private void flushPage(long fileId, long pageIndex, ODirectMemoryPointer dataPointer)
throws IOException {
if (writeAheadLog != null) {
OLogSequenceNumber lsn = ODurablePage.getLogSequenceNumberFromPage(dataPointer);
OLogSequenceNumber flushedLSN = writeAheadLog.getFlushedLSN();
if (flushedLSN == null || flushedLSN.compareTo(lsn) < 0) writeAheadLog.flush();
}
final byte[] content = dataPointer.get(0, pageSize);
OLongSerializer.INSTANCE.serializeNative(MAGIC_NUMBER, content, 0);
final int crc32 = calculatePageCrc(content);
OIntegerSerializer.INSTANCE.serializeNative(crc32, content, OLongSerializer.LONG_SIZE);
final OFileClassic fileClassic = files.get(fileId);
fileClassic.write(pageIndex * pageSize, content);
if (syncOnPageFlush) fileClassic.synch();
}