/**
   * Read the basic log entry header, leaving the buffer mark at the beginning of the checksummed
   * header data.
   */
  private void readBasicHeader(ByteBuffer dataBuffer) throws ChecksumException, DatabaseException {

    /* Read the header for this entry. */
    currentEntryHeader = new LogEntryHeader(dataBuffer, window.logVersion);

    /*
     * currentEntryPrevOffset is a separate field, and is not obtained
     * directly from the currentEntryHeader, because it is initialized and
     * used before any log entry was read.
     */
    currentEntryPrevOffset = currentEntryHeader.getPrevOffset();
  }