code: public long addRecord(final ORecordId iRid, final byte[] iContent) throws IOException {
  
      if (iContent.length == 0)
        // AVOID UNUSEFUL CREATION OF EMPTY RECORD: IT WILL BE CREATED AT FIRST UPDATE
        return -1;
  
      final int recordSize = iContent.length + RECORD_FIX_SIZE;
  
      acquireExclusiveLock();
      try {
  
        final long[] newFilePosition = getFreeSpace(recordSize);
        writeRecord(newFilePosition, iRid.clusterId, iRid.clusterPosition, iContent);
        return getAbsolutePosition(newFilePosition);
  
      } finally {
        releaseExclusiveLock();
      }
    }
docs: Add the record content in file.
  
  @param iContent
  The content to write
  @return The record offset.
  @throws IOException