Unity边玩边下限制下载速度

public class CustomDownloadHandler : DownloadHandlerScript
{
    FileStream fileStream;
    private int m_receiveLength = 0;

    ulong m_ContentLength;
    public CustomDownloadHandler(byte[] preallocatedBuffer) : base(preallocatedBuffer)
    {
        int size = preallocatedBuffer.Length;
        fileStream = new FileStream(Application.persistentDataPath + "/1.bundle", FileMode.OpenOrCreate, FileAccess.Write, FileShare.ReadWrite, size);
    }
    protected override bool ReceiveData(byte[] data, int dataLength)
    {
      
        Debug.Log(Time.frameCount + " " + dataLength); //1帧内需要写入大量数据导致IO卡住
        m_receiveLength += dataLength;
        fileStream.Write(data, 0, dataLength);
        return true;
    }
    //....略
}

using System;
using System.IO;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
using UnityEngine;


public class DownloadHandler 
{
    public struct Result
    {
        public string error;
        public bool isHttpError => !string.IsNullOrEmpty(error);
    }
   
    static int DEFAULT_SLEEP_TIME = 33;
    static int DEFAULT_DOWNLOAD_SPEED = 1024;
    static byte[] DEFAULT_BUFFER = new byte[DEFAULT_DOWNLOAD_SPEED / 30 * 1024];
    static int DEFAULT_DOWNLOAD_TIMEOUT = 5;


    public event Action<Result> completed;
    public float Progress;
    public ulong DownloadedBytes;
    public bool IsDone;

    private string m_File;
    private string m_Url;
    private int m_SleepTime;
    private Result m_Result;
    private Stream m_Stream;
    private FileStream m_FileStream;
    private HttpWebRequest m_Request;
    private HttpWebResponse m_Response;
    private CancellationTokenSource m_Cts;

    /// <summary>
    /// 创建下载对象
    /// </summary>
    /// <param name="url">下载路径</param>
    /// <param name="file">保存路径</param>
    /// <param name="speed">每秒最大小速度，KB单位</param>
    public DownloadHandler(string url,string file,int speed)
    {
        m_File = file;
        m_Url = url;
        m_SleepTime = (int)(DEFAULT_SLEEP_TIME * Mathf.Max(1, (float)DEFAULT_DOWNLOAD_SPEED / speed));
    }

    //开始下载
    public void StartDownload()
    {
        Download();
    }
    //停止正在下载中的文件
    public void Dispose()
    {
        m_Cts?.Cancel();
        Close();
    }


    async void Download()
    {
        m_Cts = new CancellationTokenSource();
        CancellationToken token = m_Cts.Token;
        m_Result = default(Result);
        DownloadedBytes = 0;
        IsDone = false;
        await Task.Run(() =>
        {
            try
            {
                m_Request = (HttpWebRequest)WebRequest.Create(m_Url);
                m_Response = (HttpWebResponse)m_Request.GetResponse();
                long content = m_Response.ContentLength;
                m_Stream = m_Response.GetResponseStream();
                m_Stream.ReadTimeout = DEFAULT_DOWNLOAD_TIMEOUT*1000;
                m_FileStream = new FileStream(m_File, FileMode.Create, FileAccess.Write, FileShare.ReadWrite, DEFAULT_BUFFER.Length);
                int read = 0;
                while (!token.IsCancellationRequested &&
                    (read = m_Stream.Read(DEFAULT_BUFFER, 0, DEFAULT_BUFFER.Length)) > 0)
                {
                    DownloadedBytes += (ulong)read;
                    m_FileStream.Write(DEFAULT_BUFFER, 0, read);
                    Thread.Sleep(m_SleepTime);
                }
            }
            catch (WebException ex)
            {
                m_Result.error = ex.ToString();
            }
            finally
            {
                Close();
            }

        }, token);

        try
        {
            if (!token.IsCancellationRequested)
            {
                IsDone = true;
                completed?.Invoke(m_Result);
            }
        }
        catch (Exception ex)
        {
            Debug.LogError(ex.ToString());
        }
        
    }

    void Close()
    {
        m_FileStream?.Dispose();
        m_Stream?.Dispose();
        m_Response?.Dispose();
        m_Cts?.Dispose();
        m_Cts = null;
        m_FileStream = null;
        m_Stream = null;
        m_Response = null;
        m_Request = null;
    }

}

        if (GUILayout.Button("<size=200>下载 </size>"))
        {
            string url = "https://xxxxxxx.bundle";
            string file = Application.persistentDataPath + "/1.bundle";
            float t = Time.time;
            downloadHandler = new DownloadHandler(url, file, 1024);//1024表示每秒下载1M，还可以传512或者256让下载速度继续往下降
            downloadHandler.StartDownload();
            downloadHandler.completed += (info) =>
            {
                if (info.isHttpError)
                {
                    Debug.LogError(info.error);
                }
                else
                {
                    finishTime = Time.time - t;

                    Debug.LogError("fininsh " + finishTime);
                }

            };
        }

      if (GUILayout.Button("<size=200>取消下载 </size>"))
        {
            downloadHandler?.Dispose();
        }

m_Request = (HttpWebRequest)WebRequest.Create(m_Url);
m_Response = (HttpWebResponse)m_Request.GetResponse();