1 | <?php |
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2 | |||
3 | declare(strict_types=1); |
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4 | |||
5 | namespace BitWasp\Bitcoin\Block; |
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6 | |||
7 | use BitWasp\Bitcoin\Exceptions\MerkleTreeEmpty; |
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8 | use BitWasp\Bitcoin\Math\Math; |
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9 | use BitWasp\Bitcoin\Transaction\TransactionInterface; |
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10 | use BitWasp\Buffertools\Buffer; |
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11 | use BitWasp\Buffertools\BufferInterface; |
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12 | use Pleo\Merkle\FixedSizeTree; |
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13 | |||
14 | class MerkleRoot |
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15 | { |
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16 | /** |
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17 | * @var TransactionInterface[] |
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18 | */ |
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19 | private $transactions; |
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20 | |||
21 | /** |
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22 | * @var Math |
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23 | */ |
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24 | private $math; |
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25 | |||
26 | /** |
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27 | * @var BufferInterface |
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28 | */ |
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29 | private $lastHash; |
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30 | |||
31 | /** |
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32 | * Instantiate the class when given a block |
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33 | * |
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34 | * @param Math $math |
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35 | * @param TransactionInterface[] $txCollection |
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36 | */ |
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37 | 8 | public function __construct(Math $math, array $txCollection) |
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38 | { |
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39 | 8 | $this->math = $math; |
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40 | 8 | $this->transactions = $txCollection; |
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41 | 8 | } |
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42 | |||
43 | /** |
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44 | * @param callable|null $hashFunction |
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45 | * @return BufferInterface |
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46 | * @throws MerkleTreeEmpty |
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47 | */ |
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48 | 8 | public function calculateHash(callable $hashFunction = null): BufferInterface |
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49 | { |
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50 | 8 | if ($this->lastHash instanceof BufferInterface) { |
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51 | 3 | return $this->lastHash; |
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52 | } |
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53 | |||
54 | 8 | $hashFxn = $hashFunction ?: function ($value) { |
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55 | 7 | return hash('sha256', hash('sha256', $value, true), true); |
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56 | 8 | }; |
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57 | |||
58 | $txCount = count($this->transactions); |
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59 | if ($txCount === 0) { |
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60 | // TODO: Probably necessary. Should always have a coinbase at least. |
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61 | throw new MerkleTreeEmpty('Cannot compute Merkle root of an empty tree'); |
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62 | } |
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63 | |||
64 | if ($txCount === 1) { |
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65 | $binary = $hashFxn($this->transactions[0]->getBinary()); |
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66 | } else { |
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67 | // Create a fixed size Merkle Tree |
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68 | $tree = new FixedSizeTree($txCount + ($txCount % 2), $hashFxn); |
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69 | |||
70 | // Compute hash of each transaction |
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71 | $last = ''; |
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72 | foreach ($this->transactions as $i => $transaction) { |
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73 | $last = $transaction->getBinary(); |
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74 | $tree->set($i, $last); |
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75 | } |
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76 | |||
77 | // Check if we need to repeat the last hash (odd number of transactions) |
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78 | if (!($txCount % 2 === 0)) { |
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79 | $tree->set($txCount, $last); |
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80 | } |
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81 | |||
82 | $binary = $tree->hash(); |
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83 | } |
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84 | |||
85 | $this->lastHash = (new Buffer($binary))->flip(); |
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86 | return $this->lastHash; |
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87 | } |
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88 | } |
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89 |