async&await的前世今生

最新推荐文章于 2023-07-01 00:26:00 发布

转载最新推荐文章于 2023-07-01 00:26:00 发布 · 196 阅读

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原文链接：http://www.cnblogs.com/Microex/p/8360457.html

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#runtime #数据结构与算法

本文通过遍历树形结构的实例，比较了async/await与IAsyncStateMachine两种异步编程方式在线程ID及线程上下文标识上的表现。结果显示两者在实际运行中并无差别。

async&await=custom IAsyncStateMachine
async&await是IAsyncStateMachine的语法糖

验证

分别使用async&await和IAsyncStateMachine遍历一棵树，查看二者的线程id和线程上下文标识是否相同

数据结构

public class Node
{
    private static List<Node> _nodes = new List<Node>(); private static int _id = 1; public Node() { this.Id = _id++; _nodes.Add(this); } public int Id { get; } public Node Left { get; set; } public Node Right { get; set; } public bool IsLeaf => this.Left == null && this.Right == null; public bool IsTraveled { get; set; } = false; public override string ToString() { return $"{Left?.Id ?? 0}|{this.Id}|{Right?.Id ?? 0}"; } }

使用async&await遍历树

public static async Task<int> Travle(Node node) { node.IsTraveled = true; if (!node.IsLeaf) { Console.WriteLine("线程id:" + Thread.CurrentThread.ManagedThreadId + "|线程上下文标识:" + Thread.CurrentThread.ExecutionContext.GetHashCode() + ":" + await Travle(node.Left)); Console.WriteLine("线程id:" + Thread.CurrentThread.ManagedThreadId + "|线程上下文标识:" + Thread.CurrentThread.ExecutionContext.GetHashCode() + ":" + await Travle(node.Right)); } return node.Id; }

使用IAsyncStateMachine遍历树

public static Task<int> StateMechineTravle(Node node) { StateMechine stateMechine = new StateMechine(); stateMechine.node = node; stateMechine.builder = AsyncTaskMethodBuilder<int>.Create(); stateMechine.state = -1; AsyncTaskMethodBuilder<int> next_builder = stateMechine.builder; next_builder.Start<StateMechine>(ref stateMechine); return stateMechine.builder.Task; }

这里StateMechine是实现IAsyncStateMachine接口的一个类

public struct StateMechine : IAsyncStateMachine
{
    public int state; public AsyncTaskMethodBuilder<int> builder; public Node node; private object wrap1; private object wrap2; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { int num = this.state; int id; try { TaskAwaiter<int> taskAwaiter; if (num != 0) { if (num == 1) { taskAwaiter = this.awaiter; this.awaiter = default(TaskAwaiter<int>); this.state = -1; goto IL_1AB; } this.node.IsTraveled = true; if (this.node.IsLeaf) { goto IL_20C; } this.wrap1 = Thread.CurrentThread.ManagedThreadId; this.wrap2 = Thread.CurrentThread.ExecutionContext.GetHashCode(); taskAwaiter = Program.StateMechineTravle(this.node.Left).GetAwaiter(); if (!taskAwaiter.IsCompleted) { this.state = 0; this.awaiter = taskAwaiter; this.builder.AwaitUnsafeOnCompleted<TaskAwaiter<int>, StateMechine>(ref taskAwaiter, ref this); return; } } else { taskAwaiter = this.awaiter; this.awaiter = default(TaskAwaiter<int>); this.state = -1; } int arg_CC_0 = taskAwaiter.GetResult(); taskAwaiter = default(TaskAwaiter<int>); object obj = arg_CC_0; Console.WriteLine(string.Concat(new object[] { "线程id:", this.wrap1, "|线程上下文标识:", this.wrap2, ":", obj })); this.wrap1 = null; this.wrap2 = null; this.wrap2 = Thread.CurrentThread.ManagedThreadId; this.wrap1 = Thread.CurrentThread.ExecutionContext.GetHashCode(); taskAwaiter = Program.StateMechineTravle(this.node.Right).GetAwaiter(); if (!taskAwaiter.IsCompleted) { this.state = 1; this.awaiter = taskAwaiter; this.builder.AwaitUnsafeOnCompleted<TaskAwaiter<int>, StateMechine>(ref taskAwaiter, ref this); return; } IL_1AB: int arg_1BA_0 = taskAwaiter.GetResult(); taskAwaiter = default(TaskAwaiter<int>); obj = arg_1BA_0; Console.WriteLine(string.Concat(new object[] { "线程id:", this.wrap2, "|线程上下文标识:", this.wrap1, ":", obj })); this.wrap2 = null; this.wrap1 = null; IL_20C: id = this.node.Id; } catch (Exception exception) { this.state = -2; this.builder.SetException(exception); return; } this.state = -2; this.builder.SetResult(id); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.builder.SetStateMachine(stateMachine); } }