question: protected static void writeDataPage ( ByteBuffer buffer , DataPage dataPage , int tdefPageNumber , JetFormat format ) throws IOException { buffer . put ( dataPage . isLeaf ( ) ? PageTypes . INDEX_LEAF : PageTypes . INDEX_NODE ) ; buffer . put ( ( byte ) 0x01 ) ; buffer . putShort ( ( short ) 0 ) ; buffer . putInt ( tdefPageNumber ) ; buffer . putInt ( 0 ) ; buffer . putInt ( dataPage . getPrevPageNumber ( ) ) ; buffer . putInt ( dataPage . getNextPageNumber ( ) ) ; buffer . putInt ( dataPage . getChildTailPageNumber ( ) ) ; byte [ ] entryPrefix = dataPage . getEntryPrefix ( ) ; buffer . putShort ( ( short ) entryPrefix . length ) ; buffer . put ( ( byte ) 0 ) ; byte [ ] entryMask = new byte [ format . SIZE_INDEX_ENTRY_MASK ] ; int totalSize = entryPrefix . length ; for ( Entry entry : dataPage . getEntries ( ) ) { totalSize += ( entry . size ( ) - entryPrefix . length ) ; int idx = totalSize / 8 ; entryMask [ idx ] |= ( 1 << ( totalSize % 8 ) ) ; } buffer . put ( entryMask ) ; buffer . put ( entryPrefix ) ; for ( Entry entry : dataPage . getEntries ( ) ) { entry . write ( buffer , entryPrefix ) ; } buffer . putShort ( 2 , ( short ) ( format . PAGE_SIZE - buffer . position ( ) ) ) ; }
target:  Writes the data page info to the given buffer.