CPartialMerkleTree Class Reference

#include <merkleblock.h>

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

Public Attributes
	ADD_SERIALIZE_METHODS

Protected Member Functions
unsigned int	CalcTreeWidth (int height)
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)

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 explorer 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.

Definition at line 50 of file merkleblock.h.

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

Definition at line 134 of file merkleblock.cpp.

CPartialMerkleTree() [2/2]

CPartialMerkleTree::CPartialMerkleTree

(

)

Definition at line 148 of file merkleblock.cpp.

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)

Definition at line 63 of file merkleblock.cpp.

CalcTreeWidth()

unsigned int CPartialMerkleTree::CalcTreeWidth ( int  height )

inlineprotected

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

Definition at line 66 of file merkleblock.h.

Referenced by CPartialMerkleTree(), and ExtractMatches().

ExtractMatches()

uint256 CPartialMerkleTree::ExtractMatches

(

std::vector< uint256 > &

vMatch

)

extract the matching txid's represented by this partial merkle tree. returns the merkle root, or 0 in case of failure

Definition at line 150 of file merkleblock.cpp.

SerializationOp()

template<typename Stream , typename Operation >

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

inline

Definition at line 88 of file merkleblock.h.

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

Definition at line 80 of file merkleblock.cpp.

Referenced by CPartialMerkleTree().

TraverseAndExtract()

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

protected

recursive function that traverses tree nodes, consuming the bits and hashes produced by TraverseAndBuild. it returns the hash of the respective node.

Definition at line 98 of file merkleblock.cpp.

Referenced by ExtractMatches().

Member Data Documentation

ADD_SERIALIZE_METHODS

CPartialMerkleTree::ADD_SERIALIZE_METHODS

serialization implementation

Definition at line 85 of file merkleblock.h.

fBad

bool CPartialMerkleTree::fBad

protected

flag set when encountering invalid data

Definition at line 63 of file merkleblock.h.

Referenced by ExtractMatches(), and SerializationOp().

nTransactions

unsigned int CPartialMerkleTree::nTransactions

protected

the total number of transactions in the block

Definition at line 54 of file merkleblock.h.

Referenced by CalcTreeWidth(), ExtractMatches(), and SerializationOp().

vBits

std::vector<bool> CPartialMerkleTree::vBits

protected

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

Definition at line 57 of file merkleblock.h.

Referenced by CPartialMerkleTree(), ExtractMatches(), and SerializationOp().

vHash

std::vector<uint256> CPartialMerkleTree::vHash

protected

txids and internal hashes

Definition at line 60 of file merkleblock.h.

Referenced by CPartialMerkleTree(), ExtractMatches(), and SerializationOp().

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

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