UnityWebRequest实现断点续传下载

DownloadHandlerFileRange

using UnityEngine.Networking;
using System.IO;
using System;

/// <summary>
/// 使用方式:
/// UnityWebRequest unityWebRequest = new UnityWebRequest("url");
/// unityWebRequest.downloadHandler = new DownloadHandlerFileRange("文件保存的路径", unityWebRequest);
/// unityWebRequest.SendWebRequest();
/// </summary>
public class DownloadHandlerFileRange : DownloadHandlerScript
{
    /// <summary>
    /// 文件正式开始下载事件,此事件触发以后即可获取到文件的总大小
    /// </summary>
    public event System.Action StartDownloadEvent;

    #region 属性
    /// <summary>
    /// 下载速度,单位:KB/S 保留两位小数
    /// </summary>
    public float Speed
    {
        get
        {
            return ((int)(DownloadSpeed / 1024 * 100)) / 100.0f;
        }
    }

    /// <summary>
    /// 文件的总大小
    /// </summary>
    public long FileSize
    {
        get
        {
            return TotalFileSize;
        }
    }

    /// <summary>
    /// 下载进度[0,1]
    /// </summary>
    public float DownloadProgress
    {
        get
        {
            return GetProgress();
        }
    }
    #endregion

    #region 公共方法
    /// <summary>
    /// 使用1MB的缓存,在补丁2017.2.1p1中对DownloadHandlerScript的优化中,目前最大传入数据量也仅仅是1024*1024,再多也没用
    /// </summary>
    /// <param name="path">文件保存的路径</param>
    /// <param name="request">UnityWebRequest对象,用来获文件大小,设置断点续传的请求头信息</param>
    public DownloadHandlerFileRange(string path, UnityWebRequest request) : base(new byte[1024 * 1024])
    {
        Path = path;
        FileStream = new FileStream(Path, FileMode.Append, FileAccess.Write);
        UnityWebRequest = request;
        if (File.Exists(path))
        {
            LocalFileSize = new System.IO.FileInfo(path).Length;
        }
        CurFileSize = LocalFileSize;
        UnityWebRequest.SetRequestHeader("Range", "bytes=" + LocalFileSize + "-");
    }

    /// <summary>
    /// 清理资源,该方法没办法重写,只能隐藏,如果想要强制中止下载,并清理资源(UnityWebRequest.Dispose()),该方法并不会被调用,这让人很苦恼
    /// </summary>
    new public void Dispose()
    {
        Clean();
    }
    #endregion

    #region 私有方法
    /// <summary>
    /// 关闭文件流
    /// </summary>
    private void Clean()
    {
        DownloadSpeed = 0.0f;
        if (FileStream != null)
        {
            FileStream.Flush();
            FileStream.Dispose();
            FileStream = null;
        }
    }
    #endregion

    #region 私有继承的方法
    /// <summary>
    /// 下载完成后清理资源
    /// </summary>
    protected override void CompleteContent()
    {
        base.CompleteContent();
        Clean();
    }

    /// <summary>
    /// 调用UnityWebRequest.downloadHandler.data属性时,将会调用该方法,用于以byte[]的方式返回下载的数据,目前总是返回null
    /// </summary>
    /// <returns></returns>
    protected override byte[] GetData()
    {
        return null;
    }

    /// <summary>
    /// 调用UnityWebRequest.downloadProgress属性时,将会调用该方法,用于返回下载进度
    /// </summary>
    /// <returns></returns>
    protected override float GetProgress()
    {
        return TotalFileSize == 0 ? 0 : ((float)CurFileSize) / TotalFileSize;
    }

    /// <summary>
    /// 调用UnityWebRequest.downloadHandler.text属性时,将会调用该方法,用于以string的方式返回下载的数据,目前总是返回null
    /// </summary>
    /// <returns></returns>
    protected override string GetText()
    {
        return null;
    }

    //Note:当下载的文件数据大于2G时,该int类型的参数将会数据溢出,所以先自己通过响应头来获取长度,获取不到再使用参数的方式
    protected override void ReceiveContentLength(int contentLength)
    {
        string contentLengthStr = UnityWebRequest.GetResponseHeader("Content-Length");
        if (!string.IsNullOrEmpty(contentLengthStr))
        {
            try
            {
                TotalFileSize = long.Parse(contentLengthStr);
            }
            catch (System.FormatException e)
            {
                UnityEngine.Debug.Log("获取文件长度失败,contentLengthStr:" + contentLengthStr + "," + e.Message);
                TotalFileSize = contentLength;
            }
            catch (System.Exception e)
            {
                UnityEngine.Debug.Log("获取文件长度失败,contentLengthStr:" + contentLengthStr + "," + e.Message);
                TotalFileSize = contentLength;
            }
        }
        else
        {
            TotalFileSize = contentLength;
        }
        //这里拿到的下载大小是待下载的文件大小,需要加上本地已下载文件的大小才等于总大小
        TotalFileSize += LocalFileSize;
        LastTime = UnityEngine.Time.time;
        LastDataSize = CurFileSize;
        if (StartDownloadEvent != null)
        {
            StartDownloadEvent();
        }
    }

    //在2017.3.0(包括该版本)以下的正式版本中存在一个性能上的问题
    //该回调方法有性能上的问题,每次传入的数据量最大不会超过65536(2^16)个字节,不论缓存区有多大
    //在下载速度中的体现,大约相当于每秒下载速度不会超过3.8MB/S
    //这个问题在 "补丁2017.2.1p1" 版本中被优化(2017.12.21发布)(https://unity3d.com/cn/unity/qa/patch-releases/2017.2.1p1)
    //(965165) - Web: UnityWebRequest: improve performance for DownloadHandlerScript.
    //优化后,每次传入数据量最大不会超过1048576(2^20)个字节(1MB),基本满足下载使用
    protected override bool ReceiveData(byte[] data, int dataLength)
    {
        if (data == null || dataLength == 0 || UnityWebRequest.responseCode > 400)
        {
            return false;
        }
        FileStream.Write(data, 0, dataLength);
        CurFileSize += dataLength;
        //统计下载速度
        if (UnityEngine.Time.time - LastTime >= 1.0f)
        {
            DownloadSpeed = (CurFileSize - LastDataSize) / (UnityEngine.Time.time - LastTime);
            LastTime = UnityEngine.Time.time;
            LastDataSize = CurFileSize;
        }
        return true;
    }

    ~DownloadHandlerFileRange()
    {
        Clean();
    }
    #endregion

    #region 私有字段
    private string Path;//文件保存的路径
    private FileStream FileStream;
    private UnityWebRequest UnityWebRequest;
    private long LocalFileSize = 0;//本地已经下载的文件的大小
    private long TotalFileSize = 0;//文件的总大小
    private long CurFileSize = 0;//当前的文件大小
    private float LastTime = 0;//用作下载速度的时间统计
    private float LastDataSize = 0;//用来作为下载速度的大小统计
    private float DownloadSpeed = 0;//下载速度,单位:Byte/S
    #endregion
}

@liuhuixin 你好,你是指的unityWebRequest.isDone永远为false,还是unityWebRequest.downloadHandler.isDone永远为false!

unityWebRequest.isDone永远为false这种情况我没遇到过,能否提供你的代码片段呢.

unityWebRequest.downloadHandler.isDone永远为false这种情况确实存在,而且不使用DownloadHandlerFileRange,直接使用DownloadHandlerScript也会出现这种情况,甚至我在unity官方文档的案例也有这种情况,我不知道这是unity的一个bug,还是我做错了什么?

@dgaenko
Thanks for your suggestion, but can you tell me why? I think this condition will never be true. Within ReceiveData, UnityWebRequest.responseCode will always return 0. When the download is over, ReceiveData should not be called again.

No. It's not! UnityWebRequest.responseCode can be any within ReceiveData. The Unity Api is stupid. It take me long time to detect this bug!

The error string is from server side:"Maximum number of open connections reached."
Unity treat this as file content and call ReceiveData. Within ReceiveData, we can use responseCode to detect error. The isHttpError has a little delay, it maybe setted by another thread.

@dgaenko
Thanks for your suggestion, but can you tell me why? I think this condition will never be true. Within ReceiveData, UnityWebRequest.responseCode will always return 0. When the download is over, ReceiveData should not be called again.

No. It's not! UnityWebRequest.responseCode can be any within ReceiveData. The Unity Api is stupid. It take me long time to detect this bug!

I understand, thanks.