Package org.bitcoinj.core

Class CheckpointManager

java.lang.Object

org.bitcoinj.core.CheckpointManager

public class CheckpointManager
extends Object

Vends hard-coded StoredBlocks for blocks throughout the chain. Checkpoints serve two purposes:

1. They act as a safety mechanism against huge re-orgs that could rewrite large chunks of history, thus constraining the block chain to be a consensus mechanism only for recent parts of the timeline.
2. They allow synchronization to the head of the chain for new wallets/users much faster than syncing all headers from the genesis block.

Checkpoints are used by the SPV BlockChain to initialize fresh SPVBlockStores. They are not used by fully validating mode, which instead has a different concept of checkpoints that are used to hard-code the validity of blocks that violate BIP30 (duplicate coinbase transactions). Those "checkpoints" can be found in NetworkParameters.

Checkpoints are read from a text file, one value per line. It consists of the magic string "TXT CHECKPOINTS 1", followed by the number of signatures to read. The value may not be larger than 256. If the number of signatures is larger than zero, each 65 byte ECDSA secp256k1 signature then follows. The signatures sign the hash of all bytes that follow the last signature.

After the signatures come the number of checkpoints in the file. Then each checkpoint follows one per line in compact format (as written by StoredBlock.serializeCompactV2(ByteBuffer)) as a base64-encoded blob.

Field Summary

Fields

Modifier and Type	Field	Description
static final com.google.common.io.BaseEncoding	BASE64
protected final TreeMap<Instant,StoredBlock>	checkpoints
protected final Sha256Hash	dataHash
protected final NetworkParameters	params

Constructor Summary

Constructors

Constructor	Description
CheckpointManager(NetworkParameters params)	Loads the default checkpoints bundled with bitcoinj
CheckpointManager(NetworkParameters params, InputStream inputStream)	Loads the checkpoints from the given stream

Method Summary

Modifier and Type	Method	Description
static void	checkpoint(NetworkParameters params, InputStream checkpoints, BlockStore store, long timeSecs)	Deprecated. use checkpoint(NetworkParameters, InputStream, BlockStore, Instant)
static void	checkpoint(NetworkParameters params, InputStream checkpoints, BlockStore store, Instant time)	Convenience method that creates a CheckpointManager, loads the given data, gets the checkpoint for the given time, then inserts it into the store and sets that to be the chain head.
StoredBlock	getCheckpointBefore(long timeSecs)	Deprecated. use getCheckpointBefore(Instant)
StoredBlock	getCheckpointBefore(Instant time)	Returns a StoredBlock representing the last checkpoint before the given time, for example, normally you would want to know the checkpoint before the earliest wallet birthday.
Sha256Hash	getDataHash()	Returns a hash of the concatenated checkpoint data.
int	numCheckpoints()	Returns the number of checkpoints that were loaded.
static InputStream	openStream(NetworkParameters params)	Returns a checkpoints stream pointing to inside the bitcoinj JAR

Methods inherited from class java.lang.Object

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

Field Details

checkpoints

protected final TreeMap<Instant,StoredBlock> checkpoints

params

protected final NetworkParameters params

dataHash

protected final Sha256Hash dataHash

BASE64

public static final com.google.common.io.BaseEncoding BASE64

Constructor Details

CheckpointManager

public CheckpointManager(NetworkParameters params)
                  throws IOException

Loads the default checkpoints bundled with bitcoinj

Throws:

IOException

CheckpointManager

public CheckpointManager(NetworkParameters params,
 @Nullable
 InputStream inputStream)
                  throws IOException

Loads the checkpoints from the given stream

Throws:

IOException

Method Details

openStream

public static InputStream openStream(NetworkParameters params)

Returns a checkpoints stream pointing to inside the bitcoinj JAR

getCheckpointBefore

public StoredBlock getCheckpointBefore(Instant time)

Returns a StoredBlock representing the last checkpoint before the given time, for example, normally you would want to know the checkpoint before the earliest wallet birthday.

getCheckpointBefore

@Deprecated
public StoredBlock getCheckpointBefore(long timeSecs)

Deprecated.

use getCheckpointBefore(Instant)

numCheckpoints

public int numCheckpoints()

Returns the number of checkpoints that were loaded.

getDataHash

public Sha256Hash getDataHash()

Returns a hash of the concatenated checkpoint data.

checkpoint

public static void checkpoint(NetworkParameters params,
 InputStream checkpoints,
 BlockStore store,
 Instant time)
                       throws IOException,
BlockStoreException

Convenience method that creates a CheckpointManager, loads the given data, gets the checkpoint for the given time, then inserts it into the store and sets that to be the chain head. Useful when you have just created a new store from scratch and want to use configure it all in one go.

Note that time is adjusted backwards by a week to account for possible clock drift in the block headers.

Throws:

IOException

BlockStoreException

checkpoint

@Deprecated
public static void checkpoint(NetworkParameters params,
 InputStream checkpoints,
 BlockStore store,
 long timeSecs)
                       throws IOException,
BlockStoreException

Deprecated.

use checkpoint(NetworkParameters, InputStream, BlockStore, Instant)

Throws:

IOException

BlockStoreException