| /** |
| * 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: FreePhysicalRowIdPage.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $ |
| */ |
| package jdbm.recman; |
| |
| |
| /** |
| * Class describing a page that holds physical rowids that were freed. |
| */ |
| final class FreePhysicalRowIdPage extends PageHeader |
| { |
| // offsets |
| private static final short O_COUNT = PageHeader.SIZE; // short count |
| static final short O_FREE = O_COUNT + Magic.SZ_SHORT; |
| static final short ELEMS_PER_PAGE = ( RecordFile.BLOCK_SIZE - O_FREE ) / FreePhysicalRowId.SIZE; |
| |
| // slots we returned. |
| FreePhysicalRowId[] slots = new FreePhysicalRowId[ELEMS_PER_PAGE]; |
| |
| |
| /** |
| * Constructs a data page view from the indicated block. |
| */ |
| FreePhysicalRowIdPage( BlockIo block ) |
| { |
| super( block ); |
| } |
| |
| |
| /** |
| * Factory method to create or return a data page for the indicated block. |
| */ |
| static FreePhysicalRowIdPage getFreePhysicalRowIdPageView( BlockIo block ) |
| { |
| BlockView view = block.getView(); |
| if ( view != null && view instanceof FreePhysicalRowIdPage ) |
| { |
| return ( FreePhysicalRowIdPage ) view; |
| } |
| else |
| { |
| return new FreePhysicalRowIdPage( block ); |
| } |
| } |
| |
| |
| /** Returns the number of free rowids */ |
| short getCount() |
| { |
| return block.readShort( O_COUNT ); |
| } |
| |
| |
| /** Sets the number of free rowids */ |
| private void setCount( short i ) |
| { |
| block.writeShort( O_COUNT, i ); |
| } |
| |
| |
| /** Frees a slot */ |
| void free( int slot ) |
| { |
| get( slot ).setSize( 0 ); |
| setCount( ( short ) ( getCount() - 1 ) ); |
| } |
| |
| |
| /** Allocates a slot */ |
| FreePhysicalRowId alloc( int slot ) |
| { |
| setCount( ( short ) ( getCount() + 1 ) ); |
| return get( slot ); |
| } |
| |
| |
| /** Returns true if a slot is allocated */ |
| boolean isAllocated( int slot ) |
| { |
| return get( slot ).getSize() != 0; |
| } |
| |
| |
| /** Returns true if a slot is free */ |
| boolean isFree( int slot ) |
| { |
| return ! isAllocated( slot ); |
| } |
| |
| |
| /** Returns the value of the indicated slot */ |
| FreePhysicalRowId get( int slot ) |
| { |
| if ( slots[slot] == null ) |
| { |
| slots[slot] = new FreePhysicalRowId( block, slotToOffset( slot ) ) ; |
| } |
| |
| return slots[slot]; |
| } |
| |
| |
| /** Converts slot to offset */ |
| short slotToOffset( int slot ) |
| { |
| return ( short ) ( O_FREE + ( slot * FreePhysicalRowId.SIZE ) ); |
| } |
| |
| |
| /** |
| * Returns first free slot, -1 if no slots are available |
| */ |
| int getFirstFree() |
| { |
| for ( int i = 0; i < ELEMS_PER_PAGE; i++ ) |
| { |
| if ( isFree( i ) ) |
| { |
| return i; |
| } |
| } |
| |
| return -1; |
| } |
| |
| |
| /** |
| * Returns first slot with available size >= indicated size, or -1 if no |
| * slots are available. |
| */ |
| int getFirstLargerThan( int size ) |
| { |
| for ( int i = 0; i < ELEMS_PER_PAGE; i++ ) |
| { |
| if ( isAllocated( i ) && get( i ).getSize() >= size ) |
| { |
| return i; |
| } |
| } |
| |
| return -1; |
| } |
| } |