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.
パッチ適用のシステムにおいて、より難しい問題は、置き換えるべきアセットバンドルの特定です。パッチシステムは次の 2 種類の情報のリストを必要とします。
パッチャーは、サーバー側のアセットバンドルのリストをダウンロードし、アセットバンドルのリストを照合する必要があります。欠落したアセットバンドルやバージョン情報が変わったアセットバンドルは、再ダウンロードされる必要があります。
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.