gio/ginitable.c

   1 /* GIO - GLib Input, Output and Streaming Library
   2  *
   3  * Copyright (C) 2009 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, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Alexander Larsson <alexl@redhat.com>
  19  */
  20
  21 #include "config.h"
  22 #include "ginitable.h"
  23 #include "glibintl.h"
  24
  25
  26 /**
  27  * SECTION:ginitable
  28  * @short_description: Failable object initialization interface
  29  * @include: gio/gio.h
  30  * @see_also: #GAsyncInitable
  31  *
  32  * #GInitable is implemented by objects that can fail during
  33  * initialization. If an object implements this interface then
  34  * it must be initialized as the first thing after construction,
  35  * either via g_initable_init() or g_async_initable_init_async()
  36  * (the latter is only available if it also implements #GAsyncInitable).
  37  *
  38  * If the object is not initialized, or initialization returns with an
  39  * error, then all operations on the object except g_object_ref() and
  40  * g_object_unref() are considered to be invalid, and have undefined
  41  * behaviour. They will often fail with g_critical() or g_warning(), but
  42  * this must not be relied on.
  43  *
  44  * Users of objects implementing this are not intended to use
  45  * the interface method directly, instead it will be used automatically
  46  * in various ways. For C applications you generally just call
  47  * g_initable_new() directly, or indirectly via a foo_thing_new() wrapper.
  48  * This will call g_initable_init() under the cover, returning %NULL and
  49  * setting a #GError on failure (at which point the instance is
  50  * unreferenced).
  51  *
  52  * For bindings in languages where the native constructor supports
  53  * exceptions the binding could check for objects implemention %GInitable
  54  * during normal construction and automatically initialize them, throwing
  55  * an exception on failure.
  56  */
  57
  58 typedef GInitableIface GInitableInterface;
  59 G_DEFINE_INTERFACE (GInitable, g_initable, G_TYPE_OBJECT)
  60
  61 static void
  62 g_initable_default_init (GInitableInterface *iface)
  63 {
  64 }
  65
  66 /**
  67  * g_initable_init:
  68  * @initable: a #GInitable.
  69  * @cancellable: optional #GCancellable object, %NULL to ignore.
  70  * @error: a #GError location to store the error occurring, or %NULL to
  71  * ignore.
  72  *
  73  * Initializes the object implementing the interface.
  74  *
  75  * The object must be initialized before any real use after initial
  76  * construction, either with this function or g_async_initable_init_async().
  77  *
  78  * Implementations may also support cancellation. If @cancellable is not %NULL,
  79  * then initialization can be cancelled by triggering the cancellable object
  80  * from another thread. If the operation was cancelled, the error
  81  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL and
  82  * the object doesn't support cancellable initialization the error
  83  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
  84  *
  85  * If the object is not initialized, or initialization returns with an
  86  * error, then all operations on the object except g_object_ref() and
  87  * g_object_unref() are considered to be invalid, and have undefined
  88  * behaviour. See the [introduction][ginitable] for more details.
  89  *
  90  * Implementations of this method must be idempotent, i.e. multiple calls
  91  * to this function with the same argument should return the same results.
  92  * Only the first call initializes the object, further calls return the result
  93  * of the first call. This is so that it's safe to implement the singleton
  94  * pattern in the GObject constructor function.
  95  *
  96  * Returns: %TRUE if successful. If an error has occurred, this function will
  97  *     return %FALSE and set @error appropriately if present.
  98  *
  99  * Since: 2.22
 100  */
 101 gboolean
 102 g_initable_init (GInitable     *initable,
 103                  GCancellable  *cancellable,
 104                  GError       **error)
 105 {
 106   GInitableIface *iface;
 107
 108   g_return_val_if_fail (G_IS_INITABLE (initable), FALSE);
 109
 110   iface = G_INITABLE_GET_IFACE (initable);
 111
 112   return (* iface->init) (initable, cancellable, error);
 113 }
 114
 115 /**
 116  * g_initable_new:
 117  * @object_type: a #GType supporting #GInitable.
 118  * @cancellable: optional #GCancellable object, %NULL to ignore.
 119  * @error: a #GError location to store the error occurring, or %NULL to
 120  *    ignore.
 121  * @first_property_name: (nullable): the name of the first property, or %NULL if no
 122  *     properties
 123  * @...:  the value if the first property, followed by and other property
 124  *    value pairs, and ended by %NULL.
 125  *
 126  * Helper function for constructing #GInitable object. This is
 127  * similar to g_object_new() but also initializes the object
 128  * and returns %NULL, setting an error on failure.
 129  *
 130  * Returns: (type GObject.Object) (transfer full): a newly allocated
 131  *      #GObject, or %NULL on error
 132  *
 133  * Since: 2.22
 134  */
 135 gpointer
 136 g_initable_new (GType          object_type,
 137                 GCancellable  *cancellable,
 138                 GError       **error,
 139                 const gchar   *first_property_name,
 140                 ...)
 141 {
 142   GObject *object;
 143   va_list var_args;
 144
 145   va_start (var_args, first_property_name);
 146   object = g_initable_new_valist (object_type,
 147                                   first_property_name, var_args,
 148                                   cancellable, error);
 149   va_end (var_args);
 150
 151   return object;
 152 }
 153
 154 /**
 155  * g_initable_newv:
 156  * @object_type: a #GType supporting #GInitable.
 157  * @n_parameters: the number of parameters in @parameters
 158  * @parameters: (array length=n_parameters): the parameters to use to construct the object
 159  * @cancellable: optional #GCancellable object, %NULL to ignore.
 160  * @error: a #GError location to store the error occurring, or %NULL to
 161  *     ignore.
 162  *
 163  * Helper function for constructing #GInitable object. This is
 164  * similar to g_object_newv() but also initializes the object
 165  * and returns %NULL, setting an error on failure.
 166  *
 167  * Returns: (type GObject.Object) (transfer full): a newly allocated
 168  *      #GObject, or %NULL on error
 169  *
 170  * Since: 2.22
 171  */
 172 gpointer
 173 g_initable_newv (GType          object_type,
 174                  guint          n_parameters,
 175                  GParameter    *parameters,
 176                  GCancellable  *cancellable,
 177                  GError       **error)
 178 {
 179   GObject *obj;
 180
 181   g_return_val_if_fail (G_TYPE_IS_INITABLE (object_type), NULL);
 182
 183   obj = g_object_newv (object_type, n_parameters, parameters);
 184
 185   if (!g_initable_init (G_INITABLE (obj), cancellable, error))
 186     {
 187       g_object_unref (obj);
 188       return NULL;
 189     }
 190
 191   return (gpointer)obj;
 192 }
 193
 194 /**
 195  * g_initable_new_valist:
 196  * @object_type: a #GType supporting #GInitable.
 197  * @first_property_name: the name of the first property, followed by
 198  * the value, and other property value pairs, and ended by %NULL.
 199  * @var_args: The var args list generated from @first_property_name.
 200  * @cancellable: optional #GCancellable object, %NULL to ignore.
 201  * @error: a #GError location to store the error occurring, or %NULL to
 202  *     ignore.
 203  *
 204  * Helper function for constructing #GInitable object. This is
 205  * similar to g_object_new_valist() but also initializes the object
 206  * and returns %NULL, setting an error on failure.
 207  *
 208  * Returns: (type GObject.Object) (transfer full): a newly allocated
 209  *      #GObject, or %NULL on error
 210  *
 211  * Since: 2.22
 212  */
 213 GObject*
 214 g_initable_new_valist (GType          object_type,
 215                        const gchar   *first_property_name,
 216                        va_list        var_args,
 217                        GCancellable  *cancellable,
 218                        GError       **error)
 219 {
 220   GObject *obj;
 221
 222   g_return_val_if_fail (G_TYPE_IS_INITABLE (object_type), NULL);
 223
 224   obj = g_object_new_valist (object_type,
 225                              first_property_name,
 226                              var_args);
 227
 228   if (!g_initable_init (G_INITABLE (obj), cancellable, error))
 229     {
 230       g_object_unref (obj);
 231       return NULL;
 232     }
 233
 234   return obj;
 235 }