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
  28 /**
  29  * SECTION:gasyncresult
  30  * @short_description: Asynchronous Function Results
  31  * @include: gio/gio.h
  32  * @see_also: #GSimpleAsyncResult
  33  *
  34  * Provides a base class for implementing asynchronous function results.
  35  *
  36  * Asynchronous operations are broken up into two separate operations
  37  * which are chained together by a #GAsyncReadyCallback. To begin
  38  * an asynchronous operation, provide a #GAsyncReadyCallback to the
  39  * asynchronous function. This callback will be triggered when the
  40  * operation has completed, and will be passed a #GAsyncResult instance
  41  * filled with the details of the operation's success or failure, the
  42  * object the asynchronous function was started for and any error codes
  43  * returned. The asynchronous callback function is then expected to call
  44  * the corresponding "_finish()" function, passing the object the
  45  * function was called for, the #GAsyncResult instance, and (optionally)
  46  * an @error to grab any error conditions that may have occurred.
  47  *
  48  * The "_finish()" function for an operation takes the generic result
  49  * (of type #GAsyncResult) and returns the specific result that the
  50  * operation in question yields (e.g. a #GFileEnumerator for a
  51  * "enumerate children" operation). If the result or error status of the
  52  * operation is not needed, there is no need to call the "_finish()"
  53  * function; GIO will take care of cleaning up the result and error
  54  * information after the #GAsyncReadyCallback returns. You can pass
  55  * %NULL for the #GAsyncReadyCallback if you don't need to take any
  56  * action at all after the operation completes. Applications may also
  57  * take a reference to the #GAsyncResult and call "_finish()" later;
  58  * however, the "_finish()" function may be called at most once.
  59  *
  60  * Example of a typical asynchronous operation flow:
  61  * |[
  62  * void _theoretical_frobnitz_async (Theoretical         *t,
  63  *                                   GCancellable        *c,
  64  *                                   GAsyncReadyCallback *cb,
  65  *                                   gpointer             u);
  66  *
  67  * gboolean _theoretical_frobnitz_finish (Theoretical   *t,
  68  *                                        GAsyncResult  *res,
  69  *                                        GError       **e);
  70  *
  71  * static void
  72  * frobnitz_result_func (GObject      *source_object,
  73  *                       GAsyncResult *res,
  74  *                       gpointer      user_data)
  75  * {
  76  *   gboolean success = FALSE;
  77  *
  78  *   success = _theoretical_frobnitz_finish (source_object, res, NULL);
  79  *
  80  *   if (success)
  81  *     g_printf ("Hurray!\n");
  82  *   else
  83  *     g_printf ("Uh oh!\n");
  84  *
  85  *   /<!-- -->* ... *<!-- -->/
  86  *
  87  * }
  88  *
  89  * int main (int argc, void *argv[])
  90  * {
  91  *    /<!-- -->* ... *<!-- -->/
  92  *
  93  *    _theoretical_frobnitz_async (theoretical_data,
  94  *                                 NULL,
  95  *                                 frobnitz_result_func,
  96  *                                 NULL);
  97  *
  98  *    /<!-- -->* ... *<!-- -->/
  99  * }
 100  * ]|
 101  *
 102  * The callback for an asynchronous operation is called only once, and is
 103  * always called, even in the case of a cancelled operation. On cancellation
 104  * the result is a %G_IO_ERROR_CANCELLED error.
 105  **/
 106
 107 typedef GAsyncResultIface GAsyncResultInterface;
 108 G_DEFINE_INTERFACE (GAsyncResult, g_async_result, G_TYPE_OBJECT)
 109
 110 static void
 111 g_async_result_default_init (GAsyncResultInterface *iface)
 112 {
 113 }
 114
 115 /**
 116  * g_async_result_get_user_data:
 117  * @res: a #GAsyncResult.
 118  *
 119  * Gets the user data from a #GAsyncResult.
 120  *
 121  * Returns: (transfer full): the user data for @res.
 122  **/
 123 gpointer
 124 g_async_result_get_user_data (GAsyncResult *res)
 125 {
 126   GAsyncResultIface *iface;
 127
 128   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
 129
 130   iface = G_ASYNC_RESULT_GET_IFACE (res);
 131
 132   return (* iface->get_user_data) (res);
 133 }
 134
 135 /**
 136  * g_async_result_get_source_object:
 137  * @res: a #GAsyncResult
 138  *
 139  * Gets the source object from a #GAsyncResult.
 140  *
 141  * Returns: (transfer full): a new reference to the source object for the @res,
 142  *    or %NULL if there is none.
 143  */
 144 GObject *
 145 g_async_result_get_source_object (GAsyncResult *res)
 146 {
 147   GAsyncResultIface *iface;
 148
 149   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), NULL);
 150
 151   iface = G_ASYNC_RESULT_GET_IFACE (res);
 152
 153   return (* iface->get_source_object) (res);
 154 }