/**
* @param callable|null $hashFunction
* @return Buffer
* @throws MerkleTreeEmpty
*/
public function calculateHash(callable $hashFunction = null)
{
$hashFxn = $hashFunction ?: function ($value) {
return hash('sha256', hash('sha256', $value, true), true);
};
$txCount = count($this->transactions);
if ($txCount === 0) {
// TODO: Probably necessary. Should always have a coinbase at least.
throw new MerkleTreeEmpty('Cannot compute Merkle root of an empty tree');
}
if ($txCount === 1) {
$binary = $hashFxn($this->transactions[0]->getBinary());
} else {
// Create a fixed size Merkle Tree
$tree = new FixedSizeTree($txCount + $txCount % 2, $hashFxn);
// Compute hash of each transaction
$last = '';
foreach ($this->transactions as $i => $transaction) {
$last = $transaction->getBinary();
$tree->set($i, $last);
}
// Check if we need to repeat the last hash (odd number of transactions)
if (!$this->math->isEven($txCount)) {
$tree->set($txCount, $last);
}
$binary = $tree->hash();
}
$this->setLastHash((new Buffer($binary))->flip());
return $this->getLastHash();
}
