There are no docs. All I got are the dll and some C# examples like this:

[DllImport("FFACE.dll", EntryPoint = "GetInventoryItem")] public static extern INVENTORYITEM InventoryItem(int index);

and the working statment:

INVENTORYITEM x = FFACE.Inventory.InventoryItem(1);

Thats about it. Next to that I got the fface.h file (which is outdated).

The C# and the JNA run against the same dll and the dll access a running
application. I do let both run with the same running process of that application. I am using
the same parameters in C# and JNA.

I tried even to change the JNA method to use a single parameter only aswell as
the C# implementation does. The return value still was empty.

Thanks for explaining. I ran into the effect, that when I call GetInventoryItem
before that JNA method with the PointerByReference parameter the access violation gets not
triggered.

Something must be wrong with GetInventoryItem, indeed. No other method could
trigger the access violation (but none other is returning a struct anyway).

Regards, Armin