public static void OnDownloadProgress(System.IntPtr callback, System.UInt64 taskId, System.UInt64 nowSize, System.UInt64 totalSize)
{
GCHandle handle = GCHandle.FromIntPtr(callback);
mImpCB = (IIPSMobilePufferCallbackInterface)handle.Target;
mImpCB.OnPufferDownloadProgress(taskId, nowSize, totalSize);
}