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  * A typical implementation might look something like this:
  50  *
  51  * |[
  52  * enum {
  53  *    NOT_INITIALIZED,
  54  *    INITIALIZING,
  55  *    INITIALIZED
  56  * };
  57  *
  58  * static void
  59  * _foo_ready_cb (Foo *self)
  60  * {
  61  *   GList *l;
  62  *
  63  *   self->priv->state = INITIALIZED;
  64  *
  65  *   for (l = self->priv->init_results; l != NULL; l = l->next)
  66  *     {
  67  *       GSimpleAsyncResult *simple = l->data;
  68  *
  69  *       if (!self->priv->success)
  70  *         g_simple_async_result_set_error (simple, ...);
  71  *
  72  *       g_simple_async_result_complete (simple);
  73  *       g_object_unref (simple);
  74  *     }
  75  *
  76  *   g_list_free (self->priv->init_results);
  77  *   self->priv->init_results = NULL;
  78  * }
  79  *
  80  * static void
  81  * foo_init_async (GAsyncInitable       *initable,
  82  *                 int                   io_priority,
  83  *                 GCancellable         *cancellable,
  84  *                 GAsyncReadyCallback   callback,
  85  *                 gpointer              user_data)
  86  * {
  87  *   Foo *self = FOO (initable);
  88  *   GSimpleAsyncResult *simple;
  89  *
  90  *   simple = g_simple_async_result_new (G_OBJECT (initable)
  91  *                                       callback,
  92  *                                       user_data,
  93  *                                       foo_init_async);
  94  *
  95  *   switch (self->priv->state)
  96  *     {
  97  *       case NOT_INITIALIZED:
  98  *         _foo_get_ready (self);
  99  *         self->priv->init_results = g_list_append (self->priv->init_results,
 100  *                                                   simple);
 101  *         self->priv->state = INITIALIZING;
 102  *         break;
 103  *       case INITIALIZING:
 104  *         self->priv->init_results = g_list_append (self->priv->init_results,
 105  *                                                   simple);
 106  *         break;
 107  *       case INITIALIZED:
 108  *         if (!self->priv->success)
 109  *           g_simple_async_result_set_error (simple, ...);
 110  *
 111  *         g_simple_async_result_complete_in_idle (simple);
 112  *         g_object_unref (simple);
 113  *         break;
 114  *     }
 115  * }
 116  *
 117  * static gboolean
 118  * foo_init_finish (GAsyncInitable       *initable,
 119  *                  GAsyncResult         *result,
 120  *                  GError              **error)
 121  * {
 122  *   g_return_val_if_fail (g_simple_async_result_is_valid (result,
 123  *       G_OBJECT (initable), foo_init_async), FALSE);
 124  *
 125  *   if (g_simple_async_result_propagate_error (G_SIMPLE_ASYNC_RESULT (result),
 126  *           error))
 127  *     return FALSE;
 128  *
 129  *   return TRUE;
 130  * }
 131  *
 132  * static void
 133  * foo_async_initable_iface_init (gpointer g_iface,
 134  *                                gpointer data)
 135  * {
 136  *   GAsyncInitableIface *iface = g_iface;
 137  *
 138  *   iface->init_async = foo_init_async;
 139  *   iface->init_finish = foo_init_finish;
 140  * }
 141  * ]|
 142  */
 143
 144 static void     g_async_initable_real_init_async  (GAsyncInitable       *initable,
 145                                                    int                   io_priority,
 146                                                    GCancellable         *cancellable,
 147                                                    GAsyncReadyCallback   callback,
 148                                                    gpointer              user_data);
 149 static gboolean g_async_initable_real_init_finish (GAsyncInitable       *initable,
 150                                                    GAsyncResult         *res,
 151                                                    GError              **error);
 152
 153
 154 typedef GAsyncInitableIface GAsyncInitableInterface;
 155 G_DEFINE_INTERFACE (GAsyncInitable, g_async_initable, G_TYPE_OBJECT)
 156
 157
 158 static void
 159 g_async_initable_default_init (GAsyncInitableInterface *iface)
 160 {
 161   iface->init_async = g_async_initable_real_init_async;
 162   iface->init_finish = g_async_initable_real_init_finish;
 163 }
 164
 165 /**
 166  * g_async_initable_init_async:
 167  * @initable: a #GAsyncInitable.
 168  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 169  *     of the operation.
 170  * @cancellable: optional #GCancellable object, %NULL to ignore.
 171  * @callback: a #GAsyncReadyCallback to call when the request is satisfied
 172  * @user_data: the data to pass to callback function
 173  *
 174  * Starts asynchronous initialization of the object implementing the
 175  * interface. This must be done before any real use of the object after
 176  * initial construction. If the object also implements #GInitable you can
 177  * optionally call g_initable_init() instead.
 178  *
 179  * When the initialization is finished, @callback will be called. You can
 180  * then call g_async_initable_init_finish() to get the result of the
 181  * initialization.
 182  *
 183  * Implementations may also support cancellation. If @cancellable is not
 184  * %NULL, then initialization can be cancelled by triggering the cancellable
 185  * object from another thread. If the operation was cancelled, the error
 186  * %G_IO_ERROR_CANCELLED will be returned. If @cancellable is not %NULL, and
 187  * the object doesn't support cancellable initialization, the error
 188  * %G_IO_ERROR_NOT_SUPPORTED will be returned.
 189  *
 190  * As with #GInitable, if the object is not initialized, or initialization
 191  * returns with an error, then all operations on the object except
 192  * g_object_ref() and g_object_unref() are considered to be invalid, and
 193  * have undefined behaviour. They will often fail with g_critical() or
 194  * g_warning(), but this must not be relied on.
 195  *
 196  * Implementations of this method must be idempotent: i.e. multiple calls
 197  * to this function with the same argument should return the same results.
 198  * Only the first call initializes the object; further calls return the result
 199  * of the first call. This is so that it's safe to implement the singleton
 200  * pattern in the GObject constructor function.
 201  *
 202  * For classes that also support the #GInitable interface, the default
 203  * implementation of this method will run the g_initable_init() function
 204  * in a thread, so if you want to support asynchronous initialization via
 205  * threads, just implement the #GAsyncInitable interface without overriding
 206  * any interface methods.
 207  *
 208  * Since: 2.22
 209  */
 210 void
 211 g_async_initable_init_async (GAsyncInitable      *initable,
 212                              int                  io_priority,
 213                              GCancellable        *cancellable,
 214                              GAsyncReadyCallback  callback,
 215                              gpointer             user_data)
 216 {
 217   GAsyncInitableIface *iface;
 218
 219   g_return_if_fail (G_IS_ASYNC_INITABLE (initable));
 220
 221   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 222
 223   (* iface->init_async) (initable, io_priority, cancellable, callback, user_data);
 224 }
 225
 226 /**
 227  * g_async_initable_init_finish:
 228  * @initable: a #GAsyncInitable.
 229  * @res: a #GAsyncResult.
 230  * @error: a #GError location to store the error occurring, or %NULL to
 231  * ignore.
 232  *
 233  * Finishes asynchronous initialization and returns the result.
 234  * See g_async_initable_init_async().
 235  *
 236  * Returns: %TRUE if successful. If an error has occurred, this function
 237  * will return %FALSE and set @error appropriately if present.
 238  *
 239  * Since: 2.22
 240  */
 241 gboolean
 242 g_async_initable_init_finish (GAsyncInitable  *initable,
 243                               GAsyncResult    *res,
 244                               GError         **error)
 245 {
 246   GAsyncInitableIface *iface;
 247
 248   g_return_val_if_fail (G_IS_ASYNC_INITABLE (initable), FALSE);
 249   g_return_val_if_fail (G_IS_ASYNC_RESULT (res), FALSE);
 250
 251   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 252     {
 253       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 254       if (g_simple_async_result_propagate_error (simple, error))
 255         return FALSE;
 256     }
 257
 258   iface = G_ASYNC_INITABLE_GET_IFACE (initable);
 259
 260   return (* iface->init_finish) (initable, res, error);
 261 }
 262
 263 static void
 264 async_init_thread (GSimpleAsyncResult *res,
 265                    GObject            *object,
 266                    GCancellable       *cancellable)
 267 {
 268   GError *error = NULL;
 269
 270   if (!g_initable_init (G_INITABLE (object), cancellable, &error))
 271     g_simple_async_result_take_error (res, error);
 272 }
 273
 274 static void
 275 g_async_initable_real_init_async (GAsyncInitable      *initable,
 276                                   int                  io_priority,
 277                                   GCancellable        *cancellable,
 278                                   GAsyncReadyCallback  callback,
 279                                   gpointer             user_data)
 280 {
 281   GSimpleAsyncResult *res;
 282
 283   g_return_if_fail (G_IS_INITABLE (initable));
 284
 285   res = g_simple_async_result_new (G_OBJECT (initable), callback, user_data,
 286                                    g_async_initable_real_init_async);
 287   g_simple_async_result_run_in_thread (res, async_init_thread,
 288                                        io_priority, cancellable);
 289   g_object_unref (res);
 290 }
 291
 292 static gboolean
 293 g_async_initable_real_init_finish (GAsyncInitable  *initable,
 294                                    GAsyncResult    *res,
 295                                    GError         **error)
 296 {
 297   /* Although g_async_initable_init_finish() does this error handling
 298    * as well, we do it here too, so that a class that reimplements
 299    * GAsyncInitable can properly run its parent class's implementation
 300    * by directly invoking its ->init_async() and ->init_finish().
 301    */
 302   if (G_IS_SIMPLE_ASYNC_RESULT (res))
 303     {
 304       GSimpleAsyncResult *simple = G_SIMPLE_ASYNC_RESULT (res);
 305       if (g_simple_async_result_propagate_error (simple, error))
 306         return FALSE;
 307     }
 308
 309   return TRUE;
 310 }
 311
 312 /**
 313  * g_async_initable_new_async:
 314  * @object_type: a #GType supporting #GAsyncInitable.
 315  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 316  *     of the operation.
 317  * @cancellable: optional #GCancellable object, %NULL to ignore.
 318  * @callback: a #GAsyncReadyCallback to call when the initialization is
 319  *     finished
 320  * @user_data: the data to pass to callback function
 321  * @first_property_name: the name of the first property, or %NULL if no
 322  *     properties
 323  * @...:  the value of the first property, followed by other property
 324  *    value pairs, and ended by %NULL.
 325  *
 326  * Helper function for constructing #GAsyncInitable object. This is
 327  * similar to g_object_new() but also initializes the object asynchronously.
 328  *
 329  * When the initialization is finished, @callback will be called. You can
 330  * then call g_async_initable_new_finish() to get the new object and check
 331  * for any errors.
 332  *
 333  * Since: 2.22
 334  */
 335 void
 336 g_async_initable_new_async (GType                object_type,
 337                             int                  io_priority,
 338                             GCancellable        *cancellable,
 339                             GAsyncReadyCallback  callback,
 340                             gpointer             user_data,
 341                             const gchar         *first_property_name,
 342                             ...)
 343 {
 344   va_list var_args;
 345
 346   va_start (var_args, first_property_name);
 347   g_async_initable_new_valist_async (object_type,
 348                                      first_property_name, var_args,
 349                                      io_priority, cancellable,
 350                                      callback, user_data);
 351   va_end (var_args);
 352 }
 353
 354 /**
 355  * g_async_initable_newv_async:
 356  * @object_type: a #GType supporting #GAsyncInitable.
 357  * @n_parameters: the number of parameters in @parameters
 358  * @parameters: the parameters to use to construct the object
 359  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 360  *     of the operation.
 361  * @cancellable: optional #GCancellable object, %NULL to ignore.
 362  * @callback: a #GAsyncReadyCallback to call when the initialization is
 363  *     finished
 364  * @user_data: the data to pass to callback function
 365  *
 366  * Helper function for constructing #GAsyncInitable object. This is
 367  * similar to g_object_newv() but also initializes the object asynchronously.
 368  *
 369  * When the initialization is finished, @callback will be called. You can
 370  * then call g_async_initable_new_finish() to get the new object and check
 371  * for any errors.
 372  *
 373  * Since: 2.22
 374  */
 375 void
 376 g_async_initable_newv_async (GType                object_type,
 377                              guint                n_parameters,
 378                              GParameter          *parameters,
 379                              int                  io_priority,
 380                              GCancellable        *cancellable,
 381                              GAsyncReadyCallback  callback,
 382                              gpointer             user_data)
 383 {
 384   GObject *obj;
 385
 386   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 387
 388   obj = g_object_newv (object_type, n_parameters, parameters);
 389
 390   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 391                                io_priority, cancellable,
 392                                callback, user_data);
 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 <link linkend="io-priority">I/O priority</link>
 402  *     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: (transfer full): a newly created #GObject, or %NULL on error.
 451  *     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 (initable);
 462   else
 463     return NULL;
 464 }