目錄

打包與資源加載框架目錄

正文

下載AB包之前，要檢查該AB包是否下載中斷過，例如用戶殺程序，卡死等情況。

前文有講解過，下載AB包會先下載到臨時文件夾，全部下載成功后，全部剪切到persistentDataPath沙盒目錄中。

回顧一下之前的篩選機(jī)制，哪些AB包可以加入下載列表，其中并沒有臨時下載目錄的判斷。

該AB包數(shù)據(jù)是否加入列表要經(jīng)過下面幾個篩選

1. 判斷persistentDataPath沙盒目錄是否存在該AB包，如果存在證明之前下載過，無需加入下載列表。

2. 判斷StreamingAsset目錄中是否存在該AB包，如果存在證明打包時該AB包已經(jīng)在包體里，無需加入下載列表。

3. 如果該AB包的下載類型是游戲內(nèi)下載，或者叫邊玩邊下，那么不需要在游戲啟動熱更時下載，無需加入下載列表

檢查是否在臨時下載目錄中是否存在的代碼如下

private IEnumerator CheckTempFileComplete(List<PatchElement> list, bool isPostCheck)
{
    PatchEventDispatcher.SendCheckDownloadedFileMd5();
    var sw = new Stopwatch();
    sw.Start();
    var buf = new byte[10240];
    this.totalDownloadSizeKB = 0;
    this.currentDownloadSizeKB = 0;
    this.currentDownloadCount = 0;
    using (var md5 = System.Security.Cryptography.MD5.Create())
    {
        foreach (var ele in list)
        {
            this.totalDownloadSizeKB += ele.SizeKB;
            string savePath = AssetPathHelper.MakeDownloadTempPath(ele.Name);
            if (!File.Exists(savePath))
            {
                //下載后的檢查需要拋出異常，下載前的檢查跳過不存在文件
                if (isPostCheck)
                {
                    PatchHelper.Log(ELogLevel.Error, $"[checking md5] file is not existed: {ele.Name}");
                    failedOnCheckDownload = true;
                    yield break;
                }
                else
                {
                    continue;
                }
            }
            
            using (var fs = new FileStream(savePath, FileMode.Open, FileAccess.Read))
            {
                int byteRead;
                md5.Initialize();
                while ((byteRead = fs.Read(buf, 0, buf.Length)) > 0)
                {
                    md5.TransformBlock(buf, 0, byteRead, null, 0);
                    if (sw.ElapsedMilliseconds > 250)
                    {
                        yield return null;
                        sw.Restart();
                    }
                }
                md5.TransformFinalBlock(buf, 0, 0);
                fs.Close();
                string localMd5 = BitConverter.ToString(md5.Hash).Replace("-", "");
                if (string.Equals(ele.MD5, localMd5, StringComparison.OrdinalIgnoreCase))
                {
                    //MotionLog.Log(ELogLevel.Log, StringFormat.Format("skip download existed file: {0}", savePath));
                    ele.SkipDownload = true;
                    this.currentDownloadSizeKB += ele.SizeKB;
                    this.currentDownloadCount++;
                }
                else if (isPostCheck)
                {
                    PatchHelper.Log(ELogLevel.Error, $"Web file md5 verification error : {ele.Name}");
                    PatchHelper.Log(ELogLevel.Error, $"local md5 is : {localMd5}");
                    PatchHelper.Log(ELogLevel.Error, $"md5 in manifest is : {ele.MD5}");
                    PatchEventDispatcher.SendWebFileMD5VerifyFailedMsg(ele.Name);
                    failedOnCheckDownload = true;
                    File.Delete(savePath);
                    yield break;
                }
            }
        }
    }
}

布爾值isPostCheck的作用是是否是二次檢測，先不管它

按流程來走

1. 檢查該AB包是否在臨時文件夾中存在，如果不存在則跳過

2. 如果已存在，創(chuàng)建該臨時下載文件的MD5，與下載清單中的MD5做對比

3. 如果MD5對比一致，則標(biāo)記該AB包數(shù)據(jù)為SkipDownload，同時標(biāo)記下載數(shù)據(jù)長度，供UI顯示

我們項(xiàng)目里目前的代碼被人改了，我也有有點(diǎn)看不懂為何要用 md5.TransformBlock的方式

下面是一套生成MD5碼的代碼，加載文件，MD5CryptoServiceProvider會根據(jù)加載的stream生成hash，

readonly MD5CryptoServiceProvider _provider = new MD5CryptoServiceProvider();
public static string StreamMD5()
{
? ? using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
? ? {
    ? ? byte[] hashBytes = _provider.ComputeHash(stream);
    ? ? return ToString(hashBytes);
? ? }
}
private static string ToString(byte[] hashBytes)
{
? ? var sb = new StringBuilder();
? ? foreach (var t in hashBytes)
? ? sb.Append(t.ToString("x2"));
? ? return sb.ToString();
}

首先要判斷臨時下載目錄中是否存在該文件，如果沒有，我們項(xiàng)目文章來源地址http://www.zghlxwxcb.cn/news/detail-490922.html

private IEnumerator Download()
{
    // 計(jì)算下載文件的總大小
    totalDownloadCount = _patcher.DownloadList.Count;
    if (totalDownloadCount == 0)
    {
        _patcher.SwitchNext();
        yield break;
    }
    //先檢查一遍temp目錄有沒有下載完的, 計(jì)算這次實(shí)際需要下載的個數(shù)和size
    yield return CheckTempFileComplete(_patcher.DownloadList, false);

    // 開始下載列表里的所有資源
    PatchHelper.Log(ELogLevel.Log, $"Begine download web files : {totalDownloadCount-currentDownloadCount}");
    PatchEventDispatcher.SendPatchStatesChangeMsg(EPatchStates.DownloadWebFiles);
    var startTime = Time.realtimeSinceStartup;
    var newDownloaded = new List<PatchElement>(_patcher.DownloadList.Count);
    foreach (var element in _patcher.DownloadList)
    {
        if (element.SkipDownload) continue;
        newDownloaded.Add(element);
    }

    if (useMultiRequest)
    {
        yield return DownloadWithMultiTask(newDownloaded);
    }
    else
    {
        yield return DownloadWithSingleTask(newDownloaded);
    }
    if (failedOnDownload)
    {
        yield break;
    }
    MotionLog.Log(ELogLevel.Log, $"<color=#ff0000>Downloading {newDownloaded.Count} files cost {Time.realtimeSinceStartup-startTime} sec.</color>");
    //全部下載完成后把這次新下載的文件再校驗(yàn)一遍，如果有文件失敗就退出
    yield return CheckTempFileComplete(newDownloaded, true);
    if (failedOnCheckDownload)
    {
        yield break;
    }
    
    if (_patcher.MiniAndroid)
    {
        var fileCount = _patcher.DownloadList[0].Version; // tricky storing filecount in field [version]
        var zipFileName = _patcher.DownloadList[0].Name;
        yield return DecompressInitPack(zipFileName, fileCount);
    }
    else
    {
        yield return DeployDownloadFiles();
    }

    // 最后清空下載列表
    _patcher.DownloadList.Clear();
    _patcher.SwitchNext();
}