Initial Vexta Core v0.1.0 release

src/merkleblock.h

@@ -0,0 +1,159 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_MERKLEBLOCK_H
+#define DIGIBYTE_MERKLEBLOCK_H
+
+#include <serialize.h>
+#include <uint256.h>
+#include <primitives/block.h>
+#include <bloom.h>
+
+#include <vector>
+
+// Helper functions for serialization.
+std::vector<unsigned char> BitsToBytes(const std::vector<bool>& bits);
+std::vector<bool> BytesToBits(const std::vector<unsigned char>& bytes);
+
+/** 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:
+
+    SERIALIZE_METHODS(CPartialMerkleTree, obj)
+    {
+        READWRITE(obj.nTransactions, obj.vHash);
+        std::vector<unsigned char> bytes;
+        SER_WRITE(obj, bytes = BitsToBytes(obj.vBits));
+        READWRITE(bytes);
+        SER_READ(obj, obj.vBits = BytesToBits(bytes));
+        SER_READ(obj, obj.fBad = false);
+    }
+
+    /** 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() {}
+
+    SERIALIZE_METHODS(CMerkleBlock, obj) { READWRITE(obj.header, obj.txn); }
+
+private:
+    // Combined constructor to consolidate code
+    CMerkleBlock(const CBlock& block, CBloomFilter* filter, const std::set<uint256>* txids);
+};
+
+#endif // DIGIBYTE_MERKLEBLOCK_H