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   return TRUE; /* Errors handled by base impl */
 298 }
 299
 300 /**
 301  * g_async_initable_new_async:
 302  * @object_type: a #GType supporting #GAsyncInitable.
 303  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 304  *     of the operation.
 305  * @cancellable: optional #GCancellable object, %NULL to ignore.
 306  * @callback: a #GAsyncReadyCallback to call when the initialization is
 307  *     finished
 308  * @user_data: the data to pass to callback function
 309  * @first_property_name: the name of the first property, or %NULL if no
 310  *     properties
 311  * @...:  the value of the first property, followed by other property
 312  *    value pairs, and ended by %NULL.
 313  *
 314  * Helper function for constructing #GAsyncInitable object. This is
 315  * similar to g_object_new() but also initializes the object asynchronously.
 316  *
 317  * When the initialization is finished, @callback will be called. You can
 318  * then call g_async_initable_new_finish() to get the new object and check
 319  * for any errors.
 320  *
 321  * Since: 2.22
 322  */
 323 void
 324 g_async_initable_new_async (GType                object_type,
 325                             int                  io_priority,
 326                             GCancellable        *cancellable,
 327                             GAsyncReadyCallback  callback,
 328                             gpointer             user_data,
 329                             const gchar         *first_property_name,
 330                             ...)
 331 {
 332   va_list var_args;
 333
 334   va_start (var_args, first_property_name);
 335   g_async_initable_new_valist_async (object_type,
 336                                      first_property_name, var_args,
 337                                      io_priority, cancellable,
 338                                      callback, user_data);
 339   va_end (var_args);
 340 }
 341
 342 /**
 343  * g_async_initable_newv_async:
 344  * @object_type: a #GType supporting #GAsyncInitable.
 345  * @n_parameters: the number of parameters in @parameters
 346  * @parameters: the parameters to use to construct the object
 347  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 348  *     of the operation.
 349  * @cancellable: optional #GCancellable object, %NULL to ignore.
 350  * @callback: a #GAsyncReadyCallback to call when the initialization is
 351  *     finished
 352  * @user_data: the data to pass to callback function
 353  *
 354  * Helper function for constructing #GAsyncInitable object. This is
 355  * similar to g_object_newv() but also initializes the object asynchronously.
 356  *
 357  * When the initialization is finished, @callback will be called. You can
 358  * then call g_async_initable_new_finish() to get the new object and check
 359  * for any errors.
 360  *
 361  * Since: 2.22
 362  */
 363 void
 364 g_async_initable_newv_async (GType                object_type,
 365                              guint                n_parameters,
 366                              GParameter          *parameters,
 367                              int                  io_priority,
 368                              GCancellable        *cancellable,
 369                              GAsyncReadyCallback  callback,
 370                              gpointer             user_data)
 371 {
 372   GObject *obj;
 373
 374   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 375
 376   obj = g_object_newv (object_type, n_parameters, parameters);
 377
 378   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 379                                io_priority, cancellable,
 380                                callback, user_data);
 381 }
 382
 383 /**
 384  * g_async_initable_new_valist_async:
 385  * @object_type: a #GType supporting #GAsyncInitable.
 386  * @first_property_name: the name of the first property, followed by
 387  * the value, and other property value pairs, and ended by %NULL.
 388  * @var_args: The var args list generated from @first_property_name.
 389  * @io_priority: the <link linkend="io-priority">I/O priority</link>
 390  *     of the operation.
 391  * @cancellable: optional #GCancellable object, %NULL to ignore.
 392  * @callback: a #GAsyncReadyCallback to call when the initialization is
 393  *     finished
 394  * @user_data: the data to pass to callback function
 395  *
 396  * Helper function for constructing #GAsyncInitable object. This is
 397  * similar to g_object_new_valist() but also initializes the object
 398  * asynchronously.
 399  *
 400  * When the initialization is finished, @callback will be called. You can
 401  * then call g_async_initable_new_finish() to get the new object and check
 402  * for any errors.
 403  *
 404  * Since: 2.22
 405  */
 406 void
 407 g_async_initable_new_valist_async (GType                object_type,
 408                                    const gchar         *first_property_name,
 409                                    va_list              var_args,
 410                                    int                  io_priority,
 411                                    GCancellable        *cancellable,
 412                                    GAsyncReadyCallback  callback,
 413                                    gpointer             user_data)
 414 {
 415   GObject *obj;
 416
 417   g_return_if_fail (G_TYPE_IS_ASYNC_INITABLE (object_type));
 418
 419   obj = g_object_new_valist (object_type,
 420                              first_property_name,
 421                              var_args);
 422
 423   g_async_initable_init_async (G_ASYNC_INITABLE (obj),
 424                                io_priority, cancellable,
 425                                callback, user_data);
 426   g_object_unref (obj); /* Passed ownership to async call */
 427 }
 428
 429 /**
 430  * g_async_initable_new_finish:
 431  * @initable: the #GAsyncInitable from the callback
 432  * @res: the #GAsyncResult from the callback
 433  * @error: return location for errors, or %NULL to ignore
 434  *
 435  * Finishes the async construction for the various g_async_initable_new
 436  * calls, returning the created object or %NULL on error.
 437  *
 438  * Returns: (transfer full): a newly created #GObject, or %NULL on error.
 439  *     Free with g_object_unref().
 440  *
 441  * Since: 2.22
 442  */
 443 GObject *
 444 g_async_initable_new_finish (GAsyncInitable  *initable,
 445                              GAsyncResult    *res,
 446                              GError         **error)
 447 {
 448   if (g_async_initable_init_finish (initable, res, error))
 449     return g_object_ref (initable);
 450   else
 451     return NULL;
 452 }