gtask.c 53.6 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
/* GIO - GLib Input, Output and Streaming Library
 *
 * Copyright 2011 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * 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 19 20 21 22 23 24 25 26 27
 */

#include "config.h"

#include "gtask.h"

#include "gasyncresult.h"
#include "gcancellable.h"

/**
 * SECTION:gtask
28 29
 * @short_description: Cancellable synchronous or asynchronous task
 *     and result
30 31 32
 * @include: gio/gio.h
 * @see_also: #GAsyncResult
 *
33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
 * A #GTask represents and manages a cancellable "task".
 *
 * ## Asynchronous operations
 *
 * The most common usage of #GTask is as a #GAsyncResult, to
 * manage data during an asynchronous operation. You call
 * g_task_new() in the "start" method, followed by
 * g_task_set_task_data() and the like if you need to keep some
 * additional data associated with the task, and then pass the
 * task object around through your asynchronous operation.
 * Eventually, you will call a method such as
 * g_task_return_pointer() or g_task_return_error(), which will
 * save the value you give it and then invoke the task's callback
 * function (waiting until the next iteration of the main
 * loop first, if necessary). The caller will pass the #GTask back
 * to the operation's finish function (as a #GAsyncResult), and
 * you can use g_task_propagate_pointer() or the like to extract
 * the return value.
 *
 * Here is an example for using GTask as a GAsyncResult:
53
 * |[<!-- language="C" -->
54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
 *     typedef struct {
 *       CakeFrostingType frosting;
 *       char *message;
 *     } DecorationData;
 *
 *     static void
 *     decoration_data_free (DecorationData *decoration)
 *     {
 *       g_free (decoration->message);
 *       g_slice_free (DecorationData, decoration);
 *     }
 *
 *     static void
 *     baked_cb (Cake     *cake,
 *               gpointer  user_data)
 *     {
 *       GTask *task = user_data;
 *       DecorationData *decoration = g_task_get_task_data (task);
 *       GError *error = NULL;
 *
 *       if (cake == NULL)
 *         {
 *           g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
 *                                    "Go to the supermarket");
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       if (!cake_decorate (cake, decoration->frosting, decoration->message, &error))
 *         {
 *           g_object_unref (cake);
 *           /&ast; g_task_return_error() takes ownership of error &ast;/
 *           g_task_return_error (task, error);
 *           g_object_unref (task);
 *           return;
 *         }
 *
91
 *       g_task_return_pointer (task, cake, g_object_unref);
92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144
 *       g_object_unref (task);
 *     }
 *
 *     void
 *     baker_bake_cake_async (Baker               *self,
 *                            guint                radius,
 *                            CakeFlavor           flavor,
 *                            CakeFrostingType     frosting,
 *                            const char          *message,
 *                            GCancellable        *cancellable,
 *                            GAsyncReadyCallback  callback,
 *                            gpointer             user_data)
 *     {
 *       GTask *task;
 *       DecorationData *decoration;
 *       Cake  *cake;
 *
 *       task = g_task_new (self, cancellable, callback, user_data);
 *       if (radius < 3)
 *         {
 *           g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_TOO_SMALL,
 *                                    "%ucm radius cakes are silly",
 *                                    radius);
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       cake = _baker_get_cached_cake (self, radius, flavor, frosting, message);
 *       if (cake != NULL)
 *         {
 *           /&ast; _baker_get_cached_cake() returns a reffed cake &ast;/
 *           g_task_return_pointer (task, cake, g_object_unref);
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       decoration = g_slice_new (DecorationData);
 *       decoration->frosting = frosting;
 *       decoration->message = g_strdup (message);
 *       g_task_set_task_data (task, decoration, (GDestroyNotify) decoration_data_free);
 *
 *       _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
 *     }
 *
 *     Cake *
 *     baker_bake_cake_finish (Baker         *self,
 *                             GAsyncResult  *result,
 *                             GError       **error)
 *     {
 *       g_return_val_if_fail (g_task_is_valid (result, self), NULL);
 *
 *       return g_task_propagate_pointer (G_TASK (result), error);
 *     }
145
 * ]|
146 147 148 149 150
 *
 * ## Chained asynchronous operations
 *
 * #GTask also tries to simplify asynchronous operations that
 * internally chain together several smaller asynchronous
151 152 153 154 155 156 157
 * operations. g_task_get_cancellable(), g_task_get_context(),
 * and g_task_get_priority() allow you to get back the task's
 * #GCancellable, #GMainContext, and [I/O priority][io-priority]
 * when starting a new subtask, so you don't have to keep track
 * of them yourself. g_task_attach_source() simplifies the case
 * of waiting for a source to fire (automatically using the correct
 * #GMainContext and priority).
158 159
 *
 * Here is an example for chained asynchronous operations:
160
 *   |[<!-- language="C" -->
161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228
 *     typedef struct {
 *       Cake *cake;
 *       CakeFrostingType frosting;
 *       char *message;
 *     } BakingData;
 *
 *     static void
 *     decoration_data_free (BakingData *bd)
 *     {
 *       if (bd->cake)
 *         g_object_unref (bd->cake);
 *       g_free (bd->message);
 *       g_slice_free (BakingData, bd);
 *     }
 *
 *     static void
 *     decorated_cb (Cake         *cake,
 *                   GAsyncResult *result,
 *                   gpointer      user_data)
 *     {
 *       GTask *task = user_data;
 *       GError *error = NULL;
 *
 *       if (!cake_decorate_finish (cake, result, &error))
 *         {
 *           g_object_unref (cake);
 *           g_task_return_error (task, error);
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       /&ast; baking_data_free() will drop its ref on the cake, so
 *        &ast; we have to take another here to give to the caller.
 *        &ast;/
 *       g_task_return_pointer (result, g_object_ref (cake), g_object_unref);
 *       g_object_unref (task);
 *     }
 *
 *     static void
 *     decorator_ready (gpointer user_data)
 *     {
 *       GTask *task = user_data;
 *       BakingData *bd = g_task_get_task_data (task);
 *
 *       cake_decorate_async (bd->cake, bd->frosting, bd->message,
 *                            g_task_get_cancellable (task),
 *                            decorated_cb, task);
 *     }
 *
 *     static void
 *     baked_cb (Cake     *cake,
 *               gpointer  user_data)
 *     {
 *       GTask *task = user_data;
 *       BakingData *bd = g_task_get_task_data (task);
 *       GError *error = NULL;
 *
 *       if (cake == NULL)
 *         {
 *           g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
 *                                    "Go to the supermarket");
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       bd->cake = cake;
 *
 *       /&ast; Bail out now if the user has already cancelled &ast;/
229
 *       if (g_task_return_error_if_cancelled (task))
230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284
 *         {
 *           g_object_unref (task);
 *           return;
 *         }
 *
 *       if (cake_decorator_available (cake))
 *         decorator_ready (task);
 *       else
 *         {
 *           GSource *source;
 *
 *           source = cake_decorator_wait_source_new (cake);
 *           /&ast; Attach @source to @task's GMainContext and have it call
 *            &ast; decorator_ready() when it is ready.
 *            &ast;/
 *           g_task_attach_source (task, source,
 *                                 G_CALLBACK (decorator_ready));
 *           g_source_unref (source);
 *         }
 *     }
 *
 *     void
 *     baker_bake_cake_async (Baker               *self,
 *                            guint                radius,
 *                            CakeFlavor           flavor,
 *                            CakeFrostingType     frosting,
 *                            const char          *message,
 *                            gint                 priority,
 *                            GCancellable        *cancellable,
 *                            GAsyncReadyCallback  callback,
 *                            gpointer             user_data)
 *     {
 *       GTask *task;
 *       BakingData *bd;
 *
 *       task = g_task_new (self, cancellable, callback, user_data);
 *       g_task_set_priority (task, priority);
 *
 *       bd = g_slice_new0 (BakingData);
 *       bd->frosting = frosting;
 *       bd->message = g_strdup (message);
 *       g_task_set_task_data (task, bd, (GDestroyNotify) baking_data_free);
 *
 *       _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
 *     }
 *
 *     Cake *
 *     baker_bake_cake_finish (Baker         *self,
 *                             GAsyncResult  *result,
 *                             GError       **error)
 *     {
 *       g_return_val_if_fail (g_task_is_valid (result, self), NULL);
 *
 *       return g_task_propagate_pointer (G_TASK (result), error);
 *     }
285
 * ]|
286 287 288 289 290 291 292 293 294
 *
 * ## Asynchronous operations from synchronous ones
 *
 * You can use g_task_run_in_thread() to turn a synchronous
 * operation into an asynchronous one, by running it in a thread
 * which will then dispatch the result back to the caller's
 * #GMainContext when it completes.
 *
 * Running a task in a thread:
295
 *   |[<!-- language="C" -->
296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361
 *     typedef struct {
 *       guint radius;
 *       CakeFlavor flavor;
 *       CakeFrostingType frosting;
 *       char *message;
 *     } CakeData;
 *
 *     static void
 *     cake_data_free (CakeData *cake_data)
 *     {
 *       g_free (cake_data->message);
 *       g_slice_free (CakeData, cake_data);
 *     }
 *
 *     static void
 *     bake_cake_thread (GTask         *task,
 *                       gpointer       source_object,
 *                       gpointer       task_data,
 *                       GCancellable  *cancellable)
 *     {
 *       Baker *self = source_object;
 *       CakeData *cake_data = task_data;
 *       Cake *cake;
 *       GError *error = NULL;
 *
 *       cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
 *                         cake_data->frosting, cake_data->message,
 *                         cancellable, &error);
 *       if (cake)
 *         g_task_return_pointer (task, cake, g_object_unref);
 *       else
 *         g_task_return_error (task, error);
 *     }
 *
 *     void
 *     baker_bake_cake_async (Baker               *self,
 *                            guint                radius,
 *                            CakeFlavor           flavor,
 *                            CakeFrostingType     frosting,
 *                            const char          *message,
 *                            GCancellable        *cancellable,
 *                            GAsyncReadyCallback  callback,
 *                            gpointer             user_data)
 *     {
 *       CakeData *cake_data;
 *       GTask *task;
 *
 *       cake_data = g_slice_new (CakeData);
 *       cake_data->radius = radius;
 *       cake_data->flavor = flavor;
 *       cake_data->frosting = frosting;
 *       cake_data->message = g_strdup (message);
 *       task = g_task_new (self, cancellable, callback, user_data);
 *       g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
 *       g_task_run_in_thread (task, bake_cake_thread);
 *     }
 *
 *     Cake *
 *     baker_bake_cake_finish (Baker         *self,
 *                             GAsyncResult  *result,
 *                             GError       **error)
 *     {
 *       g_return_val_if_fail (g_task_is_valid (result, self), NULL);
 *
 *       return g_task_propagate_pointer (G_TASK (result), error);
 *     }
362
 * ]|
363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378
 *
 * ## Adding cancellability to uncancellable tasks
 * 
 * Finally, g_task_run_in_thread() and g_task_run_in_thread_sync()
 * can be used to turn an uncancellable operation into a
 * cancellable one. If you call g_task_set_return_on_cancel(),
 * passing %TRUE, then if the task's #GCancellable is cancelled,
 * it will return control back to the caller immediately, while
 * allowing the task thread to continue running in the background
 * (and simply discarding its result when it finally does finish).
 * Provided that the task thread is careful about how it uses
 * locks and other externally-visible resources, this allows you
 * to make "GLib-friendly" asynchronous and cancellable
 * synchronous variants of blocking APIs.
 *
 * Cancelling a task:
379
 *   |[<!-- language="C" -->
380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430
 *     static void
 *     bake_cake_thread (GTask         *task,
 *                       gpointer       source_object,
 *                       gpointer       task_data,
 *                       GCancellable  *cancellable)
 *     {
 *       Baker *self = source_object;
 *       CakeData *cake_data = task_data;
 *       Cake *cake;
 *       GError *error = NULL;
 *
 *       cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
 *                         cake_data->frosting, cake_data->message,
 *                         &error);
 *       if (error)
 *         {
 *           g_task_return_error (task, error);
 *           return;
 *         }
 *
 *       /&ast; If the task has already been cancelled, then we don't
 *        &ast; want to add the cake to the cake cache. Likewise, we don't
 *        &ast; want to have the task get cancelled in the middle of
 *        &ast; updating the cache. g_task_set_return_on_cancel() will
 *        &ast; return %TRUE here if it managed to disable return-on-cancel,
 *        &ast; or %FALSE if the task was cancelled before it could.
 *        &ast;/
 *       if (g_task_set_return_on_cancel (task, FALSE))
 *         {
 *           /&ast; If the caller cancels at this point, their
 *            &ast; GAsyncReadyCallback won't be invoked until we return,
 *            &ast; so we don't have to worry that this code will run at
 *            &ast; the same time as that code does. But if there were
 *            &ast; other functions that might look at the cake cache,
 *            &ast; then we'd probably need a GMutex here as well.
 *            &ast;/
 *           baker_add_cake_to_cache (baker, cake);
 *           g_task_return_pointer (task, cake, g_object_unref);
 *         }
 *     }
 *
 *     void
 *     baker_bake_cake_async (Baker               *self,
 *                            guint                radius,
 *                            CakeFlavor           flavor,
 *                            CakeFrostingType     frosting,
 *                            const char          *message,
 *                            GCancellable        *cancellable,
 *                            GAsyncReadyCallback  callback,
 *                            gpointer             user_data)
 *     {
431
 J*       CakeData *cake_data;
432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467
 *       GTask *task;
 *
 *       cake_data = g_slice_new (CakeData);
 *       /&ast; ... &ast;/
 *
 *       task = g_task_new (self, cancellable, callback, user_data);
 *       g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
 *       g_task_set_return_on_cancel (task, TRUE);
 *       g_task_run_in_thread (task, bake_cake_thread);
 *     }
 *
 *     Cake *
 *     baker_bake_cake_sync (Baker               *self,
 *                           guint                radius,
 *                           CakeFlavor           flavor,
 *                           CakeFrostingType     frosting,
 *                           const char          *message,
 *                           GCancellable        *cancellable,
 *                           GError             **error)
 *     {
 *       CakeData *cake_data;
 *       GTask *task;
 *       Cake *cake;
 *
 *       cake_data = g_slice_new (CakeData);
 *       /&ast; ... &ast;/
 *
 *       task = g_task_new (self, cancellable, NULL, NULL);
 *       g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
 *       g_task_set_return_on_cancel (task, TRUE);
 *       g_task_run_in_thread_sync (task, bake_cake_thread);
 *
 *       cake = g_task_propagate_pointer (task, error);
 *       g_object_unref (task);
 *       return cake;
 *     }
468
 * ]|
469 470 471 472 473 474 475 476 477 478
 *
 * ## Porting from GSimpleAsyncResult
 * 
 * #GTask's API attempts to be simpler than #GSimpleAsyncResult's
 * in several ways:
 * - You can save task-specific data with g_task_set_task_data(), and
 *   retrieve it later with g_task_get_task_data(). This replaces the
 *   abuse of g_simple_async_result_set_op_res_gpointer() for the same
 *   purpose with #GSimpleAsyncResult.
 * - In addition to the task data, #GTask also keeps track of the
479
 *   [priority][io-priority], #GCancellable, and
480 481 482 483 484 485 486 487 488 489 490
 *   #GMainContext associated with the task, so tasks that consist of
 *   a chain of simpler asynchronous operations will have easy access
 *   to those values when starting each sub-task.
 * - g_task_return_error_if_cancelled() provides simplified
 *   handling for cancellation. In addition, cancellation
 *   overrides any other #GTask return value by default, like
 *   #GSimpleAsyncResult does when
 *   g_simple_async_result_set_check_cancellable() is called.
 *   (You can use g_task_set_check_cancellable() to turn off that
 *   behavior.) On the other hand, g_task_run_in_thread()
 *   guarantees that it will always run your
491
 *   `task_func`, even if the task's #GCancellable
492
 *   is already cancelled before the task gets a chance to run;
493
 *   you can start your `task_func` with a
494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510
 *   g_task_return_error_if_cancelled() check if you need the
 *   old behavior.
 * - The "return" methods (eg, g_task_return_pointer())
 *   automatically cause the task to be "completed" as well, and
 *   there is no need to worry about the "complete" vs "complete
 *   in idle" distinction. (#GTask automatically figures out
 *   whether the task's callback can be invoked directly, or
 *   if it needs to be sent to another #GMainContext, or delayed
 *   until the next iteration of the current #GMainContext.)
 * - The "finish" functions for #GTask-based operations are generally
 *   much simpler than #GSimpleAsyncResult ones, normally consisting
 *   of only a single call to g_task_propagate_pointer() or the like.
 *   Since g_task_propagate_pointer() "steals" the return value from
 *   the #GTask, it is not necessary to juggle pointers around to
 *   prevent it from being freed twice.
 * - With #GSimpleAsyncResult, it was common to call
 *   g_simple_async_result_propagate_error() from the
511
 *   `_finish()` wrapper function, and have
512 513 514 515 516
 *   virtual method implementations only deal with successful
 *   returns. This behavior is deprecated, because it makes it
 *   difficult for a subclass to chain to a parent class's async
 *   methods. Instead, the wrapper function should just be a
 *   simple wrapper, and the virtual method should call an
517
 *   appropriate `g_task_propagate_` function.
518 519 520 521
 *   Note that wrapper methods can now use
 *   g_async_result_legacy_propagate_error() to do old-style
 *   #GSimpleAsyncResult error-returning behavior, and
 *   g_async_result_is_tagged() to check if a result is tagged as
522
 *   having come from the `_async()` wrapper
523 524
 *   function (for "short-circuit" results, such as when passing
 *   0 to g_input_stream_read_async()).
525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558
 */

/**
 * GTask:
 *
 * The opaque object representing a synchronous or asynchronous task
 * and its result.
 */

struct _GTask {
  GObject parent_instance;

  gpointer source_object;
  gpointer source_tag;

  gpointer task_data;
  GDestroyNotify task_data_destroy;

  GMainContext *context;
  guint64 creation_time;
  gint priority;
  GCancellable *cancellable;
  gboolean check_cancellable;

  GAsyncReadyCallback callback;
  gpointer callback_data;

  GTaskThreadFunc task_func;
  GMutex lock;
  GCond cond;
  gboolean return_on_cancel;
  gboolean thread_cancelled;
  gboolean synchronous;
  gboolean thread_complete;
559
  gboolean blocking_other_task;
560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588

  GError *error;
  union {
    gpointer pointer;
    gssize   size;
    gboolean boolean;
  } result;
  GDestroyNotify result_destroy;
  gboolean result_set;
};

#define G_TASK_IS_THREADED(task) ((task)->task_func != NULL)

struct _GTaskClass
{
  GObjectClass parent_class;
};

static void g_task_thread_pool_resort (void);

static void g_task_async_result_iface_init (GAsyncResultIface *iface);
static void g_task_thread_pool_init (void);

G_DEFINE_TYPE_WITH_CODE (GTask, g_task, G_TYPE_OBJECT,
                         G_IMPLEMENT_INTERFACE (G_TYPE_ASYNC_RESULT,
                                                g_task_async_result_iface_init);
                         g_task_thread_pool_init ();)

static GThreadPool *task_pool;
589 590
static GMutex task_pool_mutex;
static GPrivate task_private = G_PRIVATE_INIT (NULL);
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614

static void
g_task_init (GTask *task)
{
  task->check_cancellable = TRUE;
}

static void
g_task_finalize (GObject *object)
{
  GTask *task = G_TASK (object);

  g_clear_object (&task->source_object);
  g_clear_object (&task->cancellable);

  if (task->context)
    g_main_context_unref (task->context);

  if (task->task_data_destroy)
    task->task_data_destroy (task->task_data);

  if (task->result_destroy && task->result.pointer)
    task->result_destroy (task->result.pointer);

615 616 617
  if (task->error)
      g_error_free (task->error);

618 619 620 621 622 623 624 625 626 627 628
  if (G_TASK_IS_THREADED (task))
    {
      g_mutex_clear (&task->lock);
      g_cond_clear (&task->cond);
    }

  G_OBJECT_CLASS (g_task_parent_class)->finalize (object);
}

/**
 * g_task_new:
629 630
 * @source_object: (allow-none) (type GObject): the #GObject that owns
 *   this task, or %NULL.
631 632 633 634 635
 * @cancellable: (allow-none): optional #GCancellable object, %NULL to ignore.
 * @callback: (scope async): a #GAsyncReadyCallback.
 * @callback_data: (closure): user data passed to @callback.
 *
 * Creates a #GTask acting on @source_object, which will eventually be
636 637
 * used to invoke @callback in the current
 * [thread-default main context][g-main-context-push-thread-default].
638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680
 *
 * Call this in the "start" method of your asynchronous method, and
 * pass the #GTask around throughout the asynchronous operation. You
 * can use g_task_set_task_data() to attach task-specific data to the
 * object, which you can retrieve later via g_task_get_task_data().
 *
 * By default, if @cancellable is cancelled, then the return value of
 * the task will always be %G_IO_ERROR_CANCELLED, even if the task had
 * already completed before the cancellation. This allows for
 * simplified handling in cases where cancellation may imply that
 * other objects that the task depends on have been destroyed. If you
 * do not want this behavior, you can use
 * g_task_set_check_cancellable() to change it.
 *
 * Returns: a #GTask.
 *
 * Since: 2.36
 */
GTask *
g_task_new (gpointer              source_object,
            GCancellable         *cancellable,
            GAsyncReadyCallback   callback,
            gpointer              callback_data)
{
  GTask *task;
  GSource *source;

  task = g_object_new (G_TYPE_TASK, NULL);
  task->source_object = source_object ? g_object_ref (source_object) : NULL;
  task->cancellable = cancellable ? g_object_ref (cancellable) : NULL;
  task->callback = callback;
  task->callback_data = callback_data;
  task->context = g_main_context_ref_thread_default ();

  source = g_main_current_source ();
  if (source)
    task->creation_time = g_source_get_time (source);

  return task;
}

/**
 * g_task_report_error:
681 682
 * @source_object: (allow-none) (type GObject): the #GObject that owns
 *   this task, or %NULL.
683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715
 * @callback: (scope async): a #GAsyncReadyCallback.
 * @callback_data: (closure): user data passed to @callback.
 * @source_tag: an opaque pointer indicating the source of this task
 * @error: (transfer full): error to report
 *
 * Creates a #GTask and then immediately calls g_task_return_error()
 * on it. Use this in the wrapper function of an asynchronous method
 * when you want to avoid even calling the virtual method. You can
 * then use g_async_result_is_tagged() in the finish method wrapper to
 * check if the result there is tagged as having been created by the
 * wrapper method, and deal with it appropriately if so.
 *
 * See also g_task_report_new_error().
 *
 * Since: 2.36
 */
void
g_task_report_error (gpointer             source_object,
                     GAsyncReadyCallback  callback,
                     gpointer             callback_data,
                     gpointer             source_tag,
                     GError              *error)
{
  GTask *task;

  task = g_task_new (source_object, NULL, callback, callback_data);
  g_task_set_source_tag (task, source_tag);
  g_task_return_error (task, error);
  g_object_unref (task);
}

/**
 * g_task_report_new_error:
716 717
 * @source_object: (allow-none) (type GObject): the #GObject that owns
 *   this task, or %NULL.
718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783
 * @callback: (scope async): a #GAsyncReadyCallback.
 * @callback_data: (closure): user data passed to @callback.
 * @source_tag: an opaque pointer indicating the source of this task
 * @domain: a #GQuark.
 * @code: an error code.
 * @format: a string with format characters.
 * @...: a list of values to insert into @format.
 *
 * Creates a #GTask and then immediately calls
 * g_task_return_new_error() on it. Use this in the wrapper function
 * of an asynchronous method when you want to avoid even calling the
 * virtual method. You can then use g_async_result_is_tagged() in the
 * finish method wrapper to check if the result there is tagged as
 * having been created by the wrapper method, and deal with it
 * appropriately if so.
 *
 * See also g_task_report_error().
 *
 * Since: 2.36
 */
void
g_task_report_new_error (gpointer             source_object,
                         GAsyncReadyCallback  callback,
                         gpointer             callback_data,
                         gpointer             source_tag,
                         GQuark               domain,
                         gint                 code,
                         const char          *format,
                         ...)
{
  GError *error;
  va_list ap;

  va_start (ap, format);
  error = g_error_new_valist (domain, code, format, ap);
  va_end (ap);

  g_task_report_error (source_object, callback, callback_data,
                       source_tag, error);
}

/**
 * g_task_set_task_data:
 * @task: the #GTask
 * @task_data: (allow-none): task-specific data
 * @task_data_destroy: (allow-none): #GDestroyNotify for @task_data
 *
 * Sets @task's task data (freeing the existing task data, if any).
 *
 * Since: 2.36
 */
void
g_task_set_task_data (GTask          *task,
                      gpointer        task_data,
                      GDestroyNotify  task_data_destroy)
{
  if (task->task_data_destroy)
    task->task_data_destroy (task->task_data);

  task->task_data = task_data;
  task->task_data_destroy = task_data_destroy;
}

/**
 * g_task_set_priority:
 * @task: the #GTask
784
 * @priority: the [priority][io-priority] of the request
785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935
 *
 * Sets @task's priority. If you do not call this, it will default to
 * %G_PRIORITY_DEFAULT.
 *
 * This will affect the priority of #GSources created with
 * g_task_attach_source() and the scheduling of tasks run in threads,
 * and can also be explicitly retrieved later via
 * g_task_get_priority().
 *
 * Since: 2.36
 */
void
g_task_set_priority (GTask *task,
                     gint   priority)
{
  task->priority = priority;
}

/**
 * g_task_set_check_cancellable:
 * @task: the #GTask
 * @check_cancellable: whether #GTask will check the state of
 *   its #GCancellable for you.
 *
 * Sets or clears @task's check-cancellable flag. If this is %TRUE
 * (the default), then g_task_propagate_pointer(), etc, and
 * g_task_had_error() will check the task's #GCancellable first, and
 * if it has been cancelled, then they will consider the task to have
 * returned an "Operation was cancelled" error
 * (%G_IO_ERROR_CANCELLED), regardless of any other error or return
 * value the task may have had.
 *
 * If @check_cancellable is %FALSE, then the #GTask will not check the
 * cancellable itself, and it is up to @task's owner to do this (eg,
 * via g_task_return_error_if_cancelled()).
 *
 * If you are using g_task_set_return_on_cancel() as well, then
 * you must leave check-cancellable set %TRUE.
 *
 * Since: 2.36
 */
void
g_task_set_check_cancellable (GTask    *task,
                              gboolean  check_cancellable)
{
  g_return_if_fail (check_cancellable || !task->return_on_cancel);

  task->check_cancellable = check_cancellable;
}

static void g_task_thread_complete (GTask *task);

/**
 * g_task_set_return_on_cancel:
 * @task: the #GTask
 * @return_on_cancel: whether the task returns automatically when
 *   it is cancelled.
 *
 * Sets or clears @task's return-on-cancel flag. This is only
 * meaningful for tasks run via g_task_run_in_thread() or
 * g_task_run_in_thread_sync().
 *
 * If @return_on_cancel is %TRUE, then cancelling @task's
 * #GCancellable will immediately cause it to return, as though the
 * task's #GTaskThreadFunc had called
 * g_task_return_error_if_cancelled() and then returned.
 *
 * This allows you to create a cancellable wrapper around an
 * uninterruptable function. The #GTaskThreadFunc just needs to be
 * careful that it does not modify any externally-visible state after
 * it has been cancelled. To do that, the thread should call
 * g_task_set_return_on_cancel() again to (atomically) set
 * return-on-cancel %FALSE before making externally-visible changes;
 * if the task gets cancelled before the return-on-cancel flag could
 * be changed, g_task_set_return_on_cancel() will indicate this by
 * returning %FALSE.
 *
 * You can disable and re-enable this flag multiple times if you wish.
 * If the task's #GCancellable is cancelled while return-on-cancel is
 * %FALSE, then calling g_task_set_return_on_cancel() to set it %TRUE
 * again will cause the task to be cancelled at that point.
 *
 * If the task's #GCancellable is already cancelled before you call
 * g_task_run_in_thread()/g_task_run_in_thread_sync(), then the
 * #GTaskThreadFunc will still be run (for consistency), but the task
 * will also be completed right away.
 *
 * Returns: %TRUE if @task's return-on-cancel flag was changed to
 *   match @return_on_cancel. %FALSE if @task has already been
 *   cancelled.
 *
 * Since: 2.36
 */
gboolean
g_task_set_return_on_cancel (GTask    *task,
                             gboolean  return_on_cancel)
{
  g_return_val_if_fail (task->check_cancellable || !return_on_cancel, FALSE);

  if (!G_TASK_IS_THREADED (task))
    {
      task->return_on_cancel = return_on_cancel;
      return TRUE;
    }

  g_mutex_lock (&task->lock);
  if (task->thread_cancelled)
    {
      if (return_on_cancel && !task->return_on_cancel)
        {
          g_mutex_unlock (&task->lock);
          g_task_thread_complete (task);
        }
      else
        g_mutex_unlock (&task->lock);
      return FALSE;
    }
  task->return_on_cancel = return_on_cancel;
  g_mutex_unlock (&task->lock);

  return TRUE;
}

/**
 * g_task_set_source_tag:
 * @task: the #GTask
 * @source_tag: an opaque pointer indicating the source of this task
 *
 * Sets @task's source tag. You can use this to tag a task return
 * value with a particular pointer (usually a pointer to the function
 * doing the tagging) and then later check it using
 * g_task_get_source_tag() (or g_async_result_is_tagged()) in the
 * task's "finish" function, to figure out if the response came from a
 * particular place.
 *
 * Since: 2.36
 */
void
g_task_set_source_tag (GTask    *task,
                       gpointer  source_tag)
{
  task->source_tag = source_tag;
}

/**
 * g_task_get_source_object:
 * @task: a #GTask
 *
 * Gets the source object from @task. Like
 * g_async_result_get_source_object(), but does not ref the object.
 *
936
 * Returns: (transfer none) (type GObject): @task's source object, or %NULL
937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960
 *
 * Since: 2.36
 */
gpointer
g_task_get_source_object (GTask *task)
{
  return task->source_object;
}

static GObject *
g_task_ref_source_object (GAsyncResult *res)
{
  GTask *task = G_TASK (res);

  if (task->source_object)
    return g_object_ref (task->source_object);
  else
    return NULL;
}

/**
 * g_task_get_task_data:
 * @task: a #GTask
 *
961
 * Gets @task's `task_data`.
962
 *
963
 * Returns: (transfer none): @task's `task_data`.
964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993
 *
 * Since: 2.36
 */
gpointer
g_task_get_task_data (GTask *task)
{
  return task->task_data;
}

/**
 * g_task_get_priority:
 * @task: a #GTask
 *
 * Gets @task's priority
 *
 * Returns: @task's priority
 *
 * Since: 2.36
 */
gint
g_task_get_priority (GTask *task)
{
  return task->priority;
}

/**
 * g_task_get_context:
 * @task: a #GTask
 *
 * Gets the #GMainContext that @task will return its result in (that
994 995 996
 * is, the context that was the
 * [thread-default main context][g-main-context-push-thread-default]
 * at the point when @task was created).
997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146
 *
 * This will always return a non-%NULL value, even if the task's
 * context is the default #GMainContext.
 *
 * Returns: (transfer none): @task's #GMainContext
 *
 * Since: 2.36
 */
GMainContext *
g_task_get_context (GTask *task)
{
  return task->context;
}

/**
 * g_task_get_cancellable:
 * @task: a #GTask
 *
 * Gets @task's #GCancellable
 *
 * Returns: (transfer none): @task's #GCancellable
 *
 * Since: 2.36
 */
GCancellable *
g_task_get_cancellable (GTask *task)
{
  return task->cancellable;
}

/**
 * g_task_get_check_cancellable:
 * @task: the #GTask
 *
 * Gets @task's check-cancellable flag. See
 * g_task_set_check_cancellable() for more details.
 *
 * Since: 2.36
 */
gboolean
g_task_get_check_cancellable (GTask *task)
{
  return task->check_cancellable;
}

/**
 * g_task_get_return_on_cancel:
 * @task: the #GTask
 *
 * Gets @task's return-on-cancel flag. See
 * g_task_set_return_on_cancel() for more details.
 *
 * Since: 2.36
 */
gboolean
g_task_get_return_on_cancel (GTask *task)
{
  return task->return_on_cancel;
}

/**
 * g_task_get_source_tag:
 * @task: a #GTask
 *
 * Gets @task's source tag. See g_task_set_source_tag().
 *
 * Return value: (transfer none): @task's source tag
 *
 * Since: 2.36
 */
gpointer
g_task_get_source_tag (GTask *task)
{
  return task->source_tag;
}


static void
g_task_return_now (GTask *task)
{
  g_main_context_push_thread_default (task->context);
  task->callback (task->source_object,
                  G_ASYNC_RESULT (task),
                  task->callback_data);
  g_main_context_pop_thread_default (task->context);
}

static gboolean
complete_in_idle_cb (gpointer task)
{
  g_task_return_now (task);
  g_object_unref (task);
  return FALSE;
}

typedef enum {
  G_TASK_RETURN_SUCCESS,
  G_TASK_RETURN_ERROR,
  G_TASK_RETURN_FROM_THREAD
} GTaskReturnType;

static void
g_task_return (GTask           *task,
               GTaskReturnType  type)
{
  GSource *source;

  if (type == G_TASK_RETURN_SUCCESS)
    task->result_set = TRUE;

  if (task->synchronous || !task->callback)
    return;

  /* Normally we want to invoke the task's callback when its return
   * value is set. But if the task is running in a thread, then we
   * want to wait until after the task_func returns, to simplify
   * locking/refcounting/etc.
   */
  if (G_TASK_IS_THREADED (task) && type != G_TASK_RETURN_FROM_THREAD)
    return;

  g_object_ref (task);

  /* See if we can complete the task immediately. First, we have to be
   * running inside the task's thread/GMainContext.
   */
  source = g_main_current_source ();
  if (source && g_source_get_context (source) == task->context)
    {
      /* Second, we can only complete immediately if this is not the
       * same iteration of the main loop that the task was created in.
       */
      if (g_source_get_time (source) > task->creation_time)
        {
          g_task_return_now (task);
          g_object_unref (task);
          return;
        }
    }

  /* Otherwise, complete in the next iteration */
  source = g_idle_source_new ();
  g_task_attach_source (task, source, complete_in_idle_cb);
  g_source_unref (source);
}


/**
 * GTaskThreadFunc:
 * @task: the #GTask
1147
 * @source_object: (type GObject): @task's source object
1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163
 * @task_data: @task's task data
 * @cancellable: @task's #GCancellable, or %NULL
 *
 * The prototype for a task function to be run in a thread via
 * g_task_run_in_thread() or g_task_run_in_thread_sync().
 *
 * If the return-on-cancel flag is set on @task, and @cancellable gets
 * cancelled, then the #GTask will be completed immediately (as though
 * g_task_return_error_if_cancelled() had been called), without
 * waiting for the task function to complete. However, the task
 * function will continue running in its thread in the background. The
 * function therefore needs to be careful about how it uses
 * externally-visible state in this case. See
 * g_task_set_return_on_cancel() for more details.
 *
 * Other than in that case, @task will be completed when the
1164
 * #GTaskThreadFunc returns, not when it calls a
1165
 * `g_task_return_` function.
1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186
 *
 * Since: 2.36
 */

static void task_thread_cancelled (GCancellable *cancellable,
                                   gpointer      user_data);

static void
g_task_thread_complete (GTask *task)
{
  g_mutex_lock (&task->lock);
  if (task->thread_complete)
    {
      /* The task belatedly completed after having been cancelled
       * (or was cancelled in the midst of being completed).
       */
      g_mutex_unlock (&task->lock);
      return;
    }

  task->thread_complete = TRUE;
1187 1188 1189 1190 1191 1192 1193 1194 1195

  if (task->blocking_other_task)
    {
      g_mutex_lock (&task_pool_mutex);
      g_thread_pool_set_max_threads (task_pool,
                                     g_thread_pool_get_max_threads (task_pool) - 1,
                                     NULL);
      g_mutex_unlock (&task_pool_mutex);
    }
1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
  g_mutex_unlock (&task->lock);

  if (task->cancellable)
    g_signal_handlers_disconnect_by_func (task->cancellable, task_thread_cancelled, task);

  if (task->synchronous)
    g_cond_signal (&task->cond);
  else
    g_task_return (task, G_TASK_RETURN_FROM_THREAD);
}

static void
g_task_thread_pool_thread (gpointer thread_data,
                           gpointer pool_data)
{
  GTask *task = thread_data;

1213 1214
  g_private_set (&task_private, task);

1215 1216 1217
  task->task_func (task, task->source_object, task->task_data,
                   task->cancellable);
  g_task_thread_complete (task);
1218 1219

  g_private_set (&task_private, NULL);
1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285
  g_object_unref (task);
}

static void
task_thread_cancelled (GCancellable *cancellable,
                       gpointer      user_data)
{
  GTask *task = user_data;

  g_task_thread_pool_resort ();

  g_mutex_lock (&task->lock);
  task->thread_cancelled = TRUE;

  if (!task->return_on_cancel)
    {
      g_mutex_unlock (&task->lock);
      return;
    }

  /* We don't actually set task->error; g_task_return_error() doesn't
   * use a lock, and g_task_propagate_error() will call
   * g_cancellable_set_error_if_cancelled() anyway.
   */
  g_mutex_unlock (&task->lock);
  g_task_thread_complete (task);
}

static void
task_thread_cancelled_disconnect_notify (gpointer  task,
                                         GClosure *closure)
{
  g_object_unref (task);
}

static void
g_task_start_task_thread (GTask           *task,
                          GTaskThreadFunc  task_func)
{
  g_mutex_init (&task->lock);
  g_cond_init (&task->cond);

  g_mutex_lock (&task->lock);

  task->task_func = task_func;

  if (task->cancellable)
    {
      if (task->return_on_cancel &&
          g_cancellable_set_error_if_cancelled (task->cancellable,
                                                &task->error))
        {
          task->thread_cancelled = task->thread_complete = TRUE;
          g_thread_pool_push (task_pool, g_object_ref (task), NULL);
          return;
        }

      g_signal_connect_data (task->cancellable, "cancelled",
                             G_CALLBACK (task_thread_cancelled),
                             g_object_ref (task),
                             task_thread_cancelled_disconnect_notify, 0);
    }

  g_thread_pool_push (task_pool, g_object_ref (task), &task->error);
  if (task->error)
    task->thread_complete = TRUE;
1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297
  else if (g_private_get (&task_private))
    {
      /* This thread is being spawned from another GTask thread, so
       * bump up max-threads so we don't starve.
       */
      g_mutex_lock (&task_pool_mutex);
      if (g_thread_pool_set_max_threads (task_pool,
                                         g_thread_pool_get_max_threads (task_pool) + 1,
                                         NULL))
        task->blocking_other_task = TRUE;
      g_mutex_unlock (&task_pool_mutex);
    }
1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348
}

/**
 * g_task_run_in_thread:
 * @task: a #GTask
 * @task_func: a #GTaskThreadFunc
 *
 * Runs @task_func in another thread. When @task_func returns, @task's
 * #GAsyncReadyCallback will be invoked in @task's #GMainContext.
 *
 * This takes a ref on @task until the task completes.
 *
 * See #GTaskThreadFunc for more details about how @task_func is handled.
 *
 * Since: 2.36
 */
void
g_task_run_in_thread (GTask           *task,
                      GTaskThreadFunc  task_func)
{
  g_return_if_fail (G_IS_TASK (task));

  g_object_ref (task);
  g_task_start_task_thread (task, task_func);

  /* The task may already be cancelled, or g_thread_pool_push() may
   * have failed.
   */
  if (task->thread_complete)
    {
      g_mutex_unlock (&task->lock);
      g_task_return (task, G_TASK_RETURN_FROM_THREAD);
    }
  else
    g_mutex_unlock (&task->lock);

  g_object_unref (task);
}

/**
 * g_task_run_in_thread_sync:
 * @task: a #GTask
 * @task_func: a #GTaskThreadFunc
 *
 * Runs @task_func in another thread, and waits for it to return or be
 * cancelled. You can use g_task_propagate_pointer(), etc, afterward
 * to get the result of @task_func.
 *
 * See #GTaskThreadFunc for more details about how @task_func is handled.
 *
 * Normally this is used with tasks created with a %NULL
1349
 * `callback`, but note that even if the task does
1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379
 * have a callback, it will not be invoked when @task_func returns.
 *
 * Since: 2.36
 */
void
g_task_run_in_thread_sync (GTask           *task,
                           GTaskThreadFunc  task_func)
{
  g_return_if_fail (G_IS_TASK (task));

  g_object_ref (task);

  task->synchronous = TRUE;
  g_task_start_task_thread (task, task_func);

  while (!task->thread_complete)
    g_cond_wait (&task->cond, &task->lock);

  g_mutex_unlock (&task->lock);
  g_object_unref (task);
}

/**
 * g_task_attach_source:
 * @task: a #GTask
 * @source: the source to attach
 * @callback: the callback to invoke when @source triggers
 *
 * A utility function for dealing with async operations where you need
 * to wait for a #GSource to trigger. Attaches @source to @task's
1380 1381
 * #GMainContext with @task's [priority][io-priority], and sets @source's
 * callback to @callback, with @task as the callback's `user_data`.
1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717
 *
 * This takes a reference on @task until @source is destroyed.
 *
 * Since: 2.36
 */
void
g_task_attach_source (GTask       *task,
                      GSource     *source,
                      GSourceFunc  callback)
{
  g_source_set_callback (source, callback,
                         g_object_ref (task), g_object_unref);
  g_source_set_priority (source, task->priority);
  g_source_attach (source, task->context);
}


static gboolean
g_task_propagate_error (GTask   *task,
                        GError **error)
{
  if (task->check_cancellable &&
      g_cancellable_set_error_if_cancelled (task->cancellable, error))
    return TRUE;
  else if (task->error)
    {
      g_propagate_error (error, task->error);
      task->error = NULL;
      return TRUE;
    }
  else
    return FALSE;
}

/**
 * g_task_return_pointer:
 * @task: a #GTask
 * @result: (allow-none) (transfer full): the pointer result of a task
 *     function
 * @result_destroy: (allow-none): a #GDestroyNotify function.
 *
 * Sets @task's result to @result and completes the task. If @result
 * is not %NULL, then @result_destroy will be used to free @result if
 * the caller does not take ownership of it with
 * g_task_propagate_pointer().
 *
 * "Completes the task" means that for an ordinary asynchronous task
 * it will either invoke the task's callback, or else queue that
 * callback to be invoked in the proper #GMainContext, or in the next
 * iteration of the current #GMainContext. For a task run via
 * g_task_run_in_thread() or g_task_run_in_thread_sync(), calling this
 * method will save @result to be returned to the caller later, but
 * the task will not actually be completed until the #GTaskThreadFunc
 * exits.
 *
 * Note that since the task may be completed before returning from
 * g_task_return_pointer(), you cannot assume that @result is still
 * valid after calling this, unless you are still holding another
 * reference on it.
 *
 * Since: 2.36
 */
void
g_task_return_pointer (GTask          *task,
                       gpointer        result,
                       GDestroyNotify  result_destroy)
{
  g_return_if_fail (task->result_set == FALSE);

  task->result.pointer = result;
  task->result_destroy = result_destroy;

  g_task_return (task, G_TASK_RETURN_SUCCESS);
}

/**
 * g_task_propagate_pointer:
 * @task: a #GTask
 * @error: return location for a #GError
 *
 * Gets the result of @task as a pointer, and transfers ownership
 * of that value to the caller.
 *
 * If the task resulted in an error, or was cancelled, then this will
 * instead return %NULL and set @error.
 *
 * Since this method transfers ownership of the return value (or
 * error) to the caller, you may only call it once.
 *
 * Returns: (transfer full): the task result, or %NULL on error
 *
 * Since: 2.36
 */
gpointer
g_task_propagate_pointer (GTask   *task,
                          GError **error)
{
  if (g_task_propagate_error (task, error))
    return NULL;

  g_return_val_if_fail (task->result_set == TRUE, NULL);

  task->result_destroy = NULL;
  task->result_set = FALSE;
  return task->result.pointer;
}

/**
 * g_task_return_int:
 * @task: a #GTask.
 * @result: the integer (#gssize) result of a task function.
 *
 * Sets @task's result to @result and completes the task (see
 * g_task_return_pointer() for more discussion of exactly what this
 * means).
 *
 * Since: 2.36
 */
void
g_task_return_int (GTask  *task,
                   gssize  result)
{
  g_return_if_fail (task->result_set == FALSE);

  task->result.size = result;

  g_task_return (task, G_TASK_RETURN_SUCCESS);
}

/**
 * g_task_propagate_int:
 * @task: a #GTask.
 * @error: return location for a #GError
 *
 * Gets the result of @task as an integer (#gssize).
 *
 * If the task resulted in an error, or was cancelled, then this will
 * instead return -1 and set @error.
 *
 * Since this method transfers ownership of the return value (or
 * error) to the caller, you may only call it once.
 *
 * Returns: the task result, or -1 on error
 *
 * Since: 2.36
 */
gssize
g_task_propagate_int (GTask   *task,
                      GError **error)
{
  if (g_task_propagate_error (task, error))
    return -1;

  g_return_val_if_fail (task->result_set == TRUE, -1);

  task->result_set = FALSE;
  return task->result.size;
}

/**
 * g_task_return_boolean:
 * @task: a #GTask.
 * @result: the #gboolean result of a task function.
 *
 * Sets @task's result to @result and completes the task (see
 * g_task_return_pointer() for more discussion of exactly what this
 * means).
 *
 * Since: 2.36
 */
void
g_task_return_boolean (GTask    *task,
                       gboolean  result)
{
  g_return_if_fail (task->result_set == FALSE);

  task->result.boolean = result;

  g_task_return (task, G_TASK_RETURN_SUCCESS);
}

/**
 * g_task_propagate_boolean:
 * @task: a #GTask.
 * @error: return location for a #GError
 *
 * Gets the result of @task as a #gboolean.
 *
 * If the task resulted in an error, or was cancelled, then this will
 * instead return %FALSE and set @error.
 *
 * Since this method transfers ownership of the return value (or
 * error) to the caller, you may only call it once.
 *
 * Returns: the task result, or %FALSE on error
 *
 * Since: 2.36
 */
gboolean
g_task_propagate_boolean (GTask   *task,
                          GError **error)
{
  if (g_task_propagate_error (task, error))
    return FALSE;

  g_return_val_if_fail (task->result_set == TRUE, FALSE);

  task->result_set = FALSE;
  return task->result.boolean;
}

/**
 * g_task_return_error:
 * @task: a #GTask.
 * @error: (transfer full): the #GError result of a task function.
 *
 * Sets @task's result to @error (which @task assumes ownership of)
 * and completes the task (see g_task_return_pointer() for more
 * discussion of exactly what this means).
 *
 * Note that since the task takes ownership of @error, and since the
 * task may be completed before returning from g_task_return_error(),
 * you cannot assume that @error is still valid after calling this.
 * Call g_error_copy() on the error if you need to keep a local copy
 * as well.
 *
 * See also g_task_return_new_error().
 *
 * Since: 2.36
 */
void
g_task_return_error (GTask  *task,
                     GError *error)
{
  g_return_if_fail (task->result_set == FALSE);
  g_return_if_fail (error != NULL);

  task->error = error;

  g_task_return (task, G_TASK_RETURN_ERROR);
}

/**
 * g_task_return_new_error:
 * @task: a #GTask.
 * @domain: a #GQuark.
 * @code: an error code.
 * @format: a string with format characters.
 * @...: a list of values to insert into @format.
 *
 * Sets @task's result to a new #GError created from @domain, @code,
 * @format, and the remaining arguments, and completes the task (see
 * g_task_return_pointer() for more discussion of exactly what this
 * means).
 *
 * See also g_task_return_error().
 *
 * Since: 2.36
 */
void
g_task_return_new_error (GTask           *task,
                         GQuark           domain,
                         gint             code,
                         const char      *format,
                         ...)
{
  GError *error;
  va_list args;

  va_start (args, format);
  error = g_error_new_valist (domain, code, format, args);
  va_end (args);

  g_task_return_error (task, error);
}

/**
 * g_task_return_error_if_cancelled:
 * @task: a #GTask
 *
 * Checks if @task's #GCancellable has been cancelled, and if so, sets
 * @task's error accordingly and completes the task (see
 * g_task_return_pointer() for more discussion of exactly what this
 * means).
 *
 * Return value: %TRUE if @task has been cancelled, %FALSE if not
 *
 * Since: 2.36
 */
gboolean
g_task_return_error_if_cancelled (GTask *task)
{
  GError *error = NULL;

  g_return_val_if_fail (task->result_set == FALSE, FALSE);

  if (g_cancellable_set_error_if_cancelled (task->cancellable, &error))
    {
      /* We explicitly set task->error so this works even when
       * check-cancellable is not set.
       */
      g_clear_error (&task->error);
      task->error = error;

      g_task_return (task, G_TASK_RETURN_ERROR);
      return TRUE;
    }
  else
    return FALSE;
}

/**
 * g_task_had_error:
 * @task: a #GTask.
 *
 * Tests if @task resulted in an error.
 *
 * Returns: %TRUE if the task resulted in an error, %FALSE otherwise.
 *
 * Since: 2.36
 */
gboolean
g_task_had_error (GTask *task)
{
  if (task->error != NULL)
    return TRUE;

  if (task->check_cancellable && g_cancellable_is_cancelled (task->cancellable))
    return TRUE;

  return FALSE;
}

/**
 * g_task_is_valid:
 * @result: (type Gio.AsyncResult): A #GAsyncResult
1718 1719
 * @source_object: (allow-none) (type GObject): the source object
 *   expected to be associated with the task
1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748
 *
 * Checks that @result is a #GTask, and that @source_object is its
 * source object (or that @source_object is %NULL and @result has no
 * source object). This can be used in g_return_if_fail() checks.
 *
 * Return value: %TRUE if @result and @source_object are valid, %FALSE
 * if not
 *
 * Since: 2.36
 */
gboolean
g_task_is_valid (gpointer result,
                 gpointer source_object)
{
  if (!G_IS_TASK (result))
    return FALSE;

  return G_TASK (result)->source_object == source_object;
}

static gint
g_task_compare_priority (gconstpointer a,
                         gconstpointer b,
                         gpointer      user_data)
{
  const GTask *ta = a;
  const GTask *tb = b;
  gboolean a_cancelled, b_cancelled;

1749 1750 1751 1752 1753 1754 1755 1756 1757
  /* Tasks that are causing other tasks to block have higher
   * priority.
   */
  if (ta->blocking_other_task && !tb->blocking_other_task)
    return -1;
  else if (tb->blocking_other_task && !ta->blocking_other_task)
    return 1;

  /* Let already-cancelled tasks finish right away */
1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774
  a_cancelled = (ta->check_cancellable &&
                 g_cancellable_is_cancelled (ta->cancellable));
  b_cancelled = (tb->check_cancellable &&
                 g_cancellable_is_cancelled (tb->cancellable));
  if (a_cancelled && !b_cancelled)
    return -1;
  else if (b_cancelled && !a_cancelled)
    return 1;

  /* Lower priority == run sooner == negative return value */
  return ta->priority - tb->priority;
}

static void
g_task_thread_pool_init (void)
{
  task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
1775
                                 10, FALSE, NULL);
1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814
  g_assert (task_pool != NULL);

  g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}

static void
g_task_thread_pool_resort (void)
{
  g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);
}

static void
g_task_class_init (GTaskClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  gobject_class->finalize = g_task_finalize;
}

static gpointer
g_task_get_user_data (GAsyncResult *res)
{
  return G_TASK (res)->callback_data;
}

static gboolean
g_task_is_tagged (GAsyncResult *res,
                  gpointer      source_tag)
{
  return G_TASK (res)->source_tag == source_tag;
}

static void
g_task_async_result_iface_init (GAsyncResultIface *iface)
{
  iface->get_user_data = g_task_get_user_data;
  iface->get_source_object = g_task_ref_source_object;
  iface->is_tagged = g_task_is_tagged;
}