public static extern void nim_friend_request(
     [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NimUtility.Utf8StringMarshaler))]
     string accid,
     NIMVerifyType verify_type,
     [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NimUtility.Utf8StringMarshaler))]
     string msg,
     [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NimUtility.Utf8StringMarshaler))]
     string json_extension,
     Friend.Delegate.FriendOperationDelegate cb, IntPtr user_data);
 public static extern void nim_friend_update(
     [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NimUtility.Utf8StringMarshaler))]
     string friend_json,
     [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(NimUtility.Utf8StringMarshaler))]
     string json_extension,
     Friend.Delegate.FriendOperationDelegate cb, IntPtr user_data);