org.bitcoinj.core

Class PartialMerkleTree

java.lang.Object

org.bitcoinj.core.Message

org.bitcoinj.core.PartialMerkleTree

public class PartialMerkleTree
extends Message

A data structure that contains proofs of block inclusion for one or more transactions, in an efficient manner.

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 were 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.

Instances of this class are not safe for use by multiple threads.

Field Summary

Fields inherited from class org.bitcoinj.core.Message

cursor, length, MAX_SIZE, offset, params, payload, protocolVersion, recached, serializer, UNKNOWN_LENGTH

Constructor Summary

Constructors

Constructor and Description
PartialMerkleTree(NetworkParameters params, byte[] payloadBytes, int offset)
PartialMerkleTree(NetworkParameters params, byte[] bits, List<Sha256Hash> hashes, int origTxCount) Constructs a new PMT with the given bit set (little endian) and the raw list of hashes including internal hashes, taking ownership of the list.

Method Summary

Modifier and Type	Method and Description
void	bitcoinSerializeToStream(OutputStream stream) Serializes this message to the provided stream.
static PartialMerkleTree	buildFromLeaves(NetworkParameters params, byte[] includeBits, List<Sha256Hash> allLeafHashes) Calculates a PMT given the list of leaf hashes and which leaves need to be included.
boolean	equals(Object o)
int	getTransactionCount()
Sha256Hash	getTxnHashAndMerkleRoot(List<Sha256Hash> matchedHashesOut) Extracts tx hashes that are in this merkle tree and returns the merkle root of this tree.
int	hashCode()
protected void	parse()
String	toString()

Methods inherited from class org.bitcoinj.core.Message

adjustLength, bitcoinSerialize, bitcoinSerialize, getHash, getMessageSize, getParams, hasMoreBytes, isCached, isRecached, readByteArray, readBytes, readHash, readInt64, readStr, readUint32, readUint64, readVarInt, readVarInt, unCache, unsafeBitcoinSerialize

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

PartialMerkleTree

public PartialMerkleTree(NetworkParameters params,
                         byte[] payloadBytes,
                         int offset)
                  throws ProtocolException

Throws:

ProtocolException

PartialMerkleTree

public PartialMerkleTree(NetworkParameters params,
                         byte[] bits,
                         List<Sha256Hash> hashes,
                         int origTxCount)

Constructs a new PMT with the given bit set (little endian) and the raw list of hashes including internal hashes, taking ownership of the list.

Method Detail

buildFromLeaves

public static PartialMerkleTree buildFromLeaves(NetworkParameters params,
                                                byte[] includeBits,
                                                List<Sha256Hash> allLeafHashes)

Calculates a PMT given the list of leaf hashes and which leaves need to be included. The relevant interior hashes are calculated and a new PMT returned.

bitcoinSerializeToStream

public void bitcoinSerializeToStream(OutputStream stream)
                              throws IOException

Description copied from class: Message

Serializes this message to the provided stream. If you just want the raw bytes use bitcoinSerialize().

Overrides:

bitcoinSerializeToStream in class Message

Throws:

IOException

parse

protected void parse()
              throws ProtocolException

Specified by:

parse in class Message

Throws:

ProtocolException

getTxnHashAndMerkleRoot

public Sha256Hash getTxnHashAndMerkleRoot(List<Sha256Hash> matchedHashesOut)
                                   throws VerificationException

Extracts tx hashes that are in this merkle tree and returns the merkle root of this tree. The returned root should be checked against the merkle root contained in the block header for security.

Parameters:

matchedHashesOut - A list which will contain the matched txn (will be cleared).

Returns:

the merkle root of this merkle tree

Throws:

ProtocolException - if this partial merkle tree is invalid

VerificationException

getTransactionCount

public int getTransactionCount()

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object