@Override
  RegularFile copyWithoutContent(int id, FileTime creationTime) {
    byte[][] copyBlocks = new byte[Math.max(blockCount * 2, 32)][];
    return new RegularFile(id, creationTime, disk, copyBlocks, 0, size);
  }
Gets the current size of this file in bytes. Does not do locking, so should only be called when
holding a lock.
jimfs/src/main/java/com/google/common/jimfs/RegularFile.java