gio/gasyncinitable.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 "gasyncinitable.h"
  25 #include "gasyncresult.h"
  26 #include "gsimpleasyncresult.h"
  27 #include "glibintl.h"
  28
  29
  30 /**
  31  * SECTION:gasyncinitable
  32  * @short_description: Asynchronously failable object initialization interface
  33  * @include: gio/gio.h
  34  * @see_also: #GInitable
  35  *
  36  * This is the asynchronous version of #GInitable; it behaves the same
  37  * in all ways except that initialization is asynchronous. For more details
  38  * see the descriptions on #GInitable.
  39  *
  40  * A class may implement both the #GInitable and #GAsyncInitable interfaces.
  41  *
  42  * Users of objects implementing this are not intended to use the interface
  43  * method directly; instead it will be used automatically in various ways.
  44  * For C applications you generally just call g_async_initable_new_async()
  45  * directly, or indirectly via a foo_thing_new_async() wrapper. This will call
  46  * g_async_initable_init_async() under the cover, calling back with %NULL and
  47  * a set %GError on failure.
  48  */
  49
  50 static void     g_async_initable_real_init_async  (GAsyncInitable       *initable,
  51                                                    int                   io_priority,
  52                                                    GCancellable         *cancellable,
  53                                                    GAsyncReadyCallback   callback,
  54                                                    gpointer              user_data);
  55 static gboolean g_async_initable_real_init_finish (GAsyncInitable       *initable,
  56                                                    GAsyncResult         *res,
  57                                                    GError              **error);
  58
  59
  60 typedef GAsyncInitableIface GAsyncInitableInterface;
  61 G_DEFINE_INTERFACE (GAsyncInitable, g_async_initable, G_TYPE_OBJECT)
  62
  63
  64 static void
  65 g_async_initable_default_init (GAsyncInitableInterface *iface)
  66 {
  67   iface->init_async = g_async_initable_real_init_async;
  68   iface->init_finish = g_async_initable_real_init_finish;
  69 }
  70
  71 /**
  72  * g_async_initable_init_async:
  73  * @initable: a #GAsyncInitable.
  74  * @io_priority: the <link linkend="io-priority">I/O priority</link>
  75  *     of the operation.
  76  * @cancellable: optional #GCancellable object, %NULL to ignore.
  77  * @callback: a #GAsyncReadyCallback to call when the request is satisfied
  78  * @user_data: the data to pass to callback function
  79  *
  80  * Starts asynchronous initialization of the object implementing the
  81  * interface. This must be done before any real use of the object after
  82  * initial construction. If the object also implements #GInitable you can
  83  * optionally call g_initable_init() instead.
  84  *
  85  * When the initialization is finished, @callback will be called. You can
  86  * then call g_async_initable_init_finish() to get the result of the
  87  * initialization.
  88  *
  89  * Implementations may also support cancellation. If @cancellable is not
  90  * %NULL, then initialization can be cancelled by triggering the cancellable
  91  * object from another thread. If the operation was cancelled, the error
  92  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL, and
  93  * the object doesn't support cancellable initialization, the error
  94  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
  95  *
  96  * If this function is not called, or returns with an error, then all
  97  * operations on the object should fail, generally returning the
  98  * error %G_IO_ERROR_NOT_INITIALIZED.
  99  *
 100  * Implementations of this method must be idempotent: i.e. multiple calls
 101  * to this function with the same argument should return the same results.
 102  * Only the first call initializes the object; further calls return the result
 103  * of the first call. This is so that it's safe to implement the singleton
 104  * pattern in the GObject constructor function.
 105  *
 106  * For classes that also support the #GInitable interface, the default
 107  * implementation of this method will run the g_initable_init() function
 108  * in a thread, so if you want to support asynchronous initialization via
 109  * threads, just implement the #GAsyncInitable interface without overriding
 110  * any interface methods.
 111  *
 112  * Since: 2.22
 113  */
 114 void
 115 g_async_initable_init_async (GAsyncInitable      *initable,
 116                              int                  io_priority,
 117                              GCancellable        *cancellable,
 118                              GAsyncReadyCallback  callback,
 119                              gpointer             user_data)
 120 {
 121   GAsyncInitableIface *iface;
 122
 123   g_return_if_fail (G_IS_ASYNC_INITABLE (initable));
 124
 125   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 126
 127   (* iface->init_async) (initable, io_priority, cancellable, callback, user_data);
 128 }
 129
 130 /**
 131  * g_async_initable_init_finish:
 132  * @initable: a #GAsyncInitable.
 133  * @res: a #GAsyncResult.
 134  * @error: a #GError location to store the error occuring, or %NULL to
 135  * ignore.
 136  *
 137  * Finishes asynchronous initialization and returns the result.
 138  * See g_async_initable_init_async().
 139  *
 140  * Returns: %TRUE if successful. If an error has occurred, this function
 141  * will return %FALSE and set @error appropriately if present.
 142  *
 143  * Since: 2.22
 144  */
 145 gboolean
 146 g_async_initable_init_finish (GAsyncInitable  *initable,
 147                               GAsyncResult    *res,
 148                               GError         **error)
 149 {
 150   GAsyncInitableIface *iface;
 151
 152   g_return_val_if_fail (G_IS_ASYNC_INITABLE (initable), FALSE);
 153   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
 154
 155   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 156     {
 157       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 158       if (g_simple_async_result_propagate_error (simple, error))
 159         return FALSE;
 160     }
 161
 162   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 163
 164   return (* iface->init_finish) (initable, res, error);
 165 }
 166
 167 static void
 168 async_init_thread (GSimpleAsyncResult *res,
 169                    GObject            *object,
 170                    GCancellable       *cancellable)
 171 {
 172   GError *error = NULL;
 173
 174   if (!g_initable_init (G_INITABLE (object), cancellable, &error))
 175     {
 176       g_simple_async_result_set_from_error (res, error);
 177       g_error_free (error);
 178     }
 179 }
 180
 181 static void
 182 g_async_initable_real_init_async (GAsyncInitable      *initable,
 183                                   int                  io_priority,
 184                                   GCancellable        *cancellable,
 185                                   GAsyncReadyCallback  callback,
 186                                   gpointer             user_data)
 187 {
 188   GSimpleAsyncResult *res;
 189
 190   g_return_if_fail (G_IS_INITABLE (initable));
 191
 192   res = g_simple_async_result_new (G_OBJECT (initable), callback, user_data,
 193                                    g_async_initable_real_init_async);
 194   g_simple_async_result_run_in_thread (res, async_init_thread,
 195                                        io_priority, cancellable);
 196   g_object_unref (res);
 197 }
 198
 199 static gboolean
 200 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 201                                    GAsyncResult    *res,
 202                                    GError         **error)
 203 {
 204   return TRUE; /* Errors handled by base impl */
 205 }
 206
 207 /**
 208  * g_async_initable_new_async:
 209  * @object_type: a #GType supporting #GAsyncInitable.
 210  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 211  *     of the operation.
 212  * @cancellable: optional #GCancellable object, %NULL to ignore.
 213  * @callback: a #GAsyncReadyCallback to call when the initialization is
 214  *     finished
 215  * @user_data: the data to pass to callback function
 216  * @first_property_name: the name of the first property, or %NULL if no
 217  *     properties
 218  * @...:  the value of the first property, followed by other property
 219  *    value pairs, and ended by %NULL.
 220  *
 221  * Helper function for constructing #GAsyncInitiable object. This is
 222  * similar to g_object_new() but also initializes the object asynchronously.
 223  *
 224  * When the initialization is finished, @callback will be called. You can
 225  * then call g_async_initable_new_finish() to get the new object and check
 226  * for any errors.
 227  *
 228  * Since: 2.22
 229  */
 230 void
 231 g_async_initable_new_async (GType                object_type,
 232                             int                  io_priority,
 233                             GCancellable        *cancellable,
 234                             GAsyncReadyCallback  callback,
 235                             gpointer             user_data,
 236                             const gchar         *first_property_name,
 237                             ...)
 238 {
 239   va_list var_args;
 240
 241   va_start (var_args, first_property_name);
 242   g_async_initable_new_valist_async (object_type,
 243                                      first_property_name, var_args,
 244                                      io_priority, cancellable,
 245                                      callback, user_data);
 246   va_end (var_args);
 247 }
 248
 249 /**
 250  * g_async_initable_newv_async:
 251  * @object_type: a #GType supporting #GAsyncInitable.
 252  * @n_parameters: the number of parameters in @parameters
 253  * @parameters: the parameters to use to construct the object
 254  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 255  *     of the operation.
 256  * @cancellable: optional #GCancellable object, %NULL to ignore.
 257  * @callback: a #GAsyncReadyCallback to call when the initialization is
 258  *     finished
 259  * @user_data: the data to pass to callback function
 260  *
 261  * Helper function for constructing #GAsyncInitiable object. This is
 262  * similar to g_object_newv() but also initializes the object asynchronously.
 263  *
 264  * When the initialization is finished, @callback will be called. You can
 265  * then call g_async_initable_new_finish() to get the new object and check
 266  * for any errors.
 267  *
 268  * Since: 2.22
 269  */
 270 void
 271 g_async_initable_newv_async (GType                object_type,
 272                              guint                n_parameters,
 273                              GParameter          *parameters,
 274                              int                  io_priority,
 275                              GCancellable        *cancellable,
 276                              GAsyncReadyCallback  callback,
 277                              gpointer             user_data)
 278 {
 279   GObject *obj;
 280
 281   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 282
 283   obj = g_object_newv (object_type, n_parameters, parameters);
 284
 285   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 286                                io_priority, cancellable,
 287                                callback, user_data);
 288 }
 289
 290 /**
 291  * g_async_initable_new_valist_async:
 292  * @object_type: a #GType supporting #GAsyncInitable.
 293  * @first_property_name: the name of the first property, followed by
 294  * the value, and other property value pairs, and ended by %NULL.
 295  * @var_args: The var args list generated from @first_property_name.
 296  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 297  *     of the operation.
 298  * @cancellable: optional #GCancellable object, %NULL to ignore.
 299  * @callback: a #GAsyncReadyCallback to call when the initialization is
 300  *     finished
 301  * @user_data: the data to pass to callback function
 302  *
 303  * Helper function for constructing #GAsyncInitiable object. This is
 304  * similar to g_object_new_valist() but also initializes the object
 305  * asynchronously.
 306  *
 307  * When the initialization is finished, @callback will be called. You can
 308  * then call g_async_initable_new_finish() to get the new object and check
 309  * for any errors.
 310  *
 311  * Since: 2.22
 312  */
 313 void
 314 g_async_initable_new_valist_async (GType                object_type,
 315                                    const gchar         *first_property_name,
 316                                    va_list              var_args,
 317                                    int                  io_priority,
 318                                    GCancellable        *cancellable,
 319                                    GAsyncReadyCallback  callback,
 320                                    gpointer             user_data)
 321 {
 322   GObject *obj;
 323
 324   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 325
 326   obj = g_object_new_valist (object_type,
 327                              first_property_name,
 328                              var_args);
 329
 330   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 331                                io_priority, cancellable,
 332                                callback, user_data);
 333   g_object_unref (obj); /* Passed ownership to async call */
 334 }
 335
 336 /**
 337  * g_async_initable_new_finish:
 338  * @initable: the #GAsyncInitable from the callback
 339  * @res: the #GAsyncResult.from the callback
 340  * @error: a #GError location to store the error occuring, or %NULL to
 341  *     ignore.
 342  *
 343  * Finishes the async construction for the various g_async_initable_new calls,
 344  * returning the created object or %NULL on error.
 345  *
 346  * Returns: a newly created #GObject, or %NULL on error. Free with
 347  *     g_object_unref().
 348  *
 349  * Since: 2.22
 350  */
 351 GObject *
 352 g_async_initable_new_finish (GAsyncInitable  *initable,
 353                              GAsyncResult    *res,
 354                              GError         **error)
 355 {
 356   if (g_async_initable_init_finish (initable, res, error))
 357     return g_object_ref (initable);
 358   else
 359     return NULL;
 360 }