How to get AssetBundleManifest?

Following the instructions on the official site https://docs.unity3d.com/ScriptReference/Caching.html I fail to get AssetBundleManifest neither from the server nor from local storage. The end goal is to get AssetBundle’s hash.

Main error message in the console is:

Failed to decompress data for the AssetBundle "Memory"

I tried to use the following:

UnityWebRequest - to load from server

LoadFromFile - to local from local storage

How to do it correctly?

 

After building I receive the main file and the manifest file.

In order to check cache and the updated bundle loading I have to indicate hash of the new Bundle which we can obtain only from AssetBundleManifest(for UnityWebRequest). However I cannot make AssetBundleManifest load properly. I tried to indicate path both to the main file (without extension), and to the manifest file (with .manifest extension)

I try to load AssetBundleManifest using these lines:

Code (CSharp):

1.  
2. AssetBundle manifestBundle = AssetBundle.LoadFromFile(Path.Combine(Application.streamingAssetsPath, "dispatcherminigame.manifest"));
3. AssetBundleManifest manifest = manifestBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");

So in order to get AssetBundle’s hash I have to load the file with .manifest extension, right?

 

Hi,

I am struggling with this too.

Is it a matter of downloading the manifest individually, or is it indeed available within the loading bundle?

Bye,

Jean

 

You load the main asset bundle manifest, then use https://docs.unity3d.com/ScriptReference/AssetBundleManifest.GetAssetBundleHash.html to get the hash

 

Hi,

thanks for your reply.

the problem is that I can't find the way to do what you say with code.

I have this:

AssetBundleManifest _m = (AssetBundleManifest)wwwObject.assetBundle.LoadAsset("AssetBundleManifest", typeof(AssetBundleManifest));

and that doesn't work, so I would appreciate a snippet on what to do with the wwwObject.assetBundle once it's done being downloaded, so far I haven't found a working snippet from all my searches on google.

AssetBundleManifest _m = (AssetBundleManifest)wwwObject.assetBundle.mainAsset;

that doesn't work neither.

so if you have a working code snippet to share, I would appreciate it very much.

Bye,

Jean

 

Code (CSharp):

1. wwwObject.assetBundle.LoadAsset<AssetBundleManifest>("assetbundlemanifest");

Should work. If not, define what 'doesn't work' means. Do you get an error?

Also, the bundle containing the manifest is the one named after the folder you built to. It also isn't the file with the .manifest extension, its the bundle file which doesn't have an extension.

 

Hi,

That doesn't work neither, this line returns null, while the assetbundle main asset is well and can be accessed properly.

here's the url : https://www.dropbox.com/s/bmunwj8c3ohtfoi/bundletest?dl=1

Maybe you could point me to a url of a testing asset bundle that works? that would be a good way to rule out that the production of this assetbundle is faulty.

and I confirm that the .manifest is not the file I load, but indeed the other one, without extension.

thanks for your patience on this I hope we'll get to the bottom of this!

Jean

 

Hi Jean,

Your bundle returns null on my end too, but I'm using unity 2018.2.2f1 and your manifest is built using 5.6.3f1 by the looks of it (bundles aren't guaranteed to be compatible with different versions).

What Unity version are you using to build the bundles and project?

Also, post your downloading code. I suppose unitywebrequest isn't available yet in 5.6.

Here's an example of a bundle that works for me:

https://s3-eu-west-1.amazonaws.com/byardev.mysmilez.nl/Android

 

Hi,

yes, it's built with 5.6, but it should work still right?! I'll move to 2017 and 2018 to see if I get a different results.

I need to get to the lowest working version as I am providing support for PlayMaker, so it woul dbbe good if I can make it work on 5.6

Bye,

Jean

 

Out of curiosity I downloaded the unity version the bundles were built in, and I can't load the manifest either.

What build target was the bundle built for? It has to be the same as the platform you try to load it on.

Post the script used to generate the bundles, and the script that downloads them.

 

Hi,

I am doing this all in editor for standaloneOsX platform target. does that means it will never work in editor?

Bye,

Jean

 

No, it should load in the editor.

I just used this build script in the same unity version as you to generate a manifest

Code (CSharp):

1. using System.IO;
2. using UnityEditor;
3.  
4. public class CreateAssetBundles
5. {
6.     [MenuItem("Assets/Build AssetBundles")]
7.     static void BuildAllAssetBundles()
8.     {
9.         string assetBundleDirectory = "Assets/AssetBundles";
10.         if(!Directory.Exists(assetBundleDirectory))
11.         {
12.             Directory.CreateDirectory(assetBundleDirectory);
13.         }
14.        
15.         BuildPipeline.BuildAssetBundles(assetBundleDirectory, BuildAssetBundleOptions.None, BuildTarget.StandaloneOSXUniversal);
16.     }
17. }

It outputs this bundle: https://s3-eu-west-1.amazonaws.com/byardev.mysmilez.nl/AssetBundles

And it loads just fine using the previously shared code. The problem has to be in the bundle file itself, try recreating it.

This could even be a problem with dropbox hosting. Perhaps they use some funky compression which messes up the file, try regenerating the bundles and hosting it elsewhere or even in streaming assets.

 

Hi,

ok, thanks for confirming on your end that works, I'll debug this Id save it in StreamingAssets already. but as I was loading it from that and was getting null I though it could be something that is only available when you download from the web hence why I tried to put it on the web.

thanks for your help!

Bye,

Jean

 

I came across this thread as I had the same problem. I think your mistake is that you're looking in the wrong files. When you create the asset bundles, Unity creates 2 files in your output folder, named after the build target, e.g. WebGL and WebGL.manifest. In order to retrieve the AssetBundleManifest with

Code (CSharp):

1. wwwObject.assetBundle.LoadAsset<AssetBundleManifest>("assetbundlemanifest");

You need to use the file "WebGL" (without the extension). With that AssetBundleManifest you can get all the info needed about the actual AssetBundles

 

Hi,

Thanks for your Input!

Bye,

Jean

 

Jesus. This one took me an entire day to figure out what I did wrong. Thanks for creating the thread since it gave me new ideas on how to get this solved.

However. Here is the code that loads a asset bundle manifest from a given URL:

You don't have to use the .manifest files!
This solution also handles multiple asset bundles (like different scenes).

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.Networking;
5.  
6. public class AssetBundleCacheSample : MonoBehaviour
7. {
8.  
9.     public string manifestPath = "https://www.your-domain.de/AssetBundlesiOS"; // No file extension (this file gets created when you build your bundles)
10.     public string assetBundlePath = "https://www.your-domain.de/testbundle"; // Also no extension. This is the actual content asset bundle
11.  
12.     private void Start()
13.     {
14.         StartCoroutine(DownloadAndCacheAssetBundle());
15.     }
16.  
17.     IEnumerator DownloadAndCacheAssetBundle()
18.     {
19.         // Load the manifest (from url)
20.         UnityWebRequest www = UnityWebRequestAssetBundle.GetAssetBundle(manifestPath);
21.         yield return www.SendWebRequest();
22.  
23.         AssetBundle manifestBundle = DownloadHandlerAssetBundle.GetContent(www);
24.  
25.         AssetBundleManifest manifest = manifestBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");
26.  
27.         // Use the default cache here
28.         Caching.currentCacheForWriting = Caching.defaultCache;
29.  
30.         string[] allAssetBundleNames = manifest.GetAllAssetBundles();
31.  
32.         foreach(string assetBundleName in allAssetBundleNames)
33.         {
34.             // Get hash of bundle
35.             Hash128 hash = manifest.GetAssetBundleHash(assetBundleName);
36.             Debug.Log("Hash for bundle " + assetBundleName + " is " + hash);
37.      
38.             // Download actual content bundle
39.             UnityWebRequest request = UnityWebRequestAssetBundle.GetAssetBundle(assetBundlePath, hash, 0);
40.             yield return request.SendWebRequest();
41.  
42.             // This one is crucial for debugging. Code 200 means downloaded from web and Code 0 means loaded from cache.
43.             Debug.Log(request.responseCode);
44.  
45.             // Download the actual content bundle
46.             AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(request);
47.      
48.             // List all the cached versions of the given asset bundle
49.             List<Hash128> listOfCachedVersions = new List<Hash128>();
50.             Caching.GetCachedVersions(assetBundleName, listOfCachedVersions);
51.  
52.             for (int i = 0; i < listOfCachedVersions.Count; i++)
53.             {
54.                 Debug.Log("Found cached version of " + assetBundleName + " version: " + listOfCachedVersions[i]);
55.             }
56.  
57.             // Don't forget to unload the bundle
58.             bundle.Unload(false);
59.         }
60.  
61.     }
62.  
63. }
64.  

Hope someone finds this useful.

Keep it up guys!

Greets

 

@JannickL : Thank you so much, you save my day! It work like a charm!

 

@JannickL your solution has one problem: you need to send a request every time you load the bundle. While if you use local manifest file and if you have cached bundle then you can avoid any request to server and speed up loading process.

BTW I am trying to load bundles from server for almost a week. I learned a lot about Unity and Webrequest in general. Currently Addressables has lots of bugs and limitations which cannot be fixed for more than a half year (including high delays on mobile devices) so they are not recommended to be used.

UnityWebRequestAssetBundle also has a problem with showing loading progress... it will be 0 for 98% of the time and then quickly move to 45 and then 100%. There was an answer from Unity developers that this is a feature not a bug =) So if you faced the same problem, try to create your own download handler from DownloadHandlerScript.

 

i think we all need to read this manual page carefully ,
as it states the following
Loading AssetBundle Manifests
Loading AssetBundle manifests can be incredibly useful. Especially when dealing with AssetBundle dependencies.

To get a useable AssetBundleManifest object, you’ll need to load that additional AssetBundle (the one that’s named the same thing as the folder it’s in) and load an object of type AssetBundleManifest from it.

Loading the manifest itself is done exactly the same as any other Asset from an AssetBundle:

AssetBundle assetBundle = AssetBundle.LoadFromFile(manifestFilePath);
AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");
hope this would help everyone

 

In:
AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");
the "("AssetBundleManifest")" should be same or the string name should be changed as my asset bundle is named bundle and its manifest as bundle.manifest?

 

You should not replace "AssetBundleManifest". You should provide file name in this line AssetBundle.LoadFromFile(YOU_FILE_PATH) in my case it was AssetBundle.LoadFromFile(Path.Combine(Application.streamingAssetsPath, "Android" + majorVersion)); I am using the code for more than a half year and no issues found.

 

@skjagan should be the same this is just the record that holds all the asset bundles data generated for the platform at which you will find each asset bundle name along with its hash code and crc,
i am really thinking about writing a full tutorial about it as its very ambiguous

 

So what are the.manifest files - which are created for each Assetbundle - for anyways?

When we try to load them, we get

Failed to decompress data for the AssetBundle 'Memory'.

(Just like OP)

JannickL Says, you don't have to use them whatsoever. - but his code still loads a manifest, so i suppose that is "the one that’s named the same thing as the folder it’s in" - as in the the manual.

andrew_pearce rightfully critizised, that this main-manifest file isn't cached in Jannicks code whatsover.
MaryamKamel cited the manual passage i mentioned above above - but this also just seems to refer to the overall manifest file.

But that still leaves me with (and maybe OP + skjagan) with the Question:
What are the .manifest files for each single bundle used for?


My current suspicion is: They're good for ... NOTHING.
Is seems this has just been omitted from the updated documentation.
While https://docs.unity3d.com/Manual/AssetBundles-Building.html goes into detail about what is created during the build process, and what these small manifest files contains, its complete silent about what they are supposed to be used for. Instead it references:
https://docs.unity3d.com/Manual/AssetBundles-Native.html
to learn more about the manifest - but thats only for the Manifest Bundle again.


The older 5.3 Unity doc says about them:

• This manifest file is only used for incremental build, not necessary for runtime.

https://docs.unity3d.com/530/Documentation/Manual/BuildingAssetBundles.html


thanks Unity ... for a wasted day of work ^^

 

And additionally the DownloadHandlerAssetBundle class prohibits accessing the HTTP response from a webrequest as plain text.
So in case the server responds with something else than status 200 there is NO WAY to read/show the error message from the server.
Who designs API's like this....

AGAIN Thank you unity for nothing.

 

Well, there was a bit of anger on this thread, but it eventually didn't help me much. So after a couple days working on it, here's how I solved it on my end. Hope this helps.

Put this code on your asset bundle downloader script, call StartCoroutine(Init()) and be happy.

Code (CSharp):

1. string assetName = "https://my.server.com/unity/assetBundles/StandaloneWindows/myAssetBundle";
2. Hash128 assetHash;
3. AssetBundle _myLoadedAssetBundle;
4.  
5. public IEnumerator Init()
6. {
7.     while (!Caching.ready)
8.         yield return null;
9.  
10.     if (_flushCache)
11.     {
12.         //Debug.Log("Cleared Cache");
13.         Caching.ClearAllCachedVersions(assetName);
14.     }
15.  
16.     string manifestPath = assetName + ".manifest";
17.     string assetHashFromManifest;
18.  
19.     using (UnityWebRequest request = UnityWebRequest.Get(manifestPath))
20.     {
21.         yield return request.SendWebRequest();
22.         bool debugged = false;
23.         while (!request.isDone)
24.         {
25.             if (request.downloadProgress < 0 && !debugged)
26.             {
27.                 debugged = true;
28.                 Debug.Log("Progress: " + request.downloadProgress + ". Something may have gone wrong when downloading the asset bundle");
29.             }
30.  
31.             if (request.isNetworkError || request.isHttpError)
32.             {
33.                 // handle connection timeout or loss while downloading
34.                 Debug.Log("Connection error: " + request.error);
35.             }
36.  
37.             yield return null;
38.         }
39.         Debug.Log(request.downloadHandler.text);
40.  
41.         assetHashFromManifest = request.downloadHandler.text.GetManifestHash();
42.     }
43.  
44.     // to properly check if the asset is cached, we first need to download it
45.     // this defeats the point when it's stored on our server. we only want to download if it's not yet cached
46.     // so instead, I made a tool to get and parse the asset hash from the manifest file in runtime from the server
47.     // GetAssetBundle without any Hash nor CRC will download the asset. When used with an assetHash or CRC, it will load from cache
48.     using (UnityWebRequest request =
49.         FoundCache(assetHashFromManifest) ?
50.             UnityWebRequestAssetBundle.GetAssetBundle(assetName, assetHash)
51.             :
52.             UnityWebRequestAssetBundle.GetAssetBundle(assetName)
53.         )
54.     {
55.         yield return request.SendWebRequest();
56.         bool debugged = false;
57.         while (!request.isDone)
58.         {
59.             if (request.downloadProgress < 0 && !debugged)
60.             {
61.                 debugged = true;
62.                 Debug.Log("progress: " + request.downloadProgress);
63.             }
64.  
65.             if (request.isNetworkError || request.isHttpError)
66.             {
67.                 // handle connection timeout or loss while downloading
68.                 Debug.Log("error: " + request.error);
69.             }
70.  
71.             yield return null;
72.         }
73.         _myLoadedAssetBundle = DownloadHandlerAssetBundle.GetContent(request);
74.     }
75.  
76.  
77.     if (!_myLoadedAssetBundle)
78.         Debug.LogError("No content downloaded.");
79.  
80.     yield return LoadAssetBundle();
81.  
82.     //Debug.Log("Hash: " + _myLoadedAssetBundle.GetHashCode()); //that doesn't match the hash from the manifest for checking cache
83.  
84.     yield return null;
85. }
86.  
87. public bool FoundCache(string assetHashStr)
88. {
89.     assetHash = Hash128.Parse(assetHashStr);
90.     if (Caching.IsVersionCached(assetName, assetHash))
91.     {
92.         Debug.Log("Found Cache. Parsed Hash: " + assetHash.ToString());
93.         return true;
94.     }
95.     assetHash = Hash128.Compute(assetHashStr);
96.     if (Caching.IsVersionCached(assetName, assetHash))
97.     {
98.         Debug.Log("Found Cache. Computed Hash: " + assetHash.ToString());
99.         return true;
100.     }
101.     return false;
102. }

And that's just a simple extension class I made to offload some of the generic logic

Code (CSharp):

1. using System;
2. using System.Collections;
3. using System.Collections.Generic;
4. using System.Linq;
5.  
6. public static class MyStringExtensions
7. {
8.     public static string GetManifestHash(this string manifestRawText)
9.     {
10.         return GetManifestValue(manifestRawText, "Hash:");
11.     }
12.     public static string GetManifestCRC(this string manifestRawText)
13.     {
14.         return GetManifestValue(manifestRawText, "CRC:");
15.     }
16.     public static string GetManifestValue(this string manifestRawText, string lookFor = "Hash:")
17.     {
18.         // We don't really need to chop the string, but if we did, that's how I'd do it.
19.         //string choppedManifest = manifestRawText.Substring(manifestRawText.IndexOf("AssetFileHash:"));
20.         //choppedManifest = choppedManifest.Remove(choppedManifest.IndexOf("TypeTreeHash:"));
21.  
22.         var hashes = manifestRawText
23.             // separate the text into lines, in an list/array of strings
24.             .Split(Environment.NewLine.ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
25.             // select only the lines that starts with 'lookFor', ignoring white spaces
26.             .Where(x => x.Trim().StartsWith(lookFor))
27.             // convert result to array
28.             .ToArray();
29.         string myParsedHash = hashes
30.             // on the manifest file, the hash we need is always the first (AssetFileHash), so here we just take the first one found.
31.             .FirstOrDefault()
32.             // ignore whitespaces
33.             .Trim();
34.         myParsedHash = string.IsNullOrEmpty(myParsedHash) ? "" :
35.             // get the right part of the string after what 'lookfor'. +1 because the substring index starts at zero
36.             myParsedHash.Substring(lookFor.Length + 1);
37.  
38.         return myParsedHash;
39.     }
40. }
41.  

And here's a simple implementation to load the scene. I'm working with streaming asset bundles.

Code (CSharp):

1. LoadSceneMode loadSceneMode = LoadSceneMode.Single;
2.  
3. public IEnumerator LoadAssetBundle()
4. {
5.     if (!_myLoadedAssetBundle)
6.     {
7.         Debug.LogError("Could not load null asset bundle");
8.         yield break;
9.     }
10.     string _sceneName;
11.     if (_myLoadedAssetBundle.isStreamedSceneAssetBundle)
12.     {
13.         Debug.Log("Streaming asset in");
14.  
15.         string[] scenePaths = _myLoadedAssetBundle.GetAllScenePaths();
16.         _sceneName = System.IO.Path.GetFileNameWithoutExtension(scenePaths[0]);
17.  
18.         AsyncOperation asyncLoad = SceneManager.LoadSceneAsync(_sceneName, loadSceneMode);
19.  
20.         while (!asyncLoad.isDone)
21.         {
22.             yield return null;
23.         }
24.     }
25.     else
26.     {
27.         string[] assets = _myLoadedAssetBundle.GetAllAssetNames();
28.  
29.         Debug.Log("Getting all " + assets.Length + " assets in");
30.  
31.         Debug.LogError("Scene Asset Bundle should be streaming type. Prefab loading and instancing without a main scene is not supported by this function.");
32.     }
33. }

 

I am actually looking for a solution like this. But I don't understand why it is necessary to download the asset bundle after checking for the hash. Why isn't it possible to compare the downloaded manifest's hash to the cached hash? If those are equal you don't even have to download the asset bundle completely. Or am I completely wrong?

Thank you for your solution to this problem though. I would like to hear your opinion to my idea.

- Felix

 

So awesome. Thank you! Your code solves my problem and also introduced me to some pretty cool concepts

 

Hi,
I want to apologize in advance for bringing up this old thread but it seems the most promising to me.

I tried paulo_renans approach and it pretty much did what I expected. The only problem is I don't think that anything ever gets cached for me...
I don't know why it does that because everything I have found so far tells me that UnityWebRequest is directly connected to the caching system and should cache assetbundles fully automatically.
But the "FoundCache" bool in this script always returns false for me which leads me to believe that nothing is actually cached since every other Debug information seems correct to me.
Most importantly it obtains the correct hash from the manifest which is the same everytime. So if the assetbundle was cached and the hash comparison returned true then the assetbundle shouldn't be downloaded over and over again but loaded from cache. Right now it when I download the assetbundle and load the scene - then go back and try the same again it doesnt't load from cache but always downlaods the whole thing again before loading the scene. How can I change this?

Hopefully somebody is able to point me in the right direction what the problem could be...
Thanks in advance!

 

@MSachs, have you checked the C:\Users[USER]\AppData\LocalLow\Unity folder on Windows for your app's cached files? This helps determine if caching is working. If files are missing, there's a caching issue. If present, try running your app in Unity without internet to see if cached files load. Also, ensure your code uses a consistent hash string for each execution (it can be any string, not just one loaded from manifest file). Changing or empty hash strings will cause loading asset regardless of existing cache.

 

Thanks For the quick reply! I am on Mac do you know where the respective folder would be on there?
Without internet connection nothing loads at all..
The hash string is consistent. It doesn't change unless I am rebuilding the assetbundle.

 

I think the correct path is '~/Library/Caches/Unity'. Regarding the hash string consistency, it's possible there's a logical error in the script causing this variable to change. It would be wise to use Debug.Log() to confirm it remains consistent between requests, just to be safe.

 

Thanks! I found the folder but the only thing that is in there ist this "__info" document (screenshot) which seems to change every time I enter or exit play mode but not when pressing the download button. But it contains just some seemingly random numbers which don't change themselves...

I already have a Debug.Log() which displays the hash. It is indeed the same every time.

 

Okay hold on... I just found something else

With this: https://github.com/UnityCommunity/U...ets/Scripts/AssetBundles/AssetBundleLoader.cs I get the bundle cached correctly so I took the working parts from this script and implemented it to work with paulo_renans approach which seems to do exactly what I want.

Just don't know why the approach I used from this thread didn't cache anything at all...