[go: up one dir, main page]
1// Copyright 2013 The Flutter Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef FLUTTER_FML_TASK_SOURCE_H_
6#define FLUTTER_FML_TASK_SOURCE_H_
7
8#include "flutter/fml/delayed_task.h"
9#include "flutter/fml/task_queue_id.h"
10#include "flutter/fml/task_source_grade.h"
11
12namespace fml {
13
14class MessageLoopTaskQueues;
15
16/**
17 * A Source of tasks for the `MessageLoopTaskQueues` task dispatcher. This is a
18 * wrapper around a primary and secondary task heap with the difference between
19 * them being that the secondary task heap can be paused and resumed by the task
20 * dispatcher. `TaskSourceGrade` determines what task heap the task is assigned
21 * to.
22 *
23 * Registering Tasks
24 * -----------------
25 * The task dispatcher associates a task source with each `TaskQueueID`. When
26 * the user of the task dispatcher registers a task, the task is in-turn
27 * registered with the `TaskSource` corresponding to the `TaskQueueID`.
28 *
29 * Processing Tasks
30 * ----------------
31 * Task dispatcher provides the event loop a way to acquire tasks to run via
32 * `GetNextTaskToRun`. Task dispatcher asks the underlying `TaskSource` for the
33 * next task.
34 */
35class TaskSource {
36 public:
37 struct TopTask {
38 TaskQueueId task_queue_id;
39 const DelayedTask& task;
40 };
41
42 /// Construts a TaskSource with the given `task_queue_id`.
43 explicit TaskSource(TaskQueueId task_queue_id);
44
45 ~TaskSource();
46
47 /// Drops the pending tasks from both primary and secondary task heaps.
48 void ShutDown();
49
50 /// Adds a task to the corresponding task heap as dictated by the
51 /// `TaskSourceGrade` of the `DelayedTask`.
52 void RegisterTask(const DelayedTask& task);
53
54 /// Pops the task heap corresponding to the `TaskSourceGrade`.
55 void PopTask(TaskSourceGrade grade);
56
57 /// Returns the number of pending tasks. Excludes the tasks from the secondary
58 /// heap if it's paused.
59 size_t GetNumPendingTasks() const;
60
61 /// Returns true if `GetNumPendingTasks` is zero.
62 bool IsEmpty() const;
63
64 /// Returns the top task based on scheduled time, taking into account whether
65 /// the secondary heap has been paused or not.
66 TopTask Top() const;
67
68 /// Pause providing tasks from secondary task heap.
69 void PauseSecondary();
70
71 /// Resume providing tasks from secondary task heap.
72 void ResumeSecondary();
73
74 private:
75 const fml::TaskQueueId task_queue_id_;
76 fml::DelayedTaskQueue primary_task_queue_;
77 fml::DelayedTaskQueue secondary_task_queue_;
78 int secondary_pause_requests_ = 0;
79
80 FML_DISALLOW_COPY_ASSIGN_AND_MOVE(TaskSource);
81};
82
83} // namespace fml
84
85#endif // FLUTTER_FML_TASK_SOURCE_H_
86

source code of flutter_engine/flutter/fml/task_source.h