ParagonIE\Halite\Structure\MerkleTree::calculateRoot PHP Method

    protected function calculateRoot() : string
    {
        $size = \count($this->nodes);
        if ($size < 1) {
            return '';
        }
        $order = self::getSizeRoundedUp($size);
        $hash = [];
        // Population (Use self::MERKLE_LEAF as a prefix)
        for ($i = 0; $i < $order; ++$i) {
            if ($i >= $size) {
                $hash[$i] = self::MERKLE_LEAF . $this->personalization . $this->nodes[$size - 1]->getHash(true, $this->outputSize, $this->personalization);
            } else {
                $hash[$i] = self::MERKLE_LEAF . $this->personalization . $this->nodes[$i]->getHash(true, $this->outputSize, $this->personalization);
            }
        }
        // Calculation (Use self::MERKLE_BRANCH as a prefix)
        do {
            $tmp = [];
            $j = 0;
            for ($i = 0; $i < $order; $i += 2) {
                if (empty($hash[$i + 1])) {
                    $tmp[$j] = Util::raw_hash(self::MERKLE_BRANCH . $this->personalization . $hash[$i] . $hash[$i], $this->outputSize);
                } else {
                    $tmp[$j] = Util::raw_hash(self::MERKLE_BRANCH . $this->personalization . $hash[$i] . $hash[$i + 1], $this->outputSize);
                }
                ++$j;
            }
            $hash = $tmp;
            $order >>= 1;
        } while ($order > 1);
        // We should only have one value left:t
        $this->rootCalculated = true;
        return \array_shift($hash);
    }