MerkleTree_calcBranches.java

  private void calcBranches() {
    for (int i = 0; i < height; i++) {
      List<Bytes32> parent = tree.get(i + 1);
      List<Bytes32> child = tree.get(i);
      for (int j = 0; j < child.size(); j += 2) {
        Bytes32 leftNode = child.get(j);
        Bytes32 rightNode = (j + 1 < child.size()) ? child.get(j + 1) : zeroHashes.get(i);
        parent.add(j / 2, Hash.sha2_256(Bytes.concatenate(leftNode, rightNode)));
      }
    }
    dirty = false;
  }