webrtc/api/task_queue/task_queue_base.h
Danil Chapovalov b4c6d1e6d9 Connect global task queue factory and rtc::TaskQueue
This cl allows to overwrite TaskQueue implementation
by depending on and setting the global task queue factory.

Bug: webrtc:10191
Change-Id: I69ceb139d00078d3be90eeb4e240758b88829c20
Reviewed-on: https://webrtc-review.googlesource.com/c/118060
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26345}
2019-01-21 16:08:31 +00:00

87 lines
3.7 KiB
C++

/*
* Copyright 2019 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 API_TASK_QUEUE_TASK_QUEUE_BASE_H_
#define API_TASK_QUEUE_TASK_QUEUE_BASE_H_
#include <memory>
#include "api/task_queue/queued_task.h"
#include "api/task_queue/task_queue_impl.h"
namespace webrtc {
// 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().
// TODO(bugs.webrtc.org/10191): Remove inheritence from rtc::TaskQueue::Impl
// when all implementations switch to use TaskQueueFactory instead of link-time
// injection.
class TaskQueueBase : public rtc::TaskQueue::Impl {
public:
// Starts destruction of the task queue.
// On return ensures no task are running and no new tasks are able to start
// on the task queue.
// Responsible for deallocation. Deallocation may happen syncrhoniously during
// Delete or asynchronously after Delete returns.
// Code not running on the TaskQueue should not make any assumption when
// TaskQueue is deallocated and thus should not call any methods after Delete.
// Code running on the TaskQueue should not call Delete, but can assume
// TaskQueue still exists and may call other methods, e.g. PostTask.
void Delete() override = 0;
// Schedules a task to execute. Tasks are executed in FIFO order.
// If |task->Run()| returns true, task is deleted on the task queue
// before next QueuedTask starts executing.
// When a TaskQueue is deleted, pending tasks will not be executed but they
// will be deleted. The deletion of tasks may happen synchronously on the
// TaskQueue or it may happen asynchronously after TaskQueue is deleted.
// This may vary from one implementation to the next so assumptions about
// lifetimes of pending tasks should not be made.
void PostTask(std::unique_ptr<QueuedTask> task) override = 0;
// 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.
void PostDelayedTask(std::unique_ptr<QueuedTask> task,
uint32_t milliseconds) override = 0;
// Until all TaskQueue implementations switch to using CurrentTaskQueueSetter
// below, this function may return nullptr even if code is executed by a
// TaskQueue. Keep using rtc::TaskQueue::Current() until bugs.webrtc.org/10191
// is resolved.
static TaskQueueBase* Current();
bool IsCurrent() const { return Current() == this; }
protected:
class CurrentTaskQueueSetter {
public:
explicit CurrentTaskQueueSetter(TaskQueueBase* task_queue);
CurrentTaskQueueSetter(const CurrentTaskQueueSetter&) = delete;
CurrentTaskQueueSetter& operator=(const CurrentTaskQueueSetter&) = delete;
~CurrentTaskQueueSetter();
private:
TaskQueueBase* const previous_;
};
// Users of the TaskQueue should call Delete instead of directly deleting
// this object.
~TaskQueueBase() override = default;
};
struct TaskQueueDeleter {
void operator()(TaskQueueBase* task_queue) const { task_queue->Delete(); }
};
} // namespace webrtc
#endif // API_TASK_QUEUE_TASK_QUEUE_BASE_H_