}

var (
	buildRootOnce       sync.Once
	lazyRootHuffmanNode *node
)

func getRootHuffmanNode() *node {
	buildRootOnce.Do(buildRootHuffmanNode)
	return lazyRootHuffmanNode
}

func buildRootHuffmanNode() {
	if len(huffmanCodes) != 256 {
		panic("unexpected size")
	}
	lazyRootHuffmanNode = newInternalNode()
	// allocate a leaf node for each of the 256 symbols