CPartialMerkleTree Class Reference

#include <merkleblock.h>

Public Member Functions
template<typename Stream , typename Operation >
void	SerializationOp (Stream &s, Operation ser_action)
	CPartialMerkleTree (const std::vector< uint256 > &vTxid, const std::vector< bool > &vMatch)
	CPartialMerkleTree ()
uint256	ExtractMatches (std::vector< uint256 > &vMatch, std::vector< unsigned int > &vnIndex)
unsigned int	GetNumTransactions () const

Public Attributes
	ADD_SERIALIZE_METHODS

Protected Member Functions
unsigned int	CalcTreeWidth (int height) const
uint256	CalcHash (int height, unsigned int pos, const std::vector< uint256 > &vTxid)
void	TraverseAndBuild (int height, unsigned int pos, const std::vector< uint256 > &vTxid, const std::vector< bool > &vMatch)
uint256	TraverseAndExtract (int height, unsigned int pos, unsigned int &nBitsUsed, unsigned int &nHashUsed, std::vector< uint256 > &vMatch, std::vector< unsigned int > &vnIndex)

Protected Attributes
unsigned int	nTransactions
std::vector< bool >	vBits
std::vector< uint256 >	vHash
bool	fBad

Detailed Description

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.

Constructor & Destructor Documentation

CPartialMerkleTree() [1/2]

CPartialMerkleTree::CPartialMerkleTree	(	const std::vector< uint256 > &	vTxid,
		const std::vector< bool > &	vMatch
	)

Construct a partial merkle tree from a list of transaction ids, and a mask that selects a subset of them

CPartialMerkleTree() [2/2]

CPartialMerkleTree::CPartialMerkleTree

(

)

Member Function Documentation

CalcHash()

uint256 CPartialMerkleTree::CalcHash ( int  height, unsigned int  pos, const std::vector< uint256 > &  vTxid  )

protected

calculate the hash of a node in the merkle tree (at leaf level: the txid's themselves)

CalcTreeWidth()

unsigned int CPartialMerkleTree::CalcTreeWidth ( int  height ) const

inlineprotected

helper function to efficiently calculate the number of nodes at given height in the merkle tree

ExtractMatches()

uint256 CPartialMerkleTree::ExtractMatches	(	std::vector< uint256 > &	vMatch,
		std::vector< unsigned int > &	vnIndex
	)

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

GetNumTransactions()

unsigned int CPartialMerkleTree::GetNumTransactions ( ) const

inline

Get number of transactions the merkle proof is indicating for cross-reference with local blockchain knowledge.

SerializationOp()

template<typename Stream , typename Operation >

void CPartialMerkleTree::SerializationOp ( Stream &  s, Operation  ser_action  )

inline

TraverseAndBuild()

void CPartialMerkleTree::TraverseAndBuild ( int  height, unsigned int  pos, const std::vector< uint256 > &  vTxid, const std::vector< bool > &  vMatch  )

protected

recursive function that traverses tree nodes, storing the data as bits and hashes

TraverseAndExtract()

uint256 CPartialMerkleTree::TraverseAndExtract ( int  height, unsigned int  pos, unsigned int &  nBitsUsed, unsigned int &  nHashUsed, std::vector< uint256 > &  vMatch, std::vector< unsigned int > &  vnIndex  )

protected

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.

Member Data Documentation

ADD_SERIALIZE_METHODS

CPartialMerkleTree::ADD_SERIALIZE_METHODS

serialization implementation

fBad

bool CPartialMerkleTree::fBad

protected

flag set when encountering invalid data

nTransactions

unsigned int CPartialMerkleTree::nTransactions

protected

the total number of transactions in the block

vBits

std::vector<bool> CPartialMerkleTree::vBits

protected

node-is-parent-of-matched-txid bits

vHash

std::vector<uint256> CPartialMerkleTree::vHash

protected

txids and internal hashes

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The documentation for this class was generated from the following files:

• src/merkleblock.h
• src/merkleblock.cpp