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, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Alexander Larsson <alexl@redhat.com>
  19  */
  20
  21 #include "config.h"
  22 #include "gasyncinitable.h"
  23 #include "gasyncresult.h"
  24 #include "gsimpleasyncresult.h"
  25 #include "gtask.h"
  26 #include "glibintl.h"
  27
  28
  29 /**
  30  * SECTION:gasyncinitable
  31  * @short_description: Asynchronously failable object initialization interface
  32  * @include: gio/gio.h
  33  * @see_also: #GInitable
  34  *
  35  * This is the asynchronous version of #GInitable; it behaves the same
  36  * in all ways except that initialization is asynchronous. For more details
  37  * see the descriptions on #GInitable.
  38  *
  39  * A class may implement both the #GInitable and #GAsyncInitable interfaces.
  40  *
  41  * Users of objects implementing this are not intended to use the interface
  42  * method directly; instead it will be used automatically in various ways.
  43  * For C applications you generally just call g_async_initable_new_async()
  44  * directly, or indirectly via a foo_thing_new_async() wrapper. This will call
  45  * g_async_initable_init_async() under the cover, calling back with %NULL and
  46  * a set %GError on failure.
  47  *
  48  * A typical implementation might look something like this:
  49  *
  50  * |[
  51  * enum {
  52  *    NOT_INITIALIZED,
  53  *    INITIALIZING,
  54  *    INITIALIZED
  55  * };
  56  *
  57  * static void
  58  * _foo_ready_cb (Foo *self)
  59  * {
  60  *   GList *l;
  61  *
  62  *   self->priv->state = INITIALIZED;
  63  *
  64  *   for (l = self->priv->init_results; l != NULL; l = l->next)
  65  *     {
  66  *       GTask *task = l->data;
  67  *
  68  *       if (self->priv->success)
  69  *         g_task_return_boolean (task, TRUE);
  70  *       else
  71  *         g_task_return_new_error (task, ...);
  72  *       g_object_unref (task);
  73  *     }
  74  *
  75  *   g_list_free (self->priv->init_results);
  76  *   self->priv->init_results = NULL;
  77  * }
  78  *
  79  * static void
  80  * foo_init_async (GAsyncInitable       *initable,
  81  *                 int                   io_priority,
  82  *                 GCancellable         *cancellable,
  83  *                 GAsyncReadyCallback   callback,
  84  *                 gpointer              user_data)
  85  * {
  86  *   Foo *self = FOO (initable);
  87  *   GTask *task;
  88  *
  89  *   task = g_task_new (initable, cancellable, callback, user_data);
  90  *
  91  *   switch (self->priv->state)
  92  *     {
  93  *       case NOT_INITIALIZED:
  94  *         _foo_get_ready (self);
  95  *         self->priv->init_results = g_list_append (self->priv->init_results,
  96  *                                                   task);
  97  *         self->priv->state = INITIALIZING;
  98  *         break;
  99  *       case INITIALIZING:
 100  *         self->priv->init_results = g_list_append (self->priv->init_results,
 101  *                                                   task);
 102  *         break;
 103  *       case INITIALIZED:
 104  *         if (!self->priv->success)
 105  *           g_task_return_new_error (task, ...);
 106  *         else
 107  *           g_task_return_boolean (task, TRUE);
 108  *         g_object_unref (task);
 109  *         break;
 110  *     }
 111  * }
 112  *
 113  * static gboolean
 114  * foo_init_finish (GAsyncInitable       *initable,
 115  *                  GAsyncResult         *result,
 116  *                  GError              **error)
 117  * {
 118  *   g_return_val_if_fail (g_task_is_valid (result, initable), FALSE);
 119  *
 120  *   return g_task_propagate_boolean (G_TASK (result), error);
 121  * }
 122  *
 123  * static void
 124  * foo_async_initable_iface_init (gpointer g_iface,
 125  *                                gpointer data)
 126  * {
 127  *   GAsyncInitableIface *iface = g_iface;
 128  *
 129  *   iface->init_async = foo_init_async;
 130  *   iface->init_finish = foo_init_finish;
 131  * }
 132  * ]|
 133  */
 134
 135 static void     g_async_initable_real_init_async  (GAsyncInitable       *initable,
 136                                                    int                   io_priority,
 137                                                    GCancellable         *cancellable,
 138                                                    GAsyncReadyCallback   callback,
 139                                                    gpointer              user_data);
 140 static gboolean g_async_initable_real_init_finish (GAsyncInitable       *initable,
 141                                                    GAsyncResult         *res,
 142                                                    GError              **error);
 143
 144
 145 typedef GAsyncInitableIface GAsyncInitableInterface;
 146 G_DEFINE_INTERFACE (GAsyncInitable, g_async_initable, G_TYPE_OBJECT)
 147
 148
 149 static void
 150 g_async_initable_default_init (GAsyncInitableInterface *iface)
 151 {
 152   iface->init_async = g_async_initable_real_init_async;
 153   iface->init_finish = g_async_initable_real_init_finish;
 154 }
 155
 156 /**
 157  * g_async_initable_init_async:
 158  * @initable: a #GAsyncInitable.
 159  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 160  *     of the operation.
 161  * @cancellable: optional #GCancellable object, %NULL to ignore.
 162  * @callback: a #GAsyncReadyCallback to call when the request is satisfied
 163  * @user_data: the data to pass to callback function
 164  *
 165  * Starts asynchronous initialization of the object implementing the
 166  * interface. This must be done before any real use of the object after
 167  * initial construction. If the object also implements #GInitable you can
 168  * optionally call g_initable_init() instead.
 169  *
 170  * When the initialization is finished, @callback will be called. You can
 171  * then call g_async_initable_init_finish() to get the result of the
 172  * initialization.
 173  *
 174  * Implementations may also support cancellation. If @cancellable is not
 175  * %NULL, then initialization can be cancelled by triggering the cancellable
 176  * object from another thread. If the operation was cancelled, the error
 177  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL, and
 178  * the object doesn't support cancellable initialization, the error
 179  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
 180  *
 181  * As with #GInitable, if the object is not initialized, or initialization
 182  * returns with an error, then all operations on the object except
 183  * g_object_ref() and g_object_unref() are considered to be invalid, and
 184  * have undefined behaviour. They will often fail with g_critical() or
 185  * g_warning(), but this must not be relied on.
 186  *
 187  * Implementations of this method must be idempotent: i.e. multiple calls
 188  * to this function with the same argument should return the same results.
 189  * Only the first call initializes the object; further calls return the result
 190  * of the first call. This is so that it's safe to implement the singleton
 191  * pattern in the GObject constructor function.
 192  *
 193  * For classes that also support the #GInitable interface, the default
 194  * implementation of this method will run the g_initable_init() function
 195  * in a thread, so if you want to support asynchronous initialization via
 196  * threads, just implement the #GAsyncInitable interface without overriding
 197  * any interface methods.
 198  *
 199  * Since: 2.22
 200  */
 201 void
 202 g_async_initable_init_async (GAsyncInitable      *initable,
 203                              int                  io_priority,
 204                              GCancellable        *cancellable,
 205                              GAsyncReadyCallback  callback,
 206                              gpointer             user_data)
 207 {
 208   GAsyncInitableIface *iface;
 209
 210   g_return_if_fail (G_IS_ASYNC_INITABLE (initable));
 211
 212   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 213
 214   (* iface->init_async) (initable, io_priority, cancellable, callback, user_data);
 215 }
 216
 217 /**
 218  * g_async_initable_init_finish:
 219  * @initable: a #GAsyncInitable.
 220  * @res: a #GAsyncResult.
 221  * @error: a #GError location to store the error occurring, or %NULL to
 222  * ignore.
 223  *
 224  * Finishes asynchronous initialization and returns the result.
 225  * See g_async_initable_init_async().
 226  *
 227  * Returns: %TRUE if successful. If an error has occurred, this function
 228  * will return %FALSE and set @error appropriately if present.
 229  *
 230  * Since: 2.22
 231  */
 232 gboolean
 233 g_async_initable_init_finish (GAsyncInitable  *initable,
 234                               GAsyncResult    *res,
 235                               GError         **error)
 236 {
 237   GAsyncInitableIface *iface;
 238
 239   g_return_val_if_fail (G_IS_ASYNC_INITABLE (initable), FALSE);
 240   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
 241
 242   if (g_async_result_legacy_propagate_error (res, error))
 243     return FALSE;
 244
 245   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 246
 247   return (* iface->init_finish) (initable, res, error);
 248 }
 249
 250 static void
 251 async_init_thread (GTask        *task,
 252                    gpointer      source_object,
 253                    gpointer      task_data,
 254                    GCancellable *cancellable)
 255 {
 256   GError *error = NULL;
 257
 258   if (g_initable_init (G_INITABLE (source_object), cancellable, &error))
 259     g_task_return_boolean (task, TRUE);
 260   else
 261     g_task_return_error (task, error);
 262 }
 263
 264 static void
 265 g_async_initable_real_init_async (GAsyncInitable      *initable,
 266                                   int                  io_priority,
 267                                   GCancellable        *cancellable,
 268                                   GAsyncReadyCallback  callback,
 269                                   gpointer             user_data)
 270 {
 271   GTask *task;
 272
 273   g_return_if_fail (G_IS_INITABLE (initable));
 274
 275   task = g_task_new (initable, cancellable, callback, user_data);
 276   g_task_set_priority (task, io_priority);
 277   g_task_run_in_thread (task, async_init_thread);
 278   g_object_unref (task);
 279 }
 280
 281 static gboolean
 282 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 283                                    GAsyncResult    *res,
 284                                    GError         **error)
 285 {
 286   /* For backward compatibility we have to process GSimpleAsyncResults
 287    * even though g_async_initable_real_init_async doesn't generate
 288    * them any more.
 289    */
 290   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 291     {
 292       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 293       if (g_simple_async_result_propagate_error (simple, error))
 294         return FALSE;
 295       else
 296         return TRUE;
 297     }
 298
 299   g_return_val_if_fail (g_task_is_valid (res, initable), FALSE);
 300
 301   return g_task_propagate_boolean (G_TASK (res), error);
 302 }
 303
 304 /**
 305  * g_async_initable_new_async:
 306  * @object_type: a #GType supporting #GAsyncInitable.
 307  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 308  *     of the operation.
 309  * @cancellable: optional #GCancellable object, %NULL to ignore.
 310  * @callback: a #GAsyncReadyCallback to call when the initialization is
 311  *     finished
 312  * @user_data: the data to pass to callback function
 313  * @first_property_name: (allow-none): the name of the first property, or %NULL if no
 314  *     properties
 315  * @...:  the value of the first property, followed by other property
 316  *    value pairs, and ended by %NULL.
 317  *
 318  * Helper function for constructing #GAsyncInitable object. This is
 319  * similar to g_object_new() but also initializes the object asynchronously.
 320  *
 321  * When the initialization is finished, @callback will be called. You can
 322  * then call g_async_initable_new_finish() to get the new object and check
 323  * for any errors.
 324  *
 325  * Since: 2.22
 326  */
 327 void
 328 g_async_initable_new_async (GType                object_type,
 329                             int                  io_priority,
 330                             GCancellable        *cancellable,
 331                             GAsyncReadyCallback  callback,
 332                             gpointer             user_data,
 333                             const gchar         *first_property_name,
 334                             ...)
 335 {
 336   va_list var_args;
 337
 338   va_start (var_args, first_property_name);
 339   g_async_initable_new_valist_async (object_type,
 340                                      first_property_name, var_args,
 341                                      io_priority, cancellable,
 342                                      callback, user_data);
 343   va_end (var_args);
 344 }
 345
 346 /**
 347  * g_async_initable_newv_async:
 348  * @object_type: a #GType supporting #GAsyncInitable.
 349  * @n_parameters: the number of parameters in @parameters
 350  * @parameters: the parameters to use to construct the object
 351  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 352  *     of the operation.
 353  * @cancellable: optional #GCancellable object, %NULL to ignore.
 354  * @callback: a #GAsyncReadyCallback to call when the initialization is
 355  *     finished
 356  * @user_data: the data to pass to callback function
 357  *
 358  * Helper function for constructing #GAsyncInitable object. This is
 359  * similar to g_object_newv() but also initializes the object asynchronously.
 360  *
 361  * When the initialization is finished, @callback will be called. You can
 362  * then call g_async_initable_new_finish() to get the new object and check
 363  * for any errors.
 364  *
 365  * Since: 2.22
 366  */
 367 void
 368 g_async_initable_newv_async (GType                object_type,
 369                              guint                n_parameters,
 370                              GParameter          *parameters,
 371                              int                  io_priority,
 372                              GCancellable        *cancellable,
 373                              GAsyncReadyCallback  callback,
 374                              gpointer             user_data)
 375 {
 376   GObject *obj;
 377
 378   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 379
 380   obj = g_object_newv (object_type, n_parameters, parameters);
 381
 382   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 383                                io_priority, cancellable,
 384                                callback, user_data);
 385 }
 386
 387 /**
 388  * g_async_initable_new_valist_async:
 389  * @object_type: a #GType supporting #GAsyncInitable.
 390  * @first_property_name: the name of the first property, followed by
 391  * the value, and other property value pairs, and ended by %NULL.
 392  * @var_args: The var args list generated from @first_property_name.
 393  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 394  *     of the operation.
 395  * @cancellable: optional #GCancellable object, %NULL to ignore.
 396  * @callback: a #GAsyncReadyCallback to call when the initialization is
 397  *     finished
 398  * @user_data: the data to pass to callback function
 399  *
 400  * Helper function for constructing #GAsyncInitable object. This is
 401  * similar to g_object_new_valist() but also initializes the object
 402  * asynchronously.
 403  *
 404  * When the initialization is finished, @callback will be called. You can
 405  * then call g_async_initable_new_finish() to get the new object and check
 406  * for any errors.
 407  *
 408  * Since: 2.22
 409  */
 410 void
 411 g_async_initable_new_valist_async (GType                object_type,
 412                                    const gchar         *first_property_name,
 413                                    va_list              var_args,
 414                                    int                  io_priority,
 415                                    GCancellable        *cancellable,
 416                                    GAsyncReadyCallback  callback,
 417                                    gpointer             user_data)
 418 {
 419   GObject *obj;
 420
 421   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 422
 423   obj = g_object_new_valist (object_type,
 424                              first_property_name,
 425                              var_args);
 426
 427   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 428                                io_priority, cancellable,
 429                                callback, user_data);
 430   g_object_unref (obj); /* Passed ownership to async call */
 431 }
 432
 433 /**
 434  * g_async_initable_new_finish:
 435  * @initable: the #GAsyncInitable from the callback
 436  * @res: the #GAsyncResult from the callback
 437  * @error: return location for errors, or %NULL to ignore
 438  *
 439  * Finishes the async construction for the various g_async_initable_new
 440  * calls, returning the created object or %NULL on error.
 441  *
 442  * Returns: (type GObject.Object) (transfer full): a newly created #GObject,
 443  *      or %NULL on error. Free with g_object_unref().
 444  *
 445  * Since: 2.22
 446  */
 447 GObject *
 448 g_async_initable_new_finish (GAsyncInitable  *initable,
 449                              GAsyncResult    *res,
 450                              GError         **error)
 451 {
 452   if (g_async_initable_init_finish (initable, res, error))
 453     return g_object_ref (initable);
 454   else
 455     return NULL;
 456 }