private BufferNode getCachedBufferNode(int id) throws IOException {
		if (bufferTable == null) {
			throw new ClosedException();
		}
		BufferNode bufListHead = (BufferNode) bufferTable.get(id);
		BufferNode node = null;
		if (bufListHead != null) {
			node = bufListHead.nextVersion;
		}
		return node;
	}
Get the buffer node at the current checkpoint level.
@param id buffer id.
@return buffer node or null if node not found
Ghidra/Framework/DB/src/main/java/db/buffers/BufferMgr.java