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, 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 "ginitable.h"
  25 #include "glibintl.h"
  26
  27
  28 /**
  29  * SECTION:ginitable
  30  * @short_description: Failable object initialization interface
  31  * @include: gio/gio.h
  32  * @see_also: #GAsyncInitable
  33  *
  34  * #GInitable is implemented by objects that can fail during
  35  * initialization. If an object implements this interface then
  36  * it must be initialized as the first thing after construction,
  37  * either via g_initable_init() or g_async_initable_init_async()
  38  * (the latter is only available if it also implements #GAsyncInitable).
  39  *
  40  * If the object is not initialized, or initialization returns with an
  41  * error, then all operations on the object except g_object_ref() and
  42  * g_object_unref() are considered to be invalid, and have undefined
  43  * behaviour. They will often fail with g_critical() or g_warning(), but
  44  * this must not be relied on.
  45  *
  46  * Users of objects implementing this are not intended to use
  47  * the interface method directly, instead it will be used automatically
  48  * in various ways. For C applications you generally just call
  49  * g_initable_new() directly, or indirectly via a foo_thing_new() wrapper.
  50  * This will call g_initable_init() under the cover, returning %NULL and
  51  * setting a #GError on failure (at which point the instance is
  52  * unreferenced).
  53  *
  54  * For bindings in languages where the native constructor supports
  55  * exceptions the binding could check for objects implemention %GInitable
  56  * during normal construction and automatically initialize them, throwing
  57  * an exception on failure.
  58  */
  59
  60 typedef GInitableIface GInitableInterface;
  61 G_DEFINE_INTERFACE (GInitable, g_initable, G_TYPE_OBJECT)
  62
  63 static void
  64 g_initable_default_init (GInitableInterface *iface)
  65 {
  66 }
  67
  68 /**
  69  * g_initable_init:
  70  * @initable: a #GInitable.
  71  * @cancellable: optional #GCancellable object, %NULL to ignore.
  72  * @error: a #GError location to store the error occurring, or %NULL to
  73  * ignore.
  74  *
  75  * Initializes the object implementing the interface.
  76  *
  77  * The object must be initialized before any real use after initial
  78  * construction, either with this function or g_async_initable_init_async().
  79  *
  80  * Implementations may also support cancellation. If @cancellable is not %NULL,
  81  * then initialization can be cancelled by triggering the cancellable object
  82  * from another thread. If the operation was cancelled, the error
  83  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL and
  84  * the object doesn't support cancellable initialization the error
  85  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
  86  *
  87  * If the object is not initialized, or initialization returns with an
  88  * error, then all operations on the object except g_object_ref() and
  89  * g_object_unref() are considered to be invalid, and have undefined
  90  * behaviour. See the <xref linkend="ginitable"/> section introduction
  91  * for more details.
  92  *
  93  * Implementations of this method must be idempotent, i.e. multiple calls
  94  * to this function with the same argument should return the same results.
  95  * Only the first call initializes the object, further calls return the result
  96  * of the first call. This is so that it's safe to implement the singleton
  97  * pattern in the GObject constructor function.
  98  *
  99  * Returns: %TRUE if successful. If an error has occurred, this function will
 100  *     return %FALSE and set @error appropriately if present.
 101  *
 102  * Since: 2.22
 103  */
 104 gboolean
 105 g_initable_init (GInitable     *initable,
 106                  GCancellable  *cancellable,
 107                  GError       **error)
 108 {
 109   GInitableIface *iface;
 110
 111   g_return_val_if_fail (G_IS_INITABLE (initable), FALSE);
 112
 113   iface = G_INITABLE_GET_IFACE (initable);
 114
 115   return (* iface->init) (initable, cancellable, error);
 116 }
 117
 118 /**
 119  * g_initable_new:
 120  * @object_type: a #GType supporting #GInitable.
 121  * @cancellable: optional #GCancellable object, %NULL to ignore.
 122  * @error: a #GError location to store the error occurring, or %NULL to
 123  *    ignore.
 124  * @first_property_name: (allow-none): the name of the first property, or %NULL if no
 125  *     properties
 126  * @...:  the value if the first property, followed by and other property
 127  *    value pairs, and ended by %NULL.
 128  *
 129  * Helper function for constructing #GInitable object. This is
 130  * similar to g_object_new() but also initializes the object
 131  * and returns %NULL, setting an error on failure.
 132  *
 133  * Return value: (type GObject.Object) (transfer full): a newly allocated
 134  *      #GObject, or %NULL on error
 135  *
 136  * Since: 2.22
 137  */
 138 gpointer
 139 g_initable_new (GType          object_type,
 140                 GCancellable  *cancellable,
 141                 GError       **error,
 142                 const gchar   *first_property_name,
 143                 ...)
 144 {
 145   GObject *object;
 146   va_list var_args;
 147
 148   va_start (var_args, first_property_name);
 149   object = g_initable_new_valist (object_type,
 150                                   first_property_name, var_args,
 151                                   cancellable, error);
 152   va_end (var_args);
 153
 154   return object;
 155 }
 156
 157 /**
 158  * g_initable_newv:
 159  * @object_type: a #GType supporting #GInitable.
 160  * @n_parameters: the number of parameters in @parameters
 161  * @parameters: (array length=n_parameters): the parameters to use to construct the object
 162  * @cancellable: optional #GCancellable object, %NULL to ignore.
 163  * @error: a #GError location to store the error occurring, or %NULL to
 164  *     ignore.
 165  *
 166  * Helper function for constructing #GInitable object. This is
 167  * similar to g_object_newv() but also initializes the object
 168  * and returns %NULL, setting an error on failure.
 169  *
 170  * Return value: (type GObject.Object) (transfer full): a newly allocated
 171  *      #GObject, or %NULL on error
 172  *
 173  * Since: 2.22
 174  */
 175 gpointer
 176 g_initable_newv (GType          object_type,
 177                  guint          n_parameters,
 178                  GParameter    *parameters,
 179                  GCancellable  *cancellable,
 180                  GError       **error)
 181 {
 182   GObject *obj;
 183
 184   g_return_val_if_fail (G_TYPE_IS_INITABLE (object_type), NULL);
 185
 186   obj = g_object_newv (object_type, n_parameters, parameters);
 187
 188   if (!g_initable_init (G_INITABLE (obj), cancellable, error))
 189     {
 190       g_object_unref (obj);
 191       return NULL;
 192     }
 193
 194   return (gpointer)obj;
 195 }
 196
 197 /**
 198  * g_initable_new_valist:
 199  * @object_type: a #GType supporting #GInitable.
 200  * @first_property_name: the name of the first property, followed by
 201  * the value, and other property value pairs, and ended by %NULL.
 202  * @var_args: The var args list generated from @first_property_name.
 203  * @cancellable: optional #GCancellable object, %NULL to ignore.
 204  * @error: a #GError location to store the error occurring, or %NULL to
 205  *     ignore.
 206  *
 207  * Helper function for constructing #GInitable object. This is
 208  * similar to g_object_new_valist() but also initializes the object
 209  * and returns %NULL, setting an error on failure.
 210  *
 211  * Return value: (type GObject.Object) (transfer full): a newly allocated
 212  *      #GObject, or %NULL on error
 213  *
 214  * Since: 2.22
 215  */
 216 GObject*
 217 g_initable_new_valist (GType          object_type,
 218                        const gchar   *first_property_name,
 219                        va_list        var_args,
 220                        GCancellable  *cancellable,
 221                        GError       **error)
 222 {
 223   GObject *obj;
 224
 225   g_return_val_if_fail (G_TYPE_IS_INITABLE (object_type), NULL);
 226
 227   obj = g_object_new_valist (object_type,
 228                              first_property_name,
 229                              var_args);
 230
 231   if (!g_initable_init (G_INITABLE (obj), cancellable, error))
 232     {
 233       g_object_unref (obj);
 234       return NULL;
 235     }
 236
 237   return obj;
 238 }