Patching AssetBundles is as simple as downloading a new AssetBundle and replacing the existing one. If UnityWebRequestAssetBundle.GetAssetBundle is used to manage an application’s cached AssetBundles, passing a different version or hash parameter will trigger a download of the new AssetBundles.
在修补系统中要解决的更难的问题是检测要替换的 AssetBundle。修补系统需要两个信息列表：
修补程序应下载服务器端 AssetBundle 列表并比较这些 AssetBundle 列表。应重新下载缺少的 AssetBundle 或已更改版本控制信息的 AssetBundle。
Unity does not provide any built-in mechanism for differential patching and UnityWebRequestAssetBundle.GetAssetBundle does not perform differential patching when using the built-in caching system. Instead it always downloads the new AssetBundle file in its entirety. If differential patching is a requirement, then a custom downloader must be written. Unity builds AssetBundles with data ordered in a deterministic manner, so a file patch for a rebuilt AssetBundle can potentially be much smaller than the full file. The uncompressed or chunk-based compression (LZ4) will patch better than the default full file compression (LZMA). Most developers who write their own system choose to use an industry-standard data format for their AssetBundle file lists, such as JSON, and a standard C# class for computing file content hashes, such as MD5. The file content hash can serve as an AssetBundle version, or you can use more traditional version numbers if those are generated by your build systems.