* 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 {
    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);
      } 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];
        if (!new String(header, "US-ASCII").equals(HEADER_MAGIC))
          throw new BlockStoreException("Header bytes do not equal " + HEADER_MAGIC);
      } else {
    } catch (Exception e) {
      try {
        if (randomAccessFile != null) randomAccessFile.close();
      } catch (IOException e2) {
        throw new BlockStoreException(e2);
      throw new BlockStoreException(e);
 public void close() throws BlockStoreException {
   try {
     if (System.getProperty("os.name").toLowerCase().contains("win")) {
       log.info("Windows mmap hack: Forcing buffer cleaning");
     buffer = null; // Allow it to be GCd and the underlying file mapping to go away.
   } catch (IOException e) {
     throw new BlockStoreException(e);