com.unity.uiwidgets/com.unity.uiwidgets/Runtime/async/timer.cs

/*
using System;
using System.Collections.Generic;
using Unity.UIWidgets.foundation;
using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;

#endif

namespace Unity.UIWidgets.async {
    public abstract class Timer : IDisposable {
        public abstract void cancel();

        public void Dispose() {
            cancel();
        }

        public static float timeSinceStartup {
            get {
#if UNITY_EDITOR
                return (float) EditorApplication.timeSinceStartup;
#else
                return Time.realtimeSinceStartup;
#endif
            }
        }

        public static TimeSpan timespanSinceStartup {
            get { return TimeSpan.FromSeconds(timeSinceStartup); }
        }

        static readonly object _syncObj = new object();

        static LinkedList<Action> _callbacks = new LinkedList<Action>();

        public static void runInMainFromFinalizer(Action callback) {
            lock (_syncObj) {
                _callbacks.AddLast(callback);
            }
        }

        internal static void update() {
            LinkedList<Action> callbacks;

            lock (_syncObj) {
                if (_callbacks.isEmpty()) {
                    return;
                }

                callbacks = _callbacks;
                _callbacks = new LinkedList<Action>();
            }

            foreach (var callback in callbacks) {
                try {
                    callback();
                }
                catch (Exception ex) {
                    D.logError("Error to execute runInMain callback: ", ex);
                }
            }
        }
    }

    public class TimerProvider {
        readonly PriorityQueue<TimerImpl> _queue;

        public TimerProvider() {
            _queue = new PriorityQueue<TimerImpl>();
        }

        public Timer runInMain(Action callback) {
            var timer = new TimerImpl(callback);

            lock (_queue) {
                _queue.enqueue(timer);
            }

            return timer;
        }

        public Timer run(TimeSpan duration, Action callback) {
            var timer = new TimerImpl(duration, callback);

            lock (_queue) {
                _queue.enqueue(timer);
            }

            return timer;
        }

        public Timer periodic(TimeSpan duration, Action callback) {
            var timer = new TimerImpl(duration, callback, periodic: true);

            lock (_queue) {
                _queue.enqueue(timer);
            }

            return timer;
        }

        static readonly List<TimerImpl> _timers = new List<TimerImpl>();
        static readonly List<TimerImpl> _appendList = new List<TimerImpl>();
        
        public void update(Action flushMicroTasks = null) {
            var now = Timer.timeSinceStartup;

            _timers.Clear();
            _appendList.Clear();
                
            lock (_queue) {
                while (_queue.count > 0 && _queue.peek().deadline <= now) {
                    var timer = _queue.dequeue();
                    _timers.Add(timer);
                }
            }

            if (_timers.Count != 0) {
                foreach (var timer in _timers) {
                    if (flushMicroTasks != null) {
                        flushMicroTasks();
                    }

                    timer.invoke();
                    if (timer.periodic && !timer.done) {
                        _appendList.Add(timer);
                    }
                }
            }

            if (_appendList.Count != 0) {
                lock (_queue) {
                    foreach (var timer in _appendList) {
                        _queue.enqueue(timer);
                    }
                }
            }
        }

        class TimerImpl : Timer, IComparable<TimerImpl> {
            float _deadline;
            readonly Action _callback;
            bool _done;

            public readonly bool periodic;
            readonly TimeSpan _interval;

            public TimerImpl(TimeSpan duration, Action callback, bool periodic = false) {
                _deadline = timeSinceStartup + (float) duration.TotalSeconds;
                _callback = callback;
                _done = false;

                this.periodic = periodic;
                if (periodic) {
                    _interval = duration;
                }
            }

            public TimerImpl(Action callback) {
                _deadline = 0;
                _callback = callback;
                _done = false;
            }

            public float deadline {
                get { return _deadline; }
            }

            public override void cancel() {
                _done = true;
            }

            public bool done {
                get { return _done; }
            }

            public void invoke() {
                if (_done) {
                    return;
                }

                var now = timeSinceStartup;
                if (!periodic) {
                    _done = true;
                }

                try {
                    _callback();
                }
                catch (Exception ex) {
                    D.logError("Error to execute timer callback: ", ex);
                }

                if (periodic) {
                    _deadline = now + (float) _interval.TotalSeconds;
                }
            }

            public int CompareTo(TimerImpl other) {
                return deadline.CompareTo(other.deadline);
            }
        }
    }
}*/