diff --git a/src/merkleblock.h b/src/merkleblock.h index 3f68b2ef6..d52c79f54 100644 --- a/src/merkleblock.h +++ b/src/merkleblock.h @@ -1,184 +1,184 @@ // Copyright (c) 2009-2010 Satoshi Nakamoto // Copyright (c) 2009-2016 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 #include #include #include #include /** * 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 explorer further. Otherwise, no 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 vBits; /** txids and internal hashes */ std::vector 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 &vTxid); /** * Recursive function that traverses tree nodes, storing the data as bits * and hashes. */ void TraverseAndBuild(int height, unsigned int pos, const std::vector &vTxid, const std::vector &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 &vMatch, std::vector &vnIndex); public: /** serialization implementation */ ADD_SERIALIZE_METHODS; template inline void SerializationOp(Stream &s, Operation ser_action) { READWRITE(nTransactions); READWRITE(vHash); std::vector vBytes; if (ser_action.ForRead()) { READWRITE(vBytes); CPartialMerkleTree &us = *(const_cast(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 &vTxid, const std::vector &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 &vMatch, std::vector &vnIndex); }; /** * Used to create a Merkle proof (usually from a subset of transactions), * which consists of a block header and partial Merkle Tree. * SPV clients typically use this Merkle proof to limit bandwidth and * computation requirements to process incoming transactions. * From the peer-node's perspective, the SPV client is a "filtered node". * See BIP37 for details: * https://github.com/bitcoin/bips/blob/master/bip-0037.mediawiki */ class CMerkleBlock { public: /** Public only for unit testing */ CBlockHeader header; CPartialMerkleTree txn; /** Public only for unit testing and relay testing (not relayed) */ std::vector> vMatchedTxn; /** * Create a Merkle proof according to a bloom 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); /** * Create a Merkle proof for a set of transactions. */ CMerkleBlock(const CBlock &block, const std::set &txids); CMerkleBlock() {} ADD_SERIALIZE_METHODS; template inline void SerializationOp(Stream &s, Operation ser_action) { READWRITE(header); READWRITE(txn); } }; #endif // BITCOIN_MERKLEBLOCK_H