */
    132 	NULL
    133       };
    134       GType g_define_type_id =
    135 	g_type_register_static (G_TYPE_INTERFACE, I_("GAsyncResult"),
    136 				&async_result_info, 0);
    137 
    138       g_type_interface_add_prerequisite (g_define_type_id, G_TYPE_OBJECT);
    139 
    140       g_once_init_leave (&g_define_type_id__volatile, g_define_type_id);
    141     }
    142 
    143   return g_define_type_id__volatile;
    144 }
    145 
    146 static void
    147 g_async_result_class_init (gpointer g_class,
    148 			   gpointer class_data)
    149 {
    150 }
    151 
    152 static void
    153 g_async_result_base_init (gpointer g_class)
    154 {
    155 }
    156 
    157 /**
    158  * g_async_result_get_user_data:
    159  * @res: a #GAsyncResult.
    160  *
    161  * Gets the user data from a #GAsyncResult.
    162  *
    163  * Returns: the user data for @res.
    164  **/
    165 gpointer
    166 g_async_result_get_user_data (GAsyncResult *res)
    167 {
    168   GAsyncResultIface *iface;
    169 
    170   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
    171 
    172   iface = G_ASYNC_RESULT_GET_IFACE (res);
    173 
    174   return (* iface->get_user_data) (res);
    175 }
    176 
    177 /**
    178  * g_async_result_get_source_object:
    179  * @res: a #GAsyncResult.
    180  *
    181  * Gets the source object from a #GAsyncResult.
    182  *
    183  * Returns: the source object for the @res.
    184  **/
    185 GObject *
    186 g_async_result_get_source_object (GAsyncResult *res)
    187 {
    188   GAsyncResultIface *iface;
    189 
    190   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
    191 
    192   iface = G_ASYNC_RESULT_GET_IFACE (res);
    193 
    194   return (* iface->get_source_object) (res);
    195 }
    196 
    197 #define __G_ASYNC_RESULT_C__
    198 #include "gioaliasdef.c"
    199