| /* |
| * 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. |
| */ |
| |
| #ifndef RTC_BASE_TASK_QUEUE_H_ |
| #define RTC_BASE_TASK_QUEUE_H_ |
| |
| #include <stdint.h> |
| #include <memory> |
| #include <utility> |
| |
| #include "absl/memory/memory.h" |
| #include "api/task_queue/queued_task.h" |
| #include "api/task_queue/task_queue_base.h" |
| #include "api/task_queue/task_queue_factory.h" |
| #include "rtc_base/constructor_magic.h" |
| #include "rtc_base/system/rtc_export.h" |
| #include "rtc_base/task_utils/to_queued_task.h" |
| #include "rtc_base/thread_annotations.h" |
| |
| namespace rtc { |
| |
| // TODO(danilchap): Remove the alias when all of webrtc is updated to use |
| // webrtc::QueuedTask directly. |
| using ::webrtc::QueuedTask; |
| |
| // Implements a task queue that asynchronously executes tasks in a way that |
| // guarantees that they're executed in FIFO order and that tasks never overlap. |
| // Tasks may always execute on the same worker thread and they may not. |
| // To DCHECK that tasks are executing on a known task queue, use IsCurrent(). |
| // |
| // Here are some usage examples: |
| // |
| // 1) Asynchronously running a lambda: |
| // |
| // class MyClass { |
| // ... |
| // TaskQueue queue_("MyQueue"); |
| // }; |
| // |
| // void MyClass::StartWork() { |
| // queue_.PostTask([]() { Work(); }); |
| // ... |
| // |
| // 2) Posting a custom task on a timer. The task posts itself again after |
| // every running: |
| // |
| // class TimerTask : public QueuedTask { |
| // public: |
| // TimerTask() {} |
| // private: |
| // bool Run() override { |
| // ++count_; |
| // TaskQueue::Current()->PostDelayedTask( |
| // std::unique_ptr<QueuedTask>(this), 1000); |
| // // Ownership has been transferred to the next occurance, |
| // // so return false to prevent from being deleted now. |
| // return false; |
| // } |
| // int count_ = 0; |
| // }; |
| // ... |
| // queue_.PostDelayedTask( |
| // std::unique_ptr<QueuedTask>(new TimerTask()), 1000); |
| // |
| // For more examples, see task_queue_unittests.cc. |
| // |
| // A note on destruction: |
| // |
| // When a TaskQueue is deleted, pending tasks will not be executed but they will |
| // be deleted. The deletion of tasks may happen asynchronously after the |
| // TaskQueue itself has been deleted or it may happen synchronously while the |
| // TaskQueue instance is being deleted. This may vary from one OS to the next |
| // so assumptions about lifetimes of pending tasks should not be made. |
| class RTC_LOCKABLE RTC_EXPORT TaskQueue { |
| public: |
| // TaskQueue priority levels. On some platforms these will map to thread |
| // priorities, on others such as Mac and iOS, GCD queue priorities. |
| using Priority = ::webrtc::TaskQueueFactory::Priority; |
| |
| explicit TaskQueue(std::unique_ptr<webrtc::TaskQueueBase, |
| webrtc::TaskQueueDeleter> task_queue); |
| explicit TaskQueue(const char* queue_name, |
| Priority priority = Priority::NORMAL); |
| ~TaskQueue(); |
| |
| static TaskQueue* Current(); |
| |
| // Used for DCHECKing the current queue. |
| bool IsCurrent() const; |
| |
| // Returns non-owning pointer to the task queue implementation. |
| webrtc::TaskQueueBase* Get() { return impl_; } |
| |
| // TODO(tommi): For better debuggability, implement RTC_FROM_HERE. |
| |
| // Ownership of the task is passed to PostTask. |
| void PostTask(std::unique_ptr<QueuedTask> task); |
| |
| // Schedules a task to execute a specified number of milliseconds from when |
| // the call is made. The precision should be considered as "best effort" |
| // and in some cases, such as on Windows when all high precision timers have |
| // been used up, can be off by as much as 15 millseconds (although 8 would be |
| // more likely). This can be mitigated by limiting the use of delayed tasks. |
| void PostDelayedTask(std::unique_ptr<QueuedTask> task, uint32_t milliseconds); |
| |
| // std::enable_if is used here to make sure that calls to PostTask() with |
| // std::unique_ptr<SomeClassDerivedFromQueuedTask> would not end up being |
| // caught by this template. |
| template <class Closure, |
| typename std::enable_if<!std::is_convertible< |
| Closure, |
| std::unique_ptr<QueuedTask>>::value>::type* = nullptr> |
| void PostTask(Closure&& closure) { |
| PostTask(webrtc::ToQueuedTask(std::forward<Closure>(closure))); |
| } |
| |
| // See documentation above for performance expectations. |
| template <class Closure, |
| typename std::enable_if<!std::is_convertible< |
| Closure, |
| std::unique_ptr<QueuedTask>>::value>::type* = nullptr> |
| void PostDelayedTask(Closure&& closure, uint32_t milliseconds) { |
| PostDelayedTask(webrtc::ToQueuedTask(std::forward<Closure>(closure)), |
| milliseconds); |
| } |
| |
| private: |
| webrtc::TaskQueueBase* const impl_; |
| |
| RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue); |
| }; |
| |
| } // namespace rtc |
| |
| #endif // RTC_BASE_TASK_QUEUE_H_ |