/**
* 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);
}
}
public static FileLock lock_file(String path) throws IOException, FileNotFoundException {
RandomAccessFile file = new RandomAccessFile(path, "rw");
FileChannel fileChannel = file.getChannel();
return fileChannel.tryLock();
}