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<?php |
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namespace BitWasp\Bitcoin\Block; |
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use BitWasp\Bitcoin\Math\Math; |
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use BitWasp\Bitcoin\Collection\Transaction\TransactionCollection; |
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use BitWasp\Buffertools\Buffer; |
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use BitWasp\Buffertools\BufferInterface; |
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use BitWasp\Bitcoin\Exceptions\MerkleTreeEmpty; |
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use Pleo\Merkle\FixedSizeTree; |
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class MerkleRoot |
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{ |
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/** |
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* @var TransactionCollection |
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*/ |
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private $transactions; |
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/** |
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* @var Math |
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*/ |
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private $math; |
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/** |
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* @var BufferInterface |
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*/ |
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private $lastHash; |
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/** |
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* Instantiate the class when given a block |
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* |
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* @param Math $math |
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* @param TransactionCollection $txCollection |
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*/ |
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public function __construct(Math $math, TransactionCollection $txCollection) |
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{ |
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$this->math = $math; |
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$this->transactions = $txCollection; |
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} |
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/** |
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* @param callable|null $hashFunction |
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* @return BufferInterface |
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* @throws MerkleTreeEmpty |
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*/ |
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public function calculateHash(callable $hashFunction = null) |
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{ |
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if ($this->lastHash instanceof BufferInterface) { |
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return $this->lastHash; |
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} |
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$hashFxn = $hashFunction ?: function ($value) { |
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return hash('sha256', hash('sha256', $value, true), true); |
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}; |
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$txCount = count($this->transactions); |
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if ($txCount === 0) { |
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// TODO: Probably necessary. Should always have a coinbase at least. |
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throw new MerkleTreeEmpty('Cannot compute Merkle root of an empty tree'); |
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} |
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if ($txCount === 1) { |
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$binary = $hashFxn($this->transactions[0]->getBinary()); |
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} else { |
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// Create a fixed size Merkle Tree |
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$tree = new FixedSizeTree($txCount + ($txCount % 2), $hashFxn); |
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// Compute hash of each transaction |
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$last = ''; |
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foreach ($this->transactions as $i => $transaction) { |
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$last = $transaction->getBinary(); |
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$tree->set($i, $last); |
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} |
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// Check if we need to repeat the last hash (odd number of transactions) |
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if (!$this->math->isEven($txCount)) { |
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$tree->set($txCount, $last); |
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} |
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$binary = $tree->hash(); |
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} |
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$this->lastHash = (new Buffer($binary))->flip(); |
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return $this->lastHash; |
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} |
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} |
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Bit-Wasp /
bitcoin-php
