@Override
    void setLength(long length) {
		message = "";
		
		this.length = length;
		if (isValidLength()) { 
			try {
				startAddr = block.getEnd().subtractNoWrap(length-1);
			} catch (Exception e) {
				message = "Expanded block is too large";
			}
		}
		listener.stateChanged(null);
	}
@see ghidra.app.plugin.core.memory.ExpandBlockModel#setLength(int)
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/memory/ExpandBlockUpModel.java