private void adjustAllocationOffset(int delta) {
		int adjustedOffset = placementComponent.getAllocationOffset() + delta;
		if (adjustedOffset < 0 || adjustedOffset > composite.getLength()) {
			return;
		}
		placementComponent.updateAllocation(placementComponent.getAllocationByteSize(),
			adjustedOffset);
		updateAllocationOffsetLabel();
	}
<code>BitFieldEditorPanel</code> provides the ability to add or modify bitfields
within non-packed structures.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/compositeeditor/BitFieldEditorPanel.java