Revert of New task queueing primitive for async tasks: TaskQueue.

webrtc/base/task_queue_gcd.cc

-/*
- *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-// This file contains the implementation of TaskQueue for Mac and iOS.
-// The implementation uses Grand Central Dispatch queues (GCD) to
-// do the actual task queuing.
-
-#include "webrtc/base/task_queue.h"
-
-#include <string.h>
-
-#include "webrtc/base/checks.h"
-#include "webrtc/base/logging.h"
-#include "webrtc/base/task_queue_posix.h"
-
-namespace rtc {
-using internal::GetQueuePtrTls;
-using internal::AutoSetCurrentQueuePtr;
-
-struct TaskQueue::QueueContext {
-  explicit QueueContext(TaskQueue* q) : queue(q), is_active(true) {}
-
-  static void SetNotActive(void* context) {
-    QueueContext* qc = static_cast<QueueContext*>(context);
-    qc->is_active = false;
-  }
-
-  static void DeleteContext(void* context) {
-    QueueContext* qc = static_cast<QueueContext*>(context);
-    delete qc;
-  }
-
-  TaskQueue* const queue;
-  bool is_active;
-};
-
-struct TaskQueue::TaskContext {
-  TaskContext(QueueContext* queue_ctx, std::unique_ptr<QueuedTask> task)
-      : queue_ctx(queue_ctx), task(std::move(task)) {}
-  virtual ~TaskContext() {}
-
-  static void RunTask(void* context) {
-    std::unique_ptr<TaskContext> tc(static_cast<TaskContext*>(context));
-    if (tc->queue_ctx->is_active) {
-      AutoSetCurrentQueuePtr set_current(tc->queue_ctx->queue);
-      if (!tc->task->Run())
-        tc->task.release();
-    }
-  }
-
-  QueueContext* const queue_ctx;
-  std::unique_ptr<QueuedTask> task;
-};
-
-// Special case context for holding two tasks, a |first_task| + the task
-// that's owned by the parent struct, TaskContext, that then becomes the
-// second (i.e. 'reply') task.
-struct TaskQueue::PostTaskAndReplyContext : public TaskQueue::TaskContext {
-  explicit PostTaskAndReplyContext(QueueContext* first_queue_ctx,
-                                   std::unique_ptr<QueuedTask> first_task,
-                                   QueueContext* second_queue_ctx,
-                                   std::unique_ptr<QueuedTask> second_task)
-      : TaskContext(second_queue_ctx, std::move(second_task)),
-        first_queue_ctx(first_queue_ctx),
-        first_task(std::move(first_task)) {
-    // Retain the reply queue for as long as this object lives.
-    // If we don't, we may have memory leaks and/or failures.
-    dispatch_retain(first_queue_ctx->queue->queue_);
-  }
-  ~PostTaskAndReplyContext() override {
-    dispatch_release(first_queue_ctx->queue->queue_);
-  }
-
-  static void RunTask(void* context) {
-    auto* rc = static_cast<PostTaskAndReplyContext*>(context);
-    if (rc->first_queue_ctx->is_active) {
-      AutoSetCurrentQueuePtr set_current(rc->first_queue_ctx->queue);
-      if (!rc->first_task->Run())
-        rc->first_task.release();
-    }
-    // Post the reply task.  This hands the work over to the parent struct.
-    // This task will eventually delete |this|.
-    dispatch_async_f(rc->queue_ctx->queue->queue_, rc, &TaskContext::RunTask);
-  }
-
-  QueueContext* const first_queue_ctx;
-  std::unique_ptr<QueuedTask> first_task;
-};
-
-TaskQueue::TaskQueue(const char* queue_name)
-    : queue_(dispatch_queue_create(queue_name, DISPATCH_QUEUE_SERIAL)),
-      context_(new QueueContext(this)) {
-  RTC_DCHECK(queue_name);
-  RTC_CHECK(queue_);
-  dispatch_set_context(queue_, context_);
-  // Assign a finalizer that will delete the context when the last reference
-  // to the queue is released.  This may run after the TaskQueue object has
-  // been deleted.
-  dispatch_set_finalizer_f(queue_, &QueueContext::DeleteContext);
-}
-
-TaskQueue::~TaskQueue() {
-  RTC_DCHECK(!IsCurrent());
-  // Implementation/behavioral note:
-  // Dispatch queues are reference counted via calls to dispatch_retain and
-  // dispatch_release. Pending blocks submitted to a queue also hold a
-  // reference to the queue until they have finished. Once all references to a
-  // queue have been released, the queue will be deallocated by the system.
-  // This is why we check the context before running tasks.
-
-  // Use dispatch_sync to set the context to null to guarantee that there's not
-  // a race between checking the context and using it from a task.
-  dispatch_sync_f(queue_, context_, &QueueContext::SetNotActive);
-  dispatch_release(queue_);
-}
-
-// static
-TaskQueue* TaskQueue::Current() {
-  return static_cast<TaskQueue*>(pthread_getspecific(GetQueuePtrTls()));
-}
-
-// static
-bool TaskQueue::IsCurrent(const char* queue_name) {
-  TaskQueue* current = Current();
-  return current &&
-         strcmp(queue_name, dispatch_queue_get_label(current->queue_)) == 0;
-}
-
-bool TaskQueue::IsCurrent() const {
-  RTC_DCHECK(queue_);
-  return this == Current();
-}
-
-void TaskQueue::PostTask(std::unique_ptr<QueuedTask> task) {
-  auto* context = new TaskContext(context_, std::move(task));
-  dispatch_async_f(queue_, context, &TaskContext::RunTask);
-}
-
-void TaskQueue::PostDelayedTask(std::unique_ptr<QueuedTask> task,
-                                uint32_t milliseconds) {
-  auto* context = new TaskContext(context_, std::move(task));
-  dispatch_after_f(
-      dispatch_time(DISPATCH_TIME_NOW, milliseconds * NSEC_PER_MSEC), queue_,
-      context, &TaskContext::RunTask);
-}
-
-void TaskQueue::PostTaskAndReply(std::unique_ptr<QueuedTask> task,
-                                 std::unique_ptr<QueuedTask> reply,
-                                 TaskQueue* reply_queue) {
-  auto* context = new PostTaskAndReplyContext(
-      context_, std::move(task), reply_queue->context_, std::move(reply));
-  dispatch_async_f(queue_, context, &PostTaskAndReplyContext::RunTask);
-}
-
-void TaskQueue::PostTaskAndReply(std::unique_ptr<QueuedTask> task,
-                                 std::unique_ptr<QueuedTask> reply) {
-  return PostTaskAndReply(std::move(task), std::move(reply), Current());
-}
-
-}  // namespace rtc