84 lines
3.4 KiB
C++
84 lines
3.4 KiB
C++
/*
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* Copyright 2019 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef API_TASK_QUEUE_TASK_QUEUE_BASE_H_
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#define API_TASK_QUEUE_TASK_QUEUE_BASE_H_
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#include <memory>
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#include "api/task_queue/queued_task.h"
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#include "rtc_base/system/rtc_export.h"
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#include "rtc_base/thread_annotations.h"
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namespace webrtc {
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// Asynchronously executes tasks in a way that guarantees that they're executed
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// in FIFO order and that tasks never overlap. Tasks may always execute on the
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// same worker thread and they may not. To DCHECK that tasks are executing on a
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// known task queue, use IsCurrent().
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class RTC_LOCKABLE RTC_EXPORT TaskQueueBase {
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public:
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// Starts destruction of the task queue.
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// On return ensures no task are running and no new tasks are able to start
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// on the task queue.
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// Responsible for deallocation. Deallocation may happen syncrhoniously during
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// Delete or asynchronously after Delete returns.
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// Code not running on the TaskQueue should not make any assumption when
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// TaskQueue is deallocated and thus should not call any methods after Delete.
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// Code running on the TaskQueue should not call Delete, but can assume
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// TaskQueue still exists and may call other methods, e.g. PostTask.
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virtual void Delete() = 0;
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// Schedules a task to execute. Tasks are executed in FIFO order.
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// If |task->Run()| returns true, task is deleted on the task queue
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// before next QueuedTask starts executing.
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// When a TaskQueue is deleted, pending tasks will not be executed but they
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// will be deleted. The deletion of tasks may happen synchronously on the
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// TaskQueue or it may happen asynchronously after TaskQueue is deleted.
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// This may vary from one implementation to the next so assumptions about
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// lifetimes of pending tasks should not be made.
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virtual void PostTask(std::unique_ptr<QueuedTask> task) = 0;
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// Schedules a task to execute a specified number of milliseconds from when
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// the call is made. The precision should be considered as "best effort"
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// and in some cases, such as on Windows when all high precision timers have
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// been used up, can be off by as much as 15 millseconds.
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virtual void PostDelayedTask(std::unique_ptr<QueuedTask> task,
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uint32_t milliseconds) = 0;
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// Returns the task queue that is running the current thread.
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// Returns nullptr if this thread is not associated with any task queue.
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static TaskQueueBase* Current();
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bool IsCurrent() const { return Current() == this; }
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protected:
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class CurrentTaskQueueSetter {
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public:
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explicit CurrentTaskQueueSetter(TaskQueueBase* task_queue);
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CurrentTaskQueueSetter(const CurrentTaskQueueSetter&) = delete;
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CurrentTaskQueueSetter& operator=(const CurrentTaskQueueSetter&) = delete;
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~CurrentTaskQueueSetter();
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private:
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TaskQueueBase* const previous_;
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};
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// Users of the TaskQueue should call Delete instead of directly deleting
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// this object.
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virtual ~TaskQueueBase() = default;
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};
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struct TaskQueueDeleter {
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void operator()(TaskQueueBase* task_queue) const { task_queue->Delete(); }
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};
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} // namespace webrtc
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#endif // API_TASK_QUEUE_TASK_QUEUE_BASE_H_
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