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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 "api/task_queue/queued_task.h"
#include "api/task_queue/task_queue_base.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "rtc_base/task_utils/pending_task_safety_flag.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();
class RepeatingTaskBase : public QueuedTask {
public:
RepeatingTaskBase(TaskQueueBase* task_queue,
TaskQueueBase::DelayPrecision precision,
TimeDelta first_delay,
Clock* clock,
rtc::scoped_refptr<PendingTaskSafetyFlag> alive_flag);
~RepeatingTaskBase() override;
private:
virtual TimeDelta RunClosure() = 0;
bool Run() final;
TaskQueueBase* const task_queue_;
const TaskQueueBase::DelayPrecision precision_;
Clock* const clock_;
// This is always finite.
Timestamp next_run_time_ RTC_GUARDED_BY(task_queue_);
rtc::scoped_refptr<PendingTaskSafetyFlag> alive_flag_
RTC_GUARDED_BY(task_queue_);
};
// The template closure pattern is based on rtc::ClosureTask. The provided
// closure should have a TimeDelta return value, specifing the desired
// non-negative interval to next repetition, or TimeDelta::PlusInfinity to
// indicate that the task should be deleted and not called again.
template <class Closure>
class RepeatingTaskImpl final : public RepeatingTaskBase {
public:
RepeatingTaskImpl(TaskQueueBase* task_queue,
TaskQueueBase::DelayPrecision precision,
TimeDelta first_delay,
Closure&& closure,
Clock* clock,
rtc::scoped_refptr<PendingTaskSafetyFlag> alive_flag)
: RepeatingTaskBase(task_queue,
precision,
first_delay,
clock,
std::move(alive_flag)),
closure_(std::forward<Closure>(closure)) {
static_assert(
std::is_same<TimeDelta,
typename std::invoke_result<decltype(&Closure::operator()),
Closure>::type>::value,
"");
}
private:
TimeDelta RunClosure() override {
RepeatingTaskImplDTraceProbeRun();
return closure_();
}
typename std::remove_const<
typename std::remove_reference<Closure>::type>::type closure_;
};
} // 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.
template <class Closure>
static RepeatingTaskHandle Start(TaskQueueBase* task_queue,
Closure&& closure,
TaskQueueBase::DelayPrecision precision =
TaskQueueBase::DelayPrecision::kLow,
Clock* clock = Clock::GetRealTimeClock()) {
auto alive_flag = PendingTaskSafetyFlag::CreateDetached();
webrtc_repeating_task_impl::RepeatingTaskHandleDTraceProbeStart();
task_queue->PostTask(
std::make_unique<
webrtc_repeating_task_impl::RepeatingTaskImpl<Closure>>(
task_queue, precision, TimeDelta::Zero(),
std::forward<Closure>(closure), clock, alive_flag));
return RepeatingTaskHandle(std::move(alive_flag));
}
// DelayedStart is equivalent to Start except that the first invocation of the
// closure will be delayed by the given amount.
template <class Closure>
static RepeatingTaskHandle DelayedStart(
TaskQueueBase* task_queue,
TimeDelta first_delay,
Closure&& closure,
TaskQueueBase::DelayPrecision precision =
TaskQueueBase::DelayPrecision::kLow,
Clock* clock = Clock::GetRealTimeClock()) {
auto alive_flag = PendingTaskSafetyFlag::CreateDetached();
webrtc_repeating_task_impl::RepeatingTaskHandleDTraceProbeDelayedStart();
task_queue->PostDelayedTaskWithPrecision(
precision,
std::make_unique<
webrtc_repeating_task_impl::RepeatingTaskImpl<Closure>>(
task_queue, precision, first_delay, std::forward<Closure>(closure),
clock, alive_flag),
first_delay.ms());
return RepeatingTaskHandle(std::move(alive_flag));
}
// 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_