/src/merkleblock.h
C Header | 173 lines | 65 code | 29 blank | 79 comment | 5 complexity | 89b976c64a5c909cb7fcbb92c002f236 MD5 | raw file
Possible License(s): GPL-3.0, BSD-3-Clause, MIT
- // Copyright (c) 2009-2010 Satoshi Nakamoto
- // Copyright (c) 2009-2018 The Bitcoin Core developers
- // Distributed under the MIT software license, see the accompanying
- // file COPYING or http://www.opensource.org/licenses/mit-license.php.
- #ifndef BITCOIN_MERKLEBLOCK_H
- #define BITCOIN_MERKLEBLOCK_H
- #include <serialize.h>
- #include <uint256.h>
- #include <primitives/block.h>
- #include <bloom.h>
- #include <vector>
- /** Data structure that represents a partial merkle tree.
- *
- * It represents a subset of the txid's of a known block, in a way that
- * allows recovery of the list of txid's and the merkle root, in an
- * authenticated way.
- *
- * The encoding works as follows: we traverse the tree in depth-first order,
- * storing a bit for each traversed node, signifying whether the node is the
- * parent of at least one matched leaf txid (or a matched txid itself). In
- * case we are at the leaf level, or this bit is 0, its merkle node hash is
- * stored, and its children are not explored further. Otherwise, no hash is
- * stored, but we recurse into both (or the only) child branch. During
- * decoding, the same depth-first traversal is performed, consuming bits and
- * hashes as they written during encoding.
- *
- * The serialization is fixed and provides a hard guarantee about the
- * encoded size:
- *
- * SIZE <= 10 + ceil(32.25*N)
- *
- * Where N represents the number of leaf nodes of the partial tree. N itself
- * is bounded by:
- *
- * N <= total_transactions
- * N <= 1 + matched_transactions*tree_height
- *
- * The serialization format:
- * - uint32 total_transactions (4 bytes)
- * - varint number of hashes (1-3 bytes)
- * - uint256[] hashes in depth-first order (<= 32*N bytes)
- * - varint number of bytes of flag bits (1-3 bytes)
- * - byte[] flag bits, packed per 8 in a byte, least significant bit first (<= 2*N-1 bits)
- * The size constraints follow from this.
- */
- class CPartialMerkleTree
- {
- protected:
- /** the total number of transactions in the block */
- unsigned int nTransactions;
- /** node-is-parent-of-matched-txid bits */
- std::vector<bool> vBits;
- /** txids and internal hashes */
- std::vector<uint256> vHash;
- /** flag set when encountering invalid data */
- bool fBad;
- /** helper function to efficiently calculate the number of nodes at given height in the merkle tree */
- unsigned int CalcTreeWidth(int height) const {
- return (nTransactions+(1 << height)-1) >> height;
- }
- /** calculate the hash of a node in the merkle tree (at leaf level: the txid's themselves) */
- uint256 CalcHash(int height, unsigned int pos, const std::vector<uint256> &vTxid);
- /** recursive function that traverses tree nodes, storing the data as bits and hashes */
- void TraverseAndBuild(int height, unsigned int pos, const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch);
- /**
- * recursive function that traverses tree nodes, consuming the bits and hashes produced by TraverseAndBuild.
- * it returns the hash of the respective node and its respective index.
- */
- uint256 TraverseAndExtract(int height, unsigned int pos, unsigned int &nBitsUsed, unsigned int &nHashUsed, std::vector<uint256> &vMatch, std::vector<unsigned int> &vnIndex);
- public:
- /** serialization implementation */
- ADD_SERIALIZE_METHODS;
- template <typename Stream, typename Operation>
- inline void SerializationOp(Stream& s, Operation ser_action) {
- READWRITE(nTransactions);
- READWRITE(vHash);
- std::vector<unsigned char> vBytes;
- if (ser_action.ForRead()) {
- READWRITE(vBytes);
- CPartialMerkleTree &us = *(const_cast<CPartialMerkleTree*>(this));
- us.vBits.resize(vBytes.size() * 8);
- for (unsigned int p = 0; p < us.vBits.size(); p++)
- us.vBits[p] = (vBytes[p / 8] & (1 << (p % 8))) != 0;
- us.fBad = false;
- } else {
- vBytes.resize((vBits.size()+7)/8);
- for (unsigned int p = 0; p < vBits.size(); p++)
- vBytes[p / 8] |= vBits[p] << (p % 8);
- READWRITE(vBytes);
- }
- }
- /** Construct a partial merkle tree from a list of transaction ids, and a mask that selects a subset of them */
- CPartialMerkleTree(const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch);
- CPartialMerkleTree();
- /**
- * extract the matching txid's represented by this partial merkle tree
- * and their respective indices within the partial tree.
- * returns the merkle root, or 0 in case of failure
- */
- uint256 ExtractMatches(std::vector<uint256> &vMatch, std::vector<unsigned int> &vnIndex);
- /** Get number of transactions the merkle proof is indicating for cross-reference with
- * local blockchain knowledge.
- */
- unsigned int GetNumTransactions() const { return nTransactions; };
- };
- /**
- * Used to relay blocks as header + vector<merkle branch>
- * to filtered nodes.
- *
- * NOTE: The class assumes that the given CBlock has *at least* 1 transaction. If the CBlock has 0 txs, it will hit an assertion.
- */
- class CMerkleBlock
- {
- public:
- /** Public only for unit testing */
- CBlockHeader header;
- CPartialMerkleTree txn;
- /**
- * Public only for unit testing and relay testing (not relayed).
- *
- * Used only when a bloom filter is specified to allow
- * testing the transactions which matched the bloom filter.
- */
- std::vector<std::pair<unsigned int, uint256> > vMatchedTxn;
- /**
- * Create from a CBlock, filtering transactions according to filter
- * Note that this will call IsRelevantAndUpdate on the filter for each transaction,
- * thus the filter will likely be modified.
- */
- CMerkleBlock(const CBlock& block, CBloomFilter& filter) : CMerkleBlock(block, &filter, nullptr) { }
- // Create from a CBlock, matching the txids in the set
- CMerkleBlock(const CBlock& block, const std::set<uint256>& txids) : CMerkleBlock(block, nullptr, &txids) { }
- CMerkleBlock() {}
- ADD_SERIALIZE_METHODS;
- template <typename Stream, typename Operation>
- inline void SerializationOp(Stream& s, Operation ser_action) {
- READWRITE(header);
- READWRITE(txn);
- }
- private:
- // Combined constructor to consolidate code
- CMerkleBlock(const CBlock& block, CBloomFilter* filter, const std::set<uint256>* txids);
- };
- #endif // BITCOIN_MERKLEBLOCK_H