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Diffstat (limited to 'third_party/libwebrtc/webrtc/rtc_base/task_queue.h')
| -rw-r--r-- | third_party/libwebrtc/webrtc/rtc_base/task_queue.h | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/third_party/libwebrtc/webrtc/rtc_base/task_queue.h b/third_party/libwebrtc/webrtc/rtc_base/task_queue.h new file mode 100644 index 0000000000..2f247e6038 --- /dev/null +++ b/third_party/libwebrtc/webrtc/rtc_base/task_queue.h @@ -0,0 +1,243 @@ +/* + * 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 <list> +#include <memory> +#include <queue> +#include <type_traits> +#include <utility> + +#include "rtc_base/constructormagic.h" +#include "rtc_base/criticalsection.h" +#include "rtc_base/ptr_util.h" +#include "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(Closure&& closure) + : closure_(std::forward<Closure>(closure)) {} + + private: + bool Run() override { + closure_(); + return true; + } + + typename std::remove_const< + typename std::remove_reference<Closure>::type>::type 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(Closure&& closure, Cleanup&& cleanup) + : ClosureTask<Closure>(std::forward<Closure>(closure)), + cleanup_(std::forward<Cleanup>(cleanup)) {} + ~ClosureTaskWithCleanup() { cleanup_(); } + + private: + typename std::remove_const< + typename std::remove_reference<Cleanup>::type>::type 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(Closure&& closure) { + return rtc::MakeUnique<ClosureTask<Closure>>(std::forward<Closure>(closure)); +} + +template <class Closure, class Cleanup> +static std::unique_ptr<QueuedTask> NewClosure(Closure&& closure, + Cleanup&& cleanup) { + return rtc::MakeUnique<ClosureTaskWithCleanup<Closure, Cleanup>>( + std::forward<Closure>(closure), std::forward<Cleanup>(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([]() { RTC_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_convertible< + Closure, + std::unique_ptr<QueuedTask>>::value>::type* = nullptr> + void PostTask(Closure&& closure) { + PostTask(NewClosure(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(NewClosure(std::forward<Closure>(closure)), milliseconds); + } + + template <class Closure1, class Closure2> + void PostTaskAndReply(Closure1&& task, + Closure2&& reply, + TaskQueue* reply_queue) { + PostTaskAndReply(NewClosure(std::forward<Closure1>(task)), + NewClosure(std::forward<Closure2>(reply)), reply_queue); + } + + template <class Closure> + void PostTaskAndReply(std::unique_ptr<QueuedTask> task, Closure&& reply) { + PostTaskAndReply(std::move(task), NewClosure(std::forward<Closure>(reply))); + } + + template <class Closure> + void PostTaskAndReply(Closure&& task, std::unique_ptr<QueuedTask> reply) { + PostTaskAndReply(NewClosure(std::forward<Closure>(task)), std::move(reply)); + } + + template <class Closure1, class Closure2> + void PostTaskAndReply(Closure1&& task, Closure2&& reply) { + PostTaskAndReply(NewClosure(std::forward(task)), + NewClosure(std::forward(reply))); + } + + private: + class Impl; + const scoped_refptr<Impl> impl_; + + RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue); +}; + +} // namespace rtc + +#endif // RTC_BASE_TASK_QUEUE_H_ |