| /** |
| * JDBM LICENSE v1.00 |
| * |
| * Redistribution and use of this software and associated documentation |
| * ("Software"), with or without modification, are permitted provided |
| * that the following conditions are met: |
| * |
| * 1. Redistributions of source code must retain copyright |
| * statements and notices. Redistributions must also contain a |
| * copy of this document. |
| * |
| * 2. Redistributions in binary form must reproduce the |
| * above copyright notice, this list of conditions and the |
| * following disclaimer in the documentation and/or other |
| * materials provided with the distribution. |
| * |
| * 3. The name "JDBM" must not be used to endorse or promote |
| * products derived from this Software without prior written |
| * permission of Cees de Groot. For written permission, |
| * please contact cg@cdegroot.com. |
| * |
| * 4. Products derived from this Software may not be called "JDBM" |
| * nor may "JDBM" appear in their names without prior written |
| * permission of Cees de Groot. |
| * |
| * 5. Due credit should be given to the JDBM Project |
| * (http://jdbm.sourceforge.net/). |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS |
| * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT |
| * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND |
| * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL |
| * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
| * OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * Copyright 2000 (C) Cees de Groot. All Rights Reserved. |
| * Contributions are Copyright (C) 2000 by their associated contributors. |
| * |
| * $Id: PageHeader.java,v 1.2 2003/09/21 15:47:01 boisvert Exp $ |
| */ |
| package jdbm.recman; |
| |
| |
| import org.apache.directory.server.i18n.I18n; |
| |
| |
| /** |
| * This class represents a page header. It is the common superclass for |
| * all different page views. It contains the following information: |
| * |
| * <ol> |
| * <li>2 bytes: the short block type code</li> |
| * <li>8 bytes: the long block id of the next block in the block list</li> |
| * <li>8 bytes: the long block id of the previous block in the block list</li> |
| * </ol> |
| * |
| * The page header block view hence sees 18 bytes of page header data. |
| */ |
| public class PageHeader implements BlockView |
| { |
| // offsets into page header's (BlockIo's) buffer |
| |
| /** the page (BlockIo's type code) short magic code */ |
| private static final short O_MAGIC = 0; |
| /** the long block id of the next block in the block list */ |
| private static final short O_NEXT = Magic.SZ_SHORT; |
| /** the long block id of the previous block in the block list */ |
| private static final short O_PREV = O_NEXT + Magic.SZ_LONG; |
| |
| /** the size of this page header = 18 bytes */ |
| protected static final short SIZE = O_PREV + Magic.SZ_LONG; |
| |
| /** the page header block this view is associated with */ |
| protected BlockIo block; |
| |
| |
| /** |
| * Constructs a PageHeader object from a block |
| * |
| * @param block The block that contains the page header |
| * @throws IOException if the block is too short to keep the page header. |
| */ |
| protected PageHeader( BlockIo block ) |
| { |
| this.block = block; |
| block.setView( this ); |
| if ( ! magicOk() ) |
| { |
| throw new Error( I18n.err( I18n.ERR_546, block.getBlockId(), getMagic() ) ); |
| } |
| } |
| |
| |
| /** |
| * Constructs a new PageHeader of the indicated type. Used for newly |
| * created pages. |
| */ |
| PageHeader( BlockIo block, short type ) |
| { |
| this.block = block; |
| block.setView( this ); |
| setType( type ); |
| } |
| |
| |
| /** |
| * Factory method to create or return a page header for the indicated block. |
| */ |
| static PageHeader getView ( BlockIo block ) |
| { |
| BlockView view = block.getView(); |
| if ( view != null && view instanceof PageHeader ) |
| { |
| return ( PageHeader ) view; |
| } |
| else |
| { |
| return new PageHeader( block ); |
| } |
| } |
| |
| |
| /** |
| * Returns true if the magic corresponds with the fileHeader magic. |
| */ |
| private boolean magicOk() |
| { |
| int magic = getMagic(); |
| return magic >= Magic.BLOCK |
| && magic <= ( Magic.BLOCK + Magic.FREEPHYSIDS_PAGE ); |
| } |
| |
| |
| /** |
| * For paranoia mode |
| */ |
| protected void paranoiaMagicOk() |
| { |
| if ( ! magicOk() ) |
| { |
| throw new Error( I18n.err( I18n.ERR_547, getMagic() ) ); |
| } |
| } |
| |
| |
| /** Returns the magic code */ |
| short getMagic() |
| { |
| return block.readShort( O_MAGIC ); |
| } |
| |
| |
| /** Returns the next block. */ |
| long getNext() |
| { |
| paranoiaMagicOk(); |
| return block.readLong( O_NEXT ); |
| } |
| |
| |
| /** Sets the next block. */ |
| void setNext( long next ) |
| { |
| paranoiaMagicOk(); |
| block.writeLong( O_NEXT, next ); |
| } |
| |
| |
| /** Returns the previous block. */ |
| long getPrev() |
| { |
| paranoiaMagicOk(); |
| return block.readLong( O_PREV ); |
| } |
| |
| |
| /** Sets the previous block. */ |
| void setPrev( long prev ) |
| { |
| paranoiaMagicOk(); |
| block.writeLong( O_PREV, prev ); |
| } |
| |
| |
| /** Sets the type of the page header */ |
| void setType ( short type ) |
| { |
| block.writeShort( O_MAGIC, ( short ) ( Magic.BLOCK + type ) ); |
| } |
| } |