| /* |
| * 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 WEBRTC_RTC_BASE_TASK_QUEUE_H_ |
| #define WEBRTC_RTC_BASE_TASK_QUEUE_H_ |
| |
| #include <list> |
| #include <memory> |
| #include <queue> |
| #include <type_traits> |
| |
| #if defined(WEBRTC_MAC) |
| #include <dispatch/dispatch.h> |
| #endif |
| |
| #include "webrtc/rtc_base/constructormagic.h" |
| #include "webrtc/rtc_base/criticalsection.h" |
| #include "webrtc/rtc_base/scoped_ref_ptr.h" |
| |
| namespace rtc { |
| |
| // Base interface for asynchronously executed tasks. |
| // The interface basically consists of a single function, Run(), that executes |
| // on the target queue. For more details see the Run() method and TaskQueue. |
| class QueuedTask { |
| public: |
| QueuedTask() {} |
| virtual ~QueuedTask() {} |
| |
| // Main routine that will run when the task is executed on the desired queue. |
| // The task should return |true| to indicate that it should be deleted or |
| // |false| to indicate that the queue should consider ownership of the task |
| // having been transferred. Returning |false| can be useful if a task has |
| // re-posted itself to a different queue or is otherwise being re-used. |
| virtual bool Run() = 0; |
| |
| private: |
| RTC_DISALLOW_COPY_AND_ASSIGN(QueuedTask); |
| }; |
| |
| // Simple implementation of QueuedTask for use with rtc::Bind and lambdas. |
| template <class Closure> |
| class ClosureTask : public QueuedTask { |
| public: |
| explicit ClosureTask(const Closure& closure) : closure_(closure) {} |
| |
| private: |
| bool Run() override { |
| closure_(); |
| return true; |
| } |
| |
| Closure closure_; |
| }; |
| |
| // Extends ClosureTask to also allow specifying cleanup code. |
| // This is useful when using lambdas if guaranteeing cleanup, even if a task |
| // was dropped (queue is too full), is required. |
| template <class Closure, class Cleanup> |
| class ClosureTaskWithCleanup : public ClosureTask<Closure> { |
| public: |
| ClosureTaskWithCleanup(const Closure& closure, Cleanup cleanup) |
| : ClosureTask<Closure>(closure), cleanup_(cleanup) {} |
| ~ClosureTaskWithCleanup() { cleanup_(); } |
| |
| private: |
| Cleanup cleanup_; |
| }; |
| |
| // Convenience function to construct closures that can be passed directly |
| // to methods that support std::unique_ptr<QueuedTask> but not template |
| // based parameters. |
| template <class Closure> |
| static std::unique_ptr<QueuedTask> NewClosure(const Closure& closure) { |
| return std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure)); |
| } |
| |
| template <class Closure, class Cleanup> |
| static std::unique_ptr<QueuedTask> NewClosure(const Closure& closure, |
| const Cleanup& cleanup) { |
| return std::unique_ptr<QueuedTask>( |
| new ClosureTaskWithCleanup<Closure, Cleanup>(closure, cleanup)); |
| } |
| |
| // 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) Doing work asynchronously on a worker queue and providing a notification |
| // callback on the current queue, when the work has been done: |
| // |
| // void MyClass::StartWorkAndLetMeKnowWhenDone( |
| // std::unique_ptr<QueuedTask> callback) { |
| // DCHECK(TaskQueue::Current()) << "Need to be running on a queue"; |
| // queue_.PostTaskAndReply([]() { Work(); }, std::move(callback)); |
| // } |
| // ... |
| // my_class->StartWorkAndLetMeKnowWhenDone( |
| // NewClosure([]() { LOG(INFO) << "The work is done!";})); |
| // |
| // 3) 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 TaskQueue { |
| public: |
| // TaskQueue priority levels. On some platforms these will map to thread |
| // priorities, on others such as Mac and iOS, GCD queue priorities. |
| enum class Priority { |
| NORMAL = 0, |
| HIGH, |
| LOW, |
| }; |
| |
| explicit TaskQueue(const char* queue_name, |
| Priority priority = Priority::NORMAL); |
| ~TaskQueue(); |
| |
| static TaskQueue* Current(); |
| |
| // Used for DCHECKing the current queue. |
| bool IsCurrent() const; |
| |
| // TODO(tommi): For better debuggability, implement RTC_FROM_HERE. |
| |
| // Ownership of the task is passed to PostTask. |
| void PostTask(std::unique_ptr<QueuedTask> task); |
| void PostTaskAndReply(std::unique_ptr<QueuedTask> task, |
| std::unique_ptr<QueuedTask> reply, |
| TaskQueue* reply_queue); |
| void PostTaskAndReply(std::unique_ptr<QueuedTask> task, |
| std::unique_ptr<QueuedTask> reply); |
| |
| // 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_copy_constructible<Closure>::value>::type* = nullptr> |
| void PostTask(const Closure& closure) { |
| PostTask(std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure))); |
| } |
| |
| // See documentation above for performance expectations. |
| template <class Closure> |
| void PostDelayedTask(const Closure& closure, uint32_t milliseconds) { |
| PostDelayedTask( |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(closure)), |
| milliseconds); |
| } |
| |
| template <class Closure1, class Closure2> |
| void PostTaskAndReply(const Closure1& task, |
| const Closure2& reply, |
| TaskQueue* reply_queue) { |
| PostTaskAndReply( |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure1>(task)), |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure2>(reply)), |
| reply_queue); |
| } |
| |
| template <class Closure> |
| void PostTaskAndReply(std::unique_ptr<QueuedTask> task, |
| const Closure& reply) { |
| PostTaskAndReply(std::move(task), std::unique_ptr<QueuedTask>( |
| new ClosureTask<Closure>(reply))); |
| } |
| |
| template <class Closure> |
| void PostTaskAndReply(const Closure& task, |
| std::unique_ptr<QueuedTask> reply) { |
| PostTaskAndReply( |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure>(task)), |
| std::move(reply)); |
| } |
| |
| template <class Closure1, class Closure2> |
| void PostTaskAndReply(const Closure1& task, const Closure2& reply) { |
| PostTaskAndReply( |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure1>(task)), |
| std::unique_ptr<QueuedTask>(new ClosureTask<Closure2>(reply))); |
| } |
| |
| private: |
| #if defined(WEBRTC_MAC) |
| struct QueueContext; |
| struct TaskContext; |
| struct PostTaskAndReplyContext; |
| dispatch_queue_t queue_; |
| QueueContext* const context_; |
| #else |
| class Impl; |
| const scoped_refptr<Impl> impl_; |
| #endif |
| |
| RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue); |
| }; |
| |
| } // namespace rtc |
| |
| #endif // WEBRTC_RTC_BASE_TASK_QUEUE_H_ |