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 2.1 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  * |[<!-- language="C" -->
  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 [I/O priority][io-priority] of the operation
 160  * @cancellable: optional #GCancellable object, %NULL to ignore.
 161  * @callback: a #GAsyncReadyCallback to call when the request is satisfied
 162  * @user_data: the data to pass to callback function
 163  *
 164  * Starts asynchronous initialization of the object implementing the
 165  * interface. This must be done before any real use of the object after
 166  * initial construction. If the object also implements #GInitable you can
 167  * optionally call g_initable_init() instead.
 168  *
 169  * This method is intended for language bindings. If writing in C,
 170  * g_async_initable_new_async() should typically be used instead.
 171  *
 172  * When the initialization is finished, @callback will be called. You can
 173  * then call g_async_initable_init_finish() to get the result of the
 174  * initialization.
 175  *
 176  * Implementations may also support cancellation. If @cancellable is not
 177  * %NULL, then initialization can be cancelled by triggering the cancellable
 178  * object from another thread. If the operation was cancelled, the error
 179  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL, and
 180  * the object doesn't support cancellable initialization, the error
 181  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
 182  *
 183  * As with #GInitable, if the object is not initialized, or initialization
 184  * returns with an error, then all operations on the object except
 185  * g_object_ref() and g_object_unref() are considered to be invalid, and
 186  * have undefined behaviour. They will often fail with g_critical() or
 187  * g_warning(), but this must not be relied on.
 188  *
 189  * Callers should not assume that a class which implements #GAsyncInitable can
 190  * be initialized multiple times; for more information, see g_initable_init().
 191  * If a class explicitly supports being initialized multiple times,
 192  * implementation requires yielding all subsequent calls to init_async() on the
 193  * results of the first call.
 194  *
 195  * For classes that also support the #GInitable interface, the default
 196  * implementation of this method will run the g_initable_init() function
 197  * in a thread, so if you want to support asynchronous initialization via
 198  * threads, just implement the #GAsyncInitable interface without overriding
 199  * any interface methods.
 200  *
 201  * Since: 2.22
 202  */
 203 void
 204 g_async_initable_init_async (GAsyncInitable      *initable,
 205                              int                  io_priority,
 206                              GCancellable        *cancellable,
 207                              GAsyncReadyCallback  callback,
 208                              gpointer             user_data)
 209 {
 210   GAsyncInitableIface *iface;
 211
 212   g_return_if_fail (G_IS_ASYNC_INITABLE (initable));
 213
 214   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 215
 216   (* iface->init_async) (initable, io_priority, cancellable, callback, user_data);
 217 }
 218
 219 /**
 220  * g_async_initable_init_finish:
 221  * @initable: a #GAsyncInitable.
 222  * @res: a #GAsyncResult.
 223  * @error: a #GError location to store the error occurring, or %NULL to
 224  * ignore.
 225  *
 226  * Finishes asynchronous initialization and returns the result.
 227  * See g_async_initable_init_async().
 228  *
 229  * Returns: %TRUE if successful. If an error has occurred, this function
 230  * will return %FALSE and set @error appropriately if present.
 231  *
 232  * Since: 2.22
 233  */
 234 gboolean
 235 g_async_initable_init_finish (GAsyncInitable  *initable,
 236                               GAsyncResult    *res,
 237                               GError         **error)
 238 {
 239   GAsyncInitableIface *iface;
 240
 241   g_return_val_if_fail (G_IS_ASYNC_INITABLE (initable), FALSE);
 242   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
 243
 244   if (g_async_result_legacy_propagate_error (res, error))
 245     return FALSE;
 246
 247   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 248
 249   return (* iface->init_finish) (initable, res, error);
 250 }
 251
 252 static void
 253 async_init_thread (GTask        *task,
 254                    gpointer      source_object,
 255                    gpointer      task_data,
 256                    GCancellable *cancellable)
 257 {
 258   GError *error = NULL;
 259
 260   if (g_initable_init (G_INITABLE (source_object), cancellable, &error))
 261     g_task_return_boolean (task, TRUE);
 262   else
 263     g_task_return_error (task, error);
 264 }
 265
 266 static void
 267 g_async_initable_real_init_async (GAsyncInitable      *initable,
 268                                   int                  io_priority,
 269                                   GCancellable        *cancellable,
 270                                   GAsyncReadyCallback  callback,
 271                                   gpointer             user_data)
 272 {
 273   GTask *task;
 274
 275   g_return_if_fail (G_IS_INITABLE (initable));
 276
 277   task = g_task_new (initable, cancellable, callback, user_data);
 278   g_task_set_source_tag (task, g_async_initable_real_init_async);
 279   g_task_set_priority (task, io_priority);
 280   g_task_run_in_thread (task, async_init_thread);
 281   g_object_unref (task);
 282 }
 283
 284 static gboolean
 285 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 286                                    GAsyncResult    *res,
 287                                    GError         **error)
 288 {
 289   /* For backward compatibility we have to process GSimpleAsyncResults
 290    * even though g_async_initable_real_init_async doesn't generate
 291    * them any more.
 292    */
 293   G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 294   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 295     {
 296       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 297       if (g_simple_async_result_propagate_error (simple, error))
 298         return FALSE;
 299       else
 300         return TRUE;
 301     }
 302   G_GNUC_END_IGNORE_DEPRECATIONS
 303
 304   g_return_val_if_fail (g_task_is_valid (res, initable), FALSE);
 305
 306   return g_task_propagate_boolean (G_TASK (res), error);
 307 }
 308
 309 /**
 310  * g_async_initable_new_async:
 311  * @object_type: a #GType supporting #GAsyncInitable.
 312  * @io_priority: the [I/O priority][io-priority] of the operation
 313  * @cancellable: optional #GCancellable object, %NULL to ignore.
 314  * @callback: a #GAsyncReadyCallback to call when the initialization is
 315  *     finished
 316  * @user_data: the data to pass to callback function
 317  * @first_property_name: (nullable): the name of the first property, or %NULL if no
 318  *     properties
 319  * @...:  the value of the first property, followed by other property
 320  *    value pairs, and ended by %NULL.
 321  *
 322  * Helper function for constructing #GAsyncInitable object. This is
 323  * similar to g_object_new() but also initializes the object asynchronously.
 324  *
 325  * When the initialization is finished, @callback will be called. You can
 326  * then call g_async_initable_new_finish() to get the new object and check
 327  * for any errors.
 328  *
 329  * Since: 2.22
 330  */
 331 void
 332 g_async_initable_new_async (GType                object_type,
 333                             int                  io_priority,
 334                             GCancellable        *cancellable,
 335                             GAsyncReadyCallback  callback,
 336                             gpointer             user_data,
 337                             const gchar         *first_property_name,
 338                             ...)
 339 {
 340   va_list var_args;
 341
 342   va_start (var_args, first_property_name);
 343   g_async_initable_new_valist_async (object_type,
 344                                      first_property_name, var_args,
 345                                      io_priority, cancellable,
 346                                      callback, user_data);
 347   va_end (var_args);
 348 }
 349
 350 /**
 351  * g_async_initable_newv_async:
 352  * @object_type: a #GType supporting #GAsyncInitable.
 353  * @n_parameters: the number of parameters in @parameters
 354  * @parameters: the parameters to use to construct the object
 355  * @io_priority: the [I/O priority][io-priority] of the operation
 356  * @cancellable: optional #GCancellable object, %NULL to ignore.
 357  * @callback: a #GAsyncReadyCallback to call when the initialization is
 358  *     finished
 359  * @user_data: the data to pass to callback function
 360  *
 361  * Helper function for constructing #GAsyncInitable object. This is
 362  * similar to g_object_newv() but also initializes the object asynchronously.
 363  *
 364  * When the initialization is finished, @callback will be called. You can
 365  * then call g_async_initable_new_finish() to get the new object and check
 366  * for any errors.
 367  *
 368  * Since: 2.22
 369  * Deprecated: 2.54: Use g_object_new_with_properties() and
 370  * g_async_initable_init_async() instead. See #GParameter for more information.
 371  */
 372 void
 373 g_async_initable_newv_async (GType                object_type,
 374                              guint                n_parameters,
 375                              GParameter          *parameters,
 376                              int                  io_priority,
 377                              GCancellable        *cancellable,
 378                              GAsyncReadyCallback  callback,
 379                              gpointer             user_data)
 380 {
 381   GObject *obj;
 382
 383   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 384
 385 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 386   obj = g_object_newv (object_type, n_parameters, parameters);
 387 G_GNUC_END_IGNORE_DEPRECATIONS
 388
 389   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 390                                io_priority, cancellable,
 391                                callback, user_data);
 392   g_object_unref (obj); /* Passed ownership to async call */
 393 }
 394
 395 /**
 396  * g_async_initable_new_valist_async:
 397  * @object_type: a #GType supporting #GAsyncInitable.
 398  * @first_property_name: the name of the first property, followed by
 399  * the value, and other property value pairs, and ended by %NULL.
 400  * @var_args: The var args list generated from @first_property_name.
 401  * @io_priority: the [I/O priority][io-priority] of the operation
 402  * @cancellable: optional #GCancellable object, %NULL to ignore.
 403  * @callback: a #GAsyncReadyCallback to call when the initialization is
 404  *     finished
 405  * @user_data: the data to pass to callback function
 406  *
 407  * Helper function for constructing #GAsyncInitable object. This is
 408  * similar to g_object_new_valist() but also initializes the object
 409  * asynchronously.
 410  *
 411  * When the initialization is finished, @callback will be called. You can
 412  * then call g_async_initable_new_finish() to get the new object and check
 413  * for any errors.
 414  *
 415  * Since: 2.22
 416  */
 417 void
 418 g_async_initable_new_valist_async (GType                object_type,
 419                                    const gchar         *first_property_name,
 420                                    va_list              var_args,
 421                                    int                  io_priority,
 422                                    GCancellable        *cancellable,
 423                                    GAsyncReadyCallback  callback,
 424                                    gpointer             user_data)
 425 {
 426   GObject *obj;
 427
 428   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 429
 430   obj = g_object_new_valist (object_type,
 431                              first_property_name,
 432                              var_args);
 433
 434   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 435                                io_priority, cancellable,
 436                                callback, user_data);
 437   g_object_unref (obj); /* Passed ownership to async call */
 438 }
 439
 440 /**
 441  * g_async_initable_new_finish:
 442  * @initable: the #GAsyncInitable from the callback
 443  * @res: the #GAsyncResult from the callback
 444  * @error: return location for errors, or %NULL to ignore
 445  *
 446  * Finishes the async construction for the various g_async_initable_new
 447  * calls, returning the created object or %NULL on error.
 448  *
 449  * Returns: (type GObject.Object) (transfer full): a newly created #GObject,
 450  *      or %NULL on error. Free with g_object_unref().
 451  *
 452  * Since: 2.22
 453  */
 454 GObject *
 455 g_async_initable_new_finish (GAsyncInitable  *initable,
 456                              GAsyncResult    *res,
 457                              GError         **error)
 458 {
 459   if (g_async_initable_init_finish (initable, res, error))
 460     return g_object_ref (G_OBJECT (initable));
 461   else
 462     return NULL;
 463 }