repeating_task.h - mozsearch

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/*

 *  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 RTC_BASE_TASK_UTILS_REPEATING_TASK_H_

#define RTC_BASE_TASK_UTILS_REPEATING_TASK_H_

#include <memory>

#include <type_traits>

#include <utility>

#include "absl/functional/any_invocable.h"

#include "api/task_queue/pending_task_safety_flag.h"

#include "api/task_queue/task_queue_base.h"

#include "api/units/time_delta.h"

#include "system_wrappers/include/clock.h"

namespace webrtc {

namespace webrtc_repeating_task_impl {

// Methods simplifying external tracing of RepeatingTaskHandle operations.

void RepeatingTaskHandleDTraceProbeStart();

void RepeatingTaskHandleDTraceProbeDelayedStart();

void RepeatingTaskImplDTraceProbeRun();

}  // namespace webrtc_repeating_task_impl

// Allows starting tasks that repeat themselves on a TaskQueue indefinately

// until they are stopped or the TaskQueue is destroyed. It allows starting and

// stopping multiple times, but you must stop one task before starting another

// and it can only be stopped when in the running state. The public interface is

// not thread safe.

class RepeatingTaskHandle {

 public:

  RepeatingTaskHandle() = default;

  ~RepeatingTaskHandle() = default;

  RepeatingTaskHandle(RepeatingTaskHandle&& other) = default;

  RepeatingTaskHandle& operator=(RepeatingTaskHandle&& other) = default;

  RepeatingTaskHandle(const RepeatingTaskHandle&) = delete;

  RepeatingTaskHandle& operator=(const RepeatingTaskHandle&) = delete;

  // Start can be used to start a task that will be reposted with a delay

  // determined by the return value of the provided closure. The actual task is

  // owned by the TaskQueue and will live until it has been stopped or the

  // TaskQueue deletes it. It's perfectly fine to destroy the handle while the

  // task is running, since the repeated task is owned by the TaskQueue.

  // The tasks are scheduled onto the task queue using the specified precision.

  static RepeatingTaskHandle Start(

      TaskQueueBase* task_queue,

      absl::AnyInvocable<TimeDelta()> closure,

      TaskQueueBase::DelayPrecision precision =

          TaskQueueBase::DelayPrecision::kLow,

      Clock* clock = Clock::GetRealTimeClockRaw(),

      const Location& location = Location::Current());

  // DelayedStart is equivalent to Start except that the first invocation of the

  // closure will be delayed by the given amount.

  static RepeatingTaskHandle DelayedStart(

      TaskQueueBase* task_queue,

      TimeDelta first_delay,

      absl::AnyInvocable<TimeDelta()> closure,

      TaskQueueBase::DelayPrecision precision =

          TaskQueueBase::DelayPrecision::kLow,

      Clock* clock = Clock::GetRealTimeClockRaw(),

      const Location& location = Location::Current());

  // Stops future invocations of the repeating task closure. Can only be called

  // from the TaskQueue where the task is running. The closure is guaranteed to

  // not be running after Stop() returns unless Stop() is called from the

  // closure itself.

  void Stop();

  // Returns true until Stop() was called.

  // Can only be called from the TaskQueue where the task is running.

  bool Running() const;

 private:

  explicit RepeatingTaskHandle(

      rtc::scoped_refptr<PendingTaskSafetyFlag> alive_flag)

      : repeating_task_(std::move(alive_flag)) {}

  rtc::scoped_refptr<PendingTaskSafetyFlag> repeating_task_;

};

}  // namespace webrtc

#endif  // RTC_BASE_TASK_UTILS_REPEATING_TASK_H_