Line data    Source code

       1             : // Copyright (c) 2009-2010 Satoshi Nakamoto
       2             : // Copyright (c) 2009-2016 The Bitcoin developers
       3             : // Copyright (c) 2017-2020 The PIVX Core developers
       4             : // Distributed under the MIT software license, see the accompanying
       5             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       6             : 
       7             : #ifndef PIVX_MERKLEBLOCK_H
       8             : #define PIVX_MERKLEBLOCK_H
       9             : 
      10             : #include "bloom.h"
      11             : #include "primitives/block.h"
      12             : #include "serialize.h"
      13             : #include "uint256.h"
      14             : 
      15             : #include <vector>
      16             : 
      17             : // Helper functions for serialization.
      18             : std::vector<unsigned char> BitsToBytes(const std::vector<bool>& bits);
      19             : std::vector<bool> BytesToBits(const std::vector<unsigned char>& bytes);
      20             : 
      21             : /** Data structure that represents a partial merkle tree.
      22             :  *
      23             :  * It represents a subset of the txid's of a known block, in a way that
      24             :  * allows recovery of the list of txid's and the merkle root, in an
      25             :  * authenticated way.
      26             :  *
      27             :  * The encoding works as follows: we traverse the tree in depth-first order,
      28             :  * storing a bit for each traversed node, signifying whether the node is the
      29             :  * parent of at least one matched leaf txid (or a matched txid itself). In
      30             :  * case we are at the leaf level, or this bit is 0, its merkle node hash is
      31             :  * stored, and its children are not explorer further. Otherwise, no hash is
      32             :  * stored, but we recurse into both (or the only) child branch. During
      33             :  * decoding, the same depth-first traversal is performed, consuming bits and
      34             :  * hashes as they written during encoding.
      35             :  *
      36             :  * The serialization is fixed and provides a hard guarantee about the
      37             :  * encoded size:
      38             :  *
      39             :  *   SIZE <= 10 + ceil(32.25*N)
      40             :  *
      41             :  * Where N represents the number of leaf nodes of the partial tree. N itself
      42             :  * is bounded by:
      43             :  *
      44             :  *   N <= total_transactions
      45             :  *   N <= 1 + matched_transactions*tree_height
      46             :  *
      47             :  * The serialization format:
      48             :  *  - uint32     total_transactions (4 bytes)
      49             :  *  - varint     number of hashes   (1-3 bytes)
      50             :  *  - uint256[]  hashes in depth-first order (<= 32*N bytes)
      51             :  *  - varint     number of bytes of flag bits (1-3 bytes)
      52             :  *  - byte[]     flag bits, packed per 8 in a byte, least significant bit first (<= 2*N-1 bits)
      53             :  * The size constraints follow from this.
      54             :  */
      55             : class CPartialMerkleTree
      56             : {
      57             : protected:
      58             :     /** the total number of transactions in the block */
      59             :     unsigned int nTransactions;
      60             : 
      61             :     /** node-is-parent-of-matched-txid bits */
      62             :     std::vector<bool> vBits;
      63             : 
      64             :     /** txids and internal hashes */
      65             :     std::vector<uint256> vHash;
      66             : 
      67             :     /** flag set when encountering invalid data */
      68             :     bool fBad;
      69             : 
      70             :     /** helper function to efficiently calculate the number of nodes at given height in the merkle tree */
      71      291843 :     unsigned int CalcTreeWidth(int height)
      72             :     {
      73      291843 :         return (nTransactions + (1 << height) - 1) >> height;
      74             :     }
      75             : 
      76             :     /** calculate the hash of a node in the merkle tree (at leaf level: the txid's themselves) */
      77             :     uint256 CalcHash(int height, unsigned int pos, const std::vector<uint256>& vTxid);
      78             : 
      79             :     /** recursive function that traverses tree nodes, storing the data as bits and hashes */
      80             :     void TraverseAndBuild(int height, unsigned int pos, const std::vector<uint256>& vTxid, const std::vector<bool>& vMatch);
      81             : 
      82             :     /**
      83             :      * recursive function that traverses tree nodes, consuming the bits and hashes produced by TraverseAndBuild.
      84             :      * it returns the hash of the respective node.
      85             :      */
      86             :     uint256 TraverseAndExtract(int height, unsigned int pos, unsigned int& nBitsUsed, unsigned int& nHashUsed, std::vector<uint256>& vMatch);
      87             : 
      88             : public:
      89             : 
      90         673 :     SERIALIZE_METHODS(CPartialMerkleTree, obj)
      91             :     {
      92         337 :         READWRITE(obj.nTransactions, obj.vHash);
      93         674 :         std::vector<unsigned char> bytes;
      94         675 :         SER_WRITE(obj, bytes = BitsToBytes(obj.vBits));
      95         337 :         READWRITE(bytes);
      96         673 :         SER_READ(obj, obj.vBits = BytesToBits(bytes));
      97         337 :         SER_READ(obj, obj.fBad = false);
      98         337 :     }
      99             : 
     100             :     /** Construct a partial merkle tree from a list of transaction id's, and a mask that selects a subset of them */
     101             :     CPartialMerkleTree(const std::vector<uint256>& vTxid, const std::vector<bool>& vMatch);
     102             : 
     103             :     CPartialMerkleTree();
     104             : 
     105             :     /**
     106             :      * extract the matching txid's represented by this partial merkle tree.
     107             :      * returns the merkle root, or 0 in case of failure
     108             :      */
     109             :     uint256 ExtractMatches(std::vector<uint256>& vMatch);
     110             : };
     111             : 
     112             : 
     113             : /**
     114             :  * Used to relay blocks as header + vector<merkle branch>
     115             :  * to filtered nodes.
     116             :  */
     117             : class CMerkleBlock
     118             : {
     119             : public:
     120             :     /** Public only for unit testing */
     121             :     CBlockHeader header;
     122             :     CPartialMerkleTree txn;
     123             : 
     124             :     /**
     125             :      * Public only for unit testing and relay testing (not relayed).
     126             :      *
     127             :      * Used only when a bloom filter is specified to allow
     128             :      * testing the transactions which matched the bloom filter.
     129             :      */
     130             :     std::vector<std::pair<unsigned int, uint256> > vMatchedTxn;
     131             : 
     132             :     /**
     133             :      * Create from a CBlock, filtering transactions according to filter
     134             :      * Note that this will call IsRelevantAndUpdate on the filter for each transaction,
     135             :      * thus the filter will likely be modified.
     136             :      */
     137          11 :     CMerkleBlock(const CBlock& block, CBloomFilter& filter) : CMerkleBlock(block, &filter, nullptr) { }
     138             : 
     139             :     // Create from a CBlock, matching the txids in the set
     140           2 :     CMerkleBlock(const CBlock& block, const std::set<uint256>& txids) : CMerkleBlock(block, nullptr, &txids) { }
     141             : 
     142           0 :     CMerkleBlock() {}
     143             : 
     144           1 :     SERIALIZE_METHODS(CMerkleBlock, obj) { READWRITE(obj.header, obj.txn); }
     145             : 
     146             : private:
     147             :     // Combined constructor to consolidate code
     148             :     CMerkleBlock(const CBlock& block, CBloomFilter* filter, const std::set<uint256>* txids);
     149             : 
     150             : };
     151             : 
     152             : #endif // PIVX_MERKLEBLOCK_H