Struct PartialMerkleTree

pub struct PartialMerkleTree { /* private fields */ }

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.

Implementations

impl PartialMerkleTree

pub fn num_transactions(&self) -> u32

Returns the total number of transactions in the block.

pub fn bits(&self) -> &Vec<bool>

Returns the node-is-parent-of-matched-txid bits of the partial merkle tree.

pub fn hashes(&self) -> &Vec<TxMerkleNode>

Returns the transaction ids and internal hashes of the partial merkle tree.

pub fn from_txids(txids: &[Txid], matches: &[bool]) -> Self

Construct a partial merkle tree The txids are the transaction hashes of the block and the matches is the contains flags wherever a tx hash should be included in the proof.

Panics when txids is empty or when matches has a different length

Examples

use bitcoin::hash_types::Txid;
use bitcoin::hex::FromHex;
use bitcoin::merkle_tree::{MerkleBlock, PartialMerkleTree};

// Block 80000
let txids: Vec<Txid> = [
    "c06fbab289f723c6261d3030ddb6be121f7d2508d77862bb1e484f5cd7f92b25",
    "5a4ebf66822b0b2d56bd9dc64ece0bc38ee7844a23ff1d7320a88c5fdb2ad3e2",
]
.iter()
.map(|hex| hex.parse::<Txid>().unwrap())
.collect();

// Select the second transaction
let matches = vec![false, true];
let tree = PartialMerkleTree::from_txids(&txids, &matches);
assert!(tree.extract_matches(&mut vec![], &mut vec![]).is_ok());

pub fn extract_matches( &self, matches: &mut Vec<Txid>, indexes: &mut Vec<u32>, ) -> Result<TxMerkleNode, MerkleBlockError>

Extract the matching txid’s represented by this partial merkle tree and their respective indices within the partial tree. returns the merkle root, or error in case of failure

Trait Implementations

impl Clone for PartialMerkleTree

fn clone(&self) -> PartialMerkleTree

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PartialMerkleTree

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Decodable for PartialMerkleTree

fn consensus_decode_from_finite_reader<R: Read + ?Sized>( r: &mut R, ) -> Result<Self, Error>

Decode Self from a size-limited reader.

fn consensus_decode<R: Read + ?Sized>(reader: &mut R) -> Result<Self, Error>

Decode an object with a well-defined format.

impl Encodable for PartialMerkleTree

fn consensus_encode<W: Write + ?Sized>(&self, w: &mut W) -> Result<usize, Error>

Encodes an object with a well-defined format.

impl PartialEq for PartialMerkleTree

fn eq(&self, other: &PartialMerkleTree) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for PartialMerkleTree

impl StructuralPartialEq for PartialMerkleTree