public static void OnDownloadReturn(System.IntPtr callback, System.UInt64 taskId, System.UInt32 fileid, bool isSuccess, System.UInt32 errorCode)
{
GCHandle handle = GCHandle.FromIntPtr(callback);
mImpCB = (IIPSMobilePufferCallbackInterface)handle.Target;
mImpCB.OnPufferDownloadReturn(taskId, fileid, isSuccess, errorCode);
}