jdbm/src/main/java/jdbm/recman/PageManager.java - directory-server - Git at Google

 /**
  * 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: PageManager.java,v 1.3 2005/06/25 23:12:32 doomdark Exp $
  */
 package jdbm.recman;


 import java.io.*;

 import org.apache.directory.server.i18n.I18n;


 /**
  * This class manages the linked lists of pages that make up a recordFile.
  */
 final class PageManager
 {
     // our record recordFile
     private RecordFile recordFile;

     // header data
     private FileHeader header;

     // recordFile header containing block
     private BlockIo headerBuf;


     /**
      * Creates a new page manager using the indicated record recordFile.
      */
     PageManager( RecordFile recordFile ) throws IOException
     {
         this.recordFile = recordFile;

         // Note that we hold on to the recordFile header node.
         headerBuf = recordFile.get( 0 );

         // Assume recordFile is new if the recordFile header's magic number is 0.
         if ( headerBuf.readShort( 0 ) == 0 )
         {
             header = new FileHeader( headerBuf, true );
         }
         else // header is for existing recordFile
         {
             header = new FileHeader( headerBuf, false );
         }
     }


     /**
      * Allocates a page of the indicated type. Returns recid of the page.
      */
     long allocate( short type ) throws IOException
     {
         if ( type == Magic.FREE_PAGE )
         {
             throw new Error( I18n.err( I18n.ERR_548 ) );
         }

         boolean isNew = false;

         // Do we have something on the free list?
         long retval = header.getFirstOf( Magic.FREE_PAGE );
         if ( retval != 0 )
         {
             // yes. Point to it and make the next of that page the
             // new first free page.
             header.setFirstOf( Magic.FREE_PAGE, getNext( retval ) );
         }
         else
         {
             // nope. make a new record
             retval = header.getLastOf( Magic.FREE_PAGE );

             if ( retval == 0 )
             {
                 // very new recordFile - allocate record #1
                 retval = 1;
             }

             header.setLastOf( Magic.FREE_PAGE, retval + 1 );
             isNew = true;
         }

         // Cool. We have a record, add it to the correct list
         BlockIo buf = recordFile.get( retval );
         PageHeader pageHdr = null;

         if ( isNew )
         {
             pageHdr = new PageHeader( buf, type );
         }
         else
         {
             pageHdr = PageHeader.getView( buf );
         }

         long oldLast = header.getLastOf( type );

         // Clean data.
         System.arraycopy( RecordFile.cleanData, 0, buf.getData(), 0, RecordFile.BLOCK_SIZE );
         pageHdr.setType( type );
         pageHdr.setPrev( oldLast );
         pageHdr.setNext( 0 );

         if ( oldLast == 0 )
         {
             // This was the first one of this type
             header.setFirstOf( type, retval );
         }

         header.setLastOf( type, retval );
         recordFile.release( retval, true );

         // If there's a previous, fix up its pointer
         if ( oldLast != 0 )
         {
             buf = recordFile.get( oldLast );
             pageHdr = PageHeader.getView( buf );
             pageHdr.setNext( retval );
             recordFile.release( oldLast, true );
         }

         // remove the view, we have modified the type.
         buf.setView( null );

         return retval;
     }


     /**
      * Frees a page of the indicated type.
      */
     void free( short type, long recid ) throws IOException
     {
         if ( type == Magic.FREE_PAGE )
         {
             throw new Error( I18n.err( I18n.ERR_549 ) );
         }

         if ( recid == 0 )
         {
             throw new Error( I18n.err( I18n.ERR_550 ) );
         }

         // get the page and read next and previous pointers
         BlockIo buf = recordFile.get( recid );
         PageHeader pageHdr = PageHeader.getView( buf );
         long prev = pageHdr.getPrev();
         long next = pageHdr.getNext();

         // put the page at the front of the free list.
         pageHdr.setType( Magic.FREE_PAGE );
         pageHdr.setNext( header.getFirstOf( Magic.FREE_PAGE ) );
         pageHdr.setPrev( 0 );

         header.setFirstOf( Magic.FREE_PAGE, recid );
         recordFile.release( recid, true );

         // remove the page from its old list
         if ( prev != 0 )
         {
             buf = recordFile.get( prev );
             pageHdr = PageHeader.getView( buf );
             pageHdr.setNext( next );
             recordFile.release( prev, true );
         }
         else
         {
             header.setFirstOf( type, next );
         }

         if ( next != 0 )
         {
             buf = recordFile.get( next );
             pageHdr = PageHeader.getView( buf );
             pageHdr.setPrev( prev );
             recordFile.release( next, true );
         }
         else
         {
             header.setLastOf( type, prev );
         }
     }


     /**
      * Returns the page following the indicated block
      */
     long getNext( long block ) throws IOException
     {
         try
         {
             return PageHeader.getView( recordFile.get( block ) ).getNext();
         }
         finally
         {
             recordFile.release( block, false );
         }
     }


     /**
      * Returns the page before the indicated block
      */
     long getPrev( long block ) throws IOException
     {
         try
         {
             return PageHeader.getView( recordFile.get( block ) ).getPrev();
         }
         finally
         {
             recordFile.release( block, false );
         }
     }


     /**
      * Returns the first page on the indicated list.
      */
     long getFirst( short type ) throws IOException
     {
         return header.getFirstOf( type );
     }


     /**
      * Returns the last page on the indicated list.
      */
     long getLast( short type ) throws IOException
     {
         return header.getLastOf( type );
     }


     /**
      * Commit all pending (in-memory) data by flushing the page manager.
      * This forces a flush of all outstanding blocks (this is an implicit
      * {@link RecordFile#commit} as well).
      */
     void commit() throws IOException
     {
         // write the header out
         recordFile.release( headerBuf );
         recordFile.commit();

         // and obtain it again
         headerBuf = recordFile.get( 0 );
         header = new FileHeader( headerBuf, false );
     }


     /**
      * Flushes the page manager. This forces a flush of all outstanding
      * blocks (this is an implicit {@link RecordFile#commit} as well).
      *
      * @TODO completely wrong description of method
      */
     void rollback() throws IOException
     {
         // release header
         recordFile.discard( headerBuf );
         recordFile.rollback();
         // and obtain it again
         headerBuf = recordFile.get( 0 );

         if ( headerBuf.readShort( 0 ) == 0 )
         {
             header = new FileHeader( headerBuf, true );
         }
         else
         {
             header = new FileHeader( headerBuf, false );
         }
     }


     /**
      * Closes the page manager. This flushes the page manager and releases
      * the lock on the header.
      */
     void close() throws IOException
     {
         recordFile.release( headerBuf );
         recordFile.commit();
         headerBuf = null;
         header = null;
         recordFile = null;
     }


     /**
      *  Returns the recordFile header.
      */
     FileHeader getFileHeader()
     {
         return header;
     }

     RecordFile getRecordFile()
     {
         return recordFile;
     }
 }
	/**
	* 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: PageManager.java,v 1.3 2005/06/25 23:12:32 doomdark Exp $
	*/
	package jdbm.recman;


	import java.io.*;

	import org.apache.directory.server.i18n.I18n;


	/**
	* This class manages the linked lists of pages that make up a recordFile.
	*/
	final class PageManager
	{
	// our record recordFile
	private RecordFile recordFile;

	// header data
	private FileHeader header;

	// recordFile header containing block
	private BlockIo headerBuf;


	/**
	* Creates a new page manager using the indicated record recordFile.
	*/
	PageManager( RecordFile recordFile ) throws IOException
	{
	this.recordFile = recordFile;

	// Note that we hold on to the recordFile header node.
	headerBuf = recordFile.get( 0 );

	// Assume recordFile is new if the recordFile header's magic number is 0.
	if ( headerBuf.readShort( 0 ) == 0 )
	{
	header = new FileHeader( headerBuf, true );
	}
	else // header is for existing recordFile
	{
	header = new FileHeader( headerBuf, false );
	}
	}


	/**
	* Allocates a page of the indicated type. Returns recid of the page.
	*/
	long allocate( short type ) throws IOException
	{
	if ( type == Magic.FREE_PAGE )
	{
	throw new Error( I18n.err( I18n.ERR_548 ) );
	}

	boolean isNew = false;

	// Do we have something on the free list?
	long retval = header.getFirstOf( Magic.FREE_PAGE );
	if ( retval != 0 )
	{
	// yes. Point to it and make the next of that page the
	// new first free page.
	header.setFirstOf( Magic.FREE_PAGE, getNext( retval ) );
	}
	else
	{
	// nope. make a new record
	retval = header.getLastOf( Magic.FREE_PAGE );

	if ( retval == 0 )
	{
	// very new recordFile - allocate record #1
	retval = 1;
	}

	header.setLastOf( Magic.FREE_PAGE, retval + 1 );
	isNew = true;
	}

	// Cool. We have a record, add it to the correct list
	BlockIo buf = recordFile.get( retval );
	PageHeader pageHdr = null;

	if ( isNew )
	{
	pageHdr = new PageHeader( buf, type );
	}
	else
	{
	pageHdr = PageHeader.getView( buf );
	}

	long oldLast = header.getLastOf( type );

	// Clean data.
	System.arraycopy( RecordFile.cleanData, 0, buf.getData(), 0, RecordFile.BLOCK_SIZE );
	pageHdr.setType( type );
	pageHdr.setPrev( oldLast );
	pageHdr.setNext( 0 );

	if ( oldLast == 0 )
	{
	// This was the first one of this type
	header.setFirstOf( type, retval );
	}

	header.setLastOf( type, retval );
	recordFile.release( retval, true );

	// If there's a previous, fix up its pointer
	if ( oldLast != 0 )
	{
	buf = recordFile.get( oldLast );
	pageHdr = PageHeader.getView( buf );
	pageHdr.setNext( retval );
	recordFile.release( oldLast, true );
	}

	// remove the view, we have modified the type.
	buf.setView( null );

	return retval;
	}


	/**
	* Frees a page of the indicated type.
	*/
	void free( short type, long recid ) throws IOException
	{
	if ( type == Magic.FREE_PAGE )
	{
	throw new Error( I18n.err( I18n.ERR_549 ) );
	}

	if ( recid == 0 )
	{
	throw new Error( I18n.err( I18n.ERR_550 ) );
	}

	// get the page and read next and previous pointers
	BlockIo buf = recordFile.get( recid );
	PageHeader pageHdr = PageHeader.getView( buf );
	long prev = pageHdr.getPrev();
	long next = pageHdr.getNext();

	// put the page at the front of the free list.
	pageHdr.setType( Magic.FREE_PAGE );
	pageHdr.setNext( header.getFirstOf( Magic.FREE_PAGE ) );
	pageHdr.setPrev( 0 );

	header.setFirstOf( Magic.FREE_PAGE, recid );
	recordFile.release( recid, true );

	// remove the page from its old list
	if ( prev != 0 )
	{
	buf = recordFile.get( prev );
	pageHdr = PageHeader.getView( buf );
	pageHdr.setNext( next );
	recordFile.release( prev, true );
	}
	else
	{
	header.setFirstOf( type, next );
	}

	if ( next != 0 )
	{
	buf = recordFile.get( next );
	pageHdr = PageHeader.getView( buf );
	pageHdr.setPrev( prev );
	recordFile.release( next, true );
	}
	else
	{
	header.setLastOf( type, prev );
	}
	}


	/**
	* Returns the page following the indicated block
	*/
	long getNext( long block ) throws IOException
	{
	try
	{
	return PageHeader.getView( recordFile.get( block ) ).getNext();
	}
	finally
	{
	recordFile.release( block, false );
	}
	}


	/**
	* Returns the page before the indicated block
	*/
	long getPrev( long block ) throws IOException
	{
	try
	{
	return PageHeader.getView( recordFile.get( block ) ).getPrev();
	}
	finally
	{
	recordFile.release( block, false );
	}
	}


	/**
	* Returns the first page on the indicated list.
	*/
	long getFirst( short type ) throws IOException
	{
	return header.getFirstOf( type );
	}


	/**
	* Returns the last page on the indicated list.
	*/
	long getLast( short type ) throws IOException
	{
	return header.getLastOf( type );
	}


	/**
	* Commit all pending (in-memory) data by flushing the page manager.
	* This forces a flush of all outstanding blocks (this is an implicit
	* {@link RecordFile#commit} as well).
	*/
	void commit() throws IOException
	{
	// write the header out
	recordFile.release( headerBuf );
	recordFile.commit();

	// and obtain it again
	headerBuf = recordFile.get( 0 );
	header = new FileHeader( headerBuf, false );
	}


	/**
	* Flushes the page manager. This forces a flush of all outstanding
	* blocks (this is an implicit {@link RecordFile#commit} as well).
	*
	* @TODO completely wrong description of method
	*/
	void rollback() throws IOException
	{
	// release header
	recordFile.discard( headerBuf );
	recordFile.rollback();
	// and obtain it again
	headerBuf = recordFile.get( 0 );

	if ( headerBuf.readShort( 0 ) == 0 )
	{
	header = new FileHeader( headerBuf, true );
	}
	else
	{
	header = new FileHeader( headerBuf, false );
	}
	}


	/**
	* Closes the page manager. This flushes the page manager and releases
	* the lock on the header.
	*/
	void close() throws IOException
	{
	recordFile.release( headerBuf );
	recordFile.commit();
	headerBuf = null;
	header = null;
	recordFile = null;
	}


	/**
	* Returns the recordFile header.
	*/
	FileHeader getFileHeader()
	{
	return header;
	}

	RecordFile getRecordFile()
	{
	return recordFile;
	}
	}