public static void main(String[] args) throws Exception {
fc = new RandomAccessFile("test.dat", "rw").getChannel();
MappedByteBuffer out = fc.map(FileChannel.MapMode.READ_WRITE, 0, LENGTH);
for (int i = 0; i < LENGTH; i++) out.put((byte) 'x');
new LockAndModify(out, 0, 0 + LENGTH / 3);
new LockAndModify(out, LENGTH / 2, LENGTH / 2 + LENGTH / 4);
}
public static long checksumMappedFile(Path filename) throws IOException {
try (FileChannel channel = FileChannel.open(filename)) {
CRC32 crc = new CRC32();
int length = (int) channel.size();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length);
for (int p = 0; p < length; p++) {
int c = buffer.get(p);
crc.update(c);
}
return crc.getValue();
}
}
@Override
public void setChainHead(StoredBlock chainHead) throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
lastChainHead = chainHead;
byte[] headHash = chainHead.getHeader().getHash().getBytes();
buffer.position(8);
buffer.put(headHash);
} finally {
lock.unlock();
}
}
@Override
@Nullable
public StoredBlock get(Sha256Hash hash) throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
StoredBlock cacheHit = blockCache.get(hash);
if (cacheHit != null) return cacheHit;
if (notFoundCache.get(hash) != null) return null;
// Starting from the current tip of the ring work backwards until we have either found the
// block or
// wrapped around.
int cursor = getRingCursor(buffer);
final int startingPoint = cursor;
final int fileSize = getFileSize();
final byte[] targetHashBytes = hash.getBytes();
byte[] scratch = new byte[32];
do {
cursor -= RECORD_SIZE;
if (cursor < FILE_PROLOGUE_BYTES) {
// We hit the start, so wrap around.
cursor = fileSize - RECORD_SIZE;
}
// Cursor is now at the start of the next record to check, so read the hash and compare it.
buffer.position(cursor);
buffer.get(scratch);
if (Arrays.equals(scratch, targetHashBytes)) {
// Found the target.
StoredBlock storedBlock = StoredBlock.deserializeCompact(params, buffer);
blockCache.put(hash, storedBlock);
return storedBlock;
}
} while (cursor != startingPoint);
// Not found.
notFoundCache.put(hash, notFoundMarker);
return null;
} catch (ProtocolException e) {
throw new RuntimeException(e); // Cannot happen.
} finally {
lock.unlock();
}
}
/**
* Creates and initializes an SPV block store. Will create the given file if it's missing. This
* operation will block on disk.
*/
public SPVBlockStore(NetworkParameters params, File file) throws BlockStoreException {
checkNotNull(file);
this.params = checkNotNull(params);
try {
this.numHeaders = DEFAULT_NUM_HEADERS;
boolean exists = file.exists();
// Set up the backing file.
randomAccessFile = new RandomAccessFile(file, "rw");
long fileSize = getFileSize();
if (!exists) {
log.info("Creating new SPV block chain file " + file);
randomAccessFile.setLength(fileSize);
} else if (randomAccessFile.length() != fileSize) {
throw new BlockStoreException(
"File size on disk does not match expected size: "
+ randomAccessFile.length()
+ " vs "
+ fileSize);
}
FileChannel channel = randomAccessFile.getChannel();
fileLock = channel.tryLock();
if (fileLock == null)
throw new BlockStoreException("Store file is already locked by another process");
// Map it into memory read/write. The kernel will take care of flushing writes to disk at the
// most
// efficient times, which may mean that until the map is deallocated the data on disk is
// randomly
// inconsistent. However the only process accessing it is us, via this mapping, so our own
// view will
// always be correct. Once we establish the mmap the underlying file and channel can go away.
// Note that
// the details of mmapping vary between platforms.
buffer = channel.map(FileChannel.MapMode.READ_WRITE, 0, fileSize);
// Check or initialize the header bytes to ensure we don't try to open some random file.
byte[] header;
if (exists) {
header = new byte[4];
buffer.get(header);
if (!new String(header, "US-ASCII").equals(HEADER_MAGIC))
throw new BlockStoreException("Header bytes do not equal " + HEADER_MAGIC);
} else {
initNewStore(params);
}
} catch (Exception e) {
try {
if (randomAccessFile != null) randomAccessFile.close();
} catch (IOException e2) {
throw new BlockStoreException(e2);
}
throw new BlockStoreException(e);
}
}
@Override
public void close() throws BlockStoreException {
try {
buffer.force();
if (System.getProperty("os.name").toLowerCase().contains("win")) {
log.info("Windows mmap hack: Forcing buffer cleaning");
WindowsMMapHack.forceRelease(buffer);
}
buffer = null; // Allow it to be GCd and the underlying file mapping to go away.
randomAccessFile.close();
} catch (IOException e) {
throw new BlockStoreException(e);
}
}
@Override
public StoredBlock getChainHead() throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
if (lastChainHead == null) {
byte[] headHash = new byte[32];
buffer.position(8);
buffer.get(headHash);
Sha256Hash hash = new Sha256Hash(headHash);
StoredBlock block = get(hash);
if (block == null)
throw new BlockStoreException(
"Corrupted block store: could not find chain head: " + hash);
lastChainHead = block;
}
return lastChainHead;
} finally {
lock.unlock();
}
}
@Override
public void put(StoredBlock block) throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
int cursor = getRingCursor(buffer);
if (cursor == getFileSize()) {
// Wrapped around.
cursor = FILE_PROLOGUE_BYTES;
}
buffer.position(cursor);
Sha256Hash hash = block.getHeader().getHash();
notFoundCache.remove(hash);
buffer.put(hash.getBytes());
block.serializeCompact(buffer);
setRingCursor(buffer, buffer.position());
blockCache.put(hash, block);
} finally {
lock.unlock();
}
}
private void initNewStore(NetworkParameters params) throws Exception {
byte[] header;
header = HEADER_MAGIC.getBytes("US-ASCII");
buffer.put(header);
// Insert the genesis block.
lock.lock();
try {
setRingCursor(buffer, FILE_PROLOGUE_BYTES);
} finally {
lock.unlock();
}
Block genesis = params.getGenesisBlock().cloneAsHeader();
StoredBlock storedGenesis = new StoredBlock(genesis, genesis.getWork(), 0);
put(storedGenesis);
setChainHead(storedGenesis);
}