gio/gasyncresult.c

   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@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"