private long updateBtreeHeader()

in mavibot/src/main/java/org/apache/directory/mavibot/btree/RecordManager.java [2488:2581]
60 lines of code
8 McCabe index (conditional complexity)

    private <K, V> long updateBtreeHeader( BTree<K, V> btree, long btreeHeaderOffset, boolean onPlace )
        throws EndOfFileExceededException, IOException
    {
        // Read the pageIOs associated with this B-tree
        PageIO[] pageIos;
        long newBtreeHeaderOffset = NO_PAGE;
        long offset = ( ( PersistedBTree<K, V> ) btree ).getBtreeOffset();

        if ( onPlace )
        {
            // We just have to update the existing BTreeHeader
            long headerSize = LONG_SIZE + LONG_SIZE + LONG_SIZE;

            pageIos = readPageIOs( offset, headerSize );

            // Now, update the revision
            long position = 0;

            position = store( position, btree.getRevision(), pageIos );
            position = store( position, btree.getNbElems(), pageIos );
            position = store( position, btreeHeaderOffset, pageIos );

            // Write the pages on disk
            if ( LOG.isDebugEnabled() )
            {
                LOG.debug( "-----> Flushing the '{}' B-treeHeader", btree.getName() );
                LOG.debug( "  revision : " + btree.getRevision() + ", NbElems : " + btree.getNbElems()
                    + ", btreeHeader offset : 0x"
                    + Long.toHexString( btreeHeaderOffset ) );
            }

            // Get new place on disk to store the modified BTreeHeader if it's not onPlace
            // Rewrite the pages at the same place
            LOG.debug( "Rewriting the B-treeHeader on place for B-tree " + btree.getName() );
            flushPages( pageIos );
        }
        else
        {
            // We have to read and copy the existing BTreeHeader and to create a new one
            pageIos = readPageIOs( offset, Long.MAX_VALUE );

            // Now, copy every read page
            PageIO[] newPageIOs = new PageIO[pageIos.length];
            int pos = 0;

            for ( PageIO pageIo : pageIos )
            {
                // Fetch a free page
                newPageIOs[pos] = fetchNewPage();

                // keep a track of the allocated and copied pages so that we can
                // free them when we do a commit or rollback, if the btree is an management one
                if ( ( btree.getType() == BTreeTypeEnum.BTREE_OF_BTREES )
                    || ( btree.getType() == BTreeTypeEnum.COPIED_PAGES_BTREE ) )
                {
                    freedPages.add( pageIo );
                    allocatedPages.add( newPageIOs[pos] );
                }

                pageIo.copy( newPageIOs[pos] );

                if ( pos > 0 )
                {
                    newPageIOs[pos - 1].setNextPage( newPageIOs[pos].getOffset() );
                }

                pos++;
            }

            // store the new btree header offset
            // and update the revision
            long position = 0;

            position = store( position, btree.getRevision(), newPageIOs );
            position = store( position, btree.getNbElems(), newPageIOs );
            position = store( position, btreeHeaderOffset, newPageIOs );

            // Get new place on disk to store the modified BTreeHeader if it's not onPlace
            // Flush the new B-treeHeader on disk
            LOG.debug( "Rewriting the B-treeHeader on place for B-tree " + btree.getName() );
            flushPages( newPageIOs );

            newBtreeHeaderOffset = newPageIOs[0].getOffset();
        }

        nbUpdateBtreeHeader.incrementAndGet();

        if ( LOG_CHECK.isDebugEnabled() )
        {
            MavibotInspector.check( this );
        }

        return newBtreeHeaderOffset;
    }