code: @Override
      public void enlargeFile(long toEnlarge) throws IOException {
          size += (long) Math.ceil((double) toEnlarge / incrementSize) * incrementSize;
          logger.debug("Enlarge filesize of {} to {}", osFile, size);
          contentEnd = size;
          accessFile.setLength(size);
  
          // TODO check buffer size
          // if there are more chunks than the index can contain
          if ((size - contentStart) / chunkSize > indexSize) {
              logger.error("File-Enlargement not possible. The index becomes too large.");
              throw new IOException("File-Enlargement not possible. The index becomes too large.");
          }
          calcIndexInformations();
      }
docs: Rounds up the given size to the next full chunk, and enlarges the file by these amounts of bytes.
  
  @param toEnlarge
  @throws IOException