[fpc-pascal]How to translate an Union from C to Pascal?

[milimeter]

Hello, every one

  Does anybody know how to translate an Union in a C code to Pascal?
  Please see the following codes in C (from source of gedit 2.0.2):

struct _GeditUndoAction
{
	GeditUndoActionType action_type;
	
	union {
		GeditUndoInsertAction	insert;
		GeditUndoDeleteAction   delete;
	} action;

	gboolean mergeable;

	gint order_in_group;
};

  I want to translate it to Pascal, but I don't know how to handle the union 
Action in it.

  Thank you very much.
  mili