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 "gtask.h"
  28 #include "glibintl.h"
  29
  30
  31 /**
  32  * SECTION:gasyncinitable
  33  * @short_description: Asynchronously failable object initialization interface
  34  * @include: gio/gio.h
  35  * @see_also: #GInitable
  36  *
  37  * This is the asynchronous version of #GInitable; it behaves the same
  38  * in all ways except that initialization is asynchronous. For more details
  39  * see the descriptions on #GInitable.
  40  *
  41  * A class may implement both the #GInitable and #GAsyncInitable interfaces.
  42  *
  43  * Users of objects implementing this are not intended to use the interface
  44  * method directly; instead it will be used automatically in various ways.
  45  * For C applications you generally just call g_async_initable_new_async()
  46  * directly, or indirectly via a foo_thing_new_async() wrapper. This will call
  47  * g_async_initable_init_async() under the cover, calling back with %NULL and
  48  * a set %GError on failure.
  49  *
  50  * A typical implementation might look something like this:
  51  *
  52  * |[
  53  * enum {
  54  *    NOT_INITIALIZED,
  55  *    INITIALIZING,
  56  *    INITIALIZED
  57  * };
  58  *
  59  * static void
  60  * _foo_ready_cb (Foo *self)
  61  * {
  62  *   GList *l;
  63  *
  64  *   self->priv->state = INITIALIZED;
  65  *
  66  *   for (l = self->priv->init_results; l != NULL; l = l->next)
  67  *     {
  68  *       GTask *task = l->data;
  69  *
  70  *       if (self->priv->success)
  71  *         g_task_return_boolean (task, TRUE);
  72  *       else
  73  *         g_task_return_new_error (task, ...);
  74  *       g_object_unref (task);
  75  *     }
  76  *
  77  *   g_list_free (self->priv->init_results);
  78  *   self->priv->init_results = NULL;
  79  * }
  80  *
  81  * static void
  82  * foo_init_async (GAsyncInitable       *initable,
  83  *                 int                   io_priority,
  84  *                 GCancellable         *cancellable,
  85  *                 GAsyncReadyCallback   callback,
  86  *                 gpointer              user_data)
  87  * {
  88  *   Foo *self = FOO (initable);
  89  *   GTask *task;
  90  *
  91  *   task = g_task_new (initable, cancellable, callback, user_data);
  92  *
  93  *   switch (self->priv->state)
  94  *     {
  95  *       case NOT_INITIALIZED:
  96  *         _foo_get_ready (self);
  97  *         self->priv->init_results = g_list_append (self->priv->init_results,
  98  *                                                   task);
  99  *         self->priv->state = INITIALIZING;
 100  *         break;
 101  *       case INITIALIZING:
 102  *         self->priv->init_results = g_list_append (self->priv->init_results,
 103  *                                                   task);
 104  *         break;
 105  *       case INITIALIZED:
 106  *         if (!self->priv->success)
 107  *           g_task_return_new_error (task, ...);
 108  *         else
 109  *           g_task_return_boolean (task, TRUE);
 110  *         g_object_unref (task);
 111  *         break;
 112  *     }
 113  * }
 114  *
 115  * static gboolean
 116  * foo_init_finish (GAsyncInitable       *initable,
 117  *                  GAsyncResult         *result,
 118  *                  GError              **error)
 119  * {
 120  *   g_return_val_if_fail (g_task_is_valid (result, initable), FALSE);
 121  *
 122  *   return g_task_propagate_boolean (G_TASK (result), error);
 123  * }
 124  *
 125  * static void
 126  * foo_async_initable_iface_init (gpointer g_iface,
 127  *                                gpointer data)
 128  * {
 129  *   GAsyncInitableIface *iface = g_iface;
 130  *
 131  *   iface->init_async = foo_init_async;
 132  *   iface->init_finish = foo_init_finish;
 133  * }
 134  * ]|
 135  */
 136
 137 static void     g_async_initable_real_init_async  (GAsyncInitable       *initable,
 138                                                    int                   io_priority,
 139                                                    GCancellable         *cancellable,
 140                                                    GAsyncReadyCallback   callback,
 141                                                    gpointer              user_data);
 142 static gboolean g_async_initable_real_init_finish (GAsyncInitable       *initable,
 143                                                    GAsyncResult         *res,
 144                                                    GError              **error);
 145
 146
 147 typedef GAsyncInitableIface GAsyncInitableInterface;
 148 G_DEFINE_INTERFACE (GAsyncInitable, g_async_initable, G_TYPE_OBJECT)
 149
 150
 151 static void
 152 g_async_initable_default_init (GAsyncInitableInterface *iface)
 153 {
 154   iface->init_async = g_async_initable_real_init_async;
 155   iface->init_finish = g_async_initable_real_init_finish;
 156 }
 157
 158 /**
 159  * g_async_initable_init_async:
 160  * @initable: a #GAsyncInitable.
 161  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 162  *     of the operation.
 163  * @cancellable: optional #GCancellable object, %NULL to ignore.
 164  * @callback: a #GAsyncReadyCallback to call when the request is satisfied
 165  * @user_data: the data to pass to callback function
 166  *
 167  * Starts asynchronous initialization of the object implementing the
 168  * interface. This must be done before any real use of the object after
 169  * initial construction. If the object also implements #GInitable you can
 170  * optionally call g_initable_init() 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  * Implementations of this method must be idempotent: i.e. multiple calls
 190  * to this function with the same argument should return the same results.
 191  * Only the first call initializes the object; further calls return the result
 192  * of the first call. This is so that it's safe to implement the singleton
 193  * pattern in the GObject constructor function.
 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_priority (task, io_priority);
 279   g_task_run_in_thread (task, async_init_thread);
 280   g_object_unref (task);
 281 }
 282
 283 static gboolean
 284 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 285                                    GAsyncResult    *res,
 286                                    GError         **error)
 287 {
 288   /* For backward compatibility we have to process GSimpleAsyncResults
 289    * even though g_async_initable_real_init_async doesn't generate
 290    * them any more.
 291    */
 292   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 293     {
 294       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 295       if (g_simple_async_result_propagate_error (simple, error))
 296         return FALSE;
 297       else
 298         return TRUE;
 299     }
 300
 301   g_return_val_if_fail (g_task_is_valid (res, initable), FALSE);
 302
 303   return g_task_propagate_boolean (G_TASK (res), error);
 304 }
 305
 306 /**
 307  * g_async_initable_new_async:
 308  * @object_type: a #GType supporting #GAsyncInitable.
 309  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 310  *     of the operation.
 311  * @cancellable: optional #GCancellable object, %NULL to ignore.
 312  * @callback: a #GAsyncReadyCallback to call when the initialization is
 313  *     finished
 314  * @user_data: the data to pass to callback function
 315  * @first_property_name: (allow-none): the name of the first property, or %NULL if no
 316  *     properties
 317  * @...:  the value of the first property, followed by other property
 318  *    value pairs, and ended by %NULL.
 319  *
 320  * Helper function for constructing #GAsyncInitable object. This is
 321  * similar to g_object_new() but also initializes the object asynchronously.
 322  *
 323  * When the initialization is finished, @callback will be called. You can
 324  * then call g_async_initable_new_finish() to get the new object and check
 325  * for any errors.
 326  *
 327  * Since: 2.22
 328  */
 329 void
 330 g_async_initable_new_async (GType                object_type,
 331                             int                  io_priority,
 332                             GCancellable        *cancellable,
 333                             GAsyncReadyCallback  callback,
 334                             gpointer             user_data,
 335                             const gchar         *first_property_name,
 336                             ...)
 337 {
 338   va_list var_args;
 339
 340   va_start (var_args, first_property_name);
 341   g_async_initable_new_valist_async (object_type,
 342                                      first_property_name, var_args,
 343                                      io_priority, cancellable,
 344                                      callback, user_data);
 345   va_end (var_args);
 346 }
 347
 348 /**
 349  * g_async_initable_newv_async:
 350  * @object_type: a #GType supporting #GAsyncInitable.
 351  * @n_parameters: the number of parameters in @parameters
 352  * @parameters: the parameters to use to construct the object
 353  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 354  *     of the operation.
 355  * @cancellable: optional #GCancellable object, %NULL to ignore.
 356  * @callback: a #GAsyncReadyCallback to call when the initialization is
 357  *     finished
 358  * @user_data: the data to pass to callback function
 359  *
 360  * Helper function for constructing #GAsyncInitable object. This is
 361  * similar to g_object_newv() but also initializes the object asynchronously.
 362  *
 363  * When the initialization is finished, @callback will be called. You can
 364  * then call g_async_initable_new_finish() to get the new object and check
 365  * for any errors.
 366  *
 367  * Since: 2.22
 368  */
 369 void
 370 g_async_initable_newv_async (GType                object_type,
 371                              guint                n_parameters,
 372                              GParameter          *parameters,
 373                              int                  io_priority,
 374                              GCancellable        *cancellable,
 375                              GAsyncReadyCallback  callback,
 376                              gpointer             user_data)
 377 {
 378   GObject *obj;
 379
 380   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 381
 382   obj = g_object_newv (object_type, n_parameters, parameters);
 383
 384   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 385                                io_priority, cancellable,
 386                                callback, user_data);
 387 }
 388
 389 /**
 390  * g_async_initable_new_valist_async:
 391  * @object_type: a #GType supporting #GAsyncInitable.
 392  * @first_property_name: the name of the first property, followed by
 393  * the value, and other property value pairs, and ended by %NULL.
 394  * @var_args: The var args list generated from @first_property_name.
 395  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 396  *     of the operation.
 397  * @cancellable: optional #GCancellable object, %NULL to ignore.
 398  * @callback: a #GAsyncReadyCallback to call when the initialization is
 399  *     finished
 400  * @user_data: the data to pass to callback function
 401  *
 402  * Helper function for constructing #GAsyncInitable object. This is
 403  * similar to g_object_new_valist() but also initializes the object
 404  * asynchronously.
 405  *
 406  * When the initialization is finished, @callback will be called. You can
 407  * then call g_async_initable_new_finish() to get the new object and check
 408  * for any errors.
 409  *
 410  * Since: 2.22
 411  */
 412 void
 413 g_async_initable_new_valist_async (GType                object_type,
 414                                    const gchar         *first_property_name,
 415                                    va_list              var_args,
 416                                    int                  io_priority,
 417                                    GCancellable        *cancellable,
 418                                    GAsyncReadyCallback  callback,
 419                                    gpointer             user_data)
 420 {
 421   GObject *obj;
 422
 423   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 424
 425   obj = g_object_new_valist (object_type,
 426                              first_property_name,
 427                              var_args);
 428
 429   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 430                                io_priority, cancellable,
 431                                callback, user_data);
 432   g_object_unref (obj); /* Passed ownership to async call */
 433 }
 434
 435 /**
 436  * g_async_initable_new_finish:
 437  * @initable: the #GAsyncInitable from the callback
 438  * @res: the #GAsyncResult from the callback
 439  * @error: return location for errors, or %NULL to ignore
 440  *
 441  * Finishes the async construction for the various g_async_initable_new
 442  * calls, returning the created object or %NULL on error.
 443  *
 444  * Returns: (type GObject.Object) (transfer full): a newly created #GObject,
 445  *      or %NULL on error. Free with g_object_unref().
 446  *
 447  * Since: 2.22
 448  */
 449 GObject *
 450 g_async_initable_new_finish (GAsyncInitable  *initable,
 451                              GAsyncResult    *res,
 452                              GError         **error)
 453 {
 454   if (g_async_initable_init_finish (initable, res, error))
 455     return g_object_ref (initable);
 456   else
 457     return NULL;
 458 }