org.bitcoinj.core

Class TxConfidenceTable

java.lang.Object

org.bitcoinj.core.TxConfidenceTable

public class TxConfidenceTable
extends Object

Tracks transactions that are being announced across the network. Typically one is created for you by a PeerGroup and then given to each Peer to update. The current purpose is to let Peers update the confidence (number of peers broadcasting). It helps address an attack scenario in which a malicious remote peer (or several) feeds you invalid transactions, eg, ones that spend coins which don't exist. If you don't see most of the peers announce the transaction within a reasonable time, it may be that the TX is not valid. Alternatively, an attacker may control your entire internet connection: in this scenario counting broadcasting peers does not help you.

It is not at this time directly equivalent to the Bitcoin Core memory pool, which tracks all transactions not currently included in the best chain - it's simply a cache.

Field Summary

Fields

Modifier and Type	Field and Description
protected ReentrantLock	lock
static int	MAX_SIZE The max size of a table created with the no-args constructor.

Constructor Summary

Constructors

Constructor and Description
TxConfidenceTable() Creates a table that will track at most MAX_SIZE entries.
TxConfidenceTable(int size) Creates a table that will track at most the given number of transactions (allowing you to bound memory usage).

Method Summary

Modifier and Type	Method and Description
TransactionConfidence	get(Sha256Hash hash) Returns the TransactionConfidence for the given hash if we have downloaded it, or null if that tx hash is unknown to the system at this time.
TransactionConfidence	getOrCreate(Sha256Hash hash) Returns the TransactionConfidence for the given hash if we have downloaded it, or null if that tx hash is unknown to the system at this time.
int	numBroadcastPeers(Sha256Hash txHash) Returns the number of peers that have seen the given hash recently.
TransactionConfidence	seen(Sha256Hash hash, PeerAddress byPeer) Called by peers when they see a transaction advertised in an "inv" message.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

lock

protected ReentrantLock lock

MAX_SIZE

public static final int MAX_SIZE

The max size of a table created with the no-args constructor.

See Also:

Constant Field Values

Constructor Detail

TxConfidenceTable

public TxConfidenceTable(int size)

Creates a table that will track at most the given number of transactions (allowing you to bound memory usage).

Parameters:

size - Max number of transactions to track. The table will fill up to this size then stop growing.

TxConfidenceTable

public TxConfidenceTable()

Creates a table that will track at most MAX_SIZE entries. You should normally use this constructor.

Method Detail

numBroadcastPeers

public int numBroadcastPeers(Sha256Hash txHash)

Returns the number of peers that have seen the given hash recently.

seen

public TransactionConfidence seen(Sha256Hash hash,
                                  PeerAddress byPeer)

Called by peers when they see a transaction advertised in an "inv" message. It passes the data on to the relevant TransactionConfidence object, creating it if needed.

Returns:

the number of peers that have now announced this hash (including the caller)

getOrCreate

public TransactionConfidence getOrCreate(Sha256Hash hash)

Returns the TransactionConfidence for the given hash if we have downloaded it, or null if that tx hash is unknown to the system at this time.

get

@Nullable
public TransactionConfidence get(Sha256Hash hash)

Returns the TransactionConfidence for the given hash if we have downloaded it, or null if that tx hash is unknown to the system at this time.