unity3d 加密资源并缓存加载

首先要鄙视下unity3d的文档编写人员极度不负责任，到发帖为止依然没有更新正确的示例代码。

// C# Example
    // Builds an asset bundle from the selected objects in the project view.
    // Once compiled go to "Menu" -> "Assets" and select one of the choices
    // to build the Asset Bundle
    
    using UnityEngine;
    using UnityEditor;
	using System.IO;
    public class ExportAssetBundles {
        [MenuItem("Assets/Build AssetBundle Binary file From Selection - Track dependencies ")]
        static void ExportResource () {
            // Bring up save panel
            string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
            if (path.Length != 0) {
                // Build the resource file from the active selection.
                Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
                BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, path, BuildAssetBundleOptions.CollectDependencies | BuildAssetBundleOptions.CompleteAssets);
                Selection.objects = selection;
            
		
				FileStream fs = new FileStream(path,FileMode.Open,FileAccess.ReadWrite);
				byte[] buff = new byte[fs.Length+1];
				fs.Read(buff,0,(int)fs.Length);
				buff[buff.Length-1] = 0;
				fs.Close();
				File.Delete(path);
			
				string BinPath = path.Substring(0,path.LastIndexOf('.'))+".bytes";
 //				FileStream cfs = new FileStream(BinPath,FileMode.Create);
				cfs.Write(buff,0,buff.Length);
				buff =null;
				cfs.Close();
				
//				string AssetsPath = BinPath.Substring(BinPath.IndexOf("Assets"));
//				Object ta = AssetDatabase.LoadAssetAtPath(AssetsPath,typeof(Object));
//              BuildPipeline.BuildAssetBundle(ta, null, path);
			}
        }
        [MenuItem("Assets/Build AssetBundle From Selection - No dependency tracking")]
        static void ExportResourceNoTrack () {
            // Bring up save panel
            string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
            if (path.Length != 0) {
                // Build the resource file from the active selection.
                BuildPipeline.BuildAssetBundle(Selection.activeObject, Selection.objects, path);
            }
        }
		
	
    }

　　把打包的文件转换成了binary文件并多加了一个字节加密。

　　当bytes文件生成好后再选中它，使用"Assets/Build AssetBundle From Selection - No dependency tracking"再次打包。

using UnityEngine;
using System.Collections;
using System;

public class WWWLoadTest : MonoBehaviour
{

    public string BundleURL;
    public string AssetName;
    IEnumerator Start()
    {
          WWW www =WWW.LoadFromCacheOrDownload(BundleURL,2);
        
        yield return www;
        
        TextAsset txt = www.assetBundle.Load("characters",typeof(TextAsset)) as TextAsset;
        
        byte[]  data = txt.bytes;
        
        byte[] decryptedData = Decryption(data);
        Debug.LogError("decryptedData length:"+decryptedData.Length);
        StartCoroutine(LoadBundle(decryptedData));
    }
    
    IEnumerator LoadBundle(byte[] decryptedData){        
        AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);            
        yield return acr;
        AssetBundle bundle = acr.assetBundle;        
        Instantiate(bundle.Load(AssetName));
        
    }
    
    byte[] Decryption(byte[] data){
        byte[] tmp = new byte[data.Length-1];
        for(int i=0;i<data.Length-1;i++){
            tmp[i] = data[i];    
        }
        return tmp;
        
    }

    
}

WWW.LoadFromCacheOrDownload的作用就是下载并缓存资源，要注意后面的版本号参数，如果替换了资源却没有更新版本号，客户端依然会加载缓存中的文件。

www.assetBundle.Load("characters",typeof(TextAsset)) as TextAsset  //characters是加密文件的名字

AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);           

这句是官网最坑爹的，AssetBundle.CreateFromMemory明明返回的是AssetBundleCreateRequest官网却写得是AssetBundle，而且AssetBundleCreateRequest是一个异步加载，必须用协程的方式加载官网也没有提到。跟多兄弟就倒在了这里

完。