unity 如何使用文件流读取streamingassets下的资源

var buffer = new byte[size];
FileStream stream = File.OpenRead(path);
stream.Read(buffer , pos, size);

public class XXXPlugin extends UnityPlayerNativeActivity {
    protected AssetManager assetManager;
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		assetManager = getAssets();
    }
 
	//返回字节数组
	public byte[] LoadBytes(String path,int offset,int len)
	{
         //可以缓存起来，不需每次都open
         InputStream inputStream = assetManager.open(path);
         try {
                 byte buf[] = new byte[len];
                 inputStream.reset();
                 
                //注意skip、read的可靠性
                 inputStream.skip(offset);
                 inputStream.read(buf,0,len)
 
                 inputStream.close();
                 return buf;
    
			} 
		catch (IOException e) {
				Log.v ("unity", e.getMessage());
		}
		return null;
	}
 
}

		
            public static byte[] read_streamingpath_bytes(string path,IntPtr ptr, int pos, int size) 
            {
                using (AndroidJavaClass cls = new AndroidJavaClass("com.XXX.XXXPlugin";) ) 
                {
                   AndroidJavaObject  m_AndroidJavaObject = cls.GetStatic<AndroidJavaObject>("mainActivity");
 
                    byte[] s = m_AndroidJavaObject.Call<byte[]>("LoadBytes", path, pos, size);
 
                    return s;
                }
                return null;
            }

#include "com_XXX_NativeHelper.h"
#include <android/asset_manager_jni.h>
#include <android/asset_manager.h>
#include <string>
#include <jni.h>
#include <stdint.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
static AAssetManager *assetManager = nullptr;
 
JNIEXPORT void JNICALL Java_com_XXX_NativeHelper_SetAssetManager
        (JNIEnv *env, jobject jobj, jobject jassetManager) {
    assetManager = AAssetManager_fromJava(env, jassetManager);
}
 
JNIEXPORT int32_t JNICALL ReadAssetsBytesWithOffset(uint32_t pathKey, char* fileName, unsigned char** result, int32_t offset, int32_t length){
    if(assetManager == nullptr){
        return -1;
    }
    AAsset* asset = asset = AAssetManager_open(assetManager, fileName, AASSET_MODE_UNKNOWN);
    if(asset == nullptr){
        return -1;
    }
    off_t size = AAsset_getLength(asset);
    if(size > 0){
        try {
            AAsset_seek(asset, offset, SEEK_SET);
            AAsset_read(asset, *result, length);
        }catch (std::bad_alloc){
            *result = nullptr;
            return -1;
        }
    }
    AAsset_close(asset);
    return (int32_t)length;
}
#ifdef __cplusplus
}
#endif

//XXXPlugin.java
public class XXXPlugin extends UnityPlayerNativeActivity {
    static{
        System.loadLibrary("NativeLib");
    }
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  mainActivity = this;
  
  
        //设置AssetManager， C++中要使用
  NativeHelper.SetAssetManager(getAssets());
   }
 
}
 
//NativeHelper.java
public class NativeHelper {
    public static native void SetAssetManager(AssetManager assetManager);
}

 public class ReadNativeByte
    {
 
#if UNITY_ANDROID
        [DllImport("NativeLib")]
        public static extern int ReadAssetsBytesWithOffset(uint pathKey,string name, ref IntPtr ptr, int offset, int length);
#endif
    }

byte[] bytes = new byte[len];
FileStream stream = File.OpenRead(path);
stream.Seek(offset, SeekOrigin.Begin);
stream.Read(bytes, 0, len);

//资源卸载
    

 //安卓下这两个文件夹路径相同 
    //Application.streamingAssetsPath ＝ jar:file:///data/app/com.xxx.xxx-1.apk!/assets/  == "jar:file://"+Application.dataPath+"!assets/"
    //Application.dataPath+"!assets/" ＝ /data/app/com.xxx.xxx-1.apk!assets/
    //Ios下
    //Application.dataPath + "/Raw/" == @"file:///" + Application.streamingAssetsPath + "/"
    //Editor WIN 
    //@"file:///" + Application.streamingAssetsPath + "/"
    //"file:///" + Application.dataPath + "/StreamingAssets" + "/"

private string path = string.Empty;
    public string GetSAPath()
    {
        //安卓平台 加文件名
#if UNITY_ANDROID && !UNITY_EDITOR
        path =  Application.streamingAssetsPath + "/"
#elif UNITY_IPHONE && !UNITY_EDITOR
        path = @"file:///" + Application.streamingAssetsPath + "/";
#elif UNITY_STANDLONE_WIN||UNITY_EDITOR
       path =  @"file:///" + Application.streamingAssetsPath + "/";
#endif
        return path;
    }

Application.persistentDataPath + "/tempDic", "testXml"

application.persistentdatapath指向%userprofile%\appdata\local\packages\<productName>\localstate

ios:application.persistentdatapath指向/var/mobile/containers/data/application/<guid>/documents