BizHawk/ExternalCoreProjects/Virtu/MachineEvents.cs

using System;
using System.Collections.Generic;
using System.Globalization;

namespace Jellyfish.Virtu
{
	internal sealed class MachineEvent
	{
		public MachineEvent(int delta, Action action)
		{
			Delta = delta;
			Action = action;
		}

		public override string ToString()
		{
			return string.Format(CultureInfo.InvariantCulture, "Delta = {0} Action = {{{1}.{2}}}", Delta, Action.Method.DeclaringType?.Name, Action.Method.Name);
		}

		public int Delta { get; set; }
		public Action Action { get; set; }
	}

	public sealed class MachineEvents
	{
		public void AddEvent(int delta, Action action)
		{
			var node = _used.First;
			for (; node != null; node = node.Next)
			{
				if (delta < node.Value.Delta)
				{
					node.Value.Delta -= delta;
					break;
				}
				if (node.Value.Delta > 0)
				{
					delta -= node.Value.Delta;
				}
			}

			var newNode = _free.First;
			if (newNode != null)
			{
				_free.RemoveFirst();
				newNode.Value.Delta = delta;
				newNode.Value.Action = action;
			}
			else
			{
				newNode = new LinkedListNode<MachineEvent>(new MachineEvent(delta, action));
			}

			if (node != null)
			{
				_used.AddBefore(node, newNode);
			}
			else
			{
				_used.AddLast(newNode);
			}
		}

		public int FindEvent(Action action)
		{
			int delta = 0;

			for (var node = _used.First; node != null; node = node.Next)
			{
				delta += node.Value.Delta;

				var other = node.Value.Action;

				if (other.Method == action.Method && other.Target == action.Target)
				{
					return delta;
				}
			}

			return 0;
		}

		// ReSharper disable once UnusedMember.Global
		public void HandleEvents(int delta)
		{
			var node = _used.First;
			node.Value.Delta -= delta;

			while (node.Value.Delta <= 0)
			{
				node.Value.Action();
				RemoveEvent(node);
				node = _used.First;
			}
		}

		private void RemoveEvent(LinkedListNode<MachineEvent> node)
		{
			if (node.Next != null)
			{
				node.Next.Value.Delta += node.Value.Delta;
			}

			_used.Remove(node);
			_free.AddFirst(node); // cache node; avoids garbage
		}

		// ReSharper disable once FieldCanBeMadeReadOnly.Local
		private LinkedList<MachineEvent> _used = new LinkedList<MachineEvent>();

		// ReSharper disable once FieldCanBeMadeReadOnly.Local
		private LinkedList<MachineEvent> _free = new LinkedList<MachineEvent>();
	}
}