src/main/java/org/nustaq/offheap/structs/FSTStruct.java
public FSTStructChange finishChangeTracking() {
        tracker.snapshotChanges((int) getOffset(), getBase());
        FSTStructChange res = tracker;
        tracker = null;
        return res;
    }
public FSTStructChange finishChangeTracking() {
        tracker.snapshotChanges((int) getOffset(), getBase());
        FSTStructChange res = tracker;
        tracker = null;
        return res;
    }
works only if change tracking is enabled