private synchronized boolean add(Block block, boolean tryConnecting)
throws BlockStoreException, VerificationException, ScriptException {
if (System.currentTimeMillis() - statsLastTime > 1000) {
// More than a second passed since last stats logging.
log.info("{} blocks per second", statsBlocksAdded);
statsLastTime = System.currentTimeMillis();
statsBlocksAdded = 0;
}
// We check only the chain head for double adds here to avoid potentially expensive block chain
// misses.
if (block.equals(chainHead.getHeader())) {
// Duplicate add of the block at the top of the chain, can be a natural artifact of the
// download process.
return true;
}
// Prove the block is internally valid: hash is lower than target, merkle root is correct and so
// on.
try {
block.verify();
} catch (VerificationException e) {
log.error("Failed to verify block:", e);
log.error(block.toString());
throw e;
}
// Try linking it to a place in the currently known blocks.
StoredBlock storedPrev = blockStore.get(block.getPrevBlockHash());
if (storedPrev == null) {
// We can't find the previous block. Probably we are still in the process of downloading the
// chain and a
// block was solved whilst we were doing it. We put it to one side and try to connect it later
// when we
// have more blocks.
log.warn("Block does not connect: {}", block.getHashAsString());
unconnectedBlocks.add(block);
return false;
} else {
// It connects to somewhere on the chain. Not necessarily the top of the best known chain.
//
// Create a new StoredBlock from this block. It will throw away the transaction data so when
// block goes
// out of scope we will reclaim the used memory.
StoredBlock newStoredBlock = storedPrev.build(block);
checkDifficultyTransitions(storedPrev, newStoredBlock);
blockStore.put(newStoredBlock);
// block.transactions may be null here if we received only a header and not a full block. This
// does not
// happen currently but might in future if getheaders is implemented.
connectBlock(newStoredBlock, storedPrev, block.transactions);
}
if (tryConnecting) tryConnectingUnconnected();
statsBlocksAdded++;
return true;
}
public void flush() {
Iterator<BlockPayload> iterator = dirty.values().iterator();
while (iterator.hasNext()) {
BlockPayload block = iterator.next();
iterator.remove();
store.write(block);
}
store.flush();
}
/**
* For each block in unconnectedBlocks, see if we can now fit it on top of the chain and if so, do
* so.
*/
private void tryConnectingUnconnected()
throws VerificationException, ScriptException, BlockStoreException {
// For each block in our unconnected list, try and fit it onto the head of the chain. If we
// succeed remove it
// from the list and keep going. If we changed the head of the list at the end of the round try
// again until
// we can't fit anything else on the top.
int blocksConnectedThisRound;
do {
blocksConnectedThisRound = 0;
Iterator<Block> iter = unconnectedBlocks.iterator();
while (iter.hasNext()) {
Block block = iter.next();
// Look up the blocks previous.
StoredBlock prev = blockStore.get(block.getPrevBlockHash());
if (prev == null) {
// This is still an unconnected/orphan block.
continue;
}
// Otherwise we can connect it now.
// False here ensures we don't recurse infinitely downwards when connecting huge chains.
add(block, false);
iter.remove();
blocksConnectedThisRound++;
}
if (blocksConnectedThisRound > 0) {
log.info("Connected {} floating blocks.", blocksConnectedThisRound);
}
} while (blocksConnectedThisRound > 0);
}
private void setChainHead(StoredBlock chainHead) {
this.chainHead = chainHead;
try {
blockStore.setChainHead(chainHead);
} catch (BlockStoreException e) {
throw new RuntimeException(e);
}
}
/**
* Constructs a BlockChain connected to the given wallet and store. To obtain a {@link Wallet} you
* can construct one from scratch, or you can deserialize a saved wallet from disk using {@link
* Wallet#loadFromFile(java.io.File)}
*
* <p>For the store you can use a {@link MemoryBlockStore} if you don't care about saving the
* downloaded data, or a {@link BoundedOverheadBlockStore} if you'd like to ensure fast startup
* the next time you run the program.
*/
public BlockChain(NetworkParameters params, Wallet wallet, BlockStore blockStore) {
try {
this.blockStore = blockStore;
chainHead = blockStore.getChainHead();
log.info("chain head is:\n{}", chainHead.getHeader());
} catch (BlockStoreException e) {
throw new RuntimeException(e);
}
this.params = params;
this.wallet = wallet;
}
public <T extends BlockPayload> T read(BlockPointer pos, Class<T> payloadType) {
T block = payloadType.cast(dirty.get(pos));
if (block != null) {
return block;
}
block = payloadType.cast(indexBlockCache.get(pos));
if (block != null) {
return block;
}
block = store.read(pos, payloadType);
maybeCache(block);
return block;
}
public void write(BlockPayload block) {
store.attach(block);
maybeCache(block);
dirty.put(block.getPos(), block);
}
public <T extends BlockPayload> T readFirst(Class<T> payloadType) {
T block = store.readFirst(payloadType);
maybeCache(block);
return block;
}
public void remove(BlockPayload block) {
dirty.remove(block.getPos());
indexBlockCache.remove(block.getPos());
store.remove(block);
}
public void attach(BlockPayload block) {
store.attach(block);
}
public void clear() {
dirty.clear();
indexBlockCache.clear();
store.clear();
}
public void close() {
flush();
indexBlockCache.clear();
store.close();
}
public void open(Runnable initAction, Factory factory) {
store.open(initAction, factory);
}
/** Throws an exception if the blocks difficulty is not correct. */
private void checkDifficultyTransitions(StoredBlock storedPrev, StoredBlock storedNext)
throws BlockStoreException, VerificationException {
Block prev = storedPrev.getHeader();
Block next = storedNext.getHeader();
// Is this supposed to be a difficulty transition point?
if ((storedPrev.getHeight() + 1) % params.interval != 0) {
// No ... so check the difficulty didn't actually change.
if (next.getDifficultyTarget() != prev.getDifficultyTarget())
throw new VerificationException(
"Unexpected change in difficulty at height "
+ storedPrev.getHeight()
+ ": "
+ Long.toHexString(next.getDifficultyTarget())
+ " vs "
+ Long.toHexString(prev.getDifficultyTarget()));
return;
}
// We need to find a block far back in the chain. It's OK that this is expensive because it only
// occurs every
// two weeks after the initial block chain download.
long now = System.currentTimeMillis();
StoredBlock cursor = blockStore.get(prev.getHash());
for (int i = 0; i < params.interval - 1; i++) {
if (cursor == null) {
// This should never happen. If it does, it means we are following an incorrect or busted
// chain.
throw new VerificationException(
"Difficulty transition point but we did not find a way back to the genesis block.");
}
cursor = blockStore.get(cursor.getHeader().getPrevBlockHash());
}
log.info("Difficulty transition traversal took {}msec", System.currentTimeMillis() - now);
Block blockIntervalAgo = cursor.getHeader();
int timespan = (int) (prev.getTime() - blockIntervalAgo.getTime());
// Limit the adjustment step.
if (timespan < params.targetTimespan / 4) timespan = params.targetTimespan / 4;
if (timespan > params.targetTimespan * 4) timespan = params.targetTimespan * 4;
BigInteger newDifficulty = Utils.decodeCompactBits(blockIntervalAgo.getDifficultyTarget());
newDifficulty = newDifficulty.multiply(BigInteger.valueOf(timespan));
newDifficulty = newDifficulty.divide(BigInteger.valueOf(params.targetTimespan));
if (newDifficulty.compareTo(params.proofOfWorkLimit) > 0) {
log.warn("Difficulty hit proof of work limit: {}", newDifficulty.toString(16));
newDifficulty = params.proofOfWorkLimit;
}
int accuracyBytes = (int) (next.getDifficultyTarget() >>> 24) - 3;
BigInteger receivedDifficulty = next.getDifficultyTargetAsInteger();
// The calculated difficulty is to a higher precision than received, so reduce here.
BigInteger mask = BigInteger.valueOf(0xFFFFFFL).shiftLeft(accuracyBytes * 8);
newDifficulty = newDifficulty.and(mask);
if (newDifficulty.compareTo(receivedDifficulty) != 0)
throw new VerificationException(
"Network provided difficulty bits do not match what was calculated: "
+ receivedDifficulty.toString(16)
+ " vs "
+ newDifficulty.toString(16));
}
