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  *   g_task_set_name (task, G_STRFUNC);
  91  *
  92  *   switch (self->priv->state)
  93  *     {
  94  *       case NOT_INITIALIZED:
  95  *         _foo_get_ready (self);
  96  *         self->priv->init_results = g_list_append (self->priv->init_results,
  97  *                                                   task);
  98  *         self->priv->state = INITIALIZING;
  99  *         break;
 100  *       case INITIALIZING:
 101  *         self->priv->init_results = g_list_append (self->priv->init_results,
 102  *                                                   task);
 103  *         break;
 104  *       case INITIALIZED:
 105  *         if (!self->priv->success)
 106  *           g_task_return_new_error (task, ...);
 107  *         else
 108  *           g_task_return_boolean (task, TRUE);
 109  *         g_object_unref (task);
 110  *         break;
 111  *     }
 112  * }
 113  *
 114  * static gboolean
 115  * foo_init_finish (GAsyncInitable       *initable,
 116  *                  GAsyncResult         *result,
 117  *                  GError              **error)
 118  * {
 119  *   g_return_val_if_fail (g_task_is_valid (result, initable), FALSE);
 120  *
 121  *   return g_task_propagate_boolean (G_TASK (result), error);
 122  * }
 123  *
 124  * static void
 125  * foo_async_initable_iface_init (gpointer g_iface,
 126  *                                gpointer data)
 127  * {
 128  *   GAsyncInitableIface *iface = g_iface;
 129  *
 130  *   iface->init_async = foo_init_async;
 131  *   iface->init_finish = foo_init_finish;
 132  * }
 133  * ]|
 134  */
 135
 136 static void     g_async_initable_real_init_async  (GAsyncInitable       *initable,
 137                                                    int                   io_priority,
 138                                                    GCancellable         *cancellable,
 139                                                    GAsyncReadyCallback   callback,
 140                                                    gpointer              user_data);
 141 static gboolean g_async_initable_real_init_finish (GAsyncInitable       *initable,
 142                                                    GAsyncResult         *res,
 143                                                    GError              **error);
 144
 145
 146 typedef GAsyncInitableIface GAsyncInitableInterface;
 147 G_DEFINE_INTERFACE (GAsyncInitable, g_async_initable, G_TYPE_OBJECT)
 148
 149
 150 static void
 151 g_async_initable_default_init (GAsyncInitableInterface *iface)
 152 {
 153   iface->init_async = g_async_initable_real_init_async;
 154   iface->init_finish = g_async_initable_real_init_finish;
 155 }
 156
 157 /**
 158  * g_async_initable_init_async:
 159  * @initable: a #GAsyncInitable.
 160  * @io_priority: the [I/O priority][io-priority] 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  * This method is intended for language bindings. If writing in C,
 171  * g_async_initable_new_async() should typically be used instead.
 172  *
 173  * When the initialization is finished, @callback will be called. You can
 174  * then call g_async_initable_init_finish() to get the result of the
 175  * initialization.
 176  *
 177  * Implementations may also support cancellation. If @cancellable is not
 178  * %NULL, then initialization can be cancelled by triggering the cancellable
 179  * object from another thread. If the operation was cancelled, the error
 180  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL, and
 181  * the object doesn't support cancellable initialization, the error
 182  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
 183  *
 184  * As with #GInitable, if the object is not initialized, or initialization
 185  * returns with an error, then all operations on the object except
 186  * g_object_ref() and g_object_unref() are considered to be invalid, and
 187  * have undefined behaviour. They will often fail with g_critical() or
 188  * g_warning(), but this must not be relied on.
 189  *
 190  * Callers should not assume that a class which implements #GAsyncInitable can
 191  * be initialized multiple times; for more information, see g_initable_init().
 192  * If a class explicitly supports being initialized multiple times,
 193  * implementation requires yielding all subsequent calls to init_async() on the
 194  * results of the first call.
 195  *
 196  * For classes that also support the #GInitable interface, the default
 197  * implementation of this method will run the g_initable_init() function
 198  * in a thread, so if you want to support asynchronous initialization via
 199  * threads, just implement the #GAsyncInitable interface without overriding
 200  * any interface methods.
 201  *
 202  * Since: 2.22
 203  */
 204 void
 205 g_async_initable_init_async (GAsyncInitable      *initable,
 206                              int                  io_priority,
 207                              GCancellable        *cancellable,
 208                              GAsyncReadyCallback  callback,
 209                              gpointer             user_data)
 210 {
 211   GAsyncInitableIface *iface;
 212
 213   g_return_if_fail (G_IS_ASYNC_INITABLE (initable));
 214
 215   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 216
 217   (* iface->init_async) (initable, io_priority, cancellable, callback, user_data);
 218 }
 219
 220 /**
 221  * g_async_initable_init_finish:
 222  * @initable: a #GAsyncInitable.
 223  * @res: a #GAsyncResult.
 224  * @error: a #GError location to store the error occurring, or %NULL to
 225  * ignore.
 226  *
 227  * Finishes asynchronous initialization and returns the result.
 228  * See g_async_initable_init_async().
 229  *
 230  * Returns: %TRUE if successful. If an error has occurred, this function
 231  * will return %FALSE and set @error appropriately if present.
 232  *
 233  * Since: 2.22
 234  */
 235 gboolean
 236 g_async_initable_init_finish (GAsyncInitable  *initable,
 237                               GAsyncResult    *res,
 238                               GError         **error)
 239 {
 240   GAsyncInitableIface *iface;
 241
 242   g_return_val_if_fail (G_IS_ASYNC_INITABLE (initable), FALSE);
 243   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
 244
 245   if (g_async_result_legacy_propagate_error (res, error))
 246     return FALSE;
 247
 248   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 249
 250   return (* iface->init_finish) (initable, res, error);
 251 }
 252
 253 static void
 254 async_init_thread (GTask        *task,
 255                    gpointer      source_object,
 256                    gpointer      task_data,
 257                    GCancellable *cancellable)
 258 {
 259   GError *error = NULL;
 260
 261   if (g_initable_init (G_INITABLE (source_object), cancellable, &error))
 262     g_task_return_boolean (task, TRUE);
 263   else
 264     g_task_return_error (task, error);
 265 }
 266
 267 static void
 268 g_async_initable_real_init_async (GAsyncInitable      *initable,
 269                                   int                  io_priority,
 270                                   GCancellable        *cancellable,
 271                                   GAsyncReadyCallback  callback,
 272                                   gpointer             user_data)
 273 {
 274   GTask *task;
 275
 276   g_return_if_fail (G_IS_INITABLE (initable));
 277
 278   task = g_task_new (initable, cancellable, callback, user_data);
 279   g_task_set_source_tag (task, g_async_initable_real_init_async);
 280   g_task_set_priority (task, io_priority);
 281   g_task_run_in_thread (task, async_init_thread);
 282   g_object_unref (task);
 283 }
 284
 285 static gboolean
 286 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 287                                    GAsyncResult    *res,
 288                                    GError         **error)
 289 {
 290   /* For backward compatibility we have to process GSimpleAsyncResults
 291    * even though g_async_initable_real_init_async doesn't generate
 292    * them any more.
 293    */
 294   G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 295   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 296     {
 297       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 298       if (g_simple_async_result_propagate_error (simple, error))
 299         return FALSE;
 300       else
 301         return TRUE;
 302     }
 303   G_GNUC_END_IGNORE_DEPRECATIONS
 304
 305   g_return_val_if_fail (g_task_is_valid (res, initable), FALSE);
 306
 307   return g_task_propagate_boolean (G_TASK (res), error);
 308 }
 309
 310 /**
 311  * g_async_initable_new_async:
 312  * @object_type: a #GType supporting #GAsyncInitable.
 313  * @io_priority: the [I/O priority][io-priority] of the operation
 314  * @cancellable: optional #GCancellable object, %NULL to ignore.
 315  * @callback: a #GAsyncReadyCallback to call when the initialization is
 316  *     finished
 317  * @user_data: the data to pass to callback function
 318  * @first_property_name: (nullable): the name of the first property, or %NULL if no
 319  *     properties
 320  * @...:  the value of the first property, followed by other property
 321  *    value pairs, and ended by %NULL.
 322  *
 323  * Helper function for constructing #GAsyncInitable object. This is
 324  * similar to g_object_new() but also initializes the object asynchronously.
 325  *
 326  * When the initialization is finished, @callback will be called. You can
 327  * then call g_async_initable_new_finish() to get the new object and check
 328  * for any errors.
 329  *
 330  * Since: 2.22
 331  */
 332 void
 333 g_async_initable_new_async (GType                object_type,
 334                             int                  io_priority,
 335                             GCancellable        *cancellable,
 336                             GAsyncReadyCallback  callback,
 337                             gpointer             user_data,
 338                             const gchar         *first_property_name,
 339                             ...)
 340 {
 341   va_list var_args;
 342
 343   va_start (var_args, first_property_name);
 344   g_async_initable_new_valist_async (object_type,
 345                                      first_property_name, var_args,
 346                                      io_priority, cancellable,
 347                                      callback, user_data);
 348   va_end (var_args);
 349 }
 350
 351 /**
 352  * g_async_initable_newv_async:
 353  * @object_type: a #GType supporting #GAsyncInitable.
 354  * @n_parameters: the number of parameters in @parameters
 355  * @parameters: the parameters to use to construct the object
 356  * @io_priority: the [I/O priority][io-priority] of the operation
 357  * @cancellable: optional #GCancellable object, %NULL to ignore.
 358  * @callback: a #GAsyncReadyCallback to call when the initialization is
 359  *     finished
 360  * @user_data: the data to pass to callback function
 361  *
 362  * Helper function for constructing #GAsyncInitable object. This is
 363  * similar to g_object_newv() but also initializes the object asynchronously.
 364  *
 365  * When the initialization is finished, @callback will be called. You can
 366  * then call g_async_initable_new_finish() to get the new object and check
 367  * for any errors.
 368  *
 369  * Since: 2.22
 370  * Deprecated: 2.54: Use g_object_new_with_properties() and
 371  * g_async_initable_init_async() instead. See #GParameter for more information.
 372  */
 373 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 374 void
 375 g_async_initable_newv_async (GType                object_type,
 376                              guint                n_parameters,
 377                              GParameter          *parameters,
 378                              int                  io_priority,
 379                              GCancellable        *cancellable,
 380                              GAsyncReadyCallback  callback,
 381                              gpointer             user_data)
 382 {
 383   GObject *obj;
 384
 385   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 386
 387   obj = g_object_newv (object_type, n_parameters, parameters);
 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 G_GNUC_END_IGNORE_DEPRECATIONS
 395
 396 /**
 397  * g_async_initable_new_valist_async:
 398  * @object_type: a #GType supporting #GAsyncInitable.
 399  * @first_property_name: the name of the first property, followed by
 400  * the value, and other property value pairs, and ended by %NULL.
 401  * @var_args: The var args list generated from @first_property_name.
 402  * @io_priority: the [I/O priority][io-priority] of the operation
 403  * @cancellable: optional #GCancellable object, %NULL to ignore.
 404  * @callback: a #GAsyncReadyCallback to call when the initialization is
 405  *     finished
 406  * @user_data: the data to pass to callback function
 407  *
 408  * Helper function for constructing #GAsyncInitable object. This is
 409  * similar to g_object_new_valist() but also initializes the object
 410  * asynchronously.
 411  *
 412  * When the initialization is finished, @callback will be called. You can
 413  * then call g_async_initable_new_finish() to get the new object and check
 414  * for any errors.
 415  *
 416  * Since: 2.22
 417  */
 418 void
 419 g_async_initable_new_valist_async (GType                object_type,
 420                                    const gchar         *first_property_name,
 421                                    va_list              var_args,
 422                                    int                  io_priority,
 423                                    GCancellable        *cancellable,
 424                                    GAsyncReadyCallback  callback,
 425                                    gpointer             user_data)
 426 {
 427   GObject *obj;
 428
 429   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 430
 431   obj = g_object_new_valist (object_type,
 432                              first_property_name,
 433                              var_args);
 434
 435   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 436                                io_priority, cancellable,
 437                                callback, user_data);
 438   g_object_unref (obj); /* Passed ownership to async call */
 439 }
 440
 441 /**
 442  * g_async_initable_new_finish:
 443  * @initable: the #GAsyncInitable from the callback
 444  * @res: the #GAsyncResult from the callback
 445  * @error: return location for errors, or %NULL to ignore
 446  *
 447  * Finishes the async construction for the various g_async_initable_new
 448  * calls, returning the created object or %NULL on error.
 449  *
 450  * Returns: (type GObject.Object) (transfer full): a newly created #GObject,
 451  *      or %NULL on error. Free with g_object_unref().
 452  *
 453  * Since: 2.22
 454  */
 455 GObject *
 456 g_async_initable_new_finish (GAsyncInitable  *initable,
 457                              GAsyncResult    *res,
 458                              GError         **error)
 459 {
 460   if (g_async_initable_init_finish (initable, res, error))
 461     return g_object_ref (G_OBJECT (initable));
 462   else
 463     return NULL;
 464 }