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task_runner.h
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task_runner.h
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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef FLUTTER_FML_TASK_RUNNER_H_
#define FLUTTER_FML_TASK_RUNNER_H_
#include "flutter/fml/closure.h"
#include "flutter/fml/macros.h"
#include "flutter/fml/memory/ref_counted.h"
#include "flutter/fml/memory/ref_ptr.h"
#include "flutter/fml/message_loop_task_queues.h"
#include "flutter/fml/time/time_point.h"
namespace fml {
class MessageLoopImpl;
/// An interface over the ability to schedule tasks on a \p TaskRunner.
class BasicTaskRunner {
public:
/// Schedules \p task to be executed on the TaskRunner's associated event
/// loop.
virtual void PostTask(const fml::closure& task) = 0;
};
/// The object for scheduling tasks on a \p fml::MessageLoop.
///
/// Typically there is one \p TaskRunner associated with each thread. When one
/// wants to execute an operation on that thread they post a task to the
/// TaskRunner.
///
/// \see fml::MessageLoop
class TaskRunner : public fml::RefCountedThreadSafe<TaskRunner>,
public BasicTaskRunner {
public:
virtual ~TaskRunner();
virtual void PostTask(const fml::closure& task) override;
virtual void PostTaskForTime(const fml::closure& task,
fml::TimePoint target_time);
/// Schedules a task to be run on the MessageLoop after the time \p delay has
/// passed.
/// \note There is latency between when the task is schedule and actually
/// executed so that the actual execution time is: now + delay +
/// message_loop_latency, where message_loop_latency is undefined and could be
/// tens of milliseconds.
virtual void PostDelayedTask(const fml::closure& task, fml::TimeDelta delay);
/// Returns \p true when the current executing thread's TaskRunner matches
/// this instance.
virtual bool RunsTasksOnCurrentThread();
/// Returns the unique identifier associated with the TaskRunner.
/// \see fml::MessageLoopTaskQueues
virtual TaskQueueId GetTaskQueueId();
/// Executes the \p task directly if the TaskRunner \p runner is the
/// TaskRunner associated with the current executing thread.
static void RunNowOrPostTask(fml::RefPtr<fml::TaskRunner> runner,
const fml::closure& task);
protected:
explicit TaskRunner(fml::RefPtr<MessageLoopImpl> loop);
private:
fml::RefPtr<MessageLoopImpl> loop_;
FML_FRIEND_MAKE_REF_COUNTED(TaskRunner);
FML_FRIEND_REF_COUNTED_THREAD_SAFE(TaskRunner);
FML_DISALLOW_COPY_AND_ASSIGN(TaskRunner);
};
} // namespace fml
#endif // FLUTTER_FML_TASK_RUNNER_H_